Investigation On The High-efficiency Stabilizer For Saturated Soft Clay And Strength Characteristics Of Stabilized Clay

To solve the problems of the soft clay with characteristics of high water content,low strength,high compressibility and poor effectiveness of conventional cementing materials,different types of admixtures were selected and a Portland cement-based high-efficiency soil stabilizer was developed by single factor and orthogonal testing analysis.The influence of the addition of soil stabilizer and fly ash on the fundamental parameters of soft clay was investigated and the parameters were normalized.And then,the integratedstrength-calculation models accounting for the quantitative analysisof the effects of soil stabilizer and fly ash were established.The mechanical properties of soft clay with different contents of organic matter stabilized with high-efficiency soil stabilizer and fly ash were tested and the unti-pozzolanic effect and factors were proposed.And the unti-pozzolanic factors were calculated by water-soil-stabilizer models.According to the experimental results,theintegrated strength-calculation models for stabilized organic clay accounting for fundamental parameters were established.Based on the above study,the following innovationproducts can be achieved.?1?A type of Portland cement-based high-efficiency soil stabilizer was developed and the mechanisms of the stabilizer were studied on Shanghai soft clay.On the basis of the theory of improving the pH value of the soil,increasing the early term strength and middle-long term pozzolanic effect,sodium silicate,calcium chloride and sodium hydroxide were selected to stabilize the soft clay snd silt by chemical precipitation.The composite promoter was prepared by calcium chloride and sodium hydroxide at the mass ratio of 1:1.The final formula of the stabilizer?CSCN?was confirmed by orthogonal experiment and the mass ratio of the Portland cement,sodium silicate and composite promoter is 5:1:2.Theexperimental results indicate that the compressive strength of the specimens stabilized with 12%CSCN at different curing ages almost equaled to that of specimens stabilized with20%cement.The mineral and microstructure characterization indicate that there were more cellular hydrated calcium silicate?C-S-H?gels produced in the CSCN stabilized specimen.This observation implied that the strength and structure of the stabilized soil might be influenced by the amounts,structures and types of C-S-H gels.?2?The pozzolanic factors were proposed and the the effects of admixtures on stabilized clay were quantificationally analyzed.Based on the definition of the pozzolanic materials,the admixtures in the stabilized clay can be regarded as pozzolanic materials.Hence,the use of the admixtures was assumed as the addition of a certain amount of cement.And the euqalivent cement of the admixtures could be calculated by the product of the pozzolanic factors and the content of the admixtures.According to the water-soil-cement models,the values of the pozzolanic factors of admixtures?k1,k2?could be obtained by multiple linearregression.In addition,the values of pozzolanic factors varied with curing time,and the k1 values of the assistant agent decreased with curing time and the k2 values of the composite promoter increased with curing time.The possible reason for this phenomenon was that the assistant agent plays a role of early strength agent and the long-strength pozzolanic effect of composite promoter was more remarkable.?3?The mechanisms of fly ash in stabilized clay were investigated,andthe pozzolanic and dispersing?P&D?effects were proposed.The application of fly ash in stabilized clay had several effects,such as pozzolanic and filling effects.In fact,the C-S-H gels could bond amounts of soil particles and some big gel-soil clusters were formed.Hence,the dispersing effect can be explained that the big cluters were dispersed into some small cluters by fly ash particles.Therefore,the effects of the fly ash in stabilized clay could be influenced by the amounts of the generation of the C-S-H gels.Fly ash is a type of pozzolanic material,and it can also be regarded as the addition of a certain amount of CSCN in the stabilized caly.The equivalent CSCN of fly ash can be achieved by the product of the P&D factors and fly ash content.The values of k_F were determined by the CSCN content and the curing time.The analysis results indicate that the P&D factors presented an increasing tendendy with curing time.It's notable that the increasing rate decreased with curing time.?4?The influence of organic matter?humic acid?in soft clay on the compressive strength of stabilized clay was analyzed quantitatively and the integrated strength-calculation models for CSCN-fly ash stabilized organic clay on the basis of fundamental parameters were obtained.Based on the calcution of the unti-pozzolanic factor of humic acid,the total cement content(C_fh)and effective stabilizer content(C_ec)were defined.The void ratio(e_tH)of stabilized organic soil at different curing times can be expressed by the fundamental parameters of the soft clay,C_ec and curing time.Based upon the above results,these fundamental parameters were normalized by defining some variables.The relationship of compressive strength to e_tH/C_fh was analyzed,and theintegrated models for calculating the strength of stabilized organic clay were established.In addition,the compressive strength of Lianjiang silt stabilized with CSCN and fly ash at different curing ages was measured.The testing results were compared with the predicted values calculated by the integrated strength-calculation models.It can be concluded that the strength-calculation models achieved from Shanghai soft clay is also suitable for silt.