Study On Mechanical Properties Of Carbonized Silty Clay Modified By Sisal Fiber MgO-GGBS

As a new green,low-carbon and environmentally friendly soil reinforcement technology,activated MgO carbonization technology and alkali-activated solidification technology have been widely used in highway and water conservancy fields.China’s sisal fiber production is large,and the fiber has the characteristics of corrosion resistance and excellent mechanical properties,so it is often used for soft soil reinforcement.Supported by the National Natural Science Foundation of China(41902286),the Open Foundation of State Key Laboratory of Geotechnical Mechanics and Engineering(Z019026,SKLGME021029)and the Open Research Foundation of Yangtze River Academy of Sciences(CKWV20221015 / KY),this paper,soil low-carbon reinforcement technology and fiber reinforcement technology are combined to reinforce and improve soft soil.Through a series of physical and chemical tests,unconfined compressive tests,direct shear tests,scanning electron microscopy tests and dry-wet cycle durability tests,the effects of different sisal fiber parameters,water content,curing methods and other factors on the unconfined compressive strength,shear strength and physical and chemical properties of the improved soil are studied.The improvement effect of strength and physical and chemical properties,and the durability of the improved soil under the dry-wet alternate environment.The main research results are as follows :(1)Through the test under the influence of sisal fiber parameters,it is concluded that sisal fiber can enhance the plasticity of soil,delay the formation and development of penetrating cracks,and improve the compressive strength and shear strength of the improved soil.Under the condition that the optimum content of fiber is 4‰ and the optimum length of fiber is 10 mm,the compressive strength and shear strength of carbonized or natural cured samples are the highest.The mass change rate of natural curing samples increases with the increase of fiber content and fiber length.The mass change rate of carbonized samples increases with the increase of fiber content but has little relationship with fiber length.The increase of fiber content and fiber length has little effect on the p H value and conductivity of the improved soil.(2)Through the test under the influence of water content,it is concluded that the increase of water content can reduce the compressive strength of the improved soil,and the increase of water content has a great influence on the carbonation treatment sample.The dry density and mass volume change rate decrease with the increase of water content,while the water content increases with the increase of water content after curing.The p H value of the improved soil sample is alkaline after curing,and the p H value of the improved soil increases with the increase of water content.The p H value of the 12 h carbonation sample is similar to that of the 28 dnatural curing sample.The conductivity of the improved soil sample decreases with the increase of water content.When the water content increases from 35% to 40%,the conductivity of the improved soil sample decreases significantly,and the conductivity of the carbonized sample is greatly improved compared with that before curing,and the conductivity of the natural curing sample is slightly lower than that before curing.(3)Through the test under the influence of curing methods,it is concluded that there are significant differences in the influence of carbonization and natural curing on the physical,chemical and mechanical properties of improved soil.For the carbonized sample,the compressive strength of the sample is the highest when carbonized for 12 h,and the strength of the natural curing sample increases with the extension of the curing time.Any curing method can reduce the water content of the sample.The quality of the sample increases during the carbonization process,and the quality of the sample decreases during the natural curing process.The carbonization treatment reduces the p H value of the sample.The p H value of the sample increases first and then decreases during natural curing.The conductivity increases with the extension of carbonization time and decreases with the extension of natural curing time.After combining the two single curing methods,the influence of the second stage curing treatment on the improved soil is weakened,that is,the properties of the improved soil samples mainly come from the first stage curing treatment;the natural curing strength of the improved soil sample after carbonization will increase but the increase is limited.The carbonization of the improved soil sample after natural curing will decrease the strength.(4)Through the test under the influence of dry-wet cycle,it is concluded that the strength loss of the improved soil sample is more under the condition of dry-wet cycle,and the strength loss rate is higher than 45% at the end of the first dry-wet cycle.The strength of the sample after natural curing and carbonization decreases with the continuous increase of the number of dry-wet cycles.The compressive strength of the sample after carbonization and natural curing has no obvious change with the continuous increase of dry-wet cycle.The mass and volume of the sample decrease continuously during the cycle.The addition of fiber increases the mass loss of the sample after natural curing and reduces the mass loss of the sample after natural curing.The appearance of the carbonized sample after natural curing is good in the dry-wet cycle,and the appearance of the carbonized sample after natural curing is obvious.