Research On The Mechanism Of Biomimetic Mineralized Based On Crystal Modulation

Microorganism-induced calcium carbonate production(MICP)is the use of microorganisms to induce calcium carbonate to precipitate on soil particles,so that soil particles are cemented and the soil has strength.It is widely used in calcareous sand reinforcement,foundation treatment,impermeability,etc.space.However,problems such as enzyme activity,efficiency,economic benefits,and by-products of microorganisms themselves are difficult to solve during the induction process.In view of the above problems,this paper proposes biomimetic induced calcium carbonate precipitation(CICP),which is based on inheriting the performance advantages of microorganism-induced calcium carbonate.On the other hand,the compound reaction of calcium ions and carbonate ions is regulated by crystal form regulators to form calcium carbonate adsorbed in the voids of soil particles,so that the soil particles have overall strength after cementation,which overcomes the grouting efficiency,enzyme activity,particle pore size,etc.throat,etc.This biomimetic mineralization reinforcement method forms a chelate through the pre-organization of the crystal form regulator and calcium ions,and reacts with carbonate ions to form calcium carbonate precipitates and adsorbed on the soil particles,which greatly improves the overall strength of the soil.In this paper,a method for strengthening the foundation by biomimetic mineralization is proposed.The cementing liquid is directly injected into the soil particles in batches by the gravity infiltration method to generate a certain strength.The strength and failure form of the cemented soil column are tested by the direct shear test and the unconfined compression test.,by SEM,XRD,FTIR,XPS and other methods for microscopic characterization.Boric acid as a crystal form inducer is proposed to induce calcium carbonate precipitation to strengthen the foundation,and the main research results are as follows:(1)It is proposed that after boric acid forms a chelate with calcium ions through the polar group hydroxyl(-OH),the calcium ions combine with carbonate to form calcium carbonate,and the resulting calcium carbonate is adsorbed on soil particles and has an overall When the height-diameter ratio reaches 2.4,the unconfined compressive strength of Toyoura sand reaches 4.1MPa.(2)By comparing and studying the cementation status of particles under different concentrations of cementing liquid,different boric acid concentrations and different p H values,it is proposed that boric acid,as a crystal form regulator and binder,can generate amorphous calcium carbonate with high adsorption effect,which is adsorbed on After the surface of the particles,due to the limited time for boric acid to stabilize the amorphous calcium carbonate,the amorphous calcium carbonate is converted into calcite,and the boric acid and calcium ions react with carbonate ions to form calcium carbonate precipitation after pre-organization,and the calcium carbonate forms hydrogen bonds with the particle surface.The double action of adsorption and chemical adsorption produces bonding strength.0.4mol/L boric acid-2mol/L calcium chloride and 2mol/L sodium carbonate were proposed as the best reinforcement formula.By increasing the concentration of the cementitious solution,the grouting efficiency of calcium carbonate precipitation induced by microorganisms is improved,and the water content of the sample is lower.(3)By verifying the applicability of the boric acid-induced calcium carbonate deposition method in different environments,it is proved that the boric acid-induced calcium carbonate deposition method has better performance in different particle sizes,gradation,tailings reinforcement,calcareous sand treatment,and impermeability.good effect.It is verified that the boric acid-induced calcium carbonate deposition method can overcome the problem of reduced grouting efficiency due to particle pore throats in the microbial-induced calcium carbonate method.