Study On Effect Of CMC Content And Aggregate Particle Size On Performance Of Ecological Concrete With Slope Protection

In this experiment,CMC(carboxymethyl cellulose)was used as an admixture in the production of ecological concrete to prepare ecological concrete with dual functions of good compressive strength and excellent water purification capacity.Meanwhile,the most applicable sewage types of ecological concrete under different conditions were explored.Under the conditions of different particle size and CMC dosage,the difference between the compressive strength of ecological concrete,the influence on water p H and the water purification ability in the sewage with different concentration of pollutants was studied,and the dynamic analysis was made on the basis of this.The following research conclusions are drawn:(1)The standard curing results for 28 days show that the compressive strength of ecological concrete can be enhanced by using CMC as the admixture.When the void fraction is the same,the compressive strength of ecological concrete basically increases first and then decreases with the increase of particle size and the content of CMC,and the overall compressive strength is above 5.22 MPa.It can basically meet the mechanical requirements of ecological concrete.The ecological concrete with a particle size of 10-20 mm and CMC content of 0.1% has the highest compressive strength,which can reach 11.74 MPa.(2)The prepared ecological concrete has a certain influence on the p H of water body,and the particle size of ecological concrete is the main influencing factor.In the initial stage of high-speed alkali-releasing of ecological concrete,the p H of water body will rise to 12.After a certain period of time,the particle size of ecological concrete of 10-20 mm and 20-40 mm can be reduced to between 9.4-9.8,which has little influence on the alkaline environment of water body.The growth environment of microorganisms and plants can be guaranteed.The higher the content of CMC,the faster the p H drops to the final value.(3)With the increase of treatment time,the removal rates of the three pollutants in the water purification system of each group showed a gradually increasing trend,but the main removal time stages of different pollutants in each group were different.The pollutant removal loads of the nine groups of different water purification systems fluctuated in different weeks,and peaked at 5d and 10 d,contributing25.66-72.34%(COD),27.20-60.07%(total nitrogen)and 36.10%-87.41%(total phosphorus)of the total pollutant removal loads of the whole test period in one week,respectively.(4)The orthogonal test results show that the overall water purification effect of ecological concrete with particle size of 5-10 mm and CMC content of 0.05% is better.When the concentration of total phosphorus in sewage is 4mg/L,the concentration of total nitrogen is 30 mg/L,and the concentration of COD is 200 mg/L,The removal rates of total phosphorus,total nitrogen and COD reached 98.23%,72.33% and 88.98%,respectively.The aggregate particle size and CMC content have great influence on the water purification capacity of ecological concrete,while the sewage concentration has little influence on it.(5)Through the experimental comparison of the compressive strength,the ability to influence the p H of water and the water purification ability of ecological concrete,the best combination can be found out,which is A2B2C3,that is,the particle size of 10-20 mm,the CMC content of 0.1% ecological concrete has the best compressive strength and alkali release ability,the total phosphorus concentration is6mg/L,the total nitrogen concentration is 50mg/L,The removal effect is best in the wastewater with COD of 400 mg/L.(6)Through the preliminary planting test,tall fesfesa,an alkali-resistant plant,can normally grow on the ecological concrete,but the small void and high alkalinity caused by small particle size still have a negative impact on the growth of the plant,and the ecological concrete with large particle size has better planting ability.(7)By fitting the pollutant removal process with the first-order reaction kinetics model,it is found that the first-order kinetics model can better describe the kinetics law of the removal of total phosphorus,total nitrogen and COD in the slope protection of ecological concrete water purification system.The kinetic parameters of total phosphorus removal obtained by fitting were between 0.0118-0.1165d-1,total nitrogen between 0.0311 and 0.0468d-1,and COD between 0.0436 and 0.0724d-1.The dynamic constants are different because of the difference between the particle size of ecological concrete aggregate,the content of CMC and the concentration of pollutants.