Study On The Performance And Freeze-thaw Cycle Deterioration Of Non-fines Concrete With Different Admixtures

Pervious concrete is a new kind of functional construction material developed from the ordinary concrete technology. It is composed of non-grading coarse aggregate, cementing agent (including cement and admixtures) and water. Pervious concrete has large porosity (10%-30%) and low apparent density, which attaches high permeability to itself and extensive use in the constructions of stadium, residence public area and eco-land. Reducing road noise and surface water are the main advantages of pervious concrete applied in road engineering. At some suitable regions, pervious concrete can also help gather the rain water for recycling. High permeability improves the eco-cycle in urban environment. However, in cold temperature zone, especially in northern China, freeze-thaw damage turns out to be a serious problem. There is still little research studied on the micro-mechanism and influence factor of the freeze-thaw damage to pervious concrete. Therefore, it is necessary to design tests and do analyses on the freeze-thaw damage laws, as is done in this paper.Based on the present pervious concrete production technique, the author added several volumes of fly ash, mineral powder, silica fume, quartz sand, VAE-707 emulsion and polyethylene fiber as the admixtures to the concrete. The mix proportions were recalculated to optimize the strength and porosity of the specimens. The freeze-thaw test used the quick frost method. Porosity, permeability and strength tests were conducted for ensuring the engineering performance. The frost resistance of pervious concrete is evaluated by the mass loss and relative dynamic modulus of elasticity.The freeze-thaw test shows the influence laws of different admixtures on the frost resistance of pervious concrete. Fly ash can reduce the mass loss and relative modulus of elasticity loss of the pervious concrete under freeze-thaw cycle. Silica fume’s influence law on the frost resistance of pervious concrete is similar to fly ash, but more notable on degree. The data exhibited a peak value of the relative dynamic modulus of elasticity at the silica fume content around 8%. VAE-707 emulsion can significantly improve the frost resistance of pervious concrete, but exists a threshold beyond which the economic effect turns into negative growth. It is suggested to use low content (2%) of VAE-707 emulsion in actual engineering. Quartz sand had little impact on the frost-resistance of pervious concrete. Mineral powder reduced the mass loss of pervious concrete after freeze-thaw cycle but influenced little on the relative dynamic modulus of elasticity. Polyethylene fiber can improve the frost resistance while the improving effect was not sensitive to its content.In addition, this study attempted to find an optimum mix proportion of all admixtures mentioned in this paper for a pervious concrete product with the best frost-resistance. However, the test results shown that the pervious concrete specimens mixed with all kinds of admixtures have no obvious advantages in frost-resistance but high economic cost. The production theory of this kind of pervious concrete needs further study.