Effect of content and particle size distribution of coarse aggregate on the compressive strength of concrete

Coarse aggregate fraction is known to strongly influence both fresh and hardened concrete's properties. Consequently, selection of both content and particle size distribution (PSD) for concrete mixture is an important issue regarding the predicted performance of concrete. In the present study, and based on previous results obtained, four granular fractions were combined in different proportions in order to investigate the effect of the PSD of aggregate on the properties of concrete. Two types of chemical admixtures, water reducer agent (WRA) and superplasticizer (HRWRA) were used to decrease the water-cement ratio (w/c) which ranges from 0.58 to 0.40. Compressive strength function the PSD of coarse aggregate was determined at 7, 14 and 28 days. Results have revealed that the mixtures without chemical admixture made with a ternary combination of granular fraction and having a maximum size of 25 mm, that assures a continuous granular size distribution, have shown the highest compressive strength. However, decreasing the w/c by the inclusion of WRA or HRWRA requires a decrease of the maximum size of coarse aggregate and some adjustment in the granular size distribution system. The binary granular system has led to the highest compressive strength when dealing with low w/c.