Desulfurization sludge and fly ash in autoclaved aerated concrete blocks

Due to the high heavy metal content, desulfurization sludge is often treated as hazardous waste by power plants, leading to high disposal costs. In this study, fly ash and desulfurized sludge were used as raw materials, and sludge was used to replace desulfurized gypsum to prepare aerated concrete blocks. Results showed that sludge could completely replace gypsum, improving the mechanical properties and pore structure as sludge content increased. SEM-EDS and XRD analyses confirmed that tobermorite was the primary hydration product, with sludge promoting its crystallization. The optimal formulation included a water-to-solid ratio of 0.65, a calcium-to-silicon ratio of 30:65, 8% sludge content, a cement-lime ratio of 1:1, 1‰ aluminum powder, and 0.5‰ stabilizer. The aerated concrete blocks produced had a compressive strength of 4.4 MPa, dry density of 534.15 kg/m³, and met the B06A3.5 standard, with good durability and high safety. These blocks were harmless building materials, with an annual economic benefit of 59.461 million RMB. This research can not only reduce the waste disposal costs of the energy industry, but also bring significant environmental and social benefits, and provide technical support for the sustainable development of the energy industry. The possibility of using desulfurized sludge in aerated concrete was studied.The effects of sludge incorporation on AAC hydration products and pore structure werePhysico-mechanical, hydration products, environmental impact, and economic cost of AAC are examined. The possibility of using desulfurized sludge in aerated concrete was studied. The effects of sludge incorporation on AAC hydration products and pore structure were Physico-mechanical, hydration products, environmental impact, and economic cost of AAC are examined.