Research on innovative green building materials from waste oyster shells into foamed heat-insulating bricks

To avoid climate change, the world must reach net-zero carbon emissions by 2025 to achieve the goal of a sustainable environment. Improving resource efficiency is one of the important strategies to achieve a sustainable environment. Effectively recycling resources and reducing energy consumption have become important international issues today. Therefore, this research was to recycle waste oyster shells, combined it with geopolymer technology, and added foaming agents to create an innovative building material that is 100% recyclable after use – "Foam heat-insulating bricks", thereby reducing carbon emissions and building energy consumption. Through physical properties (apparent density, porosity, water absorption, etc.) and mechanical properties (compressive strength and flexural strength), discussed factors such as lime-sand ratio, alkaline solution concentration, foaming agent, etc., effected on the heat-insulating performance and environmental protection performance of foam heat-insulating bricks. The newly prepared foam heat-insulating bricks were also evaluated for their environmental and economic aspects according to relevant standards. The results show that::(1) The higher the concentration of alkaline solution and the greater the proportion of lime-sand, which the mechanical properties of the finished product were the higher. Samples 10 M−55, 10 M−64 and RWITGP-60 can meet the G2 lightweight bricks standard; Samples WITGP-46, WITGP-55 and WITGP-64 can meet the roof heat-insulating brick standard. (2) The better the foaming performance, the higher the porosity and water absorption, which the thermal heat-insulating effect were better, but the worse the compressive strength and flexural strength. The foaming performance of the foaming agent is Sodium-perborate(NaBO3) > Aluminum(Al) > Nothing-added(WITGP). (3) Oyster shell foamed heat-insulating bricks are 100 % recyclable, have better performance after remanufacturing, and have extremely high development potential. (4) It could pass the "Toxicity Characteristics Leaching Procedure" test and comply with Taiwan's general specifications for green building materials. (5) The heat flow resistance of adding different foaming agents is aluminum with the greatest benefit, and the order is: Aluminum (Al = 133.4)W/m2 > Sodium-perborate (NaBO3 = 93.6)W/m2 > Nothing-added (WITGP = 90.6)W/m2 > Concrete (CON = 68.2)W/m2. (6) The oyster shell heat-insulating bricks produces 0.473 kg of carbon dioxide. Compared with concrete heat-insulating bricks, it can reduce carbon emissions by 48.7 % and save an economic price of 451.15 yuan/brick.