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The shortage of land resources around the world has led to the increasing pressure of clay brick production in recent years. On the other side, as a by-product of the sewage treatment, the mineral crystalline phase and chemical composition of municipal sewage sludge (MSS) are similar to those of clay, which also need to be treated urgently. Owing to the porous structure originating from large amounts of organics evaporation at elevated temperature in MSS, it can be utilized as the thermal insulation bricks. However, the component complexity of MSS will result in the decrease of strength and durability of bricks, thus the replacement amount of MSS was generally less than 30%. To achieve optimal experimental conditions for thermal insulation bricks with large amounts of MSS, up to 40% dried MSS, amorphous rice husk ash (RHA) and anhydrous Na 2 CO 3 (ANC) as the raw materials in this work, the dosage and temperature were set as variable parameters. The results showed that 0.178 W/(m•K) of thermal conductivity of bricks with 9.6 MPa of compressive strength, and 1336.2 kg/m3 of bulk density were obtained under the optimal conditions: 4: 5: 1 of the weight ratio of MSS: Clay: RHA, 3% of additional dose of ANC, 1075 °C of sintering temperature. The obtained bricks revealed excellent durability and sorption properties for heavy metals through the freeze-thaw cycle test and leachability test. Overall results manifested one effective approach for solid waste treatment through cleaner production and paved one way for sustainable, economical and energy-saving construction. [ABSTRACT FROM AUTHOR]

• Nano-pores introduced by silica fume affected thermal conductivity and strength. • Effects of amorphous phase on thermal conductivity of bricks were analyzed. • Effects of pore structure and continuous dense phase were quantified. • Thermal insulation properties and strength performance were enhanced simultaneously. As the inevitable by-product of sewage treatment, millions of tons of municipal sewage sludge (MSS) are increasingly stockpiled every year around the globe, creating enormous pressure on the environment and society. The preparation of porous insulation bricks based on MSS is put forward to realize environment protection and waste reclamation. However, the excessive amount of MSS will lead to the deterioration of strength and durability in the bricks. In this paper, the pore structure and crystalline phase of bricks were adjusted by the introduction of the ultra-fine amorphous phase, to improve the thermal insulation performance as well as the compressive strength. The thermal conductivity of the bricks could reach the lowest value of 0.194 W/(m·K) with the compressive strength of 10.2 MPa. Under the requirement of the mechanical strength, adding 3% of borax into bricks can increase the compressive strength to 18.8 MPa. The effects of the continuous dense phase and pore structure on thermal conductivity and compressive strength of bricks were investigated in reference to Bauer and Gibson model, respectively. The results provide a development direction for the preparation of thermal insulation bricks with high content MSS and alleviating the pressure of the shortage of clay. [ABSTRACT FROM AUTHOR]