Study On Properties Of Silica Sol Modified Superfine Cement Grouting Material

This research is based on the project “The basic study on the application of fissure sealing materials in the deep geological disposal repository ”.The superfine cement grouting material used to close the rock mass of the natural barrier between rock mass and 100 um width is mainly studied in the deep geological disposal project,At the same time,the superfine cement grouting material needs high flow state,high durability,excellent expansibility and low pH properties.The laboratory pulverizing the ordinary portland cement for two times and the ultrafine Portland cement was prepared by adding different kinds of grinding aids and micro abrasive medium.The pH of the grouting material is regulated by the nano silica sol and the relationship between rheological properties,mechanical properties and volume stability of grouting material and water and cement ratio,mineral admixture,nano silica sol,superplasticizer and expansive agent is studied.Meanwhile,the grouting ability of grouting material is simulated indoor.The optimal dosage of various control materials is explored to get the best proportion of each amount,so as to prepare the silica sol modified superfine cement grouting material for this project.This article is mainly discussed in the following aspects:Adding micro grinding medium and different kinds of grindingin into ordinary portland cement for two times grinding,in order to obtain superfine Portland cement.and the grinding effect of different kinds of grinding aids was determined by the microcosmic measurement method,such as the particle size distribution of laser and SEM.The results show that the system D95 doped with 0.06% glycerol grinding aids is 13.54 mu m to meet the requirements of superfine cement D95<20um,and is superior to the other two systems.When the dosage of the grinding agent glycerol is 0.06%,the grinding effect is the best.Studying the internal relations between the performance indexes of superfine Portland cement and water cement ratio,nano silica sol,mineral admixture,water reducing agent,MgO expansive agent.The experimental results show that the large water cement ratio can significantly improve the rheological properties of the superfine cement grouting material,but it also reduces the stability of the slurry.The Nano silica sol can significantly reduce the pH value of grouting material,and increase the compressive strength of grouting material in a certain range,but it is very unfavorable for the fluidity of grouting material.Polycarboxylic water reducer can effectively improve the rheological and mechanical properties of the slurry,but its stability will be reduced.The expansion agent MgO can be used to compensate the shrinkage of the grouting material system,and the expansion rate of the system is effectively controlled within the required range.using 10% fly ash,5% mineral powder,6% expansive agent MgO,2% polycarboxylate superplasticizer,14% and 15% two groups of nano silica sol to design and prepare silica sol modified ultrafine cement grouting material,and study its important performance indicators.The experiment shows that the silica sol-modified superfine cement grouting material has good rheological properties and irrigability.The pH also meets the basic requirements of the project,and the compressive strength of the grouting material will not shrink steadily.But the design of silica sol modified superfine cement grouting material is not satisfied with the requirement of this study on the viscosity less than 50 mPa·s of the grouting material.The experimental results show that when the superfine Portland cement: Fly Ash: expansive agent MgO: polycarboxylate superplasticizer: nano silica sol =76:10:6:2:14,the silica sol modified superfine cement grouting material is easy to pour into the fissure with the width of 100 um.and Its pH value,rheological properties,mechanical properties,volume stability and other performance indicators all meet the requirements of the project.