粉煤灰水泥的护筋性探讨

Property of Protecting Reinforcing Steel Bar in Fly Ash Cement

在使用粉煤灰水泥时,常常担心粉煤灰水泥因二次水化反应消耗掉水泥水化产物中的Ca(OH)2,使粉煤灰水泥的护筋性欠佳.通过测试掺入粉煤灰的水泥水化28d的pH值,可以看出即使是粉煤灰掺量在70%时,其水化28d的pH值也大于11.5,不会导致粉煤灰水泥的碱度过低,影响其护筋性.采用浸烘循环法直接测试粉煤灰水泥在粉煤灰掺量为50%、60%时的护筋性,经过30次的循环,胶砂试件中钢筋的失重率与硅酸盐水泥处于同一水平.试验结果表明,粉煤灰水泥具有良好的护筋性.

When using fly ash cement, it is often worried about that the property of protecting reinforcing steel bar is insufficient, because the reaction will use up the Ca(OH)_(2) in the hydrated product. By testing the value of pH of fly ash cement hydrated 28 days later with the dosage of fly ash from 0～70%, it can be found that the value of pH of fly ash cement is bigger than 11.5 even hydrated 28 days, so it does not result in the alkalinity of fly ash cement too low consequently influencing the property of protecting reinforcing steel bar. The authors test directly the properties of protecting reinforcing steel bar of fly ash cement with the dosages of fly ash which are 50%,60% respectively. By utilizing the method wetting-drying cycle shows the ratio of weightless in specimen made of cement-sand is the same as in specimen made of Portland cement after 30 cycles.