Study On The Effect Of Zeolite Powder On The Mechanical Proper-ties And Damage Mechanism Of Concrete

With the vigorous development of China’s construction industry and the acceleration of urbanization,natural resources in China are constantly being consumed,while the production of construction waste is increasing.If construction waste can be recycled and utilized as a resource,it will play an important role in promoting the development of China’s construction industry and environmental protection.In this paper,recycled aggregate is used to replace natural aggregate,and zeolite powder is used to replace some cement,The Uniaxial compression tests were conducted considering different amounts of zeolite powder and different curing ages,and the characteristics of the stress-strain curve were analyzed.Based on statistical damage theory,the influence of zeolite powder on the microscopic damage mechanism of recycled aggregate concrete under two factors was explored.Mechanical performance tests of ultra-high performance concrete were conducted considering different amounts of zeolite powder,different ratios of water and cementitious materials,and different volume ratios of steel fibers.The optimal amount of zeolite powder,the optimal ratio of water and cementitious materials,and the optimal volume ratio of steel fibers were obtained.These results provide experimental basis for the application of zeolite powder in concrete.The main research work is as follows:(1)The Uniaxial compression tests were conducted considering different amounts of zeolite powder and different curing ages,and the stress-strain curves were obtained to explore the influence of zeolite powder content on the mechanical properties(peak stress,elastic modulus,and peak strain)of the specimens.The results indicate that as the replacement rate of zeolite powder increases,the compressive strength and elastic modulus of zeolite powder natural aggregate concrete and recycled aggregate concrete gradually decrease.Compared with natural aggregate concrete containing zeolite powder,recycled aggregate concrete containing zeolite powder exhibits better deformation ability.As the curing age increases,the peak stress and elastic modulus of the specimen gradually increase,while the peak strain decreases.(2)Conduct nuclear magnetic resonance testing on concrete specimens with different amounts of zeolite powder.For natural aggregate concrete and recycled aggregate concrete specimens with a zeolite powder content of 0%,scanning electron microscopy and X-ray energy spectrum analysis tests were conducted.The results indicate that zeolite powder participates in the hydration reaction,but deteriorates the internal structure of the concrete.Zeolite powder recycled aggregate concrete has a higher porosity than zeolite powder natural aggregate concrete.For recycled concrete specimens with different curing ages(28d,56 d,120d)and zeolite powder dosages of 0% and 10%,nuclear magnetic resonance(7d,28 d,56d,120d)and scanning electron microscopy(28d,56 d,120d)tests were conducted.The results showed that in the early stage of hydration reaction,the addition of zeolite powder increased cracks and pores,while in the later stage,the filling effect of zeolite powder and volcanic ash reaction played a role,The compactness of the internal structure of the specimen has increased.For natural aggregate concrete and recycled aggregate concrete specimens with a zeolite powder content of 0%,as well as recycled aggregate concrete specimens with a zeolite powder content of 0% and 10%,acoustic emission tests were conducted.The results showed that the peak value of the ringing count was lagging behind the peak stress.(3)Based on the statistical damage theory and the results of the stress-strain curve,a statistical damage constitutive model was established for the influence of two factors.Based on this model,the microscopic damage evolution law of concrete under the influence of two factors was explored.The results indicate that the microstructure damage evolution process of the specimen exhibits certain regularity,which is consistent with the macroscopic nonlinear stressstrain behavior.(4)Three sets of mix proportions were designed,including different amounts of zeolite powder,different water cement ratios,and different volume ratios of steel fibers.Ultra high performance concrete was produced,and the mechanical properties of ultra-high performance concrete were analyzed under three factors.The results showed that the optimal content of zeolite powder was 10%,the optimal ratio of water and cementitious materials was 0.18,and the optimal range of steel fiber volume ratios was 2.5% to 3.0%.