APPRAISAL ON THE STRENGTH OF CONCRETE PRODUCED WITH VARYING AGGREGATE SIZE

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 3, May June 2016, pp , Article ID: IJCIET_07_03_023 Available online at Journal Impact Factor (2016): (Calculated by GISI) ISSN Print: and ISSN Online: IAEME Publication APPRAISAL ON THE STRENGTH OF CONCRETE PRODUCED WITH VARYING AGGREGATE SIZE T.C. Nwofor and D.B. Eme Department of Civil Engineering, University of Port Harcourt, P.M.B 5323 Port Harcourt, Rivers State, Nigeria ABSTRACT Compressive strength is one of the important properties of concrete as it influences the durability requirements of concrete. This work presents the effects of varying size of aggregate on the strength of concrete. The coarse aggregates used for this study were 10mm, 12.5mm and 19mm uncrushed gravel with river sand as fine aggregate. Sieve analysis was carried out on the aggregates. A nominal mix of 1:2:4 was adopted for the mix and the mix proportions were calculated by weight. The concrete test cubes used were made in batches with each batch containing just one coarse aggregate size. Two test cubes each were made respectively for each batch making a total of 18 cubes and cured for 7, 21, and 28 days respectively. Compressive strength tests were carried out on all 18 test cubes and their compressive strength values were recorded. The compressive strength was found to increase with increase in coarse aggregate size with19mm gravel having as much as 36.31N/mm 2. Cite this Article: T.C. Nwofor and D.B. Eme, Appraisal on The Strength of Concrete Produced with Varying Aggregate Size, International Journal of Civil Engineering and Technology, 7(3), 2016, pp INTRODUCTION Coarse aggregates are relatively inert material fillers which when combined with cement and water forms a stone-like material called concrete (1-2]. Coarse aggregates predominantly range from particle sizes of 5 mm to an average of 20 mm size and most be properly graded to form dense concrete [3-7]. The coarse aggregate mainly provides the necessary weight to the concrete, hence improving the volume stability and durability of the concrete, thereby affecting the plastic and hardened state of concrete through its physical characteristics [1, 8] editor@iaeme.com

2 T.C. Nwofor and D.B. Eme Bayasi and Zhou [9] and Ruiz [10] reported that the compressive strength of concrete increases with an increase in coarse aggregate content up to an optimum proportion after which there is a marginal decrease and this strength property of concrete is an important parameter in the design of structures [11-15]. The effect of increase aggregate sizes as it affects the water-cement ratio have been studied [16]. The study suggested that increasing the maximum aggregate size reduced the total surface area of the aggregate, thus reducing the mixing water requirements. However, even with the reduction in water, a larger aggregate produced concrete with low compressive strengths compared to concrete containing smaller aggregate. This paper aims at investigating the effects of varying aggregate sizes on the strength properties of concrete noting that other characteristics of concrete such impermeability, durability and volume stability may be very important, the compressive strength is considered the most viable property. 2. MATERIALS AND METHOD The fine aggregate used in this study was natural river sand obtained from Imo River in Oyigbo Local Government area of Rivers State, Nigeria. It was washed and airdried for two weeks before it was used for concrete work. The granite aggregates were milled from crushed rock in Rivers State. The aggregates were thoroughly washed and air-dried for a period of three weeks to remove dirt and later surface dried before usage. The sizes of uncrushed gravel were 12.5mm, 19mm and 10mm respectively. The brand of ordinary portland cement used as binder in this study. They were brought to the laboratory in bags, carefully arranged and contact with moisture was avoided. The water used for this study was colourless, odourless, tasteless and fresh. The particle size distribution of fine and coarse aggregates was also carried out in accordance with the requirements of BS 812, Concrete Mix Design For the purpose of uniformity and ease in evaluating the effect of coarse aggregate size on concrete compressive strength, a nominal concrete mix of 1:2:4 was adopted for each concrete mix containing the different coarse aggregate sizes with watercement ratio of 0.6 in compliance with BS 5328: part 1. The result obtained from mix design is shown in Table 1. Table 1 Concrete Constituents Mix Proportions Mix Ratio Batch No. Quantities of Mix Constituents Cement Sand Gravel 1:2: RESULTS AND ANALYSIS The values of compressive strength obtained for different aggregate sizes at varying curing age of concrete are displayed in Table 2 to editor@iaeme.com

3 Appraisal on The Strength of Concrete Produced with Varying Aggregate Size 150x150x150 Table 2 Compressive Strength Result at 7 Days for 10mm Coarse Aggregate Size mm aggregate size 150x150x " AVERAGE Table 3 Compressive Strength Result at 21 Days for 10mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE Table 4 Compressive Strength Result at 28 Days for 10mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE Table 5 Compressive Strength Result at 7 Days for 12.5mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE Table 6 Compressive Strength Result at 21 Days for 12.5mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE editor@iaeme.com

4 T.C. Nwofor and D.B. Eme Table 7 Compressive Strength Result at 28 Days for 12.5mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE Table 8 Compressive Strength Result at 7 Days for 19mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE Table 9 Compressive Strength Result at 21 Days for 19mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE Table 10 Compressive Strength Result at 28 Days for 19mm Coarse Aggregate Size 150x150x mm aggregate size 150x150x " AVERAGE The compressive strength f cu was determined using: P f cu A Where: P Maximum load on the cube at failure A Cross-sectional area of the concrete cube specimen editor@iaeme.com

5 compressive strength Appraisal on The Strength of Concrete Produced with Varying Aggregate Size Batch No. Table 11 Average Compressive Strength Values for Each Concrete Batch 7-Day Strength 21-Day Strength 28-Day Strength Coarse Aggregate Size / Batch (batch 1) (batch 2) (batch 3) A summary of average compressive strength development in concrete at different curing age for the different aggregate sizes is shown in Table 11 and plotted in Figure batch 1 batch 2 batch days 21 days 28 days Figure 1 Strength Development of the Concrete Test Cubes at varying Aggregate Size For batch 1 concrete cubes made with 10mm coarse aggregate size, about 65% strength was gained after 7 days while for batch 2 and batch 3 concrete cubes made with 12.5mm and 19mm coarse aggregate sizes respectively, about 67% each of the total strength had been reached after 7 days. The bar chart below shows clearly the effect of the coarse aggregate size on the compressive strength of the different batches of concrete cubes casted using only the values for 28 th day strength editor@iaeme.com

6 28-day compressive strength 28 - day compressive strength T.C. Nwofor and D.B. Eme mm mm 32 19mm Figure th day Compressive Strength for the Concrete Cubes made with different Coarse Aggregate Size. From Figure 2, it can be observed that as aggregate size increases, the compressive strength increases generally. Thus compressive strength and aggregate size can be related as shown in Figure 3, using only the values for 28 th day strength Coarse aggregate size Figure 3 Relationship between Aggregate Size and Compressive Strength at 28 th Day Compressive strength values for 7-day strength and 28-day strength for all concrete mix batches agree favorably with Table 12 of BS 12 for concrete made with Portland cement and strength class of 32.5N (C30 grade) editor@iaeme.com

7 Appraisal on The Strength of Concrete Produced with Varying Aggregate Size Table 12 Compressive Strength Requirements for Concrete made with Portland Cement according to BS 12 Early Strength Standard Strength Class of 2 days 7 days 28 days Strength G G G G G G In compliance with Table 1 of BS 5328: part 4 shown above, the 28-day compressive strength for the concrete cubes made for all batches exceeds the characteristic strength (30N/mm 2 ) by at least 1N/mm 2, thereby satisfying the requirements in the code. Therefore, the compressive test results are within acceptable limits. 4. CONCLUSSION From the study, the following conclusions are made. After 7 days, strength had developed in the concrete cubes to approximately twothirds of the 28-day strength which is within acceptable limits. The results of this work show that for an increase in coarse aggregate size from 10mm to 19mm at constant water content, the compressive strength increased by about 16.2 percent. The slump value for the mix batch 3containing 19mm uncrushed gravel was higher than that of mix batch 2 containing 12.5mm uncrushed gravel. This indicates that water content was increased for mix batch 3 due to a poor level of workmanship. The results of this work agree with Ruiz [10] who after their investigations on the effect of aggregate size on compressive strength stated that strength increases with increase in aggregate size by about 10 percent. The result of this work then tends to disagree with Bloem [16] and Walker [20], who all concluded that compressive strength decreases with increase in aggregate size by about 10 percent Recommendation The compressive strength of concrete produced with aggregates size beyond 19 mm is recommended to be considered. Further research work considering other attributes of aggregates such as type and texture is recommended REFERENCES [1] Shetty M.S. (2005). Concrete Technology, Theory and Practice. First Multicolour Illustrative Revised Edition, S. Chard & Company Ltd, 7361, Ram Nagar, New Delhi. [2] Jackson N., Dhir R.K. (1988). Civil Engineering Materials. MacMillan Education Ltd. Hound mills, Basing Stroke Hampshire. [3] Jackson N. (1981). Civil Engineering Materials, Macmillan Press Ltd, London editor@iaeme.com

8 T.C. Nwofor and D.B. Eme [4] Rajput R.K. (2006). Engineering Materials. 3rd edition, S. Chard & Company Ltd, Ram Nagar, New Delhi. [5] Murdock L.J., Brook K.M. (1979). Concrete Material and Practice, Fifth Edition. Edward Arnold, London. [6] BS 882: Part 2: Coarse and fine aggregate from natural sources. BSI, London, UK. [7] BS 882: Specification for aggregate from natural sources for concrete. BSI, London, UK. [8] Jackson N., Dnir R.K. (1991). Civil Engineering Material, Fourth Edition. Addison Wesley Longman s Limited Edinburgh Gate. [9] Bayasi, Z. and Zhou, J. (1993). Properties of Silica Fume Concrete and Mortar. ACI Materials Journal, 90 (4), [10] Ruiz, W. M. (1966). Effect of Volume of Aggregate on the Elastic and Inelastic Properties of Concrete, M.S. Thesis, Cornell University [11] Neville A.M. (2005). Properties of Concrete, ELSB 5th Edition, Pearson Education Publishing Ltd. London. [12] Nwofor, T.C. & Sule, S. (2014). Investigating geometric characteristics of cement concrete materials. International Journal of Innovative Research in Advance Engineering, 1(9), [13] Eme, D.B., Nwofor, T.C. & Umukoro, E.S. (2015). Stability of asphalt cement concrete produced from waste plastics as replacement for aggregate. International Journal of Civil Engineering and Technology, 6(5), [14] Nwofor, T.C., Sule, S. & Eme, D.B. (2015). A comparative study of the methods of concrete mix design using crushed and uncrushed coarse aggregates. International Journal of Scientific and Engineering Research, 6(8), [15] Eme, D.B. & Nwofor, T.C. (2015). Investigating the Marshall Stability requirements of asphalt concrete mix with ground scrap tyres as aggregate. International Journal of Civil Engineering and Technology, 2015, 6(9), 1 7. [16] Bloem, D. L. and Gaynor, R. D. (1963). Effects of Aggregate Properties on Strength of Concrete. ACI Journal, Proceedings 60 (10), [17] BS (1985) Testing aggregates methods for determination of particle size distribution. Section 103.1; sieve tests. [18] BS 5328: part 4 (1983), Specification for the procedures to be used in sampling, testing, and assuring compliance of concrete. [19] BS 12 (1996). Specification for Portland cement. [20] Prof. Dr. Ammar Yaser Ali and Ahmed Mohammed Mahdi, Analysis For Behavior and Ultimate Strength of Concrete Corbels with Hybrid Reinforcement, International Journal of Civil Engineering and Technology, 6(10), 2015, pp [21] Zahid Ahmad Chat, Umer Salam And Shahid Bashir, Compressive Strength of Concrete Using Natural Aggregates (Gravel) and Crushed Rock Aggregates-A Comparative Case Study, International Journal of Civil Engineering and Technology, 6(1), 2015, pp [22] Behrouz Mohebimoghaddam and S.Hossein Dianat, Evaluation of The Corrosion and Strength of Concrete Exposed To Sulfate Solution, International Journal of Civil Engineering and Technology, 3(2), 2012, pp [23] Walker, S. and Bloem, D. L. (1960). Effects of Aggregate Size on Properties of Concrete. ACI Journal, Proceedings 57 (3), editor@iaeme.com