Experimental Study On The Properties Of Cellulose Fiber-Mineral Powder Pumice Lightweight Aggregate Concrete

With the improvement of China’s scientific and technological level,as well as the improvement of market demand,the application of lightweight aggregate concrete is more and more widely,which has the advantages of light weight,high strength,heat insulation and good seismic performance.In this thesis,natural pumice widely distributed in Inner Mongolia is used as the raw material of lightweight aggregate concrete,and in response to the national call for environmental protection,waste utilization,and green development,cellulose fiber extracted from plants and industrial waste mineral powder are mixed into pumice lightweight aggregate concrete.The influence of the two mixtures on the performance of pumice lightweight aggregate concrete is studied from the aspects of macroscopic mechanical properties,dynamic impact properties,frost resistance durability,microscopic pore structure characteristics,etc.,which provides a certain theoretical reference for the application of pumice lightweight aggregate concrete in Inner Mongolia.The main research contents and results of this thesis are as follows:1.Through testing the 28d compressive strength and splitting tensile strength of pumice light aggregate concrete,it can be seen that the addition of mineral powder will reduce the compressive strength of concrete,and the optimal amount of fiber varies with the replacement rate of mineral powder.When no mineral powder is added and the replacement rate of mineral powder is 5%,the strength is the largest under the fiber content of 0.9kg/m~3,and when the replacement rate of mineral powder is 15%and 25%,the strength is the largest under the fiber content of 1.2kg/m~3.0.6kg/m~3 fiber mixed with mineral powder can improve the tensile strength and tensile-compression ratio of concrete.2.Through the 28d Hopkinson bar test of pumice light aggregate concrete,it is concluded that the replacement rate of mineral powder corresponding to the maximum peak stress and the maximum DIF value is 25%,and the fiber content is 0.9kg/m~3.The addition of fiber can increase the specific energy absorption density value of the concrete material and enhance the toughness.When cement is replaced by mineral powder at the same amount of 25%substitution rate,the specific energy absorption density value increases greatly and the mixing effect is better.3.Through the rapid freeze-thaw test of pumice light aggregate concrete,it can be known that with the dynamic elastic modulus as the evaluation index of concrete freezing resistance,the freezing resistance of most concrete in this test is about 200 times.Based on the help of nuclear magnetic resonance tests of pumice lightweight aggregate concrete under freeze-thaw cycles,it was found that the porosity of concrete increases significantly after the first 50 freeze-thaw cycles from the microscopic point of view.The addition of mineral powder can reduce the increase of concrete porosity after 200 freeze-thaw cycles.When the mineral powder replacement rate is 0%,5%,and 15%,the addition of 0.9kg/m~3 fiber can reduce the difference of free fluid saturation before and after freeze-thaw cycle,delay the development of small pores and slow down freeze-thaw damage of concrete.4.Using nuclear magnetic resonance technology to test the pumice light aggregate concrete,it was found that 15%and 25%for mineral powder under the replacement rate of concrete,due to the interaction between cellulose fiber and mineral powder,fiber incorporation on the impact of microscopic pore structure of concrete more than not mixed mineral powder and 5%under the replacement rate of concrete.