Study On Mechanical Properties And Prediction Model Of Double-mixed Steel Slag Powder And Glass Powder Recycled Concrete

With the continuous development of cement concrete application technology,more and more mineral admixtures and additives play an efficient and indispensable material role in concrete.Steel slag powder is a by-product produced in the steelmaking process,and it has certain activity and has a wide application prospect in concrete.Glass itself is an amorphous silica material.After grinding,it has a certain pozzolanic activity and can be used as an auxiliary cementing material for concrete.At the same time,a part of the recycled concrete aggregate is replaced in the concrete to realize the requirements for the reuse of waste concrete resources.In this paper,steel slag powder and glass powder are used in recycled concrete.The effects of double-mixed micro-powder on the performance of recycled concrete are summarized,so that the three wastes of steel slag,waste glass and recycled aggregate can be recycled together.In this paper,the composition and structural characteristics of steel slag powder and glass powder were studied,and the gelling properties in concrete were discussed.The compressive strength and elastic modulus of steel slag powder and glass powder recycled concrete were studied by macroscopic experiments,and the relationship between the development law of age and the mechanical properties of different blending amounts was analyzed.Based on the macroscopic experiments,the composition and micro structure of steel slag powder glass powder cement slurry and the ITZ bonding and hydration of new and old mortar were studied by XRD,SEM,EDS and MIP.On the basis of the concrete mechanics model summarized by the predecessors,the compressive strength and modulus of elasticity predicting model of double-mixed composite powder recycled concrete was established to promote the practice and application of double-mixed admixture recycled concrete in engineering.The main research contents and conclusions are as follows:(1)Macroscopic aspect:The basic mechanical properties of double-mixed recycled concrete have a tendency to decrease first and then increase with the amount of steel slag powder.When the amount of steel slag powder is 10%,the basic mechanical properties are the smallest.The basic mechanical properties of double-mixed recycled concrete have a tendency to increase first and then decrease with the amount of glass powder.When the glass powder content is 10%,the basic mechanical properties are optimal compared with other blending amounts.(2)Microscopic aspects:XRD and SEM studies show that the addition of steel slag composite micropowder makes the slurry in the initial stage of hardening more porous,and when the amount of steel slag powder is 10%,it only plays a packing and compacting effect.When the glass powder content is 10%,the volcanic ash effect is the most obvious;after EDS analysis,the percentage of(SiO2+Al2O3+CaO)content of the new mortar ITZ is higher than that of the old mortar ITZ,and the new ITZ ratio generates more C-A-H and C-A-S-H gel than the old ITZ;MIP test shows that the incorporation of steel slag powder can reduce the porosity of concrete.As the amount of steel slag powder increases,the total porosity also increases,but it is still superior to the reference concrete.(3)According to the test data,using the Origin fitting,the formula for predicting the compressive strength of the steel slag powder and glass powder recycled concrete is obtained.the formula for predicting the compressive strength is fcu(t)=fcu,28[1+0.21191n(t/28)](w/c)0.018.The modulus of elasticity calculation formula is E=4287(fcu)0.488.The error range is controlled at±12%.At the same time,the model is predicted based on other research data,and the relative error value is similar to the error range.