Recycled gypsum board acted as a mineral swelling agent for improving thermal conductivity characteristics in manufacturing of green lightweight building brick

Lightweight building bricks manufactured from non-hazardous residues incorporating mineral foaming agents have been successfully developed over past two decades. Very little information is available on recycling and reutilization of construction and demolition waste used as the pore foaming agent in manufacturing lightweight brick. In this research, the mineral swelling agent was gypsum board recycled from construction and demolition waste. The mineral swelling agent effect on the characteristics of green lightweight building materials sintered from drinking water purification (DWP) sludge was investigated. Green lightweight building materials were contained up to 50% (wt%) mineral swelling agent and fired at a temperature ranged between 950 °C and 1050 °C. The experimental results indicated that lightweight building materials have successfully sintered between 1000 °C and 1020 °C and added up to 40% (wt%) recycled gypsum board. The sintered building materials have the characteristics of relatively high compressive strength, low bulk density, and thermal conductivity that were in compliance with relevant Taiwan criteria for application in lightweight building materials. To further consider the eco-friendly and environmental safety of lightweight building materials, the recycled gypsum board can act as a good mineral swelling agent, but can also enhance the chemical stabilization and reduce the metals leachability of lightweight materials based on acidic neutralization capacity (ANC) analysis results. To estimate the carbon dioxide emission in manufacturing and transportation of lightweight materials that sintered this experimental conditions, the estimated carbon dioxide reduction rates were approximately 28.6% and 16.7%, respectively, as a result of the energy saving. Experimental results have confirmed that the feasibility of recycled gypsum board used as a swelling agent and good potential for construction works in green lightweight building materials.