Microstructure and Mechanical Behavior of Concrete Based on Crushed Sand Combined with Alluvial Sand

Abstract

The aim of this work is to reduce the overexploitation of river sand by proposing a combination of crushed sand and river sand to develop an optimal mix design for concrete. The approach used consisted of a physical, chemical, and mineralogical characterization of aggregates from three quarries located in Yaoundé (Cameroon), followed by the formulation of concrete by substituting 100%, 90%, 80%, 70%, 50%, and 0% of the river sand with crushed sand. A physical and mechanical characterization of the concrete was carried out, as well as a microstructural characterization using SEM/EDS. The results showed that the concrete made of crushed sand only had a higher drying shrinkage at a young age compared to the river sand concrete. Compared to conventional concrete (made using 100% of river sand), the concrete with 50% crushed sand reduces its slump value, has a lower porosity, and has a compressive strength value of 26.3 MPa at 28 days, which is very similar to that of conventional concrete (26.7 MPa). Moreover, it was found that the strength of the concrete increased by 14.4% and 20.6%, respectively, for concrete without crushed sand (BSR0) and concrete with 50% crushed sand (BSR50) by increasing the curing age from 28 to 90 days. The static modulus of elasticity for conventional concrete BSR0 and BSR50 concrete with 50% crushed sand at 90 days was 23.7 and 21.8 GPa, respectively. Thus, combining crushed sand with alluvial sand is a good method to reduce the depletion of alluvial sands in Cameroon.

Comparative Study of Mortars Made with Sands of Different Geological Origin

“…Te other major elements, namely potassium oxide, phosphorus oxide, and sodium oxide, show low concentrations, sometimes less than 1%. Tese results are similar to those of Elat et al [8] for gneiss and alluvial sands, those of Unčík and Kmecova [32] for basalt, and those of Gupta and Vyas [7] for granite.…”

“…Despite numerous research works carried out on mortars [7][8][9][10], questions remain unanswered concerning the interaction between cement and aggregates, especially those concerning the infuence of the nature of the aggregates on the hydration phenomenon. From this point of view, works [11] have shown that the mechanical properties of mortars based on quarry sand were close to each other and that mortars based on alluvial sands presented weaker mechanical properties than the latter.…”

Behaviour of gneiss and basalt aggregate in normal concrete subjected to high temperatures

“…Fig. 1 presents the different size aggregates used in the concrete formulations and Table 1 illustrates the chemical compositions of the aggregates obtained from previous studies [5][6]. The cement used is Portland CEM II/B-P 42.5R from Dangoté (Cameroon) with a density of 3100 kg/m 3 and a concrete compressive strength of 55 MPa at 28 days.…”

“…Durability also depends on its physical and mechanical properties, nature of the aggregate, nature of cement, its water content, the heating rate and time of exposure to fire [1][2][3][4][5][6][7]. However, numerous studies have been carried out on the physical and mechanical properties of concrete based on crushed quarry sand (limestone type) and river sand at room temperature.…”

“…However, numerous studies have been carried out on the physical and mechanical properties of concrete based on crushed quarry sand (limestone type) and river sand at room temperature. It has been generally observed that it is possible to use crushed sand as partial replacement of natural river sand to obtain similar mechanical performances of concrete [4][5][6]. Manjunatha et al [7] conducted a study on the durability of concrete by replacing 50% of natural sand with M-sand from crushed rock deposits to obtain a fine, well-graded aggregate containing large amounts of fines and less clay and silt.…”