Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1): 62- 70 © Scholarlink Research Institute Journals, 2015 (ISSN: 2141-7016) jeteas.scholarlinkresearch.com Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) Determination and Modelling of Effects of Variation in Fine Aggregate Size on Concrete Properties S. O. Osuji and I. Inerhunwa 1 Department of Civil Engineering, Faculty of Engineering, University of Benin, Benin City, Nigeria. Corresponding Author: S. O. Osuji _________________________________________________________________________________________ Abstract The properties of concrete are likely to change with changes in its composition. This paper examines the effect of variation in the sizes of fine aggregate on the workability, pulse velocity and compressive strength of concrete. To do this, fine aggregate (quarry dust) was sieved into three classes: Class 1: 2.00mm < d < 4.75mm, Class 2: 425µm < d < 2.00mm and Class 3: 75µm < d < 425µm. Workability, Ultrasonic Pulse Velocity (UPV) and compressive strength tests were carried out on concrete cubes made from the three classes of fine aggregate for two mix ratios (1:2:4 and 1:3:6). Results showed that workability reduces with reduction in the size of fine aggregate and that concrete made from Class 2 fine aggregate gave the highest value of strength and pulse velocity while concrete made from Class 1 fine aggregate gave the least values for both mix ratios. As properties of concrete changes with age, linear models were developed for the prediction of the strength of concrete from age and pulse velocity and vice versa for each class of fine aggregate and mix ratio. The linear models showed linear relationships between age, pulse velocity and compressive strength of concrete with strength and pulse velocity increasing with age and the models were found to be appropriate, accurate and consistent. The models are useful and can be utilized in obtaining and analyzing the properties of concrete for the different classes of fine aggregate. __________________________________________________________________________________________ Keywords: fine aggregate, workability, ultrasonic pulse velocity, compressive strength, linear model Physical and mineralogical properties of aggregate must be known before mixing concrete to obtain a desirable mixture. These properties include shape and texture, size gradation, moisture content, specific gravity, reactivity, soundness and bulk unit weight. These properties along with the water/cementitious material ratio determine the strength, workability, and durability of concrete (Mehta and Monteiro, 1993). INTRODUCTION Aggregate occupies 70% to 75% of the volume of conventional normal strength portland cement concrete and therefore the properties of aggregates have a dominant effect on the overall performance of concrete in its fresh and hardened state (Talbot and Richart, 1923). Among the various characteristics of aggregates that have significant influence on properties of concrete, the size distribution of aggregate particles or otherwise known as aggregate gradation plays an important role in achieving the desired properties of concrete. Aggregates can be divided into several categories according to different criteria. In accordance with size, aggregates are divided into coarse and fine aggregate. Coarse aggregate are aggregates predominately retained on the No. 4 (4.75 mm) sieve. Fine aggregate (sand) are aggregates passing No.4 (4.75 mm) sieve and predominately retained on the No. 200 (75µm) sieve (Shacklock, 1974). Aggregate gradation determines the void content within the structure of aggregate and consequently the amount of cement paste that is required to fill the void space between the aggregate and ensure a workable concrete (Mills and Fletcher, 1969). As cement is the most expensive and high carbon footprint ingredient in concrete, it is desirable to optimize the aggregate gradation to minimize the void content in the aggregate and therefore the volume of cement paste required to achieve a workable and economical concrete for a given application. Concrete containing aggregate with poor gradation can be particularly vulnerable to problems such as segregation in plastic state under vibration (Talbot and Richart, 1923). The size of aggregate plays an important role in the development of high strength concrete. The strength of concrete is affected partly by the relative proportion of cement and of the fine and coarse aggregates (Alawode and Idowu, 2012). A suitable gradation of the combined aggregate in a concrete mix is desired in order to secure workability and to secure economy in the use of cement. A well-graded 62 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) strength development, particularly when concreting in cold weather, to check serviceability conditions or compliance criteria, to ensure construction safety and, generally to estimate the quality of construction and potential durability (Mills and Fletcher, 1969). Moreover, prediction of concrete strength at late ages is significant from both technical and economical points of view. mixture produces strong concrete than a harsh or poorly graded one (Troxell et al., 1968). Smaller aggregates sizes are considered to produce high strength concrete because of less concentration of stress around the particles which are caused by difference between the elastic modulus of paste and aggregate (Yaqub and Bukhari, 2006). The grading and maximum size of aggregates is also an important parameter in any concrete mix as they affect relative proportions in mix, workability, economy, porosity and shrinkage of concrete etc. Experience has shown that very fine sands or very coarse sands are objectionable. The former is uneconomical; the latter gives harsh unworkable mixes (Agrawal et al., 2007). No clear rules have been presented to describe how the relationship between UPV and the compressive strength and other properties of concrete changes with its mixture proportion. Therefore, there exists a high uncertainty when one tries to make use of UPV or any other property of concrete to predict the strength of concrete in different mixture proportions (Alawode and Idowu, 2012). In a concrete member, variations in density can arise from non-uniform consolidation, and variations in elastic properties can occur due to variations in materials, mix proportions, or curing. Thus, by determining the wave speed at different locations in a structure, it is possible to make inferences about the uniformity of the concrete. The compression wave speed (pulse velocity) is determined by measuring the travel time of the stress pulse over a known distance (Khlef, 2012). The fine aggregate used in concrete construction is actually composed of particles of different fineness which gives the concrete a variety of particles to fill up voids. The question of “which particle size is best for concrete construction” that will give concrete of required strength and properties is a major concern in civil engineering construction. OBJECTIVE OF THE STUDY In this paper, the effect of variation of fine aggregate size on the workability (slump), compressive strength and pulse velocity for different mix ratios is studied. The paper also attempts to establish a relationship between the compressive strength and pulse velocity with the age of concrete and develop a simple mathematical model that can help predict the compressive strength and pulse velocity at any age of the concrete for different sizes of fine aggregate. Compressive strength and pulse velocity of concrete is influenced by many variables, however, including mixture proportions, aggregate type, age of concrete, moisture content, and others (Talbot and Richart, 1923). As a result, a strength estimate made with the pulse velocity method is not reliable if a preestablished calibration curve is not available (Mills and Fletcher, 1969). The relationship between Ultrasonic Pulse Velocity (UPV) and the compressive strength of concrete for a particular size of aggregate, the effect of sulphate exposure on the development of UPV and strength of concrete along with age and the influence of sulphate exposure and water/cement ratio on the UPV-strength relationship of concrete have been studied (Khlef, 2012). It was shown that the UPV in the concrete grew along with the advancement of age and at the same age, UPV with low w/c are higher than those with high w/c. MATERIALS AND METHOD Materials and methods utilized in this study are discussed below. To model the behaviour of concrete under general loading requires an understanding of the effects of aggregate type, aggregate size, and aggregate content (Kozul and Darwin, 1997). Material Selection To study the effect of variation of fine aggregate size on the properties of concrete, materials (aggregate , cement and water) were collected and necessary tests were carried out on the resulting test specimens (100mm concrete cubes) made from varying the sizes of fine aggregate in the concrete mix. For this research, materials used were Ordinary Portland Cement (OPC), water, granite for coarse aggregate and quarry dust for fine aggregate. STATEMENT OF THE PROBLEM Early age strength prediction in concrete is very useful in reducing construction cost and ensuring safety. Furthermore, early age strength prediction has several practical applications. It can be used to determine safe stripping time, prestressing application or post –tensioning time, to monitor Aggregate Fine aggregate used for this study is quarry dust. This was obtained and allowed to dry naturally in the laboratory for about two weeks for mechanical sieve analysis for the determination of its particle size distribution. The quarry dust was then later sieved into three different sizes using sieves of diameter 63 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) 2.0mm and 425µm. These gave three classes of fine aggregate sizes as follows; Class 1: 2.00mm < d < 4.75mm, Class 2: 425µm < d < 2.00mm and Class 3: 75µm < d < 425µm, where d is the size of the fine aggregate. Coarse aggregate of maximum size 20mm in diameter was used. The coarse aggregates were collected and kept at room temperature and pressure in the laboratory before they were used for the making of test specimen. cubes for the whole experiment. Standard cube moulds of size100mm were used for casting. Curing After casting, the concrete was left to set for twentyfour hours and after this period, the concrete was carefully removed from its mould to ensure that the edges are not broken off. Then they were taken to the curing bath where they were cured for seven days, fourteen days and twenty-eight days. On reaching the required number of days for testing (7th, 14th and 28th day), three cubes made from each class of concrete for each mix ratio were removed from the curing bath, allowed to dry for a day and their weight recorded before carrying out pulse velocity and compressive strength tests on them. (a) Class 1 Concrete Testing Workability test (slump test) was conducted on the fresh concrete for each class of fine aggregate, while the hardened concrete cube specimens were tested for ultrasonic pulse velocity in accordance with BS EN 12504-4 and compressive strength test in accordance with BS EN 12390-3. The specimens were tested at the end of 7, 14 and 28 days of curing. (b) Class 2 Regression Analysis of Experimental Results Regression analysis generates an equation to describe the statistical relationship between one or more predictor variables and the response variable. This equation has the form Y = b1X1 + b2X2 + ... + C (1) where Y is the response (dependent) variable to be predicted, X1, X2 and so on are the predictor (independent) variables, b1, b2 and so on are the coefficients or multipliers that describe the size of the effect the independent variables are having on the dependent variable Y, and C (constant term) is the value Y is predicted to have when all the independent variables are equal to zero. (c) Class 3 Fig 1: Picture of the classes of fine aggregate used for the study Water To mix the concrete, clean tap water from a reservoir was collected. Selecting water from a good source ensures that the hydration process goes on without influence from foreign chemical compounds that might affect the properties of the concrete adversely or otherwise. Mix Design, Batching, Mixing and Casting Concrete mix design was carried out to determine the mix composition of concrete for two mix ratios (1:2:4 and 1:3:6) with a water-cement ratio (w/c) of 0.55. Fresh concrete using Class 1 fine aggregate was then made using mix proportions obtained and mixing was done using a concrete mixer until a homogenous mix was obtained. In this study, the predictor variable is age of concrete while the response variables are compressive strength and pulse velocity. The 95% confidence level which is generally used in most regression analysis was used. Models were developed for each class of fine aggregate and analysed to check their adequacy. Microsoft Excel package was used in selecting and analyzing the models that best fit the experimental data. After mixing and before casting the concrete cubes, slump test was carried out in accordance with BS EN 12350-2 to determine the workability of the concrete. The fresh concrete was then placed in moulds, vibrated and levelled using a trowel. The same procedure was followed for the other two classes of aggregate (Class 2 and 3). RESULTS AND DISCUSSIONS Grading of Fine Aggregate Figure 2 shows result of particle size distribution of fine aggregate used for the study in the form of a particle size distribution curve. From the curve, the range of size of fine aggregate is between 4.75mm and 75µm and is distributed among coarse sand, For every class of fine aggregate, 9 cubes were each cast for a mix ratio 1:2:4 and another 9 cubes for a mix ratio of 1:3:6. This gave a total number of 54 64 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) medium sand and fine sand portions of the graph which represent the three classes of fine aggregates used for this study (Class 1, Class 2 and Class 3 respectively). aggregate. The results represent the average of three cubes tested each for a particular class, mix ratio and age. Table 1: Pulse Velocity Test Results Mix Ratio Fine Aggregate Class Class 1: 2.00mm < d < 4.75mm Class 2: 425µm < d < 2.00mm Class 3: 75µm < d < 425µm Pulse Velocity (1 x 101km/s) 1:2:4 1:3:6 7 days 14 days 28 days 7 days 14 days 28 days 0.273 0.284 0.304 0.257 0.260 0.263 0.286 0.297 0.317 0.266 0.273 0.280 0.262 0.274 0.295 0.246 0.251 0.260 Table 2: Compressive Strength Test Results for the different classes of fine Aggregates Mix Ratio Fine Aggregate Class Class 1: 2.00mm < d< 4.75mm Class 2: 425µm < d< 2.00mm Class 3: 75µm < d < 425µm Fig. 2: Particle Size Distribution of Fine Aggergate (Quarry Dust) Slump Test Results Slump test results of the fresh concrete is presented in Fig. 3. The Figure shows slump for concrete made from Class 2 and Class 3 fine aggregates for mix ratios of 1:2:4 and 1:3:6. Concrete made form Class 1 fine aggregate gave a collapse slump for both mix ratios and hence of high workability. The slump of fresh concrete made from Class 2 concrete is about twice that of Class of 3 for 1:2:4 mix ratio and about three times of class 3 for 1:3:6 mix ratio. Compressive Strength (N/mm2) 1:2:4 1:3:6 7 days 14 days 28 days 7 days 14 days 28 days 16.80 19.50 21.50 12.20 15.20 19.20 19.33 25.00 34.00 16.17 22.00 26.50 13.80 15.33 19.00 11.00 12.00 15.00 Figures 4 and 5 show the graph of Ultrasonic Pulse Velocity (UPV) against age of concrete for mix ratios 1:2:4 and 1:3:6 respectively. The graphs show almost a linear relationship between pulse velocity and age of concrete made from the three different classes of fine aggregate with pulse velocity increasing with age of concrete. Concrete made from Class 2 fine aggregate gave the highest pulse velocity with a 28 days UPV of 0.317x101km/s and 0.280x101km/s for mix ratios 1:2:4 and 1:3:6 respectively, while the concrete made from Class 3 fine aggregate gave the lowest pulse velocity with a 28 days UPV of 0.295x101km/s and 0.260x101km/s respectively for mix ratios 1:2:4 and 1:3:6. Generally, UPV values for mix ratio 1:2:4 were higher than respective UPV values for mix ratio 1:3:6. Fig. 3: Slump Test Results Pulse Velocity and Compressive Strength Results Tables 1 and 2 show the results for the concrete pulse velocity as well as the compressive strength of the concrete made from the different classes of fine 65 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) Fig.4: Graph of pulse velocity against age of concrete for mix ratio of 1:2:4 Fig.6: Graph of compressive strength against age of concrete for mix ratio of 1:2:4 Fig. 7: Graph of compressive strength (F) against age of concrete (t) for mix ratio of 1:3:6 Fig. 5: Graph of pulse velocity against age of concrete for mix ratio of 1:3:6 To check whether variation in fine aggregate size will affect relationship between compressive strength of concrete and UPV, graphs of compressive strength against UPV were plotted. Figures 8 and 9 show the graph of compressive strength and UPV of concrete for the different classes of fine aggregate for mix ratios 1:2:4 and 1:3:6. From the graphs plotted, a linear relationship is observed between compressive strength and UPV of concrete, with strength increasing as UPV increases for concrete made from the three classes of fine aggregate (Class 1, 2 and 3) and for both mix ratios (1:2:4 and 1:3:6). Figures 6 and 7 show the graph of compressive strength against age of concrete for mix ratios 1:2:4 and 1:3:6 respectively. The graph showed compressive strength increasing with age of concrete. Concrete made from Class 2 fine aggregate gave the highest compressive strength with a 28 days strength of 34.00N/mm2 and 26.5N/mm2 for mix ratios 1:2:4 and 1:3:6 respectively, while the concrete made from Class 3 fine aggregate gave the lowest compressive strength with a 28 days strength of 19.00N/mm2 and 15.00N/mm2 respectively for mix ratios 1:2:4 and 1:3:6. As for pulse velocity, compressive strength values for mix ratio 1:2:4 were higher than respective compressive strength values for mix ratio 1:3:6. 66 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) (a) Class 1 (b) Class 2 (c) Class 3 Fig. 8: Graph of compressive strength against UPV (1x101km/s) for mix ratio of 1:2:4 (a) Class 1 (b) Class 2 (c) Class 3 Fig. 9: Graph of compressive strength against UPV for mix ratio of 1:3:6 properties of concrete (compressive strength and UPV) when the age of the concrete is known for concrete made from the different classes of fine aggregates and for both mix ratios 1:2:4 and 1:3:6 . Additionally, models were also developed for the Model Development and Validation (Regression Analysis on Experimental Data) As properties of concrete change with age, models were developed for the prediction of the different 67 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) variables are well explained by the independent variables and that the linear models (regression line) fit the data and can be used for obtaining values outside the experimental range. prediction of concrete’s compressive strength from its UPV value. These models (Figures 4 - 9) were developed by carrying out a linear regression analysis on experimental results (Tables 2 and 3) using a confidence level of 95% with MS Excel spreadsheet application. Table 4 (a and b) shows a summary of the models with their coefficient of determination (R2) which is an indication of how the dependent variables can be explained by the independent variables as well as the pattern of residual plot obtained for all models developed. Furthermore, residual plots for all models developed gave a fairly random plot centered on zero through the range of fitted values. This indicates that: (1) a linear model produced a decent fit to the data (2) that the models are correct on the average for all fitted values and (3) that the models are appropriate for the data. Sample residual plots for the models developed for concrete made from the different classes of fine aggregate used in this research are presented in Figure 10 (a-f). The coefficient of determination (R2) obtained for the various models ranged from 0.9258 to as high as 0.9994. The high values showed that the dependent Table 4a: Models and their Regression Parameters for 1:2:4 Mix Ratio Class 1 Class 2 Class 3 Model Developed Linear Model R Pattern of Residual Plot F vs Age F= 0.2122t + 15.8 0.9258 Fairly Random F = 0.6906t + 14.83 0.9964 Fairly Random F = 0.2497t + 11.965 0.9981 UPV vs Age v = 0.0015t + 0.263 0.9994 Fairly Random v = 0.0015t + 0.276 0.9994 Fairly Random v = 0.0016t + 0.2515 0.9988 Fairly Random F vs UPV F = 145.34v 22.447 0.9379 Fairly Random 0.9987 Fairly Random 0.9941 Fairly Random 2 Model R Pattern of Residual Plot Model R Pattern of Residual Plot Fairly Random 2 F = 470.4v 115.01 Table 4b: Models and their Regression Parameters for 1:3:6 Mix Ratio Class 1 Class 2 Patter Patter Linear n of n of 2 2 Model R Model R Model Residu Residu al Plot al Plot Fairly Fairly F vs F = 0.3265t 0.988 F = 0.4676t 0.931 Rando Rando + 13.92 7 Age + 10.2 4 m m UPV vs Age v = 0.0003t + 0.2555 0.964 3 Fairly Rando m v = 0.0006t + 0.2625 0.964 3 Fairly Rando m F = 159.52v 28.143 2 Class 3 Model F= 0.1939t + 9.5 v= 0.0007t + 0.2415 2 R 0.991 8 0.999 3 Patter n of Residu al Plot Fairly Rando m Fairly Rando m Fairly F = 470.4v Fairly F= Fairly 0.994 Rando 115.01 0.998 Rando 159.52v Rando 1 m m 28.143 m 2 1 Where F = compressive strength in N/mm , v = Ultrasonic Pulse Velocity (UPV) in 1 x 10 km/s and t = Age of concrete in days. F vs UPV F = 145.34v - 22.447 0.937 9 68 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) Figure 10a: Residual plot of Compressive Strength vs age for 1:2:4 mix ratio using Class 1 fine aggregate Figure 10b: Residual plot of Compressive Strength vs age for 1:3:6 mix ratio using Class 1 fine aggregate Figure 10c: Residual plot of UPV vs age for 1:2:4 mix ratio using Class 2 fine aggregate Figure 10d: Residual plot of UPV vs age for 1:3:6 mix ratio using Class 2 fine aggregate Figure 10e: Residual plot of compressive strength UPV vs age for 1:2:4 mix ratio using Class 3 fine aggregate Figure 10f: Residual plot of compressive strength UPV vs age for 1:3:6 mix ratio using Class 3 fine aggregate obtained. This value of UPV was then applied to the compressive strength/UPV model (F = 470.4v – 115.01) and a compressive strength of 34.6N/mm2 was obtained which agrees with the value earlier obtained from the compressive strength/Age model and hence consistent. This value was also close to the experimental value of 34.00N/mm2 obtained. From the residual plot it is shown that predicted values obtained using models developed were close to actual data obtained from experiments. This also further validates the accuracy of the models for use in predicting and obtaining values outside experimental range. All models developed for a particular class and mix ratio were found to be consistent as values of compressive strength obtained using the compressive strength/Age model at a particular age were very close to values of compressive strength obtained using the compressive strength/UPV model with the UPV value obtained from the UPV/Age model at the same age. For example, at 28 days for class 2 fine aggregate concrete and 1:2:4 mix ratio, a value of compressive strength of 34.2N/mm2 was obtained using the compressive strength/Age model (F = 0.6906t + 14.83). From the UPV/Age model (v = 0.0015t + 0.276), a UPV of 0.318 x 101km/s was CONCLUSION The effect of variation in the sizes of fine aggregate used in the manufacture of concrete for different mix ratios have been studied. From experimental results and analysis of same, it was revealed that the size of fine aggregate used affects the workability of concrete and the finer the aggregate, the lower the workability for all mix ratios. Variation in fine aggregate size affects the compressive strength in the same manner as it affects the pulse velocity of concrete, with the concrete made 69 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 6(1):62- 70 (ISSN: 2141-7016) BS EN 12390-3, 2009. Testing Hardened Concrete: Compressive Strength of Test Specimens, British Standards Institution, UK. from the medium sized fine aggregate i.e. class 2 (425µm < d < 2.00mm) giving the highest value of compressive strength and pulse velocity for all mix ratios. Concrete made from Class 1 fine aggregate gave the lowest values of strength for all mix ratios. BS EN 12504-4, 2004. Testing Concrete: Determination of Ultrasonic Pulse Velocity, British Standards Institution, UK. For all types of concrete, the relationships between age, pulse velocity and compressive strength were linear with strength and pulse velocity increasing with age. Values of compressive strength and pulse velocity for mix ratio 1:2:4 were higher than respective values for mix ratio of 1:3:6. Khlef, F.L., 2012. Proposed UPV-Strength Relationship for Concrete Subjected to Sulfate Attack, Anbar Journal for Engineering Sciences, Iraq, p. 114 – 122 Kozul,R. and Darwin, D., 1997. Effects of Aggregate Type, Size, and Content on Concrete Strength and Fracture Energy, University Of Kansas Center For Research, Inc., Kansas. Models were developed for the prediction of compressive strength from age, pulse velocity from age and compressive strength from pulse velocity for concrete made from each of the three classes of fine aggregate and for mix ratios 1:2:4 and 1:3:6 making a total of 18 models. The models which are linear models were found to be appropriate, accurate, and consistent with predicted values from other models and experimental values with each model unique from the others. The benefit of this is that a concrete property can be obtained and analysed from another property (such as age which is usually known) and vice versa. Mehta, P. K. and Monteiro, P. J. M., 1993. Concrete Structure, Properties, and Materials, Prentice-Hall, Inc., Englewood Cliffs, NJ Mills, W. H. and Fletcher, O. S., 1969. Control and Acceptance of Aggregate Gradation by Statistical Methods, Highway Research Board, Bulletin 290, pp. 35-49. Shacklock, B. W., 1974. Concrete Constituents and Mix Proportions, Cement and Concrete Association, London For general construction purposes, it is recommended that Class 2 fine aggregate as defined in this paper be used in the manufacture of concrete as it gave the highest strength with acceptable workability. Talbot, A.N., and Richart, F.E., 1923. The Strength of Concrete and its Relation to the Cement, Aggregate and Water, Bulletin No. 137: 1-116 This paper was limited to the study of the variation of concrete properties with variation of fine aggregate size so as to determine and model the behavior of concrete for the different sizes (classes) of fine aggregate used. In order to fully understand this variation, further studies should include determination of the effects on and variation of concrete properties when a combination of two classes of fine aggregates are used and also when all three classes of fine aggregates are used, and the results compared with values obtained in this study. Troxell G. L, Davis H. S, and Kelly J.W, 1968. Composition and Properties of Concrete, 2nd Ed., Mc. Graw –Hill Book Company Yaqub, M. and Bukhari, I., 2006. Effect Of Size of Coarse Aggregate on Compressive Strength of High Strength Concerts” 31st Conference on OUR WORLD IN CONCRETE & STRUCTURES, Singapore. REFERENCES Agrawal, P., Gupta, Y. P. and Bal, S., 2007. Effect of Fineness of Sand on the Cost and Properties of Concrete, New Building Materials and Construction World (NMM&CW), India Alawode O. and Idowu O.I., 2012. Effects of WaterCement Ratios on the Compressive Strength and Workability of Concrete and Lateritic Concrete Mixes, The Pacific Journal of Science and Technology, Volume 12. Number 2, Hawaii BS EN 12350-2, 2009. Testing Fresh Concrete: Slump Test, British Standards Institution, UK. 70
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