 Open Access
 Total Downloads : 1275
 Authors : Mohammed Abas Abdela Salem, R. K. Pandey
 Paper ID : IJERTV4IS020317
 Volume & Issue : Volume 04, Issue 02 (February 2015)
 Published (First Online): 16022015
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Influence of Specific Gravity on Weight of Proportions of Concrete
Mohammed Abas Abdela Salema
1Department of Civil Engineering, Sam Higginbotom Institute of Agriculture Technology & Sciences, Allahabad , India
R. K. Pandeyb
2Department of Civil Engineering, Sam Higginbotom Institute of Agriculture Technology & Sciences , Allahabad, India,
AbstractVariation in proportions of concrete cube with cementwater ratio, concrete mix and standard cube size (15 cm * 15 cm * 15 cm), were experimentally investigated. The cube was casted and cured at 3 different locations, different specific gravities, in India. All the cubes for each location were having the same variations of cementwater ratios. It was observed that weight of cubes after 28 days of curing found to be varying from each location. It was noticed that the main cause in variations in weight of proportions of concrete mix found to be specific gravity of coarse aggregate. Specific gravity plays an important role in weight of proportions of concrete and considers the main factor used to measure strength and quality of material. It can be stated that specific gravity plays an important role in determining the compressive strength and quality of concrete mix.
Keywordsspecific gravity; compressive strength of concrete; proportions of concrete; aggregates content;

INTRODUCTION
Aggregate is a filling natural materials generally extracted and crushed, using mechanical crushing machines, from rocks. It contains 60% to 75% of total volume of concrete. The weight of aggregates in concrete is depending upon its packed size distribution and voids. Void content in concrete mix affect both water and mortar requirement. The increase in void content leads to increase in water followed by mortar in concrete mix. Void content is ranging from 30% to 45% and from 40% to 50% for coarse and fine aggregate respectively and it can be reduced by packing and using variations of aggregate sizes.
Specific gravity of coarse aggregate is the ratio of mass of a unit volume of coarse aggregate to the mass of same volume of water at specified temperature (23C). it is dimensionless value and consider the major factor to evaluate the strength and the quality of materials. The specific gravity of aggregates is commonly ranging from 2.6 to 3.0. Specific gravity is used to separate deleterious particles, lighter than other particles, from good aggregates. It is used in calculating the solid volume of aggregates in concrete mix.
Determination of the porosity of the aggregate is often necessary. Porosity defines as a ratio of the volume of the pores to the total volume of a material. Measuring the volume of pores in any material is difficult. Correlation between pores and bulk solid materials is a necessary and can be achieved using specific gravity of it. Using specific gravity in concrete mix is important to correlate the voids and the solid bulk of aggregates and to determine the volume of proportions of concrete.

METHODOLOGY

Work Materials and Specimens Preparation
The materials used in this investigation are cement, gavel and water. Allin aggregates size distributions, mixed sand and gravel, were determined by sieve analysis from which grading limit was achieved. The grading limits of allin aggregates confirm a suitable grading distribution which leads to suitable workability and durability.

Experimental Test Procedures
Mix proportions of 1:1.5:3 was determined for each location by using cement, fine aggregates and coarse aggregates respectively. A 4 kg of cement was added to 6 kg and 12 kg of fine and coarse aggregates. Water was added to cement by weight to form cementwater ratios of 1.3, 1.4, 1.5, 1.6, 1.7 and
1.8. The whole was mixed into paste. Meanwhile, the cubic moulds of concrete were oiled to ease the demolding process late.
The concrete was then poured into cubes according to its cementwater ratio and placed for 2 minutes on vibration machine to remove the tapped air from the concrete. The cubes were then covered with polythene to prevent evaporation process.
After 24 hours of sitting time, the cubes were demolded and placed in curing water tank for 28 days. The cubes were then crushed using crushing machine to determine the compressive strength of concretes.


RESULTS AND DISCUSSION
Table I shows the variation of the strength of concrete mixes with specific gravity and cementwater ratios. It was observed that the higher the specific gravity the higher the proportions of concrete. However, the higher cementwater ratio leads to the less density and weight of concrete. In addition, the cement and water content were observed to increase cement water ratio. As a result, the specific gravity is considered the main factor of determination the quality and weight of concrete.
The plot of water content of concrete mixes with variations of cementwater ratio and specific gravity is shown in Figure (1). Figure (2) shows the plot of cement content with variations of cementwater ratio and specific gravity. Figure (3) and Figure
(4) show the plots of density and aggregates of concrete versus cementwater ratios and specific gravity of concrete mix..
TABLE I. VARIATIONS OF WEIGHT, DENSITY, AND COMPRESSIVE STRENGTH OF CONCRETRE MIXES WITH SPECIFIC GRAVITY AND CEMENT WATER RATIO
280
Specific Gravity = 2.6 Specific Gravity = 2.8 Specific Gravity = 3.0
260
Cement Content (kg/m3)
240
220
200
180
S/ N
Cement
Water
Ratio
Specific gravity
Cube weight (g)
Cube Density
(g/cm3)
Crushin g load
(kg)
Concrete Strength
(kg/cm2)
A1
1.3
2.6
8201
2.430
39600
176
A2
1.4
2.6
8195
2.428
41625
185
A3
1.5
2.6
8184
2.425
42750
190
A4
1.6
2.6
8178
2.423
44550
198
A5
1.7
2.6
8171
2.421
49050
216
A6
1.8
2.6
8161
2.418
52650
234
B1
1.3
2.8
8714
2.582
31500
176
B2
1.4
2.8
8701
2.578
32400
185
B3
1.5
2.8
8687
2.574
33750
190
B4
1.6
2.8
8674
2.570
35325
198
B5
1.7
2.8
8660
2.566
36450
216
B6
1.8
2.8
8643
2.561
37800
234
C1
1.3
3.0
9214
2.730
39600
176
C2
1.4
3.0
9197
2.725
41625
185
C3
1.5
3.0
9177
2.719
42750
190
C4
1.6
3.0
9156
2.713
44550
198
C5
1.7
3.0
9133
2.706
48600
216
C6
1.8
3.0
9113
2.700
52650
234
160
140
1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8
CementWater Ratio
Fig. 2. Plot of Cement Content of Concrete vs. CementWater Ratio and Specific Gravity
Specific Gravity = 2.6 Specific Gravity = 2.8 Specific Gravity = 3.0
2600
Aggregates Content (kg/m3)
2500
2400
2300
2200
2100
Specific Gravity = 2.6 Specific Gravity = 2.8 Specific Gravity = 3.0
155
2000
150 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8
CementWater Ratio
Water Content (kg/m3)
145 Fig. 3. Plot of Aggregates Content of Concrete vs. CementWater Ratio and Specific Gravity
140
135
130
125
120
1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8
CementWater Ratio
Fig. 1. Plot of Water Content of Concrete vs. CemenWater Ratio and Specific Gravity
3300
Specific Gravity = 2.6 Specific Gravity = 2.8 Specific Gravity = 3.0
3200
3100
Concrete Density (kg/m3)
3000
2900
2800
2700
2600
2500
2400
2300
1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8
CementWater Ratio
Fig. 4. Plot of Density of Concrete vs. CementWater Ratio and Specific Gravity

RECOMMENDATION
The use of suitable specific gravity along with cementwater ratio in concrete mix can determine and evaluate the expected weight, quality and strength of concrete mix. By this concept, quality of concrete mix is related to its specific gravity.
REFERENCES

Indian Standard code practice for Methods of Test for Aggregates for Concrete, IS: 2386(part)1963.

W.H. Mosley, J.H. Bungey (2000), Reinforced Concrete Design, 5rd ed., Macmillan Publisher Limited, London, UK, 2000.

Indian Standard code practice for Specification for coarse and fine aggregates from natural sources for Concrete, IS: 383:1970.

P,K, Mehta, P.J. Monteiro (2013), Concrete: Microstructure, Properties, And Materials, 4rd ed., McGrawHill Profissional, New York, US, 2013.

P.G. Omotola, O.I. Idowu (2011),Effect of watercement Ratios on the Compressive Strength and Workability of Concrete and Lateritic Concrete Mixes, The Pacific Journal of Science and Technology, Vol 12, No 2, November 2011, pp 99105.M.