Study On Water Absorption And Water Loss Characteristics Of Soil Consolidated By Sticky Rice-Lime Composites For Earthen Site

As the important cultural heritage of the Chinese nation,earthen sites are the crystallization of the diligence and wisdom of the ancients.They are the precious cultural resources of our country and have important historical,cultural,artistic,social and scientific values.Earthen sites exist in a complex natural environment for a long time,and have been affected by various natural forces.Therefore,it is urgent to protect these earthen sites which are being destroyed.In the protection of earthen sites,protective materials play an important role and affect the development and implementation of related protection technologies.As a traditional building material in our country,the sticky rice lime mortar,which was widely used in traditional Chinese architecture,is a special organic-inorganic cementitious material invented by ancient people.The development of erosions in earthen sites is often closely related to the effect of water.The storage and transmission of water in solidified soil has a profound impact on its durability.Therefore,it is of great significance to understand the interaction mode between solidified soil and water for the scientific use of protective materials.In this paper,based on the study of water absorption and water loss characteristics of soil consolidated by sticky rice-lime composites materials,the basic physical and mechanical properties of the solidified soil were studied by the limit moisture content,drying shrinkage performance,color difference,surface hardness and unconfined compressive strength;the hygric properties of solidified soil were studied by water vapor permeability test,equilibrium moisture absorption and desorption test,capillary water absorption test and saturated water absorption test;the micro substance structure characteristics of solidified soil were studied by pH test,conductivity test,X-ray diffraction（XRD）test,Fourier transform infrared spectroscopy（FTIR）test,scanning electron microscopy（SEM）test,mercury intrusion porosimetry（MIP）test and thermogravimetric analysis（TG）test,and the internal relationship between microstructure characteristics and macro physical properties was explored.The main conclusions are as follows:（1）Sticky rice and lime have a significant effect on the limit moisture content,drying shrinkage performance and color difference of soil.The liquid limit and plastic limit increase with the increase sticky rice content and lime content,and the plasticity index is controlled by sticky rice and lime.The shrinking process of samples is consistent with its drying process.The sticky rice increases the volume shrinkage rate,while the lime reduces the volume shrinkage rate.The effect of sticky rice and lime on the color space values is opposite,and the combined use of them could weaken the effect of color difference caused by each other to a certain extent.（2）Lime can effectively improve the mechanical properties of samples,but the effect of sticky rice on mechanical properties is controlled by lime content.Appropriate amount of sticky rice improves the surface hardness and unconfined compressive strength when the lime content is less than 9%,but sticky rice acts as a retarder in a short time and is not conducive to the development of mechanical properties when the lime content is too high.（3）Sticky rice and lime affect the transfer and storage process of water vapor in soil.The water vapor permeability coefficient shows a downward trend with the increase of sticky rice content and lime content.The equilibrium moisture content of solidified soil is controlled by equilibrium path,relative humidity,sticky rice content and lime content;the Guggenheim-Andersen-de Boer（GAB）model has a high applicability in soil solidified by sticky rice and lime;sticky rice and lime change the single layer adsorption energy constant C₀ of the GAB model,which has a great influence on the surface properties of the pore walls;there is an obvious hysteresis effect between adsorption and desorption,and lime strengthens the hysteresis effect of solidified soil.（4）Sticky rice and lime affect the interaction between liquid water and soil.Sticky rice accelerates the capillary water absorption rate of samples solidified by lime,increases the capillary water absorption capacity of samples,and lead to the surface cracking of samples in the process of water absorption;lime can not only effectively prevent the rising process of capillary water,but also inhibit the cracking phenomenon caused by sticky rice in the process of water absorption.The saturated water absorption rate of solidified soil increases with the increase of sticky rice content,and decreases with the increase of lime content.（5）The macro reinforcement effect and hygric properties of solidified soil are the comprehensive performance of its micro substance structure characteristics.The carbonation reaction of lime reduces the pore size and porosity of the soil,and increases the fractal dimension of pore surface.The binding effect of sticky rice leads to the formation of a complex flocculent network structure in the soil,which enhances the integrity of the soil and leads to a decrease in pore connectivity.Appropriate amount of sticky rice makes the pore size of lime solidified soil smaller,while too much sticky rice inhibits the lime reaction and causes the pore size of the lime solidified soil to increase.The effect of sticky rice on the lime reaction process is regulated by the lime content.Sticky rice has no obvious effect on the calcium carbonate content when the lime content is 6%,while sticky rice has a retarding effect on the carbonation reaction and leads to a decrease of calcium carbonate content when the lime content reaches12%.（6）Through the comprehensive evaluation of the macro reinforcement effect,water absorption and water loss characteristics and micro substance structure characteristics of solidified soil,the lime content of 6%and the sticky rice of 0.5%is considered as the optimal proportion.