Research On Load-bearing Capacity Of Old Masonry Structrue Influenced By Acid Rain

China's acid rain pollution has become a universal problem,in the census in 1982,we found that China's acid rain has covered a land area of 40 percent and become the third largest acid rain area after Europe and North America.Acid rain contains H2SO4?HNO3 and other acidic substances,can make the brick masonry structure in the acid rain region subjected to different degree of corrosion,accelerate structural aging process,not only reduce the safety of the structure,but also bring enormous loss to national economy.At present the domestic about less research aspects of the effects of acid rain environment of masonry structure,a lot of work remains to be done.This paper uses the method of complete immersion accelerating corrosion,respectively pH1.5?pH2.5 and pH3.5 configuration of three kinds of different acidity of sulfuric acid and nitric acid mixed solution to simulated acid rain environment,do the following researchs:For the commonly used materials of masonry structure sintered clay brick and cement mortar,carrying experimental study on the view change?quality change?compressive strength change?failure process and morphology of masonry materials that corroded for different degrees.The experiment results showed that:(1)Before and after simulated acid rain erosion,the mortar have obvious apparent change,but the brick didn't.(2)The quality of pH 1.5 group of mortar specimens has been in decline in corrosion prophase.The quality of pH2.5 group of mortar specimens increased in corrosion prophase,with corrosion time increasing,quality gradually began to decline.The quality of pH3.5 group of mortar specimens has been in a rising trend;The quality of brick specimens have different degrees of increase after corrosion.(3)With the increase of corrosion time,three groups of corrosion mortar specimens compressive strength increased first and then decreased gradually,and the higher the acidity of the solution,the compressive strength enter the decreasing stage time sooner,the degrees of reduce greater;For brick specimens,with corrosion time increasing,three groups of corrosion brick specimens compressive strength decreased gradually.(4)Before and after corrosion of simulated acid rain solution,the brick and mortar specimens have no obvious differences in failure process and morphology.For the commonly used component of masonry structure brick-column,carrying experimental study on the pH of soak solution?the apparent condition?failure process and morphology?bearing capacity?load-displacement curves?stress-strain curves?modulus of elasticity of brick-columns that corroded for different degrees.The experiment results showed that:(1)Three different simulated acid rain acidity of the solution within the first 24 hours of corrosion,pH increased by a big margin,pH value rise thereafter each 24 hours period of time less than the initial 24 hours.And the lower the acidity of the solution of simulated acid rain,the same time period,the greater the magnitude of change in pH.(2)The apparent of brick-columns change significantly before and after simulated acid rain erosion.(3)Under the same pressure conditions,simulated acid rain solution eroded brick-columns was no significant difference compared with ordinary brick-columns in failure process and morphology,much the same in failure mechanism.(4)With the increase of corrosion time,subjected to simulated acid rain acidity of three brick-columns ultimate bearing capacity and elastic modulus showed a decreasing trend,and the higher the acidity,the greater the degree of lowering.(5)With the increase of corrosion time,brick-columns initial stiffness decreases,ultimate failure displacement increases.And the higher the acidity of the solution,the smaller brick-columns deformation values at peak load,the bigger the brick-columns brittleness.(6)Established brick-columns stress-strain curve rise unified mathematical expression under the acid rain environmental,this formula can better reflect the different degrees of stress corrosion brick-columns variation of strain-curve rises segment.(7)Established remaining compressive strength regression formula of ordinary sintered clay brick masonry after the acid rain,calculated and measured values are in good agreement.For the commonly used nine brick shear specimens that used for masonry shear test,carrying experimental study on the failure process and morphology?shear strength of shear specimen that corroded for different degrees.The experiment results show that(1)Under the same shear conditions,simulated acid rain solution eroded shear specimens was no significant difference compared with ordinary shear specimens in failure process and morphology,is still divided into single shear failure,double shear failure and bricks body damage.(2)With the increase of corrosion time,Jl group(pH1.5)shear strength of specimens has shown a decreasing trend.J2 Group(pH2.5)and J3 Group(pH3.5)specimens showed a gradual decrease after the first rise.And the higher the acidity of the solution,the greater the degree of shear strength decreases.(3)Established remaining shear strength regression formula of ordinary sintered clay brick masonry after the acid rain,calculated and measured values are in good agreement.(4)Brick masonry structures subjected to acid rain,compared with the ordinary masonry structures that have the same mortar strength,the shear strength decreased.