Research On The Preparation And Properties Of Sleeve Grouting Material For The Connection Of Prefabricated Building Reinforcement

Compared to traditional cast-in-place buildings,prefabricated buildings have advantages such as short construction cycle,stable component quality,high degree of standardization,and environmental friendliness.They have gradually become the mainstream of the development of the construction industry,and are the only way to upgrade and transform the construction industry.The biggest difference from traditional buildings is that the connection method of steel bars in prefabricated buildings uses sleeve grouting,which uses grouting filling method,and does not cause expansion deformation and residual stress on the steel bars,with high safety and node strength.For sleeve grouting connections,the performance of the sleeve grouting material that fills between the sleeve and the reinforcement is crucial.Currently,commercially available sleeve grouting materials generally have shortcomings such as low fluidity,insufficient durability research,and high prices.In response to the above shortcomings,this article is committed to developing a sleeve grouting material with excellent performance and low cost to meet the needs of the development of the construction market.In the early stage of this article,the initial formula of the sleeve grouting material was determined based on references and exploratory experiments.Then,through orthogonal tests and single factor analysis,the levels of factors that have a significant impact on the performance of the sleeve grouting material,such as the water cement ratio,the amount of water reducing agent,the amount of early strength agent,and the amount of sulphoaluminate cement,were determined,and the optimal basic formula was determined.After that,based on the optimal basic formula,a systematic study was conducted on the basic performance,microscopic analysis,and durability of two mineral admixtures,namely metakaolin and fly ash.The effects of two mineral admixtures on various properties of sleeve grouting materials were comprehensively discussed.Finally,the uniaxial tensile test and cost analysis of the sleeve were carried out.The main research results are as follows:(1)In the orthogonal experiment,whether it is the compressive strength index or the fluidity index,the K value of the water cement ratio is the largest,that is,the water cement ratio has the greatest impact on the performance of the sleeve grouting material.It is crucial to choose the optimal water cement ratio.After orthogonal experiments and single factor experiments,0.25 is selected as the optimal water cement ratio in this article.The optimal addition amounts of other components are 0.9% of the water reducing agent addition,0.4% of the early strength agent addition The addition amount of sulfur aluminate cement is 15%.(2)The addition of expansion agent can make the sleeve grouting material obtain better expansion performance,but it has a significant negative impact on the fluidity and compressive strength of each age.Therefore,it is necessary to add it carefully.After single factor analysis and testing,the addition amount of expansion agent is selected as 0.1%,which meets the requirements of the specification for expansion rate at this time,and has little impact on other properties.During the mixing process,sleeve grouting materials will generate more bubbles,which will have a significant impact on compressive strength and durability.Add defoamer to eliminate bubbles.When the amount of defoamer added is0.1%,the comprehensive performance of sleeve grouting materials is optimal.(3)In the range of 0% to 9%,the addition amount of metakaolin increases,the fluidity decreases,and the compressive strength increases;In the range of 0% to 8%,the addition amount of fly ash increases,the fluidity increases,and the compressive strength first increases and then decreases.According to the SEM test results,when the amount of metakaolin added increases,the internal cross-section of the sleeve grouting material changes from many pores and loose structures to a compact structure.When the amount of fly ash added increases,the microstructure of the surface of the sleeve grouting material becomes smoother,and the porosity decreases accordingly,but a certain amount of cracks occur.From the infrared spectrum test,it can be seen that with the addition of metakaolin and fly ash,the infrared spectrum wave numbers are basically the same,and the generated substances do not change.(4)The addition of metakaolin and fly ash can reduce the quality loss rate of sleeve grouting material during sulfate attack test,and also improve the compressive strength and corrosion resistance coefficient of sleeve grouting material,which both promote the sulfate attack resistance of sleeve grouting material.When the number of freeze-thaw cycles increases,the quality loss rate and strength loss rate of the sleeve grouting material will correspondingly increase.The addition of metakaolin and fly ash can reduce the mass loss rate and strength loss rate of the sleeve grouting material in the freeze-thaw cycle test,which can improve the frost resistance of the grouting material,and the improvement of the frost resistance of the sleeve grouting material by metakaolin is more obvious than that of fly ash.(5)In the practical study of sleeve grouting materials,under different types of sleeves and different diameters of steel bars,the sleeve grouting materials developed in this paper all fractured at the reinforcement outside the sleeve in the uniaxial tensile test,indicating that the performance meets the requirements.Through performance comparison and cost analysis with commercially available brand sleeve grouting materials,the price of the sleeve grouting materials developed in this article has significant advantages.The performance meets the specification requirements and the price is 758.4 yuan/ton,while the commercially available brand is 3600 yuan/ton,so it has good market competitiveness.