Sustainable Foam Concrete with Ceramic Powder and Coconut Shell Aggregate: Enhancing Environmental Sustainability and Material Performance

Coconut shell, as an agricultural waste product, has emerged as a promising alternative aggregate in foam concrete (FC), contributing to both environmental sustainability and enhanced material properties. Using ceramic powder (CP) as a partial replacement for cement in FC significantly enhances sustainability by reducing CO2 emissions from cement production. This substitution not only recycles waste materials effectively but also improves thermal insulation and durability, making FC a more eco-friendly and efficient construction material. This study aims to create eco-friendly FC by examining the combined effects of CP and coconut shell aggregate (CSA) as partial substitutes for portland cement (PC) and river sand (RS), respectively. FC mixtures were produced with 0%, 10%, and 20% CP replacing PC and 0%, 25%, 50%, and 100% CSA replacing RS. A total of 12 FC mixtures were formulated, all maintaining a constant water-to-binder (w/b) ratio of 0.6. The effects of varying CP and CSA content on fresh-state, physical, and mechanical properties; sorptivity; thermal conductivity; high-temperature resistance; freeze-thaw durability; and resistance to HCl and MgSO4 were evaluated. Additionally, the microstructure of the mixtures was analyzed using scanning electron microscopy (SEM). The findings showed that mixtures with CSA enhanced thermal insulation and decreased density, but increasing CP content often decreased flowability and fresh unit weight. The mechanical performance of FC was improved by replacing RS with CSA, notably at 25% and 50% CSA levels. In contrast, CP decreased compressive strength but improved durability, especially when exposed to high temperatures and chemicals. Notably, in terms of chemical resistance and thermal stability, the mixture containing 10% CP and 50% CSA performed the best.