Study On The Maintenance And Durability Of Microbial Cemented Samples

As a cross-disciplinary technology,compared with the traditional physical and chemical soil reinforcement technology,microbial induced calcium carbonate deposition(MICP)has the characteristics of energy saving and environmental friendliness.From the existing literature,in the academic field of improving the reinforcement effect of MICP,many scholars at home and abroad are mostly focused on studying the variables in the cementing process such as strains,cementing fluid,etc.,and the subsequent processing of cementing shaped samples lacks systematic In comparison and experimentation,most scholars did not mention the concept of conservation in the experimental link of MICP-related research.Even if some scholars carried out corresponding curing treatments on the samples before performing various index tests,these curing treatment methods are not uniform,and the specific relationship between the curing treatment and the reinforcement effect of the samples is still unclear.In this paper,the marine dredger silt on the eastern coast of Jiangsu was selected as the test soil,and Bacillus pasteurus was used as the sample strain.The microbial induced calcium carbonate deposition technology was used to consolidate the silty into microbial cement samples.Using the cemented sample as the sample material,the effect of room temperature curing and oven curing on its reinforcement effect was studied.Starting from the actual engineering application,the stability of the cemented samples was tested,and the durability of the wet and dry cycles and freeze-thaw cycles was studied.The main conclusions are as follows:(1)The unconfined compressive strength of cemented specimens gradually increases with curing time during curing at room temperature and curing in a low-temperature oven,and remains constant until the peak strength is reached.(2)Both room temperature curing and oven curing can improve the strength of the sample,but the difference in curing method will not make the final strength of the cemented sample different.When the oven is set at a high temperature,the oven curing rate increases the strength of the sample faster than room temperature curing.When the temperature is the same,the oven curing rate increases the sample strength more slowly than the room temperature curing.(3)During the curing at room temperature and in the curing of the oven,the main reason for the change in the strength of the cemented specimen is the change in the moisture content of the specimen.As the water content of the sample decreases,the strength of the sample increases.When it reaches a completely dry state,the sample reaches the peak intensity.Conversely,when it is saturated,the sample has the lowest intensity.(4)The strength of the cemented specimens exhibits a similar pattern during the immersion and dry-wet cycle:as the immersion time gradually decreases,it tends to be constant after reaching the minimum value.However,the strength of the dry-wet cycle sample is higher than that of the immersed sample.Considering that the actual immersion time of the former is less than the latter,it is speculated that the dry-wet cycle itself has a limited impact on the strength of the cemented sample and the sample strength is affected by the dry and wet process.The main reason for the weakening may be only the soaking process rather than the cycle itself.(5)The temperature change has no effect on the strength of the dried sample.During the freeze-thaw cycle,most of the strength loss of the sample occurs during the first freeze-thaw cycle.(6)The research on the effect of room temperature curing and oven curing on the reinforcement effect of the sample is convenient for the scholars in the MICP field to make reference before measuring the strength and other effects to unify the state of the sample.The influence of the dry-wet cycle and freeze-thaw cycle on the reinforcement effect of the sample shows that in actual engineering,the effect of the cycle on the reinforcement effect of the foundation soil reinforced by the MICP technology is minimal.