Performance of Foamed Concrete Incorporating Modified Expanded Perlite

This study investigates the influence of hydrophobically modified expanded perlite on the properties of foamed concrete. Expanded perlite treated with 6 wt% sodium methylsilicate was adopted as lightweight aggregate at replacement levels of 0 wt%, 5 wt%, 10 wt%, 15 wt% and 20 wt%. The physical, mechanical and durability properties including dry density, water absorption, compressive strength, drying shrinkage and freeze–thaw resistance were systematically tested. Optical microscopy and scanning electron microscopy (SEM) were further used to characterize pore characteristics and hydration products, so as to reveal the mechanisms governing the macroscopic performance of foamed concrete. The results indicate that an appropriate dosage of hydrophobically modified expanded perlite can increase the compressive strength of foamed concrete and reduce its 48 h water absorption. When the replacement dosage of modified expanded perlite reaches 10 wt%, the compressive strength reaches 7.15 MPa, which is 111% higher than that of the 0 wt% group, while the 48 h water absorption decreases from 20.18% to 8.74%. Nevertheless, drying shrinkage increases continuously with the increase in modified expanded perlite dosage. Proper addition of modified expanded perlite refines pore structure and improves the freeze–thaw resistance of foamed concrete. The mixture with 10 wt% modified expanded perlite presents relatively balanced performance considering compressive strength and frost resistance. This work provides experimental basis and technical support for the engineering application of perlite-based lightweight foamed concrete.