Improving Hydro-mechanical Performance Of Lime Treated Laterite With Metakaolin

Laterite is usually classified as "problem soil" due to its many bad properties.Lime and cement are added to treat the laterite so that its hydro-mechanical performance can meet the application standards in engineering.The research shows that laterite has better compaction performance after adding lime.However,the lime and laterite will undergo a slow mutual loss reaction under a long service period,which will induce structural damage of laterite and led to frequent engineering disasters.Therefore,it's of great engineering significance to improve the long-term hrdro-mechanical performance of lime treated laterite.Metakaolin is a kind of amorphous material with high pozzolanic activity.It can react with lime rapidly,generate a large number of cements,and fill the pores of laterite to a certain extent.Therefore,metakaolin selected to enhance the the hydro-mechanical performance of lime to improve laterite.The following research are mainly carried out:(1)The effect and mechanism of the shrinkage of laterite improved with lime and metakaolin was studied.(2)The mechanism of the water sensitivity of laterite treated with lime and metakaolin was studied.(3)The temperature effect of the hydro-mechanical performance of laterite modified with metakaolin and lime was studied.The main conclusions are as follows:1)The shrinkage of laterite can be reduced by 50% by using lime,and the linear shrinkage of laterite can be reduced by 87.5% by using lime and metakaolin.The direct shear strength indicates that the shrinkage of laterite results in internal derivative micro-cracks which cause structural damage,and then leads to the loss of bearing capacity and shear resistance of laterite,although adding lime,the strength of laterite can be improved,the degree of increase is limited and cracks will still occur during the dehumidification.The synergism of metakaolin and lime can ensure that the pore structure almost unchanged during dehumidification,effectively prevent the derivation and development of micro-cracks,and better restrain the shrinkage behavior of laterite.2)Within a certain water content,metakaolin can promote the water sensitivity of limemodified laterite,which can make the laterite have better hydro-mechanical performance under over-humidity.The reason is that metakaolin can quickly capture the calcium ions in the pore water solution and provide a large amount of amorphous silicon aluminum oxide.volcanic ash reacts tapidly with lime,forming a large number of hydrating cementing materials,filling or bonding between laterite particles(aggragates),effectively modified the water sensitivity of laterite.3)Low temperature curing obviously slows down a series of reactions within the laterite treated,which is not conductive to the development of pore structure stability in the laterite,thus counteracting the improvement of hydro-mechanical performance of the laterite by lime and / or metakaolin.w With the increase of curing temperature,the curing intensity of 28 days can be the same as that of 180 days under room temperature,and the results of pore distribution also show that raising the curing temperature can accelerate the development of pore structure in laterite to be more stable,which further refines the pore in laterite and further reduces the total pore volume.