Effect of polypropylene fiber on frost resistance and carbonation resistance of manufactured sand concrete

Abstract

Mixing fiber into manufactured sand to prepare concrete can effectively reduce the consumption of natural sand resources, improve concrete performance, improve the life of the whole building structure, and bring considerable environmental and economic benefits. To better apply it to engineering practice, this research studied the effect of polypropylene fiber (PPF) on the frost and carbonation resistance of manufactured sand concrete (MSC). In this research, PPF with different volume content (0.8%,1.0%,1.2%)and length(6 mm,12 mm,18 mm) are incorporated into (MSC). Through the design of compressive strength test, splitting tensile strength test, rapid freeze–thaw test, and carbonation test to analyze and evaluate strength, dynamic elastic modulus, and carbonation depth of MSC by Response Surface Methodology (RSM). The experimental findings demonstrated that PPF can effectively improve the compressive strength and splitting tensile strength of MSC. Compared with the control group (natural-sand concrete, NC), the compressive strength increased by 18.18% at most and 1.72% at least, and the splitting tensile strength increased by 32.14% at most and 17.86% at least. when the volume content of PPF is 1.0%, the damage of compressive strength and splitting tensile strength of MSC is the lowest, and the frost resistance is the best. The carbonation depth is the lowest (1.94 mm) when the volume content of PPF is 1.0% and the length is 12 mm, and compared with NC, the flexural strength and dynamic elastic modulus of MSC were increased by 4.65% and 16.3%, respectively. Through XRD and SEM analysis, the incorporation of PPF with moderate volume content can slow down the carbonation reaction of MSC and improve the carbonation resistance of MSC. From RSM analysis, the effect of PPF on the frost resistance of MSC is volume content > length; the effect of PPF on the carbonation resistance of MSC is length > volume content. The optimized prediction results are consistent with the analysis results: the incorporation of PPF can improve the durability of MSC, reaching or even exceeding NC specimens, which provides a theoretical basis for the promotion of PMSC in engineering. When the volume content of PPF is 1.0 % and the length is about 12 mm, the frost resistance and carbonation resistance of MSC are the best.