Experimental Study On The Production Of Water Permeable Brick Using Waterworks Sludge

With the process of urbanization, a lager area of the land covered with vegetationhas been changed into cement and concrete roads. There are more and more air-proofconcrete roads, while rainwater can hardly infiltrate to underground due to low waterpermeability, which also results in the phenomenon of hot land in city, declining ofgroundwater level and cross-flow in heavy rains.Water permeable bricks as one of new floor tiles with high permeability andstrong strength match the requirement of the time. Water permeable bricks can inhibitthe phenomenon of hot land in city effectively, and alleviate the shortage ofgroundwater and improve the phenomenon of cross-flow in heavy rains due to theirgood water permeability, water retention, air permeability and high porosity.At the same time, with the pollution of raw water, there are more and morewaterworks sludge produced in water plants, the dispose of waterworks sludge becomeanother puzzle following the dispose problem of sewage treatment. It is workable touse waterworks sludge as raw material since the composition in sludge is similar toclay. Particular contents and results in this paper were summarized as follows:(1) Physical and chemical properties analysis of raw materials: The chemicalcomposition of waterworks sludge and fly ash were analyzed by plasma emissionspectrometry, it turned out that their chemical compositions are similar to clay.Through SEM analysis, we know that both waterworks sludge and fly ash have porousstructure, which would help improve poriness of water permeable bricks.(2) Orthogonal test: Raw material ratio, sintering temperature and moldingpressure are proved out to be the most three important factors of effecting on the keycharacteristics of water permeable bricks through orthogonal test.(3) Ways of making porous: Three methods including adding foaming agents,pore-forming agents and accumulation of aggregates into holes were studied in order toimprove the permeability coefficient. As a result, the third method is proved to be thebest way.(4) Single factor influence test: The compressive strength and water permeabilityof water permeable bricks were antinomies relation. With the increasing ratio of sludge,the compressive strength of water permeable bricks decrease, while the waterpermeability increase. In a certain range, The compressive strength rises along with theincreasing of sintering temperature, while the water permeability rises first and declines later. However, when the temperature reaches to 1200℃, the brick structurewas distorted badly. The compressive strength rises obviously as the molding pressurechanging from 20 to 30 MPa, and rise slightly when the value is above 30 MPa. On thecontrary, the water permeability declines obviously as the molding pressure changingfrom 20 to 30 MPa, and drops slightly above 30MPa.