Study On Preparation Technology,Mechanical Properties And Micromechanism Of High Performance Cement-based Grouting

Cement-based grouting refers to a material composed of cement,fine aggregate,additives,etc.,filled in the gap between the sleeve and the ribbed steel bar.After mixing with water,it has good fluidity,high early strength and high late strength,slight expansion,nontoxic,harmless and other properties.It can ensure the stability of the reinforced sleeve grouting connection while ensuring the safety of the prefabricated building structure,Reduce engineering construction costs and shorten construction period,can be widely used in the field of prefabricated construction.This article studies the cement-based grouting material,the content is as follows:(1)The strength,vertical expansion rate and fluidity of the cement-based grout are mutually restrictive relationships,and this article makes an in-depth study on this.The experiment was conducted on the basis of reference to relevant achievements,and the mineral admixture composition and dosage in the cement-based grout were selected,and the waterbinder ratio,mortar ratio,fast-hardening sulfoaluminate cement dosage,and water-reducing agent dosage were selected.The blending amount with the expansion agent is taken as five factors in the orthogonal test,and the different blending amount is taken as the four levels.The sixteen sets of mix ratio molding test blocks were tested for compressive strength,flexural strength,initial fluidity,30 min fluidity and vertical expansion rate,and the main and secondary factors affecting the performance of cement-based grout were obtained,and the optimal mix ratio is proposed.(2)Through the use of orthogonal test to optimize the mix ratio,the cement-based grouting compound was tested by sleeve combination test,comparing different sizes of grouting sleeves(D16,D18,D20),different sizes of steel bars(diameter 16 mm,18mm,20 mm HRB400 steel bar)for grouting curing,after reaching the required age,the unidirectional tensile test is performed on the whole grouting sleeve to obtain its failure form and load-displacement curve,and study the mechanical properties of cement-based grouting.(3)Comparing the performance and cost of the cement-based grouting material with the optimal mix ratio,and comparing the performance and cost with the best-selling grouting material on the market,it is concluded that the cement-based grouting material has good competitiveness and the cost-performance ratio is higher than the market on similar products.(4)In order to understand the macro-mechanical performance of cement-based grouting materials,this article conducted XRD and SEM micro-test analysis on the cement-based grouting materials.The microstructure analysis showed that a large amount of ettringite crystals were generated during the hydration and hardening process make the mortar quickly produce strength;as the hydration reaction continues,the ettringite crystals continue to react to generate volume expansion of the hardened slurry.Since the ettringite crystals are needle-shaped and rod-shaped crystals,they are filled in the capillary pores of the slurry to make the slurry more dense and solid,and the performance of the cement-based grouting slurry is greatly improved.(5)Through the finite element software ABAQUS,the numerical simulation of the joint test of cement-based grouting and grouting sleeve joint was carried out.Under the unidirectional tensile test,the load-displacement curve of the numerical analysis was compared with the test curve.,Studied the overall damage of the grouting sleeve,and analyzed the reasons.