Study On Static Performance And Impact Response Of Recycled Brick Powder Mortar

Grinding waste clay bricks into recycled brick powder（RBP）as mineral admixture to replaced cement can not only reduce the occupation of land resources due to landfill or stacking treatment,but also reduce the energy consumption and carbon emission caused by cement production.It has important significance of environmental protection and resource regeneration.However,due to the low pozzolanic activity of RBP,cement mortars containing RBP tend to exhibit low mechanical and durability properties,which limits its application.Therefore,this paper attempts to improve the activity of RBP by increasing the fineness of RBP and substitute it for cement with different mass percentages（10%,20%and 30%）to prepare RBP mortar and net slurry.（1）Pore structure evolution,hydration and mechanical properties of recycled brick powder cement cementitious system were studied.（2）Dynamic mechanical properties and correlation of average strain rate with peak strain and ultimate toughness of recycled brick powder cement composite mortar at three impact pressures（0.25MPa,0.35MPa and 0.45MPa）were studied.Experimental research shows that:（1）RBP delayed cement hydration and reduced the cumulative hydration heat of recycled brick powder cement composite net slurry,and the higher the content of RBP,the more significant the reduction effect was.This is mainly due to the incorporation of RBP resulting in the reduction of available tricalcium silicate in the composite system.Increasing the fineness of RBP can compensate the cumulative heat loss of slurry and advance the peak-to-peak value of hydration heat release.The mass loss of Ca（OH）₂ decreased with the increase of the content of brick powder,and the particle size of RBP had a positive effect on the mass loss of Ca（OH）₂.（2）RBP mainly plays the role of filling effect in the early stage,and its pozzolanic activity is basically not shown.Therefore,the early compressive strength of RBP mortar decreases with the increase of RBP content.By increasing the fineness of RBP,the early pozzolanic activity of RBP mortar can be improved,the pore structure of RBP mortar can be improved,and the compressive strength of RBP mortar can be improved.Orthogonal test shows that the mortar prepared by RBP with particle size less than 75μm instead of 10%cement has the highest mechanical properties,and its compressive strength at 28 days is equivalent to that of pure cement mortar.（3）Under impact load,and when the average strain rate is 30-150 s^-1,the dynamic compressive strength of the recycled brick powder mortar continuously increases with the increase of the average strain rate.When the brick powder replacement rate is 10%,the mortars exhibit the largest dynamic compressive strength;The peak strain of the cement mortar increases firstly,and then reduces with increasing average strain,and the peak resilience continuously increases with the increase of the average strain rate.By the tests for static and dynamic mechanical properties and hydration characteristics of recycled brick powder mortar,the RBP of special mixing amount and particle size has positive effects on the properties of cement mortar,at the same time of reducing cement consumption,the compressive strength of the cement mortar can be improved,facilitating saving of non-renewable resources and resource utilization of solid waste of buildings.Figure[22]table[10]references[86]...