Research On Preparation And Performance Of Shrinkage-free Cement-based Grouting Mortar

Grouting mortar is maded up of cementitious materials,fine aggregate,super plasticizer and other materials,can flow after watering. It has strongpoint of great fluidity, minor expansion, early and high strength and is the perfect material of secondary grouting equipment, bolt anchor, concrete reinforcement, repair and other fields. It has huge foreground of marker.In this experiment, portland cement, calcium aluminate cement and dehydrate gypsum is used for cementitious materials. First of all, through the portland cement and CA testing, to identify the best composite of two cement ratio. Then consider the workable performance, mechanical performance expansion properties and setting time of grouting mortar, analyze the influence of calcium aluminate cement, dehydrate gypsum,super plasticizer, aggregate, adjustable solidification agent, defoamer, thickener, mineral admixture to various performance of mortar.settle contradiction of fluidity and stability, rapid hardening and retardation, shrinkage and expansion, adding super plasticizer and elapsed loss of mortar extensibility, finally determined optimizing mix proportion. XRD and SEM are used to analyze hydration-hardening mechanism of the compound system. The research results can be concluded as following:①The coordination interval of portland cement and calcium aluminate cement compound system in the setting time, mechanical properties and shrinkage properties is content of calcium aluminate cement is 0~20% or 80%~100%.②Single factor test showed that naphthalene water-reducing agent is better to compound type of cement mortar adaptability than sulphamate and polycarboxylates water-reducing agent, finally determine content of naphthalene is 1.2%.Grouting morter can be obtained better early strength when calcium aluminate cement replacements of portland cement are 10%, the initial setting time of mortar is significantly shortened. Grouting mortar can be obtained better expansion properties and the mechanical properties when dehydrate gypsum replacements of cement are 6%～10%. While fineness modulus of artificial gradation is 2.73, fluidity and compressive strength are preferable. Considering from fluidity and cost, cement-sand ratio is 1/1. The fluidity of 30min can be saved and the influence of the early strength can be decreased while mass ratio of sodium gluconate and tartaric acid is 5:4, the best content of compound retarder is 0.07%, lithium carbonate can improve the setting time of mortar and reduce the influence of retarder on the early strength of mortar, finally determine content of lithium carbonate is 0.2%. Organic silicon defoamer can effectively eliminate the introduction of harmful bubble when mixing mortar, the addition of defoamer can improve the fluidity of mortar and the best content is 0.6%. HPMC and hydrated lime powder could improve the bleeding, taking into account the fluidity and strength choose the content of hydrated lime is 2%. Taking into account the influence of fly ash and slag on early strength and silica fume on fluidity of mortar grately, so the individual should not be mixed.③Analyzing the influencing factor of mortar performance, determining orthogonal test programme, testing performance of mortar, defining optimization mix proportion as follows: content of portland cement is 82%, content of calcium aluminate cement is 10%, content of dehydrate gypsum is 8%, content of hydrated limer is 2%, content of sodium gluconate is 0.07%,content of tartaric acid is 0.056%, content of lithium carbonate is 0.2%, content of defoamer is 0.6%, content of super plasticizer is 1.2%, water cement ratio is 0.32,cement sand ratio is 1/1. The performance of grouting mortar according to optimization mix proportion can meet the standards of"Cement-based grouting materials"JC/T986—2005.④Result of micro-structural analysis shows that a large amount of ettringite crystal is produced in 1 day during the hydration and hardening process, which makes cement paste or concrete generate strength rapidly. With the evolution of hydration,large amount of ettringite crystal continue to produce and grow. Consequently, volume expansion of the hardened paste is generated. Due to the filling of capillary cavity with needle-shaped and bar-shaped crystals, As a result, the properities of mortar is being greatly improved.