Study On The Frost Resistance Of High-Performance Road Concrete With Mineral Admixtures

Durability is a important performance of concrete, road engineering in the northern coldregions, concrete destruction often caused by many factors such as freeze-thaw cycle and saltserosion and so on. There are many ways to improve the frost resistance of concrete. This papermainly studies the role of mineral admixtures to improve the frost resistance of concrete. Inaccordance with the characteristics of high performance concrete, water to binder ratio is0.4,the total cementitious materials440kg/m~3rate of40%sand, super plasticizer dosage is1%, thepreparation of the concrete road to meet the heavy traffic levels. Perform the resistance to saltand water frozen mechanical experiment of high performance concrete that is added differentproportion or different kinds of admixture under the conditions that the water-binder ratio is0.4.Also, after the freeze-thaw cycle experiment, analysis and compare the evaluation index ofmass loss rate and relative dynamic elastic modulus. And by mercury injection test to analysisthe micro structure and compressive strength of concrete. Through the test and analysis get thefollowing several main conclusions:(1)Suitable dosage of mineral admixture can improve the compressive and flexuralstrength of the concrete. Through the test found that: in the maintenance of28days, the ratio ofsilicon ash content less than10%or the ratio of fly ash both Level1and level2content within30%or the dosage of fine steel slag powder grinding within all can improve the concretecompressive strength and flexural strength. Fly ash and silica fume compound or finely groundsteel slag and silica fume complex, content within50%can improve the road concretecompressive and flexural strength.(2)Single-doped appropriate amount of silica fume can improve the frost resistance ofconcrete. However, not only single-doped fly ash but also grinded steel slag powder can notimprove the frost resistance of concrete. The frost resistance of the concrete which doped with30%fly ash and silica fume (the raito is2:1) is lower than the blank concrete in the water. Theconcrete of wich doped with30%or50%fly ash and silica fume has the same frost resistancewith the blank concrete in the water. The reasonable dosage of the compound admixture canreduce the extent of concrete spalling under the case of NaCl and freeze-thaw cycle worktogether. At the same time, doped with30%finely ground steel slag and silica fume compositeadmixture (the ratio is2:1) can improve the relative dynamic elastic modulus of the concrete.(3)Mineral material can improve concrete hole structure. The content of30%, a ratio of2:1finely ground steel slag powder and silica fume combination of frost resistance of concretehasthebest pore structure and freezing resistance. The pore structure of the single-doped silicafume concrete is better than the single-doped fly as concrete and single-doped grinded steel slag concrete. Doping with10%silica fume can significantly improved the pore structure of theconcrete, so can improve the concrete frost resistance.(4)After freeze-thaw cycle in water, the degree of spalling of the concrete surface issmall, its internal pore structure of concrete relative dynamic elastic modulus of the moresignificant; incorporation of mineral admixtures can increase the density of concrete, andreduce the water frozen adverse effects of concrete strength.(5)In the3%NaCl solution, due to the role of salt erosion and freeze-thaw cyclecombined effect exacerbated by the spalling of the concrete surface and inside the concrete poreaperture is significantly increased, in order to significantly reduce frost resistance.