| Plant concrete is a new kind of environmental friendly material,which is composed of concrete layer and vegetation layer.The concrete layer is porous structure,which mainly acts as a force.The porous structure not only provides a growth environment for plant roots,but also plays a role of drainage,so that surface water can be reduced to groundwater;On the one hand,vegetation layer can purify water quality,beautify the landscape,protect biodiversity and reinforce the bank,on the other hand,it can alleviate the urban heat island effect and help to adjust the temperature and humidity of the city.Because there is no relevant norms and standards of planting concrete in our country,the popularization of planting concrete has been hindered,so this paper carried out a series of research,the main results are as follows:(1)Through the research on the preparation technology of plant-grown concrete,the following conclusions can be drawn: Under the condition of keeping the coarse aggregate clean,the agitation method adopts the slurry wrapping method,the vibration method adopts the static pressure molding method under 0.4MPa,the secondary alkali reduction is adopted,the primary alkali reduction is selected by adding two alkali reducing materials of fly ash and gypsum,and the secondary alkali reduction is adopted by water immersion method,thus the high strength and low alkalinity planting concrete test block can be prepared.There is a relationship among the strength,porosity and pH value of the pore water environment of the plant-grown concrete.The water cement ratio,fly ash content,design porosity and ceramsite substitute content were selected as the four factors of orthogonal test,and the content and design porosity of different materials were taken as the four levels.By testing the compressive strength,flexural strength,splitting tensile strength,porosity and pH value of pore leaching solution of 16 groups of shaped blocks,the range,variance and efficiency coefficient of the test results are analyzed,the main and secondary factors affecting the performance of plant-grown concrete are obtained,and a group of optimum mixture ratio is selected according to the analysis results.Regression analysis was carried out on the orthogonal test results,and the regression formulas of strength,pH value of pore leachate and four factors(water cement ratio,fly ash content,design porosity and ceramsite substitution)were established,and the significance analysis was carried out on the analysis results.(2)Soak the phytoalexipharmic concrete in 3%,5% and 7% sulfate,and observe the apparent change of concrete by 15,30,60,90 and 120 times of dry-wet cycle erosion system;The relative weight change and strength corrosion resistance coefficient were calculated;The causes of the failure of the concrete under sulfate attack are analyzed.With the increase of the dry-wet cycles,the surface of the plant-grown porous concrete blocks was damaged more and more seriously,and the aggregate shedding sequence was from corner to diagonal and then to all sides,which indicated that sulfate erosion had a greater impact on the plant-grown concrete.Under the action of different concentration of sulfate,the relative weight of plant-grown porous concrete changed from negative to positive,that is,the mass of plant-grown porous concrete increased first and then decreased.The higher the sulfate concentration was,the faster the weight decreased and the larger the range was.Under the action of sulfate attack of different concentrations,the change of the coefficient of resistance to corrosion of the compressive strength of plant-grown porous concrete presents a gradually decreasing process.The compressive strength of plant-grown porous concrete shows a trend of increasing at first and then decreasing.The higher the sulfate concentration is,the faster and larger the decreasing rate of the compressive strength is.(3)through the study of planting technology of planting concrete,choose filling mixed base soil in the pore,covering natural soil on the surface,filling method of nutrient matrix according to the actual need,selecting infiltration method for cast-in-place planting concrete and immersion method for prefabricated planting concrete.In this paper,Cynodon dactylon,tall fescue,ryegrass,Trifolium repens,The results showed that all the six plants could grow on the planting concrete,among which tall fescue had the fastest growth rate and the highest survival rate,ryegrass had the second fastest growth rate and the highest survival rate,Cynodon dactylon and Cynodon dactylon could also grow well in the planting concrete,The order of the six species was tall fescue < ryegrass < Bermudagrass < Trifolium repens,and the order of survival rate was tall fescue > ryegrass > Cynodon dactylon > Bermudagrass > Trifolium repens.(4)through the ANSYSAPDL program,the porous skeleton of the planting concrete is established by using the Monte Carlo method and the pore delivery algorithm,and the Workbench program is used to simulate the compressive failure of the planting concrete,and the total displacement,stress and strain are analyzed.The results show that under the pressure load,the model changes mainly in the top of the specimen,the displacement changes from the top of the specimen to the lower gradually reduced,the maximum displacement deformation is mainly in the top of the specimen and the weak part between the pores.The deformation of the bottom part of the specimen is very small,the deformation of the upper part is large,and the stress nephogram shows a trend of gradually spreading outward from the pores,and the stress in the pores is gradually increasing,indicating that the failure of the specimen begins from the pores and gradually spreads to other parts of the specimen,which is similar to the actual test in which cracks begin to occur in the pores of the concrete and gradually spread to cause the aggregate to fall off.So that the failure of the test block is consistent.It is further explained that the compressive failure of the plant-grown concrete mainly starts from the weak interface at the pore and then begins to expand,which eventually leads to instability,loss of strength and failure of the specimen. |
PDF Full Text Request