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

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 Age

4.4.2 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.