Research And Application On Gentle Volume Expansion Concrete With Dual Source Of Calcium And Magnesium

Durability of concrete is the ability to maintain its own property under the influence of long-term environment. Shrinkage compensating concrete can effectively reduce or eliminate cracks and improve the impervious property. The expansion produced by the swelling agent will work on limiting force and compensate for volume shrinkage of concrete so as to prevent concrete cracking.This study can be devided into four parts. Firstly, the durability of double expansion source compensating shrinkage concrete with polypropylene fiber was studied, and the results were analyzed. Secondly, the three significant factors and three optimal levels of double expansion source compensating shrinkage concrete with polypropylene fiber was determined,which was combined with the results of previous mechanical and swell-shrinking properties test. Experimental study on mechanics, anti crack, expansion and shrinkage, impervious properties were conducted. Thirdly,The shrinkage of channel lining plate is calculated, and the shrinkage compensation mode is designed according to the experimental results.Finally, the shrinkage models at home and abroad were introduced and compared. And a model for the prediction of shrinkage value of compensated shrinkage concrete was obtained by comparing the predicted values with the measured values. The conclusions obtained are as follows:(1) Five yuan two times orthogonal rotation combination test was carried out. The contents of UEA-S, MgO, fly ash, water reducing admixture and polypropylene fiber were designed as the experimental research objects.The mix proportion of relevant anti permeability and frost resistance requirement can be obtained by using the regression equation. The equation is about experimental factors and relative permeability coefficient and mass loss rate and it was obtained by regression analysis and significant test. The optimal mix ratio for the anti permeability performance are as follows: UEA11.5%、 MgO3.25% 、 fly ash30% 、 polypropylene fiber 1.15kg/m3; The best combination of frost resistance performance are as follows: UEA11.5%、MgO2.75%、fly ash 25%、polypropylene fiber0.65kg/m3、water reducing admixture 0.75%. The optimal ranges of the contents of the mixedfactors on the mechanical properties and durability of the compensating shrinkage concrete were obtained, combining with the results of previous mechanical and swell-shrinking properties test.(2) By taking into account the optimal ranges and significance of the above factors, the influence of UEA-S, MgO and polypropylene fiber on the compensation shrinkage concrete is selected. Three levels were selected from the optimal dosage ranges. In order to reduce the effect of fly ash and water reducing agent on compensating shrinkage concrete and analyse the effect of UEA-S, MgO and polypropylene fiber better, the mechanical properties, limited expansion ratio and anti permeability tests were carried out with the control of fly ash and water reducing agent as a fixed amount. And carried on the variance and the range analysis.Through the experimental analysis, the best mixing amount of UEA-S, PP fiber and MgO content are 10%, 0.9kg/m3 and 3%.The shrinkage prediction accuracy comparison of compensation shrinkage concrete with the addition of MgO, UEA-S, polypropylene fiber and fly ash shows that the average relative error of ACI209 model and Model of Chinese Academy of Building Science are more than 60%, and the accuracy is relatively low.(3) Calculated ordinary lining plate of concrete shrinkage value, compensate the shrinkage and expansion, and the limit test for expansion rate statistics made corresponding to the different additives limited expansion ratio profile, combined with section crack expansion and shrinkage test results, on channels in shrinkage of compensation, this paper puts forward two methods of compensation.(4) The average relative error of GL2000, CEB-FIP and Wang Tiemeng model is between 18% and 40%, and its accuracy is higher than that of ACI209 and Model of Chinese Academy of Building Science. The accuracy of GL2000 model was the highest, followed by Wang Tiemeng model and CEB-FIP model.