Study On The Compressive Strength And Micro-mechanism Of New Limestone Soil

With the development of the times,the demand on materials in civil engineering is getting higher and higher,the slow development of strength and low strength limit the application of lime soil.But lime soil is a relatively economical and environmental engineering materials that it has the advantages of easy to obtain,easy to construct,and low cost,so it is still applied in many projects,like roadbed,dam,and foundation.Therefore,it is a meaningful study to find an effective and feasible new method to improve the compressive strength of lime soil.In this paper,lime soil was used to contrast with a new soil called limestone soil that obtained from original lime soil which lime was replaced with limestone.DAP(diammonium phosphate)was used as the additive,and then,two types of soil were treated with DAP in different contents of 1%,2%,4%and 8%respectively.The compressive strength of each group was obtained,and the micro-structure was observed by SEM and XRD experiments.Then,the reinforcement effect of the treatment method on soil and its reinforcement mechanism could be found.The results showed that:1)Replacing lime with limestone,the compressive strength of soil decreased by 17.46%at 7th day,and the strength was basically no development.The compressive strength at 108th day was 68.64%lower than that of lime soil.2)In limestone soil,when the content of DAP up to 2%,the compressive strength of the soil increases with the amount of DAP,and 8%DAP addition is the best in the experiment,which makes the compressive strength of the limestone soil at 7th day,28th day,56th day and 108th day increased by 298.07%,417.64%,469.81%and 494.34%respectively.3)In limestone soil,the best addition amount of DAP is 2%,which can increase the compressive strength at 7th day and 108th day of the lime soil by 73.02%and 13.61%respectively.Not only the early strength develops rapidly,the late strength is still increasing slowly;4)When the amount of DAP added to limestone soil increases to 4%,the compressive strength of the early period and late period was greater than that of lime soil with 2%DAP added.5)limestone soil with DAP added,relying on the reaction between CaC03 and DAP to produce gel materials which would improve the strength of soil by cement soil particles.In summary,replacing lime in lime soil with limestone and adding DAP no less than 4%is a new method to improve the compressive strength of soil.This method can not only improve the soil strength,but also reduce the use of lime in project to reduce the energy consumption and air pollution in process of producing lime,which would achieve the purpose of energy conservation and environment protection.