Preparation And Properties Of Permeable Foamed Concrete

The foamed concrete has the characteristics of multihole,convenience of pouring,high surface smoothness and cost-effective.It can be widely used in the base structure of the water permeable road in the sponge city if prepared as a material with certain permeability and water purification.The preparation and the experimental as well as theoretical research on permeable foamed concrete about physical and mechanical properties were carried out in order to lay the foundation for the engineering practice.(1)The effects of water binder ratio,water reducing agent,fly ash and fine sand on water permeability and mechanical properties of permeable foamed concrete were studied through experiments.The change of pore structure and its influence mechanism were analyzed.The results showed that the permeability coefficient of foamed concrete increases with the water binder ratio in the range of 0.20~0.36.In a certain range,the permeability coefficient of foamed concrete increased and the strength decreased with the amount of water reducing agent and fine sand increased.The fly ash had a "repair" effect on its pore structure,which will reduce the permeability coefficient.In the orthogonal test,the permeability coefficient of material reached to 1.79mm/s and the compressive strength of 28 d reached 2.5~3.5MPa maximally.The best mixture ratio was obtained through the efficiency coefficient method,and the material performance can meet the general permeable sidewalk requirement.(2)The foam properties and structural characteristics of the permeable foamed concrete were analyzed,and the formation mechanism of the connected pores was discussed.The results showed that the properties of the material and the foam will affected the formation of the connected pores.The distribution characteristics of vertical porosity of permeable foamed concrete were analyzed through industrial CT scanning and digital image processing.The results showed that the pore structure was more uniform in a certain thickness range,and the distribution of the pores was different with diverse composition materials.Based on the experimental data and the seepage model of porous materials,a permeability coefficient calculation model of porous cement foam concrete was established with a correlation coefficient of 0.9364.(3)The influence of different thickness,pore structure and influent concentration on water purification function of porous cement foam concrete was analyzed through experiments.The results showed that the removal rate of pollutants increased with the increase of the thickness of foamed concrete,but the passage time of the water sample will become longer.The influence of the connected porosity on the purification effect was obviously,because the great connected porosity will increased its contact area with the pollutants and the better the adsorption.The high pollutant concentration will aroused lower removal rate cause the limited purification ability of the water permeable cement foamed concrete.