Rehabiliation of Road Pavements to Enhanced the Durability using High Strength Concrete (H.S.C)

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  • Authors : Syed Omer Hussain Tanveer , Sohail Shafiuddin Ahmed , Mohammad Naveed Jameel, Amer Salam , Mirza Salman Baig Khaja, Dr. Ahmed Hussain
  • Paper ID : IJERTV9IS060309
  • Volume & Issue : Volume 09, Issue 06 (June 2020)
  • Published (First Online): 18-06-2020
  • ISSN (Online) : 2278-0181
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Rehabiliation of Road Pavements to Enhanced the Durability using High Strength Concrete (H.S.C)

Syed Omer Hussain Tanveer, Amer Salam, Sohail Shafiuddin Ahmed, Mirza Salman Baig Khaja, Mohammad Naveed Jameel

ISL Engineering college

Under the Guidance of

Mr. Dr. Ahmed Hussain

Assistant Professor in Civil Engineering dept.

ISL Engineering College, Hyderabad, India -500005

Abstract:- The vast amount of civil infrastructure in India includes an extensive stretch of road networks. From an economic point of view it is more cost effective to maintain the already existing pavements rather than building new ones.

Rapid civilization leads to construction of thousands of buildings in urban areas. Now days, multi-storied R.C. framed structures are common in urban regions in the cities like Hyderabad, Bangalore, New Delhi, Chennai, Maharashtra, Pune etc.

Due to thickly populated urban regions the buildings are extending vertically or going high or becoming more slender. Decades are evident that traffic volume in urban regions is high when compared to semi urban or rural regions.

A large proportion of the traffic delays on these road networks are caused by road closures and closures of individual lanes for pavement maintenance purposes. The application of early strength concrete in pavement maintenance measures will lead to a substantial reduction in the user costs involved with the road closures caused by such maintenance. These costs involve both the actual costs of the delays in terms of time and fuel consumption, but also, more importantly, the social and economic costs associated with the safety hazards resulting from these closures.

This research is aimed at selecting two four-hour mix designs out of a total of five mix designs selected in a report made by Construction Technology Laboratories Inc. (CTL), based on concrete compressive strength and freezing-thawing durability. The targeted concrete strength aimed at is a minimum of 14 MPa at four hours.

CHAPTER 1 INTRODUCTION

General Overview

All civil infrastructures have a definite life span. In other words, all structures are designed to fail at some point, and this includes the vast network of road pavements in India. Approximately 2% of lands in India are paved this consists of flexible, rigid and composite pavements. In order to ensure that pavements achieve the purpose for which they were designed they ought to be maintained regularly and at very little cost to the road user.

Road maintenance and rehabilitation form the largest percentage of this figure. It is therefore necessary to curtail the high cost of maintenance to road users by developing measures to decrease traffic delays during maintenance and rehabilitation.

There is a wide perception that concrete pavements "cost too much," "take too long," or "are too difficult to repair." However, to the contrary, although the initial cost of concrete may be higher than for asphalt pavement, however concrete costs less during the pavement's life cycle. Roads can be opened faster than ever and can be repaired easily with the proper equipment, materials, processes and or procedures. Also concrete pavement restoration can return a pavement to a near-new condition at a lesser cost to the road user if measurers to decrease delay time are put in place.

Background Information

Deteriorating asphalt and concrete pavement infrastructure worldwide demands innovative and economical rehabilitation solutions. When desired, a properly designed and constructed bonded overlay can add considerable life to an existing pavement, by taking advantage of the remaining structural capacity of the original pavement. For patchwork and total rehabilitation, two types of thin concrete pavement overlays rely on a bond between the overlay and the existing pavement for performance. Concrete overlays bonded to existing concrete pavements are called Bonded Concrete Overlays (BCO). Concrete overlays bonded to existing asphalt pavements are called Ultra-thin White-topping (UTW). Research has shown that concrete overlays over asphalt often bond to the asphalt, and that some reduction of concrete flexural stresses may be expected from this effect. These overlays have been used to address rutting of asphalt pavements.

Bond strength and resistance to cracking are important for overlay performance. In many cases these overlays are constructed on heavily traveled pavements, making early opening to traffic important. Therefore, early strength development without compromising durability is necessary. Satisfactory performance will only occur if the overlay is of sufficient thickness and is well bonded to the original pavement. The design assumption is that if the overlay bonds perfectly with the original pavement, it produces a monolithic structure. Without bond, there is very little structural benefit from an overlay, and the overlay may break apart rapidly under heavy traffic.

The use of concrete overlays for pavement and bridge deck maintenance and rehabilitation has been in existence for several decades, both un-bonded and bonded overlays have been used in rehabilitation and maintenance of deteriorating road pavements. For both BCO and UTW overlays, characteristics of the overlay concrete have important implications for early age behavior and long-term performance.

High Performance Concrete (HPC)

High performance concrete is defined as concrete made with appropriate materials combined according to a selected mix design and properly mixed, transported, placed, consolidated, and cured so that the resulting concrete will give excellent performance in the structure in which it will be exposed, and with the loads to which it will be subjected for its design life[Forster et al. 1994]. The design of high performance concrete mixes started in the 1980s in the private sector to protect parking structures and reinforced concrete high-rise buildings from chlorides, sulfates, alkali-silica reactivity and to curtail concrete shrinkage and creep.

HPC for pavements originated in the Strategic Highway Research Program under contract C205 where the mechanical properties of HPC were described and studied under actual use conditions. SHRP developed a definition of HPC (Table 1.1) and funding for limited field trials, which were to be followed by a substantial implementation period.

Category of HPC

Minimum

Maximum

Minimum Frost

Compressive Strength

Water/cement Ratio

Durability Factor

Very early strength (VES)

Option A

14 MPa

0.4

80%

(With Type III Cement)

in 6 hours

Option B

17.5 MPa

0.29

80%

(With PBC-XT Cement)

in 4 hours

High early strength (HES)

35 MPa

0.35

80%

(With Type III Cement)

in 24 hours

Very high strength

70 MPa

0.35

80%

(With Type I Cement)

in 28 hours

Table 1.1: Definition of HPC according to SHRP C-205

Performane goals for HPC pavements included an increase in pavement system service life, a decrease in construction time (including fast-track concrete paving techniques), longer life cycles such as a 30 – 50-year life, and lower maintenance costs.

      1. Early Strength / Fast Track Concrete mixes

        Early strength concrete mixes are concrete mixes that, through the use of high-early-strength cement or admixtures, are capable of attaining specified strengths at an earlier age than normal concrete. This property is very useful in road pavement maintenance and rehabilitation by reducing delay costs to the road user.

        Concrete or composite pavement repair is prime for maintaining existing roads. Before the advent of early strength concrete, there was no comparism of the costs of flexible pavements to rigid pavements in both initial and operating costs. This was because the initial material costs of rigid pavements and the cost of delays due to the longer closing time during maintenance and rehabilitation were far more than when asphalt was used. Since its inception, a lot of research and development has been done on early strength concrete. Early Strength can be broken down into two categories, Very Early Strength (VES) and High Early Strength (HES) concrete

        High early strength concrete is specified to have minimum compressive strength of 14 MPa but for a longer duration of 12 hours. In the context of our research, however, the word Early is considered to be relative; the concrete mixes to be researched will be termed Early strength, without taking into consideration the time and place of strength gain.

        These criteria were adopted after considering several factors pertinent to the construction and design of highway pavements and structures. The use of a time constraint of 4 to 6 hours for Very Early Strength, (VES) concrete is intended for projects with very tight construction schedules involving full-depth pavement replacements in urban or heavily traveled areas. The strength

        requirement of 14MPa to 17.5 MPa is selected to provide a class of concrete that would meet the need for rapid replacement and construction of pavements. Since Very Early Strength, (VES) concrete is intended for pavement applications where exposure to frost must be expected, it is essential that the concrete be frost resistant. Thus, it is appropriate to select a maximum W/C of 0.40, which is relatively low in comparison with conventional concrete. With a low W/C ratio, concrete durability is improved in all exposure conditions. Since VES concrete is expected to be in service in no more than 6 hours, the W/C selected might provide a discontinuous capillary pore system at about that age, as suggested by Powers et al (1959)

      2. High Early Strength Concrete Vs Conventional Concrete Mixtures

        Rather than using conventional concrete mixtures, High Early strength concrete mixtures are being used to decrease the delay time due to road closures. Unlike the conventional concrete mixtures, High Early strength concrete achieves its specified strength of 17.5 MPa to 21 MPa in 24 hours or less at an earlier age, from a few hours to several days.

        High strength at an early age is desirable in winter construction to reduce the length of time temporary protection is required, for high speed cast in-place construction, rapid form re-use, fast track paving and many other uses. The additional cost of high-early- strength concrete is often offset by earlier reuse of forms and removal of shores, savings in the shorter duration of temporary heating, and earlier use of the structure. In road pavement maintenance and rehabilitation, strength at an early age is beneficial when early opening of the pavement is necessary.

      3. Techniques Used In Attaining Early Strength

High early strength concrete can be achieved by using one or a combination of the following techniques.

  1. High conventional cement content.

  2. Low water – cement ratio using Type I cement (0.3-0.45 by mass).

  1. Higher temperatures for freshly mixed concrete

  2. Chemical admixtures.

  3. Higher curing temperatures.

  4. Special rapid hardening cements.

The above listed techniques can be used interchangeably or combined to achieve the desired strength. High early strength gain is not limited to the use of special proprietary cements such as Type III cement. It is now possible to achieve early strength by using locally available Portland cements, aggregates, and selected admixtures. This research uses a combination of Type III High Early Strength cement and chemical admixtures on one hand and a Low water-cement ratio and/or high conventional cement content on the other hand to attain early strength.

Literature Review

In the past, ordinary Portland cement-based mixtures were not able to achieve early strength requirement without sacrificing necessary working, placement, and finishing times. Portland cement-based concrete mixtures usually require a minimum of 24 hours and, frequently, five to fourteen days to gain sufficient strength and allow the concrete to return to service. With the advent of various techniques and materials it is now possible to use readily available local materials to achieve early strength.

In 2001, research conducted by the University of Alabama at Birmingham, titled Design and Quality Control of Concrete Overlays, developed and tested a range of plain and fiber reinforced concrete mixes that allowed reliable economic and durable overlay construction as well as early opening to traffic. The use of a lower water-cement ratio and a high percentage of normal cement was used in attaining early strength. It was concluded in this research that high strength concrete was appropriate for opening overlay to traffic in 24 hours or less, but normal strength may be used if traffic loading can be delayed for 48 or 72 hours.

Under the sponsorship of the New Jersey Department of Transportation a unique concrete mix was developed. This concrete mix attained a significant strength of 3,000 psi 3,500 psi (21 to 24.5 MPa) in a period of six to nine hours for use on pavement repair in high-traffic areas [FHWA NJ 2001-015]. The use of normal Portland cement and the reliance on chemical admixtures and insulated coverings was used to attain very high temperature levels in order to attain early strength.

Research into the performance and strength of fast track concrete was done under the Strategic Highway Research Program (SHRP). This research included Very Early Strength (VES), and High Early Strength (HES) mixes developed under the SHRP project C-205 Mechanical Behavior of High Performance Concrete. [Zia et al.,1993]. A literature review was conducted by the Construction Technology Laboratories Inc. based on 11 Fast track mixes developed under SHRP Contract C-206 documented in a report titled Optimization of Highway Concrete Technology, SHRP Report C-373 (2003). In their review report they recommended 4 mixes for further research into early strength gain. Currently there are a couple of early strength design mixes available for pavement rehabilitation, notably among them are 4 X 4 mix from Master Builders.

The Maryland State Highway Administration (MDSHA) currently requires use of a 12-hour concrete mix for patching in heavily trafficked roadways in urban areas. This mix is required in order to achieve 2,500 psi (17.5MPa) compressive strength in 12 hours. However, the MDSHA now wants to reduce the concrete set time to allow the patch to be opened to traffic about 4 hours after placing the concrete in the patch. The objective of the project is to test proper concrete material mixes both designed in the lab

and in the field, for composite pavements that will allow the repaired sections to be opened to traffic after four hours of concrete placement in the patch. A shorter patch repair time would minimize the disruption caused to traffic and ultimately provide loner lasting composite pavements. The report by the Construction Technology Laboratories (CTL) was submitted to the Maryland State Highway Administration in April 2003. Based on this report, a proposal was to be made to the Maryland State Highway Administration to test the four concrete mix designs selected in the report made by CTL.

From an earlier literature review study of eleven mixes, eight mixes were considered suitable for further study, two used at a Georgia site and six used at a Ohio site. Based on the performances of these mixes during the initial trials and, considering modifications for local materials, the VES mix, the GADOT mix in Georgia, and the VES mix and the ODOT mix in Ohio were selected as the four trial mixes to be evaluated further as part of a laboratory study. Also included as one of the trial mix designs, was a 12- hour concrete mix design currently used in Maryland for fast- track paving, and designated as the control Mix.

1.5.0 Research Objective

The objective of this research is to select two (2) concrete mixes out of the five selected that will yield a compressive strength of at least 14MPa after four hours of casting. The selected specimen should be able to withstand at least 300 cycles of freezing and thawing. The 2 selected mixes shall have passed both criteria. Based on the findings and recommendations of this report, another phase of this project is to be started to investigate the characteristics of the recommended mixes to field conditions. This will comprise the second phase of this project.

CHAPTER 2 CONCRETE AND ITS CONSTITUENTS

2. Introduction

Concrete is a construction material; it has been used for a variety of structures such as highways, bridges, buildings, dams, and tunnels over the years. Its widespread use compared to other options like steel and timber is due to its versatility, durability and economy.

The external appearance of concrete looks very simple, but it has a very complex internal structure. It is basically a simple homogeneous mixture of two components, aggregates (gravel or crushed stone) and paste (cement, water and entrapped or purposely entrained air). Cement paste normally constitutes about 25%-40% and aggregates 60%-75% of the total volume of concrete. When the paste is mixed with the aggregates, the chemical reaction of the constituents of the paste binds the aggregates into a rocklike mass as it hardens. This mass is referred to as concrete.

The quality of concrete greatly depends upon the quality of the paste and the quality of hardened concrete is determined by the amount of water used in relation to the amount of cement. Thus, the less water used, the better the quality of concrete, so far as it can be consolidated properly. Although smaller amounts of water result in stiffer mixes, these mixes are more economical and can still be used with efficient vibration during placing.

The physical and chemical properties of concrete, however, can be altered by the addition of admixtures in order to attain desirable mixes for specific purposes.

      1. Basic Components of Concrete

        Concrete is made up of various components, primarily; concrete is made up of paste, coarse aggregates and admixtures. The basic components of concrete are the following;

      2. Portland cement

        Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and usually originates from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of Portland cement are available. The most common, called ordinary Portland cement (OPC), is grey, but white Portland cement is also available. Its name is derived from its similarity to Portland stone which was quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. However, his son William Aspdin is regarded as the inventor of "modern" Portland cement due to his developments in the 1840s

      3. Types of Portland cement

Type I

Type I is a general purpose Portland cement suitable for all uses where the special properties of other types are not required. It is used where cement or concrete is not subject to specific exposures, such as sulfate attack from soil or water, or to an objectionable temperature rise due to heat generated by hydration. Its uses include pavements and sidewalks, reinforced concrete buildings, bridges, railway structures, tanks, reservoirs, culverts, sewers, water pipes and masonry units.

Type II

Type II Portland cement is used where precaution against moderate sulfate attack is important, as in drainage structures where sulfate concentrations in groundwater are higher than normal but not unusually severe. Type II cement will usually generate less heat at a slower rate than Type I. With this moderate heat of hydration, Type II cement can be used in structures of considerable mass, such as large piers, heavy abutments, and heavy retaining walls. Its use will reduce temperature rise — especially important when the concrete is laid in warm weather.

Type III

Type III is a high-early strength Portland cement that provides high strengths at an early period, usually a week or less. It is used when forms are to be removed as soon as possible, or when the structure must be put into service quickly. In cold weather, its use permits a reduction in the controlled curing period. Although richer mixtures of Type I cement can be used to gain high early strength, Type III may provide it more satisfactorily and more economically.

2.2.0 Aggregates

Aggregates play a major role in the properties of concrete, using the right kind of aggregate greatly influence concretes freshly mixed and hardened properties, mixture proportions, and economy.

Aggregates can be distinguished into two distinct types based on their particle sizes. Fine aggregate consists of natural sand or crushed stone with most particles smaller than 1/5 inch (5mm). Coarse aggregates consist of one or a combination of gravels and crushed aggregate with particles predominantly larger than 1/5 inch (5mm) and generally between 3/8 and 1-1/2 inches (9.5 and 37.5mm). Natural aggregates are obtained by either dredging or digging from a pit, river, lake or sea-bed. Crushed aggregates are produced by the crushing of quarry rock, boulders, cobbles, or large size gravels.

Aggregates must be set to some standards in order to be most useful in engineering structures. They must be clean, hard, strong, durable particles free of absorbed chemicals, coating of clay and other fine materials in amounts that could affect hydration and the bond of the cement paste. Aggregates with low resistance to weathering should be avoided in concrete mixes.

2.3.0 Aggregate Characteristics

Aggregate Grades and Grading Limits

The particle size and distribution of an aggregate is termed grading. It is determine by a sieve analysis in accordance to IS-2386-

2. The seven standard IS-2386-2 sieves for fine aggregates have openings ranging from 150µm to 3/8in (9.5mm). There are thirteen standard sieves for coarse aggregates that range from 0.046 inches to 4 inches (101.6mm). Grading and grading limits are usually expressed as percentages of materials passing through each sieve.

It is important to specify grading limits and maximum aggregate size because it affects the relative aggregate proportions as well as cement and water requirements, workability, pump-ability, economy, porosity, shrinkage and durability of concrete. It is thus important to acquire aggregates comprised of a collection of sizes so as to reduce the total volume of voids between aggregates during mixing.

Shape and Texture

The shap of aggregates influences the properties of concrete mixes. Angular, elongated particles and rough-textured aggregate produce more workable concrete than smooth, rounded, compact aggregates. Flat and elongated particles should be avoided or at least limited to 15% by weight of the total aggregate.

Strength and Shrinkage

An aggregates tensile strength ranges from 0.21MPa to 16.1MPa and its compressive strength from 70MPa to 280 MPa. This is important in high strength concrete.

Aggregates with high absorption properties may have high shrinkage on drying. Other characteristics include unit weight and voids, specific gravity, absorption, surface moisture, strength and shrinkage.

Handling and Storage of Aggregates

To minimize segregation, degradation and contamination by deleterious substances, aggregates should be handled and stored in an appropriate fashion by stockpiling them in thin layers of uniform thickness. The most appropriate and economical method of stockpiling is the truck dump method; however, when aggregates are not delivered by truck, an acceptable and less expensive way is to form the stockpile in layers using a clamshell bucket.

Washed aggregates should be stockpiled in sufficient time so that they can drain to have uniform moisture content before use.

      1. Admixture

        Admixtures are additives other than water, aggregates, hydraulic cement, and fibers that are added to the concrete batch immediately before or during mixing to improve specific characteristics of the concrete. There are two types of admixtures, chemical and mineral admixtures. These when properly used, offer certain beneficial effects to concrete, including improved quality of concrete during the stages of mixing, transporting, placing and curing in adverse weather, reduction in the cost of concrete construction, avoidance of certain emergencies during concrete mix operations, and achievement of certain properties.

        A survey by the National Ready Mix Concrete Association reported that 39% of all ready-mixed concrete producers use fly ash, and at least 70% of produced concrete contains a water-reducer admixture. The chemical composition of admixtures vary and, since many perform more than one function, it is necessary that all admixtures to be used in any concrete mix should meet specifications and tests should be made to evaluate the effect of the admixtures on the properties of the concrete mix.

        The beneficial effects admixtures have on concrete are due to the following properties they possess;

        • Water Reduction in the Mix

        • Increase in Concrete Strength

        • Corrosion Protection

        • Strength Enhancement

        • Set Retardation

        • Crack Control (shrinkage reduction)

        • Flow ability

        • Finish Enhancement

      2. Mineral Admixtures

        Mineral admixtures are usually added to concrete in large amounts to enhance its workability; improve its resistance to thermal cracking, alkali-aggregate expansion and sulfate attack; reduce permeability; increase strength; and enable a reduction in the cement content, thus improving the concrete mix properties.

        Mineral admixtures affect the nature of the hardened concrete through hydraulic or pozzolanic activity. Pozzolans are cementitious materials and include natural pozzolans (such as the volcanic ash used in Roman concrete), fly ash and silica fume.

        Fly Ash

        Fly ashes are finely divided residues resulting from combustion of ground or powdered coal. They are generally finer than cement and consist mainly of glassy-spherical particles as well as residues of hematite and magnetite, char, and some crystalline phases formed during cooling.

        Fly ash improves the workability in concrete, reduces segregation, bleeding, heat evolution and permeability, inhibits alkali- aggregate reaction, and enhances sulfate resistance. Because Portland cement concrete pavement is largely dependent on high volumes of cement, the use of fly ash as an admixture is important where economy is important factor.

        Granulated Blast Furnace Slag

        Intergrading the granulated slag with Portland cement clinker makes Portland blast furnace slag cement. Its use as a mineral admixture did not start until the late 1970s. Ground granulated blast-furnace slag is the granular material formed when molten iron blast furnace slag is rapidly chilled by immersion in water.

      3. Chemical Admixtures

Chemical admixtures are added to concrete to modify its properties. They ensure the quality of concrete during mixing/transporting/placing/curing. They are added mainly for the entrainment of air, reduction of water or cement content, plasticization of fresh concrete mixtures, or control of setting time. They are added in smaller amounts as compared to mineral admixtures. They fall into the following categories: Air entrains, Water reducers, Set retarders, Set accelerators, and Superplasticizers.

Water Reducers

Water-reducing admixtures are groups of products that are added to concrete to achieve certain workability (slump) at a lower w/c than that of control concrete. In other words they are used to reduce the quantity of mixing water required to produce concrete of a certain slump, to reduce water-cement ratio, or to increase slump. Water-reducing admixtures are used to improve the quality of concrete and to obtain specified strength at lower cement content. They also improve the properties of concrete containing marginal- or low-quality aggregates and they help in placing concrete under difficult conditions. When these are used, the water content in concrete is reduced by approximately 5% – 30% depending on whether the reducer is high range or not. Despite reduction in water content, water reducers can cause significant increases in drying shrinkage.

The basic role of water reducers is to deflocculated the cement particles bounded together and release the water tied up in these units, producing more fluid paste at lower water contents. Its effectiveness in concrete is a function of its chemical composition, concrete temperature, cement composition and fineness.

Water reducers have been used primarily in bridge decks, low-slump concrete overlays, and patching concrete. Specialty Admixture

These include corrosion inhibitors, shrinkage control, alkali-silica reactivity inhibitors, and coloring. They can be used with Portland cement, or blended cement either individually or in combinations.

2.5.0 Water for Mixing Concrete

All natural and processed water that is drinkable and has no pronounced taste or odor can be used as mixing water for making concrete if as it has no chemicals that will react with the concrete constituents to change its required properties or standards. An example of this is the use of saline water, which can cause dampness of the concrete, efflorescence (white deposits of precipitated salts on the surface of the concrete), increased risk of corrosion (rust) damage to embedded reinforcement, and damage to paint systems. It is therefore advisable not to use such water for durable concrete work, and its use is generally avoided. However, some water, which may not be suitable for drinking, may still be safe for mixing concrete.

Pipe borne drinking water supplies are generally safe for making concrete; however, if in doubt of the quality of water being used, a simple test to verify its usability is to simply make two sets of cubes or cylinders of the same mix, one with the doubtful water, and the other set with distilled water, purified water, tap water, or other drinkable water of good quality. By using the second mix as reference, if the suspected water produces concrete of twenty eight (28)-day compressive strengths for at least 90% of the strength of the reference set, then it can be considered suitable for mixing concrete. If however it falls below this percentage, its use will depend on how far below it falls, and the standards and use for hich the concrete is to be used, IS:456 2000

IS:456 2000 specifies limits of chemicals allowed in mixing water for concrete and provides a useful guide as to allowances that have worked in practice.

It is acknowledged that the quality of the constituents of a concrete mix plays an important role in the quality of the concrete; however, the best materials will fail if incorporated into a concrete mixture in an improper manner or if the concrete is subsequently incorrectly mixed or transported. It is therefore important to ensure that the batching process and sequence during loading of the concrete mixer is as important as the quality of materials that make up the concrete mix.

2.6.0 Properties of Concrete

The desired properties required in any concrete mix are the following;

Workability

This is the ease at which concrete is placed, consolidated and finished. Concrete mixes should be workable but not segregated or bleeding excessively. Entrained air improves workability and reduces the chances of segregation.

Proper consolidation of concrete makes the use of stiffer mixes possible. Stiffer mixes tend to be more economical and are achieved by reducing the water to cement ratio or using larger proportions of coarse aggregates and a smaller proportion of fine aggregates, resulting in improved quality and economy.

Permeability and Water-tightness

Permeability is the ability of concrete to resist water penetration or other substances. Pavements as well as other structures depending on their use require very little or no penetration of water. Water-tightness is the ability of the concrete to retain water without visible leakage; this property is desirable in water retaining or confined structures.

Permeability and water tightness is a function of the permeability of the paste and aggregates, the gradation of the aggregates and the relative proportion of paste to aggregate. These are related to water-cement ratio and the degree of cement hydration or length of moist curing.

Strength

This is defined as the maximum resistance of a concrete specimen to axial loading. The most common measure of concrete strength is the compressive strength. It is primarily a physical property, which is used in design calculations of structural members. General use concrete has a compressive strength of 21.0MPa 35.0 MPa at an age of twenty-eight (28) days whilst high strength concrete has a compressive strength of at least 42.0 MPa.

In pavement design, the flexural strength of concrete is used; the compressive strength can be used, however, as an index of flexural strength, once the empirical relationship between them has been established.

The flexural strength is approximated as 7.5 to 10 times the square root of the compressive strength whilst the tensile strength is approximated as 5 to 7.5 times the square root of the compressive strength. The major factors, which determine the strength of a mix, are: The free water-cement ratio, the coarse aggregate type (Harder coarse aggregates result in stronger concrete.), and the cement properties.

Wear resistance

Pavements are subjected to abrasion; thus, in this type of application concrete must have a high abrasion resistance. Abrasion resistance is closely related to the compressive strength of the concrete.

CHAPTER 3 SAMPLE PREPARATION, MATERIALS AND TEST METHODS

3.0.0 Introduction

The previous two chapters gave a brief overview of past research, into concrete as a construction material, and the essence of early strength concrete in pavement maintenance and rehabilitation. This chapter details the procedures, materials used and specifications adopted in the preparation of the concrete specimens. The various test methods and test procedures are also detailed and explained.

To attain early strength, the mix designs adopted from the IS-10262(2009) report by the Construction Technology Laboratory (CTL) made use of the following techniques:

Use of Type III High Early Strength cement.

Low water – cement ratio (0.3-0.45 by mass) using Type I cement. Use of chemical admixtures to enhance workability and durability.

The water to cement ratios varied from 0.3 to 0.45 depending on the specimen in

Question. The use of normal Portland cement (Type I), and High Early Strength Portland cement (Type III) was employed with various dosages of different kinds of admixtures depending on the concrete quality and specifications required in an attempt to attain the specified strength and durability requirements. The coarse aggregate-fine aggregate, and the cement-fine aggregate ratio were also varied in each mix.

3.2.0 Materials

Material Preparations

The aggregates were passed through a sieve to determine the gradation (the distribution of aggregate particles, by size, within a given sample) in order to determine compliance with mix design specifications. This was done using a tray shaker. Both the coarse and fine aggregates were oven dried to establish a standard uniform weight measurement throughout the test. The dry weights of the aggregates were used in this research. The amount of water was adjusted to reflect the free water necessary for the aggregate to be used in their dry state.

Figure 3.1: Fine and Coarse aggregates being dried in oven

      1. Concrete Mix

      2. Mix Characteristics and Specifications

        The mix specifications obtained from the CTL report were adjusted to match the bulk saturated surface dry specific gravity and Absorption of the aggregates to be used. The coarse and fine aggregates obtained from Aggregate Industries were found to have a Bulk SSD of 2.72 and 2.59, respectively, and absorption of 0.36% and 1.36%, respectively. All aggregates were oven dried before use. Tables 3.2 and 3.3 show the proposed mix specifications at SSD and adjusted weights (dry weights) based on the absorption properties of the coarse and fine aggregates found by laboratory methods in accordance with IS : 2386-(1963) and IS- 383 (1970), respectively.

      3. Actual mix specifications (Dry weights):

To ensure that the mix proportions were exact according to specifications for laboratory testing, the dry weights of the aggregates were calculated and the water-cement ratio adjusted. The mix design obtained from the report by CTL was based on the saturated surface dry density (SSD) of the aggregates. Because aggregates vary in SSD,the absorption of the aggregates used in this research was calculated in accordance to IS : 2386-(1963) and IS-383 (1970) for coarse and fine aggregates respectively.

To find the SSD and absorption of the aggregates, the aggregates were oven dried to a condition where there was no change in mass. The dry weights of the aggregates were measured and recorded. The aggregates were then immersed in water to a state where they were fully saturated.

The weights of the fully saturated aggregates were measuredand the absorption computed as follows; Weight at SSD = X g

Absorption (ABS) = Y%

Dry Weight =? g

Water at SSD =? g

Dry Weight + Water at SSD = weight at SSD ABS + Dry weight = weight at SSD ((100%+Y %) /100) of dry weight= X g

Dry Weight = X g / ((100+Y)/100)

Weight of water = Weight at SSD Dry weight.

Knowing the quantity of water that the aggregate will absorb when fully saturated, the dry weights of the aggregate was computed as shown above and the amount of absorbed water at SSD was added to the amount of free water to get the total weight of water required for the mix. Allowance was also allowed for the use of Polarset since each liter of Polarset added to a concrete mix will contribute 0.78 kg of water to that mix.

Table 3.3 shows the actual mix specifications for all 5 mixes.

MIX DESIGN Materials Dry Weight (Cubic yard basis)

MIX

1

2

3

4

Cement Type

III

I

III

I

I

Cement,

394.6

341.1

415.37

415.37

362.8

Coarse Aggregate,

782.96

782.96

509.83

1590

801.04

Fine Aggregate,

371.3

205.9

552.4

503.48

539.32

Water,

73.59

72.54

186.88

290.8

264.5

W/C Ratio

0.45

0.44

0.51

0.37

0.34

Table 3.3: Actual mix specifications

3.4.0 Compressive Strength Test

This phase consists of applying a compressive axial load to a molded cylinder until failure occurs in accordance with IS:456-2000 The material for each mix design was batched based on the actual mix specifications in Table 3.3 above. The concrete was mixed and cured in accordance with IS:456-2000, Standard Practice for Making and Curing Test Specimens in the Laboratory, making sure the inner surface of the mixer was wetted to compensate for the loss of free water due to absorption by the surface of the mixer.

The concrete components were mixed in an electrically driven mixer. A shovel was used to scoop the mixed concrete into a large wheelbarrow and a "slump test" was used to test the water content of the concrete. The cone was 1-0 high, with a top opening of 4 diameter and a bottom opening of 8 diameter. The mixed concrete was placed into the cone through the top, a bar was used to compact the concrete, and remove air voids, within the cone. The cone was then lifted clear. By laying a bar on top of the cone, it was possible to measure how far the concrete "slumped." 6×12 cylindrical plastic molds were filled and compacted using an

external table vibrator to remove air voids. A total of 60 cylindrical specimens were cast, four (4) for each of the 3-test conditions (4 hours, 24 hours, and 7 days) for a total of 5 different mixes. The 20 specimens were then de-molded, weighed and tested after 4 hours to obtain the compressive strength. The same procedure was repeated after 24 hours and seven (7) days to obtain the compressive strength after that period of placing. The seven (7) day-old specimen was placed in a curing tank after twenty four

(24) hrs.

Fig.3.2: Cast cylindrical specimen

Fig.3.3: De-molding the cylindrical specimens

Fig.3.4: De-molded specimen for 4 hr compressive strength test

Fig.3.5: Specimen in the compression machine

Fig. 3.6: Specimen under compression

Fig.3-11: Specimen undergoing transverse vibration

Fig.3-12: Results of transverse vibration of specimen shown on the monitor screen

3.6.0Identification of specimen

Each specimen was identified based on the nomenclature assigned to it. For the cylindrical specimen tested for compressive strength, a nomenclature of MC1A depicted Mix 1, specimen A. For a specimen used in the freeze and thaw test, a nomenclature of MU1A depicted Mix 1, specimen A.

3.7.0 Apparatus General Apparatus

  1. Concrete mixer

  2. Tamping rod 5/8 diameter and approximately 24in. long.

  3. Mallet

  4. External Vibrator (table vibrator)

  5. Small tools (shovel, trowel, wood float, straight edge, ruler, scoop, slump apparatus)

  6. Sampling and mixing pan

  7. Air content apparatus

  8. Scale (large and small scales)

  9. Curing tank

Phase I

  1. 6 x12 cylindrical molds

  2. Compression testing machine

3.8.0 Materials

The following materials were used for this research; Type I and III cements, ¾ coarse aggregates (gravel), fine aggregate (mortar sand).

Coarse Aggregate

Fine Aggregate

Portland cement

CHAPTER 4 TEST RESULTS AND DISCUSSIONS

4.0.0 Introduction

This chapter reports the results obtained from the laboratory tests of the various test specimens. It attempts to analyze the results obtained and report them in a graphical and tabular format. It deals with the compression test results as an isolated criterion and then the freeze and thaw test results as another. It finally attempts to analyze the various mixes combining both criteria.

The mixes employed in this research were designed to attain a compressive strength of at least 17.5 MPa in 4 hours or less, it was also expected that the mixes would go through at least 300 cycles of freeze and thaw without failing or excessive scaling.

A summary of the test results is discussed in the sections that follow.

4.1.0 Properties of the concrete mixes.

The property of a concrete mix depicts its strength, durability and performance under loading. Properties affecting concrete characteristics measured in this research include the following;

  • Air content

  • Consistency

When in its fresh state, concrete should be plastic or semi-fluid and generally capable of being molded by hand. This does not include a very wet concrete which can be cast in a mold, but which is not pliable and capable of being molded or shaped like a lump of modeling clay nor a dry mix, which crumbles when molded into a slump cone.

Tables 4.1 and 4.2 illustrate a summary of the properties of the concrete mixes used in this research.

It is assumed that conditions remained constant throughout the preparation and testing of the various samples.

Mix constituents per total weight of constituents

Mix 1

Mix 2

Mix 3

Mix 4

Mix 5

Cement Type

III

I

III

I

I

constituent s

Cement

0.227

0.194

0.246

0.228

0.1930

Fine Aggregates

0.214

0.259

0.323

0.281

0.2860

of

Coarse Aggregates

0.451

0.46

0.301

0.403

0.4250

Propor tion

Air entrainment

0.0007

0.0002

0.0012

0.0007

0.0002

HRWR

0.0007

0.0006

0.0008

0.0007

0.0006

Water

0.093

0.079

0.116

0.074

0.064

Table 4.1: The various ratios of mix constituents to the total weight of the mix

The slump test is the most generally accepted method used to measure the consistency of concrete. The slump results in Table 4.2 show that Mix 3 had the best consistency and Mix 4 and Mix 5 had the worst consistencies. This result was expected due to the proportions of water and water reducers in the different mixes. Mix 3 containing 11.6% and 0.08% of water and High range water reducer respectively by weight of the total constituents was expected to be most workable. The opposite was expected for Mix 4 and Mix 5 as shown in Table 4.1.

Due to poor consistency of Mix 4 and Mix 5, no slump was recorded for those mixes, the formed cone either collapse totally or did not show any slump when the slump cone was removed.

4.2.0 Compressive test results

ne of the most important strength related parameters used to define the Early strength of a concrete mix is its compressive strength. The average results are as shown in Tables 4.3a 4.3c below. Early strength concrete is widely accepted to be concrete that can gain a compressive strength in the range of 17.5MPa and 24.5MPa within 24 hours or less.

4 Hour Test Results

Specimen No

Specimen Age

Average Weight (kg)

Average Load (kg)

Comp. Strength (MPa)

Mix 1

4 hrs

(12.7)

(29,313)

(15.8)

Mix 2

4 hrs

(12.9)

(10,886)

(5.9)

Mix 3

4 hrs

(12.4)

(35,210)

(18.9)

Mix 4

4 hrs

(12.2)

(10,735)

(5.8)

Mix 4

4 hrs

(12.2)

(10,716)

(5.8)

Table 4.3a: 4 Hours Compressive Average Strength

24 Hour Test Result

Specimen No

Specimen Age

Average Weight (kg)

Average Load (kg)

Comp. Strength (MPa)

Mix 1

24 hrs

(12.7)

(72,745)

(39.1)

Mix 2

24 hrs

(12.5)

(45,983)

(24.7)

Mix 3

24 hrs

(12.5)

(78,641)

(42.3)

Mix 4

24 hrs

(12.3)

(41,163)

(22.1)

Mix 5

24 hrs

(12.3)

(42,694)

(23.0)

Table 4.3b: 24 Hours Average Compressive Strength

7 Day Test Result

Specimen No

Specimen Age

Average Weight (kg)

Average Load (kg)

Comp. Strength (MPa)

Mix 1

7days

(12.8)

(72,745)

(39.1)

Mix 2

7days

(12.6)

(45,983)

(24.7)

Mix 3

7days

(12.6)

(78,641)

(42.3)

Mix 4

7days

(12.3)

(41,163)

(22.1)

Mix 5

4 hrs

(12.3)

(42,694)

(23.0)

Table 4.3c: 7 days Average Compressive Strength

Compressive Strength versus Concrete Age

7000

6000

Compressive Strength/Psi

Compressive Strength/Psi

5000 y = 899.41Ln(x) + 1344.7

R2 = 0.9157

4000

3000

2000

1000

0

0 20 40 60 80 100 120 140 160 180

Concrete Age/Hours

Mix 1 Log. (Mix 1)

Figure 4.1a: Variation of Compressive strength of Mix 1 with Age

Compressive Strength versus Age

4500

4000

Compressive Strength/Psi

Compressive Strength/Psi

3500

3000

2500

y = 722.18Ln(x) + 311.43 R2 = 0.7539

2000

1500

1000

500

0

0 20 40 60 80 100 120 140 160 180

Figure 4.1b: Variation of Compressive strength of Mix 2 with Age.

Compressive Strength versus Age

7000

Compressive Strength/Psi

Compressive Strength/Psi

6000

5000

y = 901.56Ln(x) + 1700.5 R2 = 0.9605

4000

3000

2000

1000

0

0 20 40 60 80 100 120 140 160 180

Age/Hrs

Mix 3 Log. (Mix 3)

Figure 4.1c: Variation of Compressive strength of Mix 3 with Age.

Compressive Strength versus Age

3500

3000

y = 635.52Ln(x) – 86.364

2500 R2= 0.9965

Age/Hrs

Age/Hrs

2000

1500

1000

500

0

0 20 40 60 80 100 120140 160 180

Compressive Strength/Psi

Mix 4 Log. (Mix 4)

Figure 4.1d: Variation of Compressive strength of Mix 4 with Age.

Compressive Strength versus Age

3500

3000

Compressive Strength/Psi

Compressive Strength/Psi

y = 668.41Ln(x) – 145.93

2500 R2 = 0.9948

2000

1500

1000

500

0

0 20 40 60 80 100 120 140 160 180

Age/Hrs

Mix 5 Log. (Mix 5)

Figure 4.1e: Variation of Compressive strength of Mix 5 with Age.

Figures 4.1a-4.1e show increasing strength of the samples of concrete as a function of curing time. It can be noticed that strength gain is quite rapid at first for all samples. The results obtained from the laboratory tests shown in Tables 4.3a-4.3e show that Mix 1 and Mix 3 with compressive strength of 16.0MPa and 19.0 MPa in 4 hours and 33.5MPa and 34.7 MPa in 24 hours fall within the criteria for the definition of early strength concrete. Although Mix 2 did not achieve the compressive strength desired in four hours, its compressive strength increased drastically within 24 hours and 7days. Mix 4 and Mix 5 did not show any strength characteristics to be considered as an Early Strength mix within 4 hours to 24 hours. Although tests were not done for 14 days and 28 days, the shape of the curve makes it quite clear that strength continues toincrease well beyond a month, research has shown that under favorable conditions, concrete is still "maturing" after 18 months.

4.3.0 Summary of Compressive strength Results

A logarithmic regression line was the best trend line fit for the data acquired from the laboratory test results. The regression equations for the various mixes are tabulated in Table 4.4 below and Table 4.5 gives the compressive strength results based on this.

Mix

Logarithmic Regression Equation

R2 Value

1

y = 899.41Ln(x) + 1344.7

R2 = 0.9157

2

y = 722.18Ln(x) + 31.43

R2 = 0.7539

3

y = 901.56Ln(x) + 1700.5

R2 = 0.9605

4

y = 635.52Ln(x) – 86.364

R2 = 0.9965

5

y = 668.41Ln(x) – 145.93

R2 = 0.9948

Table 4.4: Logarithmic Regression equations for Laboratory test results

Mix

Compressive Strength(Mpa)

4hrs

24hrs

7days

1

2.592 (17.87)

28.98

41.04

2

1.033 (7.122)

16.04

25.73

3

2.950 (20.34)

31.48

43.57

4

0.795 (5.48)

13.33

21.86

5

0.781 (5.38)

13.64

22.61

Table 4.5: Compressive Strengths of various mixes

Compressive Strength Versus Age

7000

6000

Compressive Strength

Compressive Strength

5000

4000 Mix 1

2000 Mix 2

3000 Mix 3

Mix 4

Mix 5

Log. (Mix 1)

1000

Log. (Mix 2)

0 Log. (Mix 3)

180

180

0 20 40 60 80 100 120 140 160Log. (Mix 4)

Hours Log. (Mix 5)

Figure 4.2: Compressive strength of the various mixes with Age4.4.2 Durability Factor

DF = PN/M

P = Relative dynamic modulus of elasticity, at N cycles in percentage

N = Number of cycles at which P reaches the specified minimum value for discontinuing the test or the specified number of cycles at which the exposure is to be terminated, whichever is less, and

M = Specified number of cycles at which exposure is to be terminated.

To arrive at these values, the procedure used for judging the acceptability of the durability factor results obtained in the Laboratory as outlined in IS:456 2000 was used. This required finding the average of the Fundamental frequencies and standard deviation of the specimens.

Mix 1

Cycle

Mass(g)

Frequency

Relative Dynamic

Durability Factor (%)

Modulus of Elasticity (Pc) (%)

(DF)

0

7093

2149

100

100

24

7093

2079

94

94

39

7124

2093

95

95

51

7121

2071

93

93

69

7118

2035

90

90

81

7110

1996

86

86

95

7099

1956

83

83

107

7093

1967

84

84

134

7018

1947

82

82

148

7009

1912

79

79

175

7032

1875

76

76

189

7014

1852

74

74

201

6999

1764

67

67

227

6982

1819

72

72

252

6952

1769

68

68

270

6930

1752

66

66

289

6926

1843

74

74

314

6902

1800

70

70

338

6686

1708

63

63

Table 4.6a: Elastic Modulus and Durability Factors for Mix 1

Durability Factor Vesus No. of cycles

120

100

Durability Factor (%)

Durability Factor (%)

80

60

y = -0.1003x + 95.6

R2 = 0.8963

40

40

y = 96.411e-0.0013x R2 = 0.9009

20

0

0 50 100 150 200 250 300 350 400

No. of cycles

Mix1 Linear (Mix1) Expon. (Mix1)

Figure 4.3a: Graph of durability vs No of cycles for mix 1

Mix 2

Cycle

Mass

(g)

Frequency

Relative Dynamic

Durability Factor (%)

Modulus of Elasticity (Pc) (%)

(DF)

0

7254

2118

100

100

24

7254

2075

96

96

39

7247

2073

96

96

51

7242

2071

96

96

69

7226

2074

96

96

81

7211

2073

96

96

95

7182

2063

95

95

107

7194

2076

96

96

134

7179

2068

95

95

148

7166

2069

95

95

175

7150

2071

96

96

189

7139

2061

95

95

201

7126

2071

96

96

227

7126

2071

96

96

252

7110

2073

96

96

270

7095

2057

94

94

289

7087

2060

95

95

314

7089

2068

95

95

338

7075

2061

95

95

Table 4.6b: Elastic Modulus and Durability Factors for Mix 2

Durability Factor Versus No. Of Cycles

101

100

Durability Factor(%)

Durability Factor(%)

99

y = -0.0056x + 96.379

98 R2 = 0.2161

y = 96.365e-6E-05x

97 R2 = 0.2175

96

95

No. Of Cycles

Mix 2

94

0 50 100 150 200 250 300 350

Expon. (Mix 2) Linear (Mix 2)

Expon. (Mix 2) Linear (Mix 2)

Figure 4.3b: Graph of durability vs No of cycles for mix 2

Mix 3

Cycle

Mass

(g)

Frequency

Relative Dynamic

Durability Factor (%)

Modulus of Elasticity (Pc) (%)

(DF)

0

6916

2011

100

100

24

6904

1989

98

98

39

6899

1985

97

97

51

6893

1967

96

96

69

6888

1955

95

95

81

6877

1939

93

93

95

6869

1921

91

91

107

6865

1916

91

91

134

6848

1873

87

87

148

6838

1836

83

83

175

6814

1829

83

83

189

6805

1788

79

79

201

6805

1788

79

79

227

6798

1733

74

74

252

6763

1633

66

66

270

6739

1593

63

63

289

6758

1628

66

66

314

6743

1596

63

63

338

6725

1515

57

57

Table 4.6c: Elastic Modulus and Durability Factors for Mix 3

Durability Factor Versus Of No. Of Cycles

120

100

Durability Factor(%)

Durability Factor(%)

80

60

y = -0.0995x + 96.116

40 R2 = 0.5026

y = 95.964e-0.0012x

R2 = 0.4492

20

0

0 50 100 150 200 250 300 350

No. Of Cycles

Mix 3 Expon. (Mix 3) Linear (Mix 3)

Figure 4.3c: Graph of durability vs No of cycles for mix 3

Mix 4

Cycle

Mass

(g)

Frequency

Relative Dynamic

Durability Factor (

%)

Modulus of Elasticity (Pc) (%)

(DF)

0

7384

2196

100

100

24

7377

2165

97

97

39

7374

2170

98

98

51

7371

2164

97

97

69

7371

2157

97

97

81

7368

2153

96

96

95

7367

2152

96

96

107

7368

2161

97

97

134

7373

2146

95

95

148

7371

2146

96

96

175

7391

2157

96

96

189

7388

2136

95

95

201

7390

2141

95

95

227

7392

2152

96

96

252

7387

2155

96

96

270

7329

2055

88

88

289

7419

2175

98

98

314

7419

2173

98

98

338

7415

2164

97

97

Table 4.6d: Elastic Modulus and Durability Factors for Mix 4

Durability Factor Versus No. Of Cycles

102

100

Durability Factor(%)

Durability Factor(%)

98

96

94

y = -0.0098x + 97.57

92 R2 = 0.1573

y = 97.588e-0.0001x

90 R2 = 0.1562

88

No Of Cycles

Mix 4

86

0 50 100 150 200 250 300 350

Expon. (Mix 4) Linear (Mix 4)

Expon. (Mix 4) Linear (Mix 4)

Figure 4.3d: Graph of durability vs No of cycles for mix 4

For simplicity, it was decided to use the linear regression equation in predicting the durability factor at the 300th cycle because both trends were almost identical. Notably from Table 4.8,

none of the mixes fell below 60% durability factor. However, the 3 mixes with Type I cement and lowest water-cement ratio fared better in this durability test.

In a research by Powers et al. he concluded that entrained air voids act as empty chambers in the paste for the freezing and migrating water to enter, thus relieving the pressures described above and preventing damage to the concrete. Upon thawing, most of the water returns to the capillaries due to capillary action and pressure from air compressed in the bubbles.

The three mixes that fared best among the lot were mixes that may have likely more air pockets in them due to inadequate consolidation during placing.

CHAPTER 5-CONCLUSIONS, OBSERVATIONS AND RECOMMENDATIONS

5.0.0 Conclusions and Observations

The primary conclusion expected from this research was to determine if all the mixes researched into, fell into the category of High Performance concrete and thus was either Very early strength (VES), High early strength (HES) or not an Early strength mix. It was finally expected to recommend which two mixes based on the strength and durability requirements of High Performance concrete were the best.

Based on the results of this investigation, the following conclusions can be drawn;

5.1.0Strength Criterion: Compressive strength

  1. High Performance concrete can be produced with a variety of mix options including the use of;

    1. Type III Portland cement and

    2. Type I or Type III Portland cement with a low water-cement ratios by using superplasticizers to achieve moderate to high consistencies.

  2. Although the water-cement ratio plays an important role in attaining early strength, for concrete to be poured and consolidated, it has to workable. The consistency of an early strength mix should not be compromised in an attempt to acquire its strength. It was concluded in this research that mix 4 and mix 5 attained low early strengths due to inadequate consolidation.

  3. In order to make use of a lower water to cement ratio in acquiring early strength, the right dosage of superplasticizers must be used. A slump of at least 2 must be obtained in order to attain good consolidation in a laboratory setting.

  4. The two mixes with type III Portland cement mix 1 and mix 3 fell in the Very early Strength (VES) category of High Performance concrete, attaining the required strengths of a minimum of 14-17.5 MPa within four (4) hours. Mix 2, mix 4 and mix 5 can be considered as High early strength concrete (HES) accordingly, attaining a strength of approximately 2,000 psi (14.0 MPa) within twenty-four (24) hours as shown in Table 4.3.

  5. Mix 1 and mix 3 which utilizes Type III early strength Portland cement achieved the best results for the strength criterion.

5.2.0 Durability Criterion: Freeze and thaw resistance

From earlier research discussed in the literature review of this paper, it was established that;

  • Dry concrete is unaffected by repeated freeze and thaw.

  • The development of pore structure inside cement paste is fundamental to freeze thaw resistance of concrete.

  • Capillary porosity of a concrete cement paste becomes a factor in concretes resistance to freeze and thaw at water-cement ratios above 0.36. At water cement ratios below this value, the only porosity in the paste is the gel porosity, which is very minute and has no effect on frost action.

The durability of concrete depends mostly on its resistance to frost action (freeze and thaw) and can be enhanced by modifying the pore structure of the concrete. This modification depends on the water- cement ratio of the mix, the degree of saturation, and air bubbles (entrapped air and entrained air).

MIX

MIX DESIGN Materials Dry Weight (Cubic yardbasis)

1

2

3

4

5

Cement Type

III

I

III

I

I

W/C Ratio

0.410

0.410

0.470

0.320

0.320

Proportion of water content by mass in Paste

0.174

0.149

0.162

0.126

0.117

Proportion of fines by mass in paste

0.826

0.851

0.838

0.874

0.883

Proportion of Air Entrainment by mass in paste

0.001326

0.000455

0.001801

0.001220

0.0004435

Frost Resistance (Durability Factor)

66

95

66

95

97

Table 5.1: Factors affecting resistance to freeze and thaw

From Table 5.1 above, the following conclusions are made on the resistance of the various mixes to Freeze and thaw;

  1. The consistency/workability of the concrete mix should be taken into consideration when attempting to increase the strength and durability of a concrete mix by decreasing its water-cement ratio.

  2. The durability factor of a concrete prism exposed to freeze-thaw cycles depicts its durability. The higher this factor, the less susceptible the mix is to freeze and thaw. Drier mixes have a tendency to have higher durability factors. Air entrainment is also a means to attain higher durability factors in a concrete mix.

  3. Coarser cement tends to produce pastes with higher porosity than that produced by finer cement (Powers et al 1954). Type III cement is by far finer in nature thanType I, the fact that there may have been more pore spaces for freezable water to expand in mix 2 which uses Type I cement may have been the reason for the better durability performance.

  4. Cement pore structure develops by the gradual growth of gel into the space originally occupied by the anhydrous cement and mixing. Taking into consideration of the water-cement ratio and the proportion by mass of water in the paste of the various mixes, the capillary porosity of the paste in mix 2, mix 4 and mix 5 is less than that of mix 1 and mix 3. Because

    there is less freezable water in the drier mixes (mix 2, mix 4 and mix 5), there is little or no impact of the hydraulic pressures during freezing on the internal structure of the paste hence the better results obtained for durability.

  5. The ratio by mass of air entrainment in the various mixes may have aided their resistance to frost action, but its effect on mix 4 and mix 5 was negligible since there was virtually no expandable freezable water to fill the air voids.

  6. All the mixes had samples going through all 300 cycles of freeze and thaw, Mix 4 and mix 5 were more durable in this respect (resistance to freeze and thaw). They did not show any signs of deterioration after the freeze and thaw cycle had ended. The other three mixes showed some signs of scaling and some of the samples failed. Some of the failures were considered, however, as abnormalities in the mixing procedures.

    Because of the variability of water-cement ratio and superplasticizers used, no conclusion could be made as to the optimal dosage of admixtures.

  7. Adjustment of the factors that enhance either the strength or durability of the various mixes could be done for mix 1, mix 2 and mix 3 because there is room for water content adjustment to resist freeze and thaw as well as to increase strength. Since mix 4 and mix 5 make use of low water-cement ratio to achieve early strength, adjusting the water content will increase the strength a little but may compromise with its durability.

5.3.0 Recommendations

The results of this research are summarized in Table 5.2.

Mix

Durability

Factor (%)

Compressive Strength/ (MPa)

4hrs

24hrs

7days

1

66

2.592 (17.87)

4.203 (28.98)

(41.04)

2

95

1.033 (7.122)

2.327 (16.04)

(25.73)

3

66

2.950 (20.34)

4.566 (31.48)

(43.57)

4

95

0.795 (5.48)

1.933 (13.33)

(21.86)

5

97

0.781 (5.38)

1.978 (13.64)

(22.61)

Table 5.2: Summary of results

Average of Mass and Frequency for 0 cycle

+

Specimen#

A

B

C

Mass

Frequen

Pc

DF

Av. DF

Avg. Mass

Avg. Frequency

MU1A

0

0

0

7073

2000

+

177.0

2177

100

100

100

0

7093

2149

MU1B

0

0

0

7039

2000

+

139.0

2139

100

100

MU1C

0

0

0

7127

2000

+

141.5

2142

100

100

MU1D

0

0

0

7133

2000

+

139.0

2139

100

100

MU2A

0

0

0

7235

2000

+

103.0

2103

100

100

100

0

7254

2118

MU2B

0

0

0

7303

2000

+

126.5

2127

100

100

MU2C

0

0

0

7229

2000

+

127.0

2127

100

100

MU2D

0

0

0

7249

2000

+

117.0

2117

100

100

MU3A

0

0

0

6966

1800

+

217.0

2017

100

100

100

0

6916

2011

MU3B

0

0

0

6867

1800

+

217.0

2017

100

100

MU3C

0

0

0

6911

1800

211.0

2011

100

100

MU3D

0

0

0

6921

1800

+

200.0

2000

100

100

MU4A

0

0

0

7462

2000

+

198.0

2198

100

100

100

0

7384

2196

MU4B

0

0

0

7422

2000

+

185.0

2185

100

100

MU4C

0

0

0

7336

2000

+

211.0

2211

100

100

MU4D

0

0

0

7315

2000

+

190.0

2190

100

100

MU5A

0

0

0

7290

2000

+

225.5

2226

100

100

100

0

7312

2198

MU5B

0

0

0

7359

2000

+

207.5

2208

100

100

MU5C

0

0

0

7118

2000

+

153.0

2153

100

100

MU5D

0

0

0

7481

2000

+

204.5

2205

100

100

Table A-F

Table of Average Mass and Frequency for 39th cycle

Specimen#

A

B

C

Mass

Frequen

Pc

DF

Av. DF

Avg. Mass

Avg. Frequenc

MU1A

15

24

39

7073

1800

+

253.0

2053

9

94

98

0

7124

2093

MU1B

15

24

39

7049

1800

+

141.5

1942

9

91

MU1C

15

24

39

7123

1800

+

285.5

2086

9

97

MU1D

15

24

39

7125

1800

+

299.5

2100

9

98

MU2A

15

24

39

7228

1800

+

259.0

2059

9

98

98

0

7247

2073

MU2B

15

24

39

7298

1800

+

269.0

2069

9

97

MU2C

15

24

39

7220

1800

+

288.5

2089

9

98

MU2D

15

24

39

7243

1800

+

274.5

2075

9

98

MU3A

15

24

39

6913

1800

+

181.5

1982

9

98

99

0

6899

1985

MU3B

15

24

39

6933

1800

+

193.5

1994

9

99

MU3C

15

24

39

6846

1800

+

178.5

1979

9

98

MU3D

15

24

39

6903

1800

+

185.0

1985

9

99

MU4A

15

24

39

7450

1900

+

282.0

2182

9

99

99

0

7374

2170

MU4B

15

24

39

7413

1900

+

257.0

2157

9

99

MU4C

15

24

39

7327

1900

+

283.0

2183

9

99

MU4D

15

24

39

7306

1900

+

258.5

2159

9

99

MU5A

15

24

39

7277

1900

+

293.5

2194

9

99

98

0

7368

2172

MU5B

15

24

39

7352

1900

+

270.0

2170

9

98

MU5C

15

24

39

FAILE

MU5D

15

24

39

7475

1900

+

252.0

2152

9

98

D

D

Table A-FT-3

Table of Average Mass and Frequency for 69th cycle

Specimen#

A

B

C

Mass

Freuen

Pc

DF

Av. D

Avg. Mass

Avg. Frequenc

MU1A

18

51

69

7069

1800

+

207.0

2007

92

92

95

2

7118

2035

MU1B

18

51

69

7030

1700

+

116.5

1817

85

85

MU1C

18

51

69

7123

1700

+

299.5

2000

93

93

MU1D

18

51

69

7113

1700

+

369.5

2070

97

97

MU2A

18

51

69

7196

1700

+

354.0

2054

98

98

98

0

7226

2074

MU2B

18

51

69

7291

1700

+

377.0

2077

98

98

MU2C

18

51

69

7194

1700

+

389.0

2089

98

98

MU2D

18

51

69

7224

1700

+

375.5

2076

98

98

MU3A

18

51

69

6922

1700

+

259.5

1960

97

97

97

0

6888

1955

MU3B

18

51

69

6836

1700

+

270.0

1970

98

98

MU3C

18

51

69

6894

1700

+

249.0

1949

97

97

MU3D

18

51

69

6902

1700

+

243.0

1943

97

97

MU4A

18

51

69

7447

1900

+

273.5

2174

99

99

98

1

7371

2157

MU4B

18

51

69

7411

1900

+

253.0

2153

99

99

MU4C

18

51

69

7324

1900

+

270.0

2170

98

98

MU4D

18

51

69

7302

1900

+

233.0

2133

97

97

MU5A

18

51

69

7274

1900

+

284.0

2184

98

98

98

0

7362

2168

MU5B

18

51

69

7350

1900

+

271.0

2171

98

98

MU5C

18

51

69

FAILED

MU5D

18

51

69

7463

1900

+

250.0

2150

98

98

Table A-FT-5

Table of Average Mass and Frequency for 95th cycle

Specimen#

A

B

C

Mass

Frequency

Pc

DF

Av. DF

Avg. Mass

Avg. Freque

MU1A

14

81

95

7048

180

+

145.5

1946

89

89

91

4

7099

1

MU1B

14

81

95

6996

1500

+

194.5

1695

79

79

MU1C

14

81

95

7108

1700

+

172.5

1873

87

87

MU1D

14

81

95

7090

1900

+

140.0

2040

95

95

MU2A

14

81

95

7090

190

+

140.5

2041

97

97

97

0

7182

2

MU2B

14

81

95

7275

1800

+

262.5

2063

97

97

MU2C

14

81

95

7163

1900

+

178.5

2079

98

98

MU2D

14

81

95

7201

1900

+

168.5

2069

98

98

MU3A

14

81

95

6912

170

+

202.5

1903

94

94

96

1

6869

1

MU3B

14

81

95

6806

1700

+

259.5

1960

97

97

MU3C

14

81

95

6878

1700

+

211.5

1912

95

95

MU3D

14

81

95

6881

1700

+

210.0

1910

96

96

MU4A

14

81

95

7445

190

+

264.5

2165

98

98

98

1

7367

2

MU4B

14

81

95

7405

1900

+

256.5

2157

99

99

MU4C

14

81

95

7320

1900

+

265.0

2165

98

98

MU4D

14

81

95

7299

1900

+

222.0

2122

97

97

MU5A

14

81

95

7266

190

+

283.0

2183

98

98

98

1

7354

2

MU5B

14

81

95

7343

1900

+

270.0

2170

98

98

MU5C

14

81

95

FAILED

MU5D

14

69

83

7453

1900

+

241.5

2142

97

97

Table A-FT-7

Table of Average Mass and Frequency for 189th cycle

Specimen#

A

B

C

Mass

Frequency

Pc

DF

Av. DF

Avg. Mas

Avg. Frequenc

MU1A

14

175

189

6952

1500

+

54.5

1555

71

71

87

4

7014

1852

MU1B

14

175

189

FAILED

MU1C

14

175

189

7014

1500

+

260.0

1760

82

82

MU1D

14

175

189

7015

1600

+

344.0

1944

91

91

MU2A

14

175

189

7114

1700

+

322.0

2022

96

96

97

1

7139

2061

MU2B

14

175

189

7218

1700

+

360.5

2061

97

97

MU2C

14

175

189

7099

1700

+

379.0

2079

98

98

MU2D

14

175

189

7126

1700

+

382.5

2083

98

98

MU3A

14

175

189

6858

1700

+

113.5

1814

90

90

89

2

6805

1788

MU3B

14

175

189

6739

1700

+

132.0

1832

91

91

MU3C

14

175

189

6802

1700

+

38.0

1738

86

86

MU3D

14

175

189

6821

1700

+

69.0

1769

88

88

MU4A

14

175

189

7442

1800

+

341.5

2142

97

97

97

1

7388

2136

MU4B

14

175

189

7403

1800

+

342.5

2143

98

98

MU4C

14

175

189

7320

1800

+

323.5

2124

96

96

MU4D

14

175

189

7279

1800

+

236.5

2037

93

93

MU5A

14

175

189

7258

1900

+

290.0

2190

98

98

98

1

7348

2167

MU5B

14

175

189

7335

1900

+

271.0

2171

98

98

MU5C

14

175

189

FAILED

MU5D

14

175

189

7449

1900

+

240.0

2140

97

97

Table A-FT-12

Table of Average Mass and Frequency for 289th cycle

Specimen#

A

B

C

Mass

Frequency

Pc

Av. DF

Avg. Mass

Avg. Frequency

MU1A

19

270

289

FAI

MU1B

19

270

289

FAIL

MU1C

19

270

289

FAIL

MU1D

19

270

289

6926

1600

+

243.0

1843

86

86

86

0

6926

1843

MU2A

19

270

289

7039

1800

+

213.5

2014

96

96

97

1

7087

2060

MU2B

19

270

289

7169

1800

+

274.0

2074

98

98

MU2C

19

270

289

7055

1800

+

271.0

2071

97

97

MU2D

19

270

289

7083

1800

+

279.5

2080

98

98

MU3A

19

270

289

6790

1400

+

233.5

1634

81

81

81

0

6758

1628

MU3B

19

270

289

FAI

MU3C

19

270

289

6726

1400

+

223.0

1623

81

81

MU3D

19

270

289

FAI

MU4A

19

270

289

7438

1900

+

280.5

2181

99

99

99

0

7419

2175

MU4B

19

270

289

7399

1900

+

269.5

2170

99

99

MU4C

19

270

289

7330

1900

+

125.0

2025

92

92

MU4D

19

270

289

7274

1900

+

105.5

2006

92

92

MU5A

19

270

289

7261

1900

+

305.0

2205

99

99

96

1

7345

2189

MU5B

19

270

289

7329

1900

+

295.5

2196

99

99

MU5C

19

270

289

FAI

MU5D

19

270

289

7444

1900

+

266.0

2166

98

98

Table A-FT-16

Table of Average Mass and Frequency for 338th cycle

Specimen#

A

B

C

Mass

Frequen

Pc

DF

Av. DF

Avg. Mass

Avg. Frequency

MU1A

24

314

338

FAI

MU1B

24

314

338

FAIL

MU1C

24

314

338

FAIL

MU1D

24

314

338

6686

1

30

1

80

80

80

0

6686

1708

MU2A

24

314

338

7005

1

27

1

94

94

97

0

7075

2061

MU2B

24

314

338

7146

1

15

2

96

96

MU2C

24

314

338

7030

1

17

2

98

98

MU2D

24

314

338

7050

1

15

2

97

97

MU3A

24

314

338

6756

1

21

1

75

75

75

0

6725

1515

MU3B

24

314

338

FAI

MU3C

24

314

338

6695

1

21

1

76

76

MU3D

24

314

338

FAI

MU4A

24

314

338

7435

1

26

2

99

99

99

0

7415

/td>

2164

MU4B

24

314

338

7395

1

26

2

99

99

MU4C

24

314

338

7321

1

26

1

89

89

MU4D

24

314

338

7266

1

26

1

90

90

MU5A

24

314

338

7258

1

28

2

98

98

98

0

7341

2178

MU5B

24

314

338

7324

1

28

2

99

99

MU5C

24

314

338

FAI

Table A-FT-18

Compressive strength for 4hrs, 24hrs and 7days for mix 1

Mix 1

Cement, Ib

870.000

Coarse Aggregate, Ib

1726.000

Fine Aggregate, Ib

820.000

Water, Ib

356.300

Accelerator, (PolarSet), ga

6.000

HRWR (ADVA Flow), oz.

43.500

Darex II AEA, oz.

43.500

W/C Ratio

0.41

4 hourTest Resu

Specimen

Test Time

Load

Comp.Strength /

MC1A

4 hrs

65500

2316.3

MC1B

4 hrs

64000

2263.2

MC1C

4 hrs

64000

2263.2

MC1D

4 hrs

65000

2298.6

24 h

Specimen

Test Time

Load

Comp.Strength /

MC1E

24 hrs

142000

5021.6

MC1F

24 hrs

130000

4597.2

MC1G

24 hrs

142000

5021.6

MC1H

24 hrs

128000

4526.5

7 Day Test Result

Specimen

Test Time

Load / Ib

Comp.Strength / psi

MC1K

7days

160000

5658.1

MC1L

7days

159500

5640.4

MC1M

7days

158000

5587.4

MC1N

7days

164000

5799.6

Table C-S1

Compressive strength for 4hrs, 24hrs and 7days for mix 2

Mix 2

Cement, Ib

752.000

Coarse Aggregate, Ib

1781.000

Fine Aggregate, Ib

1001.000

Water, Ib

306.100

Accelerator, (PolarSet), gal.

3.500

HRWR (ADVA Flow), oz.

37.600

Darex II AEA, oz.

15.000

W/C Ratio

0.41

4 hourTest Results

Specimen

Test Time

Weight

Load / Ib

Comp.Strength / psi

MC2A

4 hrs

28.5

24000

848.7163166

MC2B

4 hrs

28.4

25000

884.0794964

MC2C

4 hrs

28.4

24000

848.7163166

MC2D

4 hrs

28.5

23000

813.3531367

24 hou

Test Resul

Specimen

Test Time

Weight

Load / Ib

Comp.Strength / psi

MC2E

24 hrs

28.2

98000

3465.591626

MC2F

24 hrs

28

99000

3500.954806

MC2G

24 hrs

28

100500

3553.999576

MC2H

24 hrs

28.2

98000

3465.591626

7 Day

Test Result

Specimen

Test Time

Weight

Load / Ib

Comp.Strength / psi

MC2K

7 days

28.2

102000

3607.044345

MC2L

7 days

28

103000

3642.407525

MC2M

7 days

28

102000

3607.044345

MC2N

7 days

28.2

98500

3483.273216

Table C-S2

Compressive strength for 4hrs, 24hrs and 7days for mix 3

Mix 3

Cement, Ib

915.000

Coarse Aggregate, Ib

1124.000

Fine Aggregate, Ib

1218.000

Water, Ib

412.000

Accelerator, (PolarSet), gal.

6.000

HRWR (ADVA Flow), oz.

45.800

Darex II AEA, oz.

73.200

W/C Ratio

0.45

4 hourTest Result

Specimen

Test Time

Weigh

Load / Ib

Comp.Strength / psi

MC3A

4 hrs

27.5

78000

2758.3

MC3B

4 hrs

27.6

79000

2793.7

MC3C

4 hrs

27.5

76000

2687.6

MC3D

4 hrs

27.5

77500

2740.6

24 hour

Test Resul

Specimen

Test Time

Weigh

Load / Ib

Comp.Strength / psi

MC3E

24 hrs

27.8

140000

4950.8

MC3F

24 hrs

27.6

140000

4950.8

MC3G

24 hrs

27.5

139000

4915.5

MC3H

24 hrs

27.5

142000

5021.6

7 Day

Test Resul

Specimen

Test Time

Weigh

Load / Ib

Comp.Strength / psi

MC3K

7days

27.8

168000

5941.0

MC3L

7days

27.7

175000

6188.6

MC3M

7days

27.6

174000

6153.2

Table C-S3

Compressive strength for 4hrs, 24hrs and 7days for mix 4

Mix 4

Cement, Ib

900.000

Coarse Aggregate, Ib

1590.000

Fine Aggregate, Ib

1110.000

Water, Ib

290.800

Accelerator, (PolarSet), gal.

6.000

HRWR (ADVA Flow), oz.

45.000

Darex II AEA, oz.

45.000

W/C Ratio

0.32

4 hourTes

Results

Specimen

Test Time

Weight

Load / Ib

Comp.Strength / ps

MC1A

4 hrs

27.5

25500

901.8

MC1B

4 hrs

27.6

22500

795.7

MC1C

4 hrs

27.5

FAILED

FAILED

MC1D

4 hrs

27.5

23000

813.4

24 hour

Test Result

Specimen

Test Time

Weight

Load / Ib

Comp.Strength / ps

MC1E

24 hrs

27.8

49000

1732.8

MC1F

24 hrs

27.6

58000

2051.1

MC1G

24 hrs

27.5

50500

1785.8

MC1H

24 hrs

27.5

52000

1838.9

7 Day Test Result

Specimen

Test Time

Weight

Load / Ib

Comp.Strength / ps

MC1K

7days

27.8

90000

3182.7

MC1L

7days

27.7

88000

3112.0

MC1M

7days

27.6

95000

3359.5

MC1N

7days

27.6

90000

3182.7

Table C-S4

Compressive strength for 4hrs, 24hrs and 7days for mix 5

Mix 5

Cement, Ib

800.0

Coarse Aggregate, Ib

1766.0

Fine Aggregate, Ib

1189.0

Water, Ib

264.5

Accelerator, (PolarSet), gal.

16.0

HRWR (ADVA Flow), oz.

40.0

Darex II AEA, oz.

16.0

W/C Ratio

0

4 hourTest Results

Specimen

Test Time

Wei

Load

Comp.Strength /

M501

4 hrs

2

230

81

M502

4 hrs

2

240

84

M503

4 hrs

2

230

81

M504

4 hrs

2

245

86

24 h

Test Res

Specimen

Test Time

Wei

Load

Comp.Strength /

M505

24 hrs

2

540

190

M506

24 hrs

2

525

185

M507

24 hrs

2

535

189

M508

24 hrs

2

520

183

7

D Test Res

Specimen

Test Time

Wei

Load

Comp.Strength /

M509

7days

2

950

335

M510

7days

2

945

334

M511

7days

2

930

328

Table C-S5

REFERENCES

  1. BTS/USDOT, Pocket guide to transportation, 2003, Bureau of Transportation Statistics, U.S. Department of Transportation, Washington, DC, 2003

  2. 1999 costs/68 urban areas; TRB SR 260.

  3. Kutz, S., Balaguru, P., Consolasio, G., Maher, A., Fast Track Concrete For Construction Repair, FHWA NJ 2001-015, NJDOT/FHWA, March 1997.

  4. S. W. Forster. High-Performance Concrete Stretching the Paradigm,1994.

  5. Powers, T. C., The Air Requirements of Frost-Resistant Concrete, Research Department Bulletin RX033, Portland cement Association, 1949.

  6. Powers, T. C., Basic Considerations Pertaining to Freezing and Thawing Tests, Research Department Bulletin RX058, Portland, 1955.

  7. Korhonen, C., Effect of High Doses of Chemical Admixtures on the FreezeThaw Durability of Portland cement Concrete, [ERDC/CRREL TR-02-5], 2002.

  8. Concrete International, Oct, Vol. 16, No. 10, pp. 33-34

  9. C. H. Goodspeed, S. Vanikar, and R. A. Cook. 1996.

  10. High-Performance Concrete Defined for Highway Structures. Concrete International, Feb, Vol. 18, No. 2, pp. 62-67.

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