Mechanism And Atomic Simulation Of Lignin-based Soil Stabilizers

Expansive soil is a common problem encountered in the construction of civil engineering.It causes huge economic losses every year.The exploration of effective,economical,low-pollution,low-energy soil stabilizers is an urgent problem for the engineering community.Lignin and its derivatives are by-products of biological products.If they are not properly handled,they will lead to serious environmental problems that have not been effectively utilized in our country.Based on the method of stabilizing expansive soils of lignosulfonate derivative calcium lignosulphonate from industrial by-products,the macroscopic properties and microscopic mechanism of calcium lignosulfonate stabilizing soils were studied,and their molecular dynamics were simulated at the atomic scale.The main research contents and results are as follows:?1?The soil has a strong adsorption effect on calcium lignosulfonate,and the soil modified by calcium lignosulfonate is mainly a physical process.calcium lignosulfonate can effectively reduce the specific surface area of soil particles,fill the internal mesopores,increase the degree of soil compaction at mesoscopic angle,and reduce the microscopic defects.Lignosulphonate calcium can reduce soil plastic limit and increase soil liquid limit and plasticity index;effectively reduce the expansion of the soil,and can improve the unconfined compressive strength and water stability of soil samples,and its optimal content is 4%.?2?The calcium lignosulfonate has adsorption effect on non-expanding minerals in the soil such as kaolin,quartz,etc.For montmorillonite,the interplanar spacing decreases as the amount of calcium lignosulfonate increases.The addition of calcium lignosulfonate in single mineral montmorillonite will increase its zeta potential;adding calcium lignosulfonate to single mineral kaolinite will reduce its zeta potential,similar to the shielding effect.Adding calcium lignosulfonate in natural soil will increase the zeta potential of the soil particles,similar to that of montmorillonite.It is suggested that the hydrophilic group in calcium lignosulfonate will preferentially adsorb on the positively charged edge of the clay mineral,and secondly,it will adsorb on the particle surface to produce a shielding effect.?3?Rheology-based explanation:Calcium lignosulphonate has an effective flocculation effect when the montmorillonite particle suspension is left standing,and the optimum content of this effect is in the vicinity of 2%to 4%;A strong structure is formed under the action of shearing and the structure also has a strong ability to resist shearing.This structure is most obvious at the 2%dosage.For kaolinite,the incorporation of calcium lignosulfonate leads to a change in the structure of the kaolin particles.The flocculating effect exhibited on standing will form a stable dispersion system under shearing action.?4?SEM test shows that the addition of calcium lignosulfonate changes the fragile and brittle nature of the pure montmorillonite mineral sheet structure,strengthens the strength of the lamellar structure,and at the same time enhances the interlaminar coupling ability and reduces the internal volume of the particles.The pores.For the compacted natural soil with the incorporation of calcium lignosulfonate,the tiny pores of the compacted soil are filled and the soil aggregates become larger.?5?The interlayer spacing of Na-montmorillonite is much larger than that of Ca-montmorillonite and K-montmorillonite,and it has the strongest swelling property.Ca-montmorillonite has the lowest interlayer spacing and the lowest expansion.The K⁺and Na⁺ions between the montmorillonite layers have a higher degree of hydration and greater interlayer spacing than Ca²⁺under the the same amount of water molecules.The diffusion capacity of Na⁺between the montmorillonite layer is the highest,while the diffusion capacity of Ca²⁺and K⁺is relatively low,and the Ca²⁺has the most stable.For the interaction between cations and water molecules,the arrangement of Na⁺,Ca²⁺and water molecules between the montmorillonite layers is more compact and has greater hydration energy.The hydration energy of K⁺is relatively low.?6?Lignosulphonate groups have a strong adsorption effect on the surface of montmorillonite,and the adsorption energy is nearly 20 times that of water molecules because of the strong interaction between the sulphonate group?-SO₃^-?and the surface of montmorillonite.The presence of lignin sulfonic acid groups is relatively stable,and the ability to move and diffuse is poor.