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The introduction of dyeing sludge in the fired brick production is an economic and practical disposal approach. Wet dyeing sludge with high moisture usually produces block mass during mixing process of raw materials, not only reduces the production efficiency but negatively impacted products engineering properties. This study proposed a highly efficient method, wet sludge firstly being pelleted and then introduced in the production of fired bricks, to reduce the negative impacts on mixing process and the products quality. It was proved that the introduction of dyeing sludge pellets remarkably improved physical and mechanical properties of fired bricks. Especially, water absorption declined by 12% and compressive strength increased by 35% comparing with dyeing sludge without pelleting. The engineering properties of fired bricks containing 25 wt% sludge pellets are similar with that containing 15 wt% sludge without pelleting. The decrease in water absorption and porosity is mainly attributed to the reduction in number and volume of pores with diameter below 100 nm. It was considered that pellets with greater density and higher strength might play a role as aggregate to improve compressive strength. However, the introduction of sludge pellets with particle size over 8 mm is adverse to improving properties of products, because a large amount of macropore with diameter over 100 μm is produced, and destroys the homogeneous and compact structure of products. The optimal sludge pellet size is in the range of 2–6 mm based on products performance. The leaching toxicity of heavy metals from products is far lower than regulatory limitation. This study provides an advanced method to promote the disposal efficiency of solid waste and improve the engineering quality of products. • The introduction amount of dyeing sludge is promoted remarkably. • Physical and mechanical properties are improved significantly. • The optimal particle size of sludge pellets is 2–6 mm. • Pore volume below 100 nm in fired brick are reduced. [ABSTRACT FROM AUTHOR]

• A novel and high efficient approach to disposal of dyeing sludge is proposed. • Physical and mechanical properties are improved significantly. • The optimal particle size of sludge pellets is 2–6 mm. • The number and volume of pores below 100 nm are reduced due to pellets. The introduction of dyeing sludge in the production of fired brick is an economic and practical disposal approach. However, wet dyeing sludge is easy to form block mass during the mixing process of raw materials due to the high moisture content, which affected the production efficiency and destroyed the homogeneous structure of the fired brick, posing a negative impact on the engineering performance of the fired brick. In this study, wet sludge firstly is firstly pelleted and then introduced in the production of fired bricks to reduce the negative impacts on mixing process and the products quality. The results showed that the introduction of dyeing sludge pellets significantly improved the physical and mechanical properties of fired bricks. Compared with bricks incorporating dyeing sludge, water absorption is reduced by 24 % and compressive strength is increased by 101.6 %. The physical and mechanical properties of fired bricks incorporating 30 wt% of pelleting sludge are similar with bricks incorporating 20 wt% dyeing sludge without pelleting. The reduction in water absorption and porosity compared to that incorporating sludge without pelleting was mainly due to the reduction in the number and volume of pores of the same size. However, the introduction of more than 30 wt% dyeing sludge pellets is not conducive to improving the performance of the product, because a large number of macropores with size larger than 100 μm will be generated, which destroys the uniform and dense structure of the product. To ensure product quality meet the standard, the maximum dosage of dyeing sludge with pelleting is controlled below 30 wt%. This study provides an advanced method to improve the treatment efficiency of solid waste and the quality of products. [ABSTRACT FROM AUTHOR]