Compressive behavior of perlite/sodium silicate composite foam modified by boric acid

In this work lightweight expanded perlite/sodium silicate composite foams were manufactured with varying quantities of boric acid (BA) 0-2.88 wt.%. The composites were characterized for density, compressive strength (CS), compressive modulus (CM), and energy absorption (EA) up to 50% strain. The compression tests were also conducted at various crosshead speeds to evaluate the strain rate dependency of the foams. The hygroscopic tests were done to evaluate water absorption properties and investigate the effects of water absorption on the compressive properties of the foams. The CS, CM, and EA of the foams increased for a boric acid content of 0.74 wt.%, but further addition of BA caused a gradual decrease in these characteristics. The range of sp. CS (3.80-5.93 MPa/(g/cm3)) achieved were found to be well compatible with the values of building materials in the literature. The foams appeared to be sensitive to the strain rate in compression, causing variations in the compressive properties as well as the trends of stress-strain curves. Furthermore, the addition of BA in the composite reduced water absorption up to a BA content of 1.46 wt.%. The compressive properties were also highly influenced by the hygrometric test.