Fiber-reinforced geopolymers made with recycled aggregates for screed flooring and repair applications

The increase in greenhouse gas emissions from cement production, along with limited landfill capacity for construction waste, has driven research into finding sustainable alternatives to replace cement and natural aggregates. While cement replacement with geopolymeric binders in mortar and concrete has been proven feasible, replacing natural aggregates with recycled counterparts has led to performance losses. To offset this drawback, different additives, including fibers, have been incorporated into such construction materials. This study evaluates the feasibility of using steel fiber (SF)-reinforced geopolymer (GP) composites incorporating recycled fine aggregates (RFA) for screed flooring and repair applications. GP mixes were prepared with RFA mass substitution up to 100 %, alongside SF volume of 0.5 % and 1 %. Flow values of 125 +/- 25 mm were attained within 35 to 70 min. The 7-day compressive strength of GP composites reached 74.0 % to 96.2 % of their 28-day values. RFA substitution reduced compressive strength, elastic modulus, tensile strength, pull-off bond strength, and energy absorption and increased impact indentation and abrasion mass loss by up to 56, 69, 60, 23, 68, 266, and 2025 %, respectively. Conversely, SF addition improved most of these properties except for compressive and pull-off bond strength, which slightly decreased. GP composites made with 0 %, 25 %, and 50 % RFA satisfied the strength requirements for use in structural repair, while those with higher RFA replacement were suitable for non-structural use. Based on BS 8204, GP mixes were categorized as Category A screed flooring except the plain mix made with 100 % RFA, which was categorized as Category B.