Influence of the Nature and Particle Size Distribution of Rolled and Crushed Coarse Aggregates on the Physico-Mechanical Properties of Concrete

An experimental study is carried out on concrete composed of two different types of coarse aggregates: crushed coarse aggregates (CCA) and rolled coarse aggregates (RCA). Aggregate shape, texture, and grading have a significant effect on the properties of the fresh and hardened concrete. This experimental study investigates the possibility to make a concrete with a binary natural coarse aggregates (crushed and rolled coarse aggregates). The experimental program reported herein was carried out to evaluate engineering properties of natural aggregates (crushed and rolled gravels) and dune sand-concrete mixtures in both fresh and hardened states. These properties were then compared to traditional concrete mixtures made with crushed gravel and dune sand to expand the beneficial use of rolled gravel concrete and underline its potential applications. Two series of coarse aggregates mixtures using crushed limestone gravel and rolled gravel have been investigated during this study; the first mixture (serie A: the first preliminary mixture proportioning method consists in obtaining the optimum mixture from a binary mixture of two fractions 3/8 mm and 8/15 mm of crushed limestone coarse aggregates at different percentages (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% and 90%). The obtained optimal mixture consists of 40 % crushed coarse aggregates (3/8 mm fraction) and 60 % crushed coarse aggregates (8/15 mm fraction). This optimal mixture of crushed coarse aggregates gave a minimal porosity and a maximal compactness. From this result the second concrete mixture formulation was prepared with two fractions (3/8 mm and 8/15 mm) of crushed coarse aggregates and one fraction (3/8 mm) of rolled coarse aggregates (serie B: the crushed coarse aggregates of 3/8 mm fraction was substituted by 3/8 mm fraction rolled coarse aggregates at various percentages 0%, 8%, 16%, 20%, 24% and 40% by fixing constant the percentage of 8/15 mm fraction crushed coarse aggregates at 60 % in all concrete mixtures prepared). The concrete with 40% of 3/8 mm fraction rolled gravel and 60% fraction crushed gravel showed a better performance than the control concrete in terms of the physical and the mechanical properties. This study allowed to better understand the influence of chemico-physical characteristics of coarse aggregates on the mechanical behavior of concrete. The inclusion of 3/8 mm fraction rolled coarse aggregates at replacement level of 40% and 60% of 8/15 mm fraction crushed coarse aggregates resulted in a increase in the mechanical strength of the concrete. The results show that, the use of 3/8 mm fraction rolled river gravel in concrete effectively improved the mechanical properties.