Mechanical Properties And Microscopic Experimental Study Of Masonry Cementing Materials For Typical Historical Buildings

Historical buildings are treasures of Chinese civilization,bearing important information of different historical periods,especially the number and types of masonry structures.However,researches on materials and properties of masonry structures of historical buildings are relatively few,which cannot meet the needs of protection and restoration of existing masonry structures of historical buildings.The main characteristics of masonry structure in this paper,based on historic buildings,based on the analysis of its structure,regional distribution,the types of cementitious materials,on the basis of four kinds of typical masonry structure of cementitious materials,based on mechanical properties,microstructure test and finite element simulation analysis,to carry out the typical historical building masonry structure research of cementing material performance.The main work and research conclusions are as follows:（1）Based on the historical documents and the manufacturing process,120 cubes of glutinous rice ash,hemp cutter ash,Tung oil ash and peach blossom ash in 20 groups were made by choosing 4 kinds of typical historical building masonry cementing materials,and the orthogonal test was carried out under the original manufacturing process.The results show that the failure processes of glutinous rice ash,Tung oil ash and peach blossom ash cubes are similar.After the appearance of vertical cracks,the cracks develop inward,and finally form a tetragonal failure mode connected from top to bottom.The cube compressive strength of glutinous rice ash gradually increased with the increase of the content of glutinous rice paste,and the maximum value was 0.253 MPa.When the content of glutinous rice paste was 5%,the compressive strength of glutinous rice ash decreased to a certain extent.The cubic compressive strength of Tung oil ash increases with the proportion of Tung oil increasing,and the maximum compressive strength is 0.43 MPa,which is Tb of specimen.The cube compressive strength of peach blossom pulp increased with the proportion of lime increasing,and the maximum compressive strength was 0.228 MPa,which was Hb of specimen.The failure mode of Hemp fiber grey is overall flattening,which has good integrity.The compressive strength of Hemp fiber grey is 102% higher than that of glutinous rice ash,18.6% higher than that of Tung oil ash,and 37.8% higher than that of peach blossom ash.Among the four kinds of typical historical building masonry cementing materials,saber ash is the best,with the highest compressive strength of 0.51 MPa and the best resistance to deformation.（2）Based on the mechanical properties test of sticky rice ash,a typical historical building masonry cementing material,the constitutive relationship of sticky rice ash cementing material was proposed,and the compression process of corresponding test blocks was simulated by ABAQUS finite element software,and compared with the test results.The results show that the stress-strain curves of the simulated glutinous rice ash test blocks have the same general trend as those of the test blocks,both of which have experienced the stages from vertical crack to continuous expansion,and finally formed a four-pyramid failure pattern of forward and backward connection.The stress distribution is basically consistent with the test failure mode,which can better reflect the failure mode of materials,and can provide a reference for the finite element simulation of typical historic building masonry structure.（3）By means of optical microscope,scanning electron microscope and X-ray phase analysis,the microstructure and composition of four kinds of masonry cementing materials of historic buildings were studied.The results show that the crystallinity of the soil is limited by the glutinous rice mortar,which makes the soil have higher strength and compactness.The friction between the soil particles and the Hemp fiber in the mortar is larger,so the compressive strength is increased by 65.4%.The microstructure of Tung oil mortar is manifested as layers of sheet objects,the structure is relatively dense,greatly reducing the porosity;Compared with the previous three kinds of mortar,this kind of connection is weaker,which leads to the decrease of mechanical properties.