Evaluation of strength, durability, and microstructure characteristics of slag-sand-induced concrete

Abstract

This paper focused on the usage and behavior of slag sand by investigating the fresh, mechanical, durability, and microstructural properties of M40 grade concrete. However, in India, more research on the effect of slag on mechanical strength is needed with in-depth microstructure & durability investigation. To fill this research gap and promote slag sand usage, a systematic and scientific investigation was conducted in which 9 concrete mixes with partial and total replacement of fine aggregate with slag sand were prepared. Compressive, split tensile strength & UPV tests are performed at 3, 7, 28, and 90 days of curing to know the mechanical properties. Linear regression analysis is done to correlate and predict the strength of concrete using different mechanical properties. According to test results, workability and mechanical properties improve with the increase in the replacement of slag sand. Slag sand concrete forms a dense network at an optimum replacement achieving Maximum rise in strength of about 17 to 33 %, referring to the control mix resulting in an environmentally friendly material. Thereby reducing the disposal of industrial effluent. Conversely, increased replacement beyond 40 % of slag sand in concrete caused a reduction in the slump and mechanical properties with increased curing age. Microstructure results revealed the formation of CSH, CASH, ettringite, calcite, and good bonding with an aggregate. Slag sand tends to absorb more water with its increased percentage due to its shape, texture, and surface area, as evidenced in its SEM images & workability. The durability of slag sand concrete has performed better and is economically feasible than M-sand mixed concrete. Hence, recycling slag sand in concrete yields an economical, eco-friendly material and proves to be a robust substrate for various construction activities in sustainable waste management.