Study On Mechanical Properties Of Geopolymer Reinforced Soil

Geopolymer is the product of polymerization reaction of aluminum silicate-rich material and alkali catalyst.Compared with traditional Portland cement,it does not require the use of fossil fuels for raw material calcination,which can significantly reduce greenhouse gas emissions and energy consumption.Geopolymers have a good potential to replace conventional cement in problems such as foundation reinforcement.In this paper,the use of sodium silicate activated slag powder to prepare geopolymer,study the mechanical properties of the polymer reinforcement soil,analyze the effect of geopolymer reinforcement soil and its influencing factors,the main research content and conclusions are as follows:(1)The effects of alkali equivalent(Na2O/slag powder),ore powder dosage(slag powder/clay quality)and water-cement ratio of geopolymer on unconfined compressive strength of geopolymer soil were studied by orthogonal test.The results show that the influence of alkali equivalent on unconfined compressive strength is the greatest,followed by the water-cement ratio of geopolymer,and the influence of the dosage of ore powder is the least.(2)A parameter sensitivity test was conducted on the alkali equivalent of the main influencing factors,and a critical value was found between 0.08 and 0.12.When the alkali equivalent is less than this value,the unconfined compressive strength increases less than that of unreinforced soil sample.When the alkali equivalent exceeds the critical value,the strength increases obviously.At the age of 28 days and the alkali equivalent of 0.16 and 0.2,the unconfined compressive strength of geopolymer soil is 2572.01kPa and 3520.97kPa,respectively.It indicates that geopolymer soil strength can reach or exceed the strength of conventional cement soil.Based on the test results,a formula for predicting unconfined compressive strength of geopolymer soil is proposed.(3)Consolidation tests show that adding geopolymer into soil can effectively improve the compression modulus and reduce the compression deformation.At the age of 28 days,the compressive modulus between 100kPa and 200kPa is 2.13,10.92,13.3 and 13.2 times that of plain soil when the alkali equivalent is 0.08,0.12,0.16 and 0.2,respectively.The compressive modulus of geopolymer soil increases with the increase of age.When the alkali equivalent is high,the samples have better compressive properties in the early stage.(4)Triaxial test shows that the shear strength of geopolymer soil increases with the increase of alkali equivalent.When the alkali equivalent is lower(less than 0.08),geopolymer soil is strain hardened.When the equivalent is higher(?0.12),the sample shows the characteristics of brittle failure.When the alkali equivalents were 0.08,0.12,0.16 and 0.2,the cohesive forces of soil samples were 70,208.5,522.6 and 566.1kPa,and the friction angles were 13.7°,33.4°,30.9° and 31.9°,respectively.The increase of strength was mainly reflected by the increase of cohesive forces.(5)Microscopic test results showed that c-S-H and C-A-S-H gels were generated from slag powder excited by sodium silicate alkali.Gel can enhance the cohesion between soil particles and fill the gap between soil particles,thus improving soil properties.