Properties of polypropylene fiber reinforced cellular lightweight high calcium fly ash geopolymer mortar

Abstract

In this study, fly ash (FA) was used as a starting material to develop an environmentally friendly polypropylene fiber (PPF) reinforced cellular lightweight high calcium fly ash geopolymer mortar (PPF-CLFAG). The high calcium FA, a by-product of coal based electrical power plant from Mae Moh, Thailand, was used as the starting material. The PPF contents of 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% by weight of FA, NaOH at concentrations of 2, 4, 6, and 8 molars, and foam contents (Fc) of 0%, 1%, and 2% of total weight were tested. The unit weight, compressive strength, flexural strength, and scanning electron microscope imaging were tested at the age of 7 days. The dry unit weight was found to decrease with the increasing PPF content and Fc. Whereas, the dry unit weight decreased as NaOH concentrations decreased. The sample with 3%PPF, 2 M NaOH, and 2% Fc had the lowest dry unit weight of 541 kg/m3. The highest compressive strength was obtained with 0.5%PPF content, whereas the highest flexural strength was observed with 2.5%PPF content, regardless of the NaOH concentration and Fc. According to Thailand Industrial Standard (TIS), all mixtures in this study passed the TIS minimum strength requirement for cellular lightweight concrete blocks. The maximum flexural strength of 3.85 MPa and density of 1279 kg/m3 were obtained with the sample with 2.5%PPF and 8 M NaOH with no foam. Empirical equations to predict dry unit weight, compressive strength, and flexural strength of PPF-CLFAG for a given NaOH concentration, PPF content, and Fc were proposed.