Mechanical properties, thermal properties and durability of lightweight thermal insulation recycled concrete

Abstract

To improve forestry solid waste reuse, reduce building energy consumption, and increase building capacity, preparing lightweight concrete with new materials has gained recent attention. This paper used waste wood and expanded perlite (EP) to design lightweight thermal insulation recycled concrete (LTIRC) with different volume admixtures. Compared to mineral aggregate, wood aggregate (WA) and EP show large differences in water absorption, particle morphology, density, and crushing index. Therefore, this paper comprehensively evaluated the dry density, mechanical properties, thermal properties, chloride ion permeability, and frost resistance of LTIRC. The results showed WA and EP introduction effectively reduced concrete bulk weight and met the dry density standard for lightweight concrete. Regarding thermal insulation performance, both WA and EP are characterized by porous, low–density, and low thermal conductivity. Consequently, LTIRC thermal conductivity was reduced by up to 76.5% versus conventional concrete, effectively increasing resistance to heat flow through concrete and providing potential for building energy savings. Additionally, WA and EP addition caused LTIRC to experience mechanical and durability property deterioration. However, some LTIRCs achieved over 80% of the strength of natural aggregate concrete. Moreover, WA addition inhibited internal crack generation in LTIRC and slowed concrete damage from increased WA and EP dosage. The maximum mass loss of LTIPC was 2.72% after 100 freeze–thaw cycles. LTIPC precast panels are suitable for preparing low–carbon insulated building wall panels.