Study On Water Absorption Characteristics Of Air-foam Treated Lightweight Soil

As a new type of geotechnical material,the air-foam treated lightweight soil has the advantages of lightness,adjustable strength and weight,good fluidity and self-reliance.It is widely used in soft foundation treatment,road widening,abutment backfilling and underground hollow backfilling engineering.When the air-foam treated lightweight soil is below the groundwater level,part of its pores will be filled with water over time,causing it to lose its lightweight properties,thereby threatening the safety of the project.Therefore,it is necessary to carry out researches on water absorption of the air-foam treated lightweight soil.In this paper,sand and clay are used as original soils.The water absorption of the air-foam treated lightweight soil and measures to reduce water absorption were studied through experiments.The main work and results are as follows:(1)The water absorption experiments of the air-foam treated lightweight soil were conducted.The effects of the type of original soil,density,water-cement ratio and environment on the water absorption of lightweight soil were analyzed.As the results shown: The volumetric water absorption increases with the increase of the immersion time,but the rate of increase gradually decreases.When the immersion time reaches 60 days,the volumetric water absorption of the air-foam treated lightweight soil tends to be stable.After immersion for 180 days,the volumetric water absorption of lightweight soil can reach 40% ～ 70%.As for the volumetric water absorption of the air-foam treated lightweight soil,the volumetric water absorption of lightweight soil with original soil as clay is lower than the lightweight soil whose original soil is sand;the greater the density of the lightweight soil,the lower the water absorption;the lightweight soil has a lower water absorption under the condition of a suitable water-cement ratio.Compared with the lightweight soil immersed in water,the water absorption of the air-foam treated lightweight soil in saturated clay or saturated sand is significantly reduced,especially when it is in saturated clay,the volumetric water absorption of the air-foam treated lightweight soil is only about half that of immersed in water.(2)An exploratory experiment to reduce the water absorption of lightweight soil was conducted,and the effects of the water repellent,water reducer,early strength agents,mineral admixtures,and the application of microbial mineralization technology on reducing the water absorption of the air-foam treated lightweight soil were analyzed,the results show that the immersion method using microbial mineralization technology is the best,when the immersion time reaches 87 days,which can reduce the volume water absorption of lightweight soil by 7%～ 12%;the second is to replace 10% cement with an equal amount of fly ash,which can reduce the volumetric water absorption of lightweight soil by 4.7%,but it is not appropriate to continue to increase the amount of fly ash,otherwise the water absorption will increase;the addition of water reducer and silica fume has no obvious effect on reducing water absorption of lightweight soil,and may even has a negative effect.Considering the economics and convenience of engineering application,it is recommended to use fly ash or water repellent to reduce the water absorption of the air-foam treated lightweight soil.