Study On The Technology Of Reducing Alkali In Planting Concrete And The Adaptability Of Plants

As a new composite material,planting concrete combines porous concrete with plants organically,which has the functions of noise reduction,greening,water purification,water and air permeability,solidification,and can be applied to ecological slope protection and roof greening projects.In recent years,Chinese scholars have done a lot of research on the basic properties of plant concrete,but the technology of reducing alkali and plant growth which restrict its popularization and application still needs to be studied,this paper has done a series of research on it,the main contents are as follows:(1)There is a contradiction between the mechanical properties and pore alkalinity of the planting concrete.The strength of the plant-growing concrete can not be guaranteed in the low alkali state,and the growth of plants is limited in the high alkali state.According to the key control parameters in the proportion design of planting concrete,the orthogonal test of four factors and four levels was designed by choosing the water-binder ratio,the content of fly ash,slag and reinforcer.The compressive strength,flexural strength and pH value of pore environment of 16 groups of planting concrete blocks were tested,and the range and variance analysis methods were used to obtain the main and secondary factors affecting the performance indicators of planting concrete;The mix proportion of low alkali and high strength planting concrete was optimized by comprehensive analysis of Z value.Orthogonal design and multiple regression analysis were used to establish the multiple linear regression equation between the four factors and the 28d pore environment pH value,compressive strength and flexural strength of planting concrete,and the regression equation was tested for significance.(2)The chemical,physical and agronomic dealkalization techniques were used to prepare the concrete blocks with the optimized mix proportion.The effects of the single dealkalization method,including soaking with citric acid solution,spraying with superphosphate solution,spraying with DPS agent,soaking with paraffin wax and modifying the matrix with alkaline buffer agent,on the strength and pore pH value of the concrete were studied.The results show that the pH value of the pore environment of the planting concrete dipped in citric acid solution decreases by 1?2 units and the compressive strength decreases by about 13%?26%compared with the reference group,so it is not suitable to use acid solution to reduce the alkali of the planting concrete;After spraying calcium phosphate solution,the compressive strength of planting concrete can be increased by 2%?13%,the pH value of pore environment can be reduced by 2?3 units,and when the concentration of superphosphate solution is 2%,the economy is good and the effect of reducing alkali is better,and the pH value is stable at about 8.2;the early stage,but the accumulation of OH~-in the late stage led to the high alkalinity of planting matrix,which was not conducive to plant growth.In practical engineering,alkali reducing treatment could be carried out by combining chemical or physical alkali sealing with agronomic alkali reducing.(3)The filling method is determined by the filling experiment of the porous matrix.The results show that the grouting method is more uniform and the filling rate is higher than the spraying method and the immersion method,and the best filling method is when the spreading degree of the matrix paste is 215 mm.According to the formula of rainstorm intensity issued by Guangzhou Water Conservancy Bureau,the simulated rainstorm intensity was designed and the experiments were carried out.The results showed that when the amount of curing agent was 1.5%and 2%,the cleaning time of 2cm thick coating substrate was 2hr40min10s and 2hr40min10s respectively.2hr53min10s,and the rainstorm often lasts less than 90min,so it is concluded that the coating matrix with curing agent has a certain degree of rain flushing.(4)According to the principle of plant species selection,the herbaceous plants suitable for the subtropical monsoon climate in Guangzhou were selected to be planted in the pure substrate.The herbaceous plant varieties with good growth condition were selected from seedling emergence time,survival rate and turf formation rate,and tall fescue,king slope protection,Bermudagrass and four green were selected for the next planting experiment.The experimental groups of single sowing,mixed sowing,grass seed broadcast sowing and turf laying were designed,the plant species suitable for the application of plant concrete in Guangzhou area were optimized by the evaluation index of plant effect.