| Under the framework of the national dual-carbon policy,vigorously develop prefabricated buildings,which can effectively save energy,reduce carbon emissions,improve construction efficiency,and realize the industrialization of buildings.In prefabricated structure buildings,autoclaved lightweight concrete can be embedded in the building as an inner wall,or can be used as an external wall to become an enclosure structure,which has a significant role in the energy-saving and thermal insulation of the building.Few scholars at home and abroad have studied the impact of different environmental factors on the impact performance of autoclaved lightweight concrete.In this paper,the uniaxial compression test,SHPB(split Hopkinson pressure bar,SHPB)impact test and microscopic treatment of autoclaved lightweight concrete are carried out under different moisture content,different numbers of dry and wet cycles,and different moisture content-freeze-thaw cycles.Test,the impact on the mechanical properties of autoclaved lightweight concrete under different environments.(1)In uniaxial compression tests with different moisture content and number of wet and dry cycles,the compressive strength and elastic modulus of autoclaved lightweight concrete were obtained,and the relationship between the compressive strength,elastic modulus and moisture content,and the number of dry and wet cycles The law of change.The results show that:when the water content increases from 0%to 20%,the compressive strength and elastic modulus decrease from 3.01 MPa to 2.10 MPa,and when the water content increases from 20%to 50%,the strength only decreases by 0.15 MPa,so the rate of decrease From fast to slow and tends to be stable.When the wet-dry cycle is 10 times,the compressive strength increases from 3.35MPa to 4.73MPa,because the hydration reaction continues,the hydration products continue to increase,and the small cracks in the specimen are filled to increase the strength;the number of wet-dry cycles increases from From 10 to 30 times,the strength decreases from 4.73MPa to 4.13MPa,because the drying shrinkage is continuously strengthened with the increase in the number of wet and dry cycles,causing micro-cracks in the specimens to decrease the compressive strength.(2)In the SHPB test,the peak stress and absorption energy of autoclaved lightweight concrete under different moisture content,the number of dry and wet cycles,and the coupling of moisture content-freeze-thaw cycles were obtained,and the peak stress and moisture content,the number of dry and wet cycles,and The law of change between the moisture content and the number of freeze-thaw cycles.The results showed that with the increase of water content,the peak stress first increased from 6.15 MPa to 6.31 MPa,and then decreased from 6.31 MPa to 4.96 MPa,showing a law of first rising and then falling;absorption energy first decreased rapidly and then slowly decreased.As the number of wet and dry cycles increases,the peak stress and absorbed energy both rise first and then fall.Under the condition of the coupling condition of moisture content-freeze-thaw cycles,under the condition of a certain moisture content,30 freeze-thaw cycles will reduce the strength of the specimen by about 20%;under the condition of a certain number of freeze-thaw cycles,moisture When the drying rate is from 10%to 10%,the peak stress will drop rapidly,and when the moisture content is greater than 10%,the peak stress will drop slowly.(3)In the microscopic test,the diffraction peak tobermorite gradually increased,reflecting that the hydration reaction has been going on during the test,forming a large amount of tobermorite,which is used as a filling material to strengthen the strength.The formation of a large amount of tobermorite in the cracks can also be clearly seen from the electron microscope.Favorably proves that the hydrothermal reaction has been going on.Fig 46 Table 7 Ref 96... |
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