Design Preparation And Engineering Application Of Low Shrinkage And High Early Strength Pavement Concrete

Because of these characteristics for example low shrinkage,high early strength and good durability,pavement concrete is widely used in which need rapid repair projects such as urban roads and airport runways,and the same to quickly scrambling to repair engineering like harbors,wharfs,bridges and tunnels.The traditional manufacturing method adopted is to use road cement or special process,but the pavement concrete usually appeared with low early strength,serious shrinkage cracking,expensive preparation cost and complicated technology.This subject is designed to develop a pavement concrete with low shrinkage and high early strength by using the conventional raw materials and common process.This thesis relies on pavement reconstruction project of Maoming City ordinary national and provincial trunk highways,aiming at the road construction for the humid and hot climate of subtropical monsoon climate region in hilly and mountainous area of southeast Guangxi,a kind of pavement concrete test mix proportion with low cost,low shrinkage,high early strength and high flexural has been exploited to meet the design requirements.Based on the raw materials detection of pavement concrete,this thesis puts forward the technical index requirements respectively of cement,fly ash,slag powder,fine aggregate,coarse aggregate,mixing water and admixture.The mix proportion of pavement concrete is designed.Taking water consumption,admixture dosage and sand coarse aggregate ratio as factors,the orthogonal experimental design scheme is adopted.The slump measurement,compressive strength and flexural strength are taken as evaluation indexes,and the range analysis method is used to analyze the influence degree of each factor.The result shows that water consumption is the main factor affecting the workability and mechanical strength of pavement concrete.The mix proportion is optimized according to the influence degree of each factor,on the basis of orthogonal experimental design,the mechanical properties performance indexes of pavement concrete compressive strength and flexural strength are further studied.The compressive strength and flexural strength of pavement concrete with different amount of fly ash and slag powder increase with the increase age of concrete,and the addition of 10%fly ash and 12%slag powder can effectively improve the later mechanical properties of pavement concrete.The flexural strength and flexural compression ratio of pavement concrete have the same trend with the changes of sand coarse aggregate ratio,both of which increase first and then decrease,indicating that the 35%sand coarse aggregate ratio can effectively improve the flexural strength of pavement concrete.The water-cement ratio is the most important factor affecting the drying shrinkage of pavement concrete.Reducing the water-cement ratio is beneficial to reducing the drying shrinkage of pavement concrete,but too low water-cement ratio will affect the construction performance.After the test,the water-cement ratio is0.32 as the criterion.10%fly ash and 12%slag powder admixtures can reduce the drying shrinkage of pavement concrete,but the sand coarse aggregate ratio has little effect on the drying shrinkage of pavement concrete,and the optimum value is 35%.The unit water consumption of pavement concrete is reduced from 145kg to130kg,and the admixture is added to reduce the hydration heat of concrete,so as to achieve the goal of low shrinkage and high early strength.When the water-binder ratio of mix proportion test is 0.32,the dosage of 10%fly ash and 12%slag powder,and the sand coarse aggregate ratio is 35%,the 7d compressive strength is over 40MPa,the 7d flexural strength is over 5.0MPa,and the 360d drying shrinkage rate is330～350*10^-6,which reaches the design target requirements of low shrinkage and high early strength pavement concrete.The raw material cost of the original construction party is 356.0 Yuan per cubic meter of pavement concrete.After improvement,the cost is reduced to 315.2 Yuan per cubic meter,saving 40.8 Yuan per cubic meter of cost.In the whole project of about24 kilometers pavement concrete construction,more than 2.8 million Yuan cost has been saved,which has brought considerable economic benefits to the company.