Modification of ultra-high molecular weight polyethylene fiber to improve mechanical properties of foamed concrete

Foamed concrete (FC) offers many advantages and has been widely applied in the construction industry. However, its unique porous structure leads to poor mechanical properties, making it prone to cracking and fracturing during service. To address this issue, ultra-high molecular weight polyethylene (UHMWPE) fibers, modified with tannic acid (TA) and ethanolamine (EA), were applied to reinforce FC to improve its mechanical performance in this research. The effects of TA/EA modification on UHMWPE fibers were investigated, and the impacts of modified UHMWPE fibers on FC were explored, including workability, physical properties, mechanical properties, and microstructural characteristics. The fibers were added in the dosages corresponding to 0.1 %, 0.3 %, 0.5 %, and 0.7 % of the mass of cementitious material. The experimental results show that modified UHMWPE fibers exhibit good thermal stability and improve adhesion with FC. Regardless of modification, UHMWPE fibers can enhance mechanical properties of FC at all dosages investigated. When the dosage of modified UHMWPE fibers is 0.5 %, the enhancement of mechanical properties of FC is most eminent. Compared to control group, the drying shrinkage decreases by 20.6 %, and the compressive, flexural, and tensile strengths increase by 216 %, 688 %, and 120 %, respectively. The bend-press ratio reaches 1/4, outperforming that of the ordinary FC. The analysis of microstructural properties reveals the underlying mechanisms behind the enhanced mechanical properties of FC. The fiber modification methods discussed in this paper can strengthen the bond between the fibers and the cement matrix, thereby enhancing the reinforcing effect of the fibers in FC. These findings provide a new insight into the efficient applications of fibers that bind poorly to cement-based materials in FC.