Experimental Study On The Effect Of Nucleating Agent On The Improvement Of Carbonate Soil By CFPK

Carbonate soil has adverse engineering characteristics such as dispersion when encountering water,and drying hard after losing water.Calcium Bicarbonate From Pseudo-Karstification（CFPK for short）is a new type of soil conditioner that is environmentally friendly and can be recycled and reused.It has achieved certain results in improving disperse soil and expansive soil.However,there are problems such as low solubility of calcium bicarbonate,slow decomposition rate,and incomplete decomposition of calcium bicarbonate,resulting in an unsatisfactory modification effect.This study takes carbonate soil as the research object,and pre mixes calcium carbonate into the soil as the nucleation agent for CFPK reaction.Through physical,chemical,mechanical,microstructure and other test methods,the influence of calcium carbonate nucleating agent on the decomposition of CFPK is analyzed,and the morphological characteristics of calcium carbonate generated by CFPK decomposition are clarified.To study the improvement effect of calcium carbonate nucleating agent-CFPK in improving carbonate soil,providing technical support for the improvement of carbonate saline soil.The research conclusions are as follows.（1）The conductivity,soluble salt content,Ca²⁺,Na⁺concentration and p H of the soil after CFPK improved carbonate soil increased,and the unconfined compressive strength and shear strength increased slightly.However,the resistance to wetting and disintegration of the soil is reduced.Therefore,the improvement of carbonate soil with CFPK alone did not achieve a good improvement effect.（2）After calcium carbonate nucleating agent improves carbonate soil,the soil conductivity,soluble salt content,Ca²⁺,Na⁺concentration and p H are slightly reduced,and the unconfined compressive strength and shear strength are slightly improved.The wet disintegration resistance of the body is almost unchanged.Not achieving the ideal improvement effect.（3）Calcium carbonate nucleating agent has the effect of accelerating the decomposition of CFPK,inducing the decomposition of CFPK to generate calcium carbonate positions and forms,achieving the goal of generating more calcium carbonate inside the soil and improving the solidification effect.At the same time,it also has an adsorption effect on the salt content in the soil and a filling effect on the internal pores of the soil.（4）The conductivity,soluble salt content,Ca²⁺,Na⁺concentration and p H of the soil were reduced after the combination of calcium carbonate nucleating agent and CFPK improved carbonate soil.Unconfined compressive strength,shear strength,and resistance to wet disintegration are significantly improved.Calcium carbonate nucleating agent and CFPK complement each other,achieving good improvement effects.The mechanism of its action is that calcium carbonate crystal nucleating agent plays a role in adsorbing salt and filling the internal pores of the soil,while CFPK mainly plays a role in consolidating the soil.Therefore,it not only effectively adsorbs salt in the soil,but also has a consolidation effect on the soil.（5）Low or high dosage of calcium carbonate nucleation agent can affect the effectiveness of soil improvement.If the dosage is too low,it cannot completely fill the pores between soil particles,and the effect of promoting the decomposition of CFPK is not strong.Excessive addition of calcium carbonate nucleating agent can form calcium carbonate interlayer between soil particles,disrupting the interaction between soil particles.Based on the experimental results,it is believed that the optimal dosage of calcium carbonate nucleation agent in the combined improvement of carbonate soil by carbonate nucleating agent-CFPK is 5%.