Experimental Investigation on the Influence of Superplasticizer on Mechanical Behavior of Recycled Aggregate Concrete

Abstract

Needs for renovation and efficient use of available land space have led to the destruction of numerous deteriorated civil structures. Consequently, a huge amount of concrete demolished waste is generated annually worldwide. This demolished concrete waste has created an extra burden on the environment and landfills, making the development projects unsustainable. Demolished waste can be recycled and reused for sustainable development and to reduce the demand for fresh natural aggregates (NA). However, the poor performance of recycled aggregate concrete (RAC) compared to natural aggregate concrete (NAC) may be a significant drawback in the recycling and reusing of demolished concrete wastes. This limitation can be overcome by using a superplasticizer, which has the ability to improve different mechanical properties of concrete. The objective of this paper is to assess the effects of the superplasticizer on the mechanical characteristics of RAC. Concrete specimens were prepared to have replacement ratios (0%, 25%, 50%, and 100%) of fresh NA by recycled stone aggregates (RSA) and recycled brick aggregates (RBA). Half of the prepared concrete specimens were admixed with the superplasticizer, having 15% water reduction for concrete mixes. The obtained test results encourage the use of superplasticizers for improving the mechanical properties of RAC. It is observed that fresh, natural coarse aggregates in a concrete mix can be replaced with 50% RSA and 25% RBA with the addition of the superplasticizer without compromising the mechanical performance.

Mechanical properties of recycled concrete aggregates with superplasticizer

“…Based on studies [6][7][8], several researchers have found that replacing 50% of the natural aggregates (NA) in RAC with RCA can reduce the RAC's compressive strength by up to 25%. Following a similar pattern to the drop in compressive strength, as reported in different studies, tensile strength splitting was seen to fall by as much as 39% with a total replacement of natural aggregates (NA) with RCA.…”

“…A small increase in mechanical strength and a reduction in the amount of water in the mixtures are the results of adding superplasticizers. PATOWARY and SIDDIQUE [8] claimed that a responsive superplasticizer may be used to control the rheology of newly manufactured cement-based products. The results of their study demonstrated that superplasticizers based on polycarboxylic ether (PCE) can be given other functions by adding certain chemical groups [12].…”