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1.概述近几年,粉煤灰在混凝土中的应用得到了普遍的推广。实践已经证明,粉煤灰适量取代水泥掺入混凝土中,可改善混凝土拌和物的和易性,降低水化热。提高混凝土耐久性,同时可提高混凝土后期强度。然而不同质量的粉煤灰对混凝土拌和物及硬化后的质量的影响差别较大。目前因受各地煤质及电厂固有设备的局限,应用于混凝土工业中的粉煤灰多为Ⅱ级磨细粉煤灰。Ⅱ级磨细粉煤灰往往活性较差,细度较低,需水量以及烧失量的缺点,与Ⅰ级粉煤灰相比,达到相同的流化效果外加剂的用量偏高。因此掺入Ⅱ级磨细粉煤灰的混凝土,粉煤灰取代水泥率低。混凝土用水量高。早期强度低。Ⅰ级粉煤灰在理论上可以改善Ⅱ级灰上述缺陷。
1. Overview In recent years, the application of fly ash in concrete has been widely promoted. Practice has proved that the appropriate amount of fly ash instead of cement mixed with concrete can improve the workability of concrete mix, reduce heat of hydration. Improve the durability of concrete, while improving the strength of concrete late. However, the impact of different quality fly ash on concrete mix and hardened quality varies greatly. At present, due to the limitation of the inherent equipment of coal and power plants all over the country, most of the fly ash used in the concrete industry is Grade II ground fly ash. Grade II ground fly ash tends to have poor activity, low fineness, water requirement and loss on ignition. Compared with Grade I fly ash, the amount of admixture used to achieve the same fluidization effect is high. Therefore, mixed with grade Ⅱ ground fly ash concrete, fly ash instead of low cement. Concrete water consumption. Low early strength. Grade I fly ash in theory can improve the grade Ⅱ gray above defects.