Investigation of Mechanical Properties of Ultra-High-Performance Polyethylene-Fiber-Reinforced Recycled-Brick-Aggregate Concrete

Abstract

The utilization of ultra-high-molecular-weight polyethylene fibers (UHMWPEFs) to enhance recycled-brick-aggregate concrete represents an efficacious approach for ameliorating the concrete’s performance. This investigation addresses the influences of recycled-brick aggregates (RAs) and UHMWPEFs on the concrete’s slump, shrinkage, flexural strength, resistance to chloride-ion ingress, and freeze–thaw durability. The mechanisms through which UHMWPEFs ameliorate the performance of the recycled-brick-aggregate concrete were elucidated at both the micro and macroscopic levels. The findings underscore that the three-dimensional network structure established by the UHMWPEFs, while resulting in a reduction in the concrete slump, substantially enhances the concrete’s mechanical properties and durability. A regression model for the multifaceted performance of the UHMWPEF-reinforced recycled-brick-aggregate concrete (F-RAC) was formulated by employing response-surface methodology, and the model’s reliability was confirmed through variance analysis. The interactive effects of the RA and UHMWPEFs on the concrete were analyzed through a combined approach involving response-surface analysis and contour plots. Subsequently, a multiobjective optimization was conducted for the F-RAC performance, yielding the optimal proportions of RA and UHMWPEFs. It was determined that the optimal performance across the dimensions of the shrinkage resistance, flexural strength, chloride-ion resistance, and freeze–thaw durability of the F-RAC could be simultaneously achieved when the substitution rate of the RA was 14.02% and the admixture of the UHMWPEFs was 1.13%.

Impact of Interfacial Transition Zone on Concrete Mechanical Properties: A Comparative Analysis of Multiphase Inclusion Theory and Numerical Simulations

“…In previous studies on ordinary concrete, the density and strength of ITZ were much lower than those of aggregates and mortar, and were generally considered as weak links in concrete [5]. Some scholars enhance the mechanical properties of ITZ in recycled concrete by adding fiber materials or nano-scale materials into RC [6][7][8], and it is beneficial to study the specific changes of ITZs in a cross-scale way. The interface situation of RC is more complex, and it is difficult to observe and analyze the impact of different ITZs on the overall mechanical properties of RC.…”