| The raw soil-based material has the advantages of adjustable indoor humidity,heat insulation,recycling,economy and pollution absorption,but it has some problems to be solved in dust pollution,modification treatment and reuse in the process of transportation.In the production process of traditional cement modified block,CO2 emission is large and energy consumption is serious,which cannot meet the demand of green,low-carbon and sustainable development.In view of the important problems to be solved in raw earth materials,this topic applies active MgO to the production of raw earth blocks,and puts forward a new green building material with negative carbon emission,early strength and high performance.The main research contents and results are as follows:(1)through indoor mixture ratio test,study different materials(MgO style,cement,fly ash,water),different mixing ratio and carbonization time(1 d,3 d,7 d,14 d and 21 d and28 d)under the condition of axial compressive strength,the results showed that the activity of MgO style carbonization of raw soil block for MgO style of proportion of raw materials:cement,fly ash,raw soil at 7:At 7:6:80,after adding clean water according to the optimal moisture content of raw soil substrate,the compressive strength of the blocks produced is higher,and the 21-day compressive strength tends to be stable,and the average value can reach about 7～ 8MPa.(2)The orthogonal test method was used to determine the optimal carbonization conditions of raw earth blocks.The range analysis,factor index analysis and variance analysis were carried out on the test results by investigating the influence of different temperatures,humidity and carbon dioxide concentrations on the compressive strength of the carbonized raw earth blocks with active MgO.The results show that the optimal carbonation conditions of active MgO carbonation raw earth blocks are as follows:carbonation temperature 20℃,carbonation humidity 60%,carbon dioxide concentration30%;The carbon emission factor calculation method is used to compare and calculate the carbon emission of active MgO carbonized raw earth blocks and ordinary concrete respectively.The carbon emission of 1m3 cement concrete is 53.68% more than that of1m3 active MgO carbonized raw earth blocks,which is about 97.24 kg.At the same time,the active MgO carbonized raw earth block can absorb more CO2 than its own emissions,up to 185.51 kg,to achieve carbon negative emissions,compared with ordinary cement concrete,more low-carbon and environmental protection,is conducive to the realization of the goal of "carbon peak,carbon neutral"(3)The failure process of carbonized raw earth blocks under uniaxial compression was investigated,and the load-displacement curve characteristics of the blocks were analyzed.Secondly,the stress-strain curve of the blocks was analyzed based on the data processing of the load-displacement curve,and a multi-stage stress-strain curve model was established according to the characteristic points.On this basis,the uniaxial compression constitutive model of activated MgO carbonized raw earth block was established by fitting the test data.Finally,the validity of the constitutive model under uniaxial compression is verified by experiments.The results show that the constitutive model under uniaxial compression can use rational fractions and cubic polynomial functions to fit the parameters of the ascending and descending segments,and the fitting results are in good agreement with the experimental data.(4)The typical carbonized samples were selected to illustrate the microscopic strengthening mechanism of carbonized raw earth blocks through chemical microscopic tests such as X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive analysis(EDS)and thermogravimetric analysis(TG).The results show that the hydration and carbonation reaction of the active MgO cement can effectively fill the pores of the mixed soil and improve the compactness.At the same time,the generated magnesium compound has its own cementing effect,which can bind and package the mixed soil to form a network structure and improve the strength of the carbonized raw soil block.(5)Based on the experimental study on the durability of masonry mortar and block,the compressive and shear properties of modified MgO cement mortar are analyzed.The results show that: The compressive strength of modified M5 and M7.5 mortar cubes is6.43 MPa and 7.79 MPa,respectively.The compressive strength of modified mortar is better than that of ordinary mortar,which can well meet the requirements of masonry block construction.The test results of water resistance and drying shrinkage performance of the blocks show that the softening coefficient of active MgO carbonized raw earth blocks is0.2637,and the drying shrinkage performance is better when the fly ash content is 30%.Figure [58] table [32] reference [63]... |
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