Multicriteria and response surface-based selection of coarse recycled aggregate and blade waste contents in environmentally friendly low-strength concrete

Abstract

The use of Coarse Recycled Aggregate (CRA) in Low-Strength Concrete (LSC), suitable for pavements, allows the sustainable revaluation of this waste material, but worsens its performance. Recycled fibers of Glass Fiber-Reinforced Polymer (GFRP) present in Raw-Crushed Wind-Turbine Blade (RCWTB) may counterbalance the detrimental effects caused by CRA addition. This research analyzes the mechanical properties, durability, cost and carbon footprint of LSC mixes with 50 % and 100 % CRA combined with 0 % and 10 % RCWTB. Stitching of the cementitious matrix by GFRP fibers improved flexural strength and energy absorption of LSC containing CRA. In addition, these fibers exerted a barrier effect against water passage and exhibited higher surface hardness, the addition of RCWTB therefore did not affect the water-absorption rate and effective porosity and increased the abrasion resistance of LSC. Finally, RCWTB also reduced the cost and carbon footprint of LSC. These enhancements caused by RCWTB were analyzed through Multi-Criteria Decision-Making (MCDM) and Response Surface Methodology (RSM), approaches novel in the literature. According to them, the joint use of CRA and RCWTB in LSC was recommended. PROMETHEE II algorithm indicated that the use of 10 % RCWTB combined with 100 % CRA was the best option due to economic and environmental advantages, as this algorithm only considered which LSC mixture was the best for each property. ELECTRE algorithm showed indifference between both CRA contents, due to the better mechanical and durability performance of 50 %-CRA LSC. TOPSIS algorithm and RSM models revealed a preference for 50 % CRA and 10 % RCWTB following quantitative calculations based on the magnitudes of the property differences between the mixes. This research demonstrates the broad suitability of LSC containing both CRA and RCWTB in construction applications, mainly regarding pavements.