The effect of incorporating recycled concrete aggregates and steel fibers in structural concrete

Abstract

The construction industry is increasingly utilizing concrete to build the contemporary skyscrapers and city infrastructure that are characteristic of the modern world. This is due to the fact that concrete has several advantages in construction, including its workability, high strength, and ability to incorporate steel reinforcement to further the load carrying capacity of the structure. However, the mining of aggregates, which are an essential component of concrete, is a process which is harmful to the environment. To add, the concrete waste generated from demolishing old or damaged structures is not biodegradable. This implies that large volumes of this concrete waste end up in landfills or other dump sites. This indicates that traditional construction and design methods used in concrete are not sustainable. Incorporating this concrete waste to replace natural quarried aggregates in concrete mixes may be a cost effective and environmentally sustainable alternative to the traditional mix design. However, previous research has shown that the concrete made from recycled concrete aggregates is significantly lower in strength than that made from natural aggregates. In this study, the effect of changing the concrete composition on the quality, namely the strength of the concrete will be studied. The composition changes include replacement by recycled concrete aggregates, reduction in water to cement ratio, and the addition of steel or polypropylene fibers. Results from this experiment show that steel fibers seemed to give the best overall enhancement in concrete quality when recycled concrete aggregates are used in place of natural ones, especially in tensile strength. However, the addition of polypropylene fibers is the better choice as it offers the greatest benefit and is much lower in cost than steel fibers. However, the most economical option for applications that are not structurally demanding with low seismic risk is replacement by recycled concrete aggregate with no fiber addition, because while it had the lowest overall strength, it also has the lowest overall cost.