Study On Macro Properties And Micro Mechanism Of Grouting Material Modified By Sodium Lignosulfonate

In order to improve the problems of poor stability,low fluidity and weak corrosion inhibition of grouting material,this paper put forward the optimal benchmark proportioning based on orthogonal test analysis,and introduced the non-uniformity coefficient to evaluate the stability.Sodium Lignosulfonate(SL)was used as the modified component of grouting material,the effects of SL on the fluidity,stability,strength and corrosion inhibition of grouting material were comprehensively evaluated by using SL instead of polycarboxylate superplasticizer(PCE)in different proportions and then with the help of macro-micro tests,the modification mechanism of SL on grouting material was revealed.Finally,using Sodium Metasilicate Pentahydrate(SMP)as a synergistic corrosion inhibitor,the mapping mechanism between macroscopic performance evolution and microstructure under the synergistic effect of SL-PCE-SMP was clarified,and then the optimal proportioning of grouting material in multi-component system under the coupling action of SL,PCE and SMP was proposed.The main research contents and conclusions were as follows:(1)The range analysis of orthogonal test showed that the W/B ratio had the greatest influence on the properties of grouting material,and the W/B ratio should be reasonably selected in engineering.The single-doped test of UEA expansion agent showed that 6%UEA made the grouting material form 0.0458%micro expansion at 28d.Combined with range analysis and expansibility test,the benchmark proportioning of slurry pressing material was determined:W/B ratio 0.28,fly ash content 10%,microspheres content 10%,PCE content 1.7%and UEA content 6%.(2)The single-doped of SL reduced the fluidity of grouting material and reduced the fluidity loss at the same time,and the slurry strength was improved.When the content of SL relative to PCE was 4%,the non-uniformity coefficient was reduced to 0.7043,and the slurry was no bleeding.The FTIR showed that SL contains sulfonate,and its adsorption rate is faster than that of carboxylic acid,but the water reduction rate is low,and it hindered the aggregation of polyoxyethylene long side chains.However,excessive content caused holes or microcracks in the slurry.SEM results showed that after SL was added,the slurry structure was wrapped by more C-S-H,the structure was more dense.SEM/EDS results showed that when the content of SL relative to PCE was 8%,the oxygen content on the surface of the steel strand was reduced to 5.9%,due to the sulfonate formed a Ca-O-S protection system on the surface of steel strand to achieve corrosion inhibition.Through the test of SL1:1,1:2 and 1:n substituting PCE,the proportioning was optimized,and four schemes were explored based on the properties of grouting material:4,6,4 and 2 parts SLS substituting 4,6,8 and 6 parts PCE respectively.(3)The single-doped test of SMP under the benchmark proportioning and the optimization test of SL-PCE-SMP multi-component system were carried out.The addition of SMP improved the fluidity of grouting material,but it was unfavorable to the strength.The SEM/EDS results showed that the content of SMP at 0.6%reduced the surface oxygen content to 3.3%.Considering the influence of SMP on the properties of the grouting material,adding 0.4%SMP into the four SL alternative schemes.The results showed that,SL made up for the poor strength of the grouting material caused by the single addition of SMP,and SMP further improved the fluidity of the press slurry in the SL-PCE-SMP multi-component system.(4)The immersion tests of steel strand in SCP solution mixed with different content SL and SMP were designed.SEM/EDS results showed that when SL-SMP were mixed,the corrosion products and oxygen content on the surface of steel strand were lower than that when only SL or SMP was mixed,and the lowest oxygen content was only 3%.The adsorption-precipitation protective film formed on the surface of steel strand by SL-SMP was more dense and stable,which enhanced the corrosion inhibition effect.The optimal proportioning of grouting material was finally determined:W/B ratio 0.28,fly ash content 10%,microspheres content 10%,UEA content 6%,SMP corrosion inhibitor content 0.4%,PCE content 1.598%,SL content 0.034%.