Experimental research on waterproof enhanced biomass-based building insulation materials

The eco-friendly biomass and geopolymer coupling foaming materials have become promising candi-dates in the field of building insulation due to their low thermal conductivity, low CO2 emissions and fire resistance. However, due to the interconnected pore structure by foaming, poor water resistance is the main disadvantage. To solve this problem, the authors suggested and evaluated three solutions, including: adding an extra geopolymer layer to the substrate surface; brushing organosilicon waterproofing agent directly on the substrate surface; and applying both extra geopolymer layer and organosilicon waterproofing agent layer. The first referred method was proposed by the authors, and the multi-layer material prepared contained two main parts, i.e., the main part was traditional biomass and geopolymer coupling foaming material, and an extra millimetric pure geopolymer layer without foaming was added to the main part surface. To assess the waterproof performance, several key parameters were analyzed in detail by experiments, namely the effect of precuring time of the substrate on the geopolymer coating appearance; the effect of different coating thicknesses on the microstructure, water and moisture absorption; the effect of different waterproofing forms on the static water contact angle, water and moisture absorption. The results showed that, the optimum precuring time and coating thickness were 9-24 h and 2 mm, respectively, and the interface between the coating and the substrate possessed a high bond-ing strength. Among the three treatments, the third way, which uses geopolymer coatings and water-proofing brushing, can obtain the best water resistance performance. The static contact angle of the treated sample was 92 degrees, and the water absorption and moisture absorption mass ratios were 3.3% (after 96 h) and 1.5% (after 168 h), respectively. The research can provide a scientific reference for the development of the multifunctional and energy-saving materials prepared by geopolymer technology. (C) 2021 Elsevier B.V. All rights reserved.