Mechanical Properties And Early Shringkage Of Geopolymer Recycle Concrete

Geopolymer Recycled Concrete（GRC）is a green and low-carbon concrete made by using accelerator technology to replace cement-based cementitious materials,using recycled aggregates to partially or completely replace natural aggregates,which can improve the utilization rate of solid waste,reduce carbon emissions from the source of building materials,and meet the national dual carbon goals and sustainable development of green building materials.The study of mechanical properties and early shrinkage law of geopolymer recycled concrete is systematically carried out,which is of great significance for promoting the engineering application and industrialization of this type of concrete.The main contents include:（1）Experimental study on working properties,mechanical properties and microstructure of geopolymer recycled concrete.The effects of various factors on the volume slump,setting time and compressive strength of geopolymer recycled concrete were analyzed,and the relationship between microstructure and macroscopic properties was revealed.The results show that the slump of geopolymer recycled concrete is 121～210mm,which can meet the needs of engineering concrete.Its dry apparent density is smaller than that of ordinary concrete,and it has a linear relationship with compressive strength.The setting time of geopolymer recycled concrete shortened with the decrease of excitation modulus,the increase of slag content and the increase of alkali-glue ratio,and the incorporation of steel fiber can effectively improve the ductility of geopolymer recycled concrete.Geopolymer mortar has good adhesion and synergistic properties with recycled aggregates.The pore structure of geopolymer recycled concrete has high uniformity and consistency.（2）Study on uniaxial compressive stress-strain full curve model of geopolymer recycled concrete.The uniaxial compressive constitutive curve tests of 12 groups of geopolymer recycled concrete were completed,and the effects of slag content,initiator modulus,steel fiber volume content,recycled coarse aggregate volume content and alkali-glue ratio on peak stress,ultimate strain,elastic modulus and compressive toughness were analyzed,and the calculation model of elastic modulus,axial compressive strength and peak strain suitable for geopolymer recycled concrete was established,and a uniaxial compressive constitutive curve model of geopolymer recycled concrete was proposed.（3）Study on early drying shrinkage performance of geopolymer recycled concrete.The early drying shrinkage test of 6 groups of geopolymer concrete was completed,the effects of slag content and recycled aggregate content on early drying shrinkage were analyzed,and the calculation model of 28D drying shrinkage strain and dry shrinkage strain prediction model of geopolymer recycled concrete were proposed considering Ca/Si（k₁）and recycled aggregate volume content（k₂）.The results show that the dry shrinkage strain of geopolymer recycled concrete increases with the increase of slag content and recycled aggregate content,and the early shrinkage rate of fly ash-slag base polymer concrete is large.The experimental results are in good agreement with the prediction model,which can well reflect the early drying shrinkage trend of geopolymer recycled concrete.The paper completed the experimental study on the mechanical properties of geopolymer recycled concrete,the experimental study of the uniaxial compressive stress-strain curve,and the early drying shrinkage experimental research,which can enrich the test data of related research,further understand the material properties of geopolymer recycled concrete,make up for the shortcomings of existing research,and have very important theoretical significance and practical value in engineering design and engineering application.