通过C30混凝土实验室配合比，配制掺30％粉煤灰的粉煤灰—水泥混凝土，分别在三个实验组中分别掺入最佳掺量的NaOH、水玻璃和CaO，振捣成型，测定碱对流动度和凝结时间的影响，用扫描电镜探求胶砂的微观结构，随后养护至龄期。按照《普通混凝土力学性能试验方法标准》测定混凝土抗压强度和劈拉强度，通过强度比较，算出强度提高率；可以得出掺碱对早期和后期强度发展的影响。结果表明，掺碱能促凝且胶砂流动度减小；掺碱粉煤灰早期强度发展快，后期发展较缓慢，90 d强度基本能够满足设计要求；扫描电镜中，由于水泥水化加快，粉煤灰活性得以激发，早期强度得到改善；经济技术效益显著。

Based on the laboratory mix ratio of C30 concrete，the fly ash-cement concrete was mixed with 30% fly ash to make three experimental groups which were also mixed with the best dosages of NaOH, sodium silicate, and CaO, respectively. After vibration molding, the impacts of alkali on the mobility and setting time were determined. The microstructure of mortar was investigated using the scanning electron microscope, and then the samples were maintained to age. According to the 《Standard for test method of mechanical properties on ordinary concrete》, the compressive strength and splitting tensile strength of the concrete were measured. Through the comparison of strengths, the intensity increasing rate was determined, which can help understand the impacts of mixing alkali on the strength development in the early and late times. The results showed that (1) mixing with alkali can coagulate and decrease the mobility of mortar；(2) the fly ash mixed with alkali has a rapid strength development in the early time and a slow strength development in the late time, and the strength at 90 days can meet the design requirements; (3) In the scanning electron microscope experiment, due to the quick cement hydration speed, the activity of fly ash motivates, and so the strength in the early time improves; and (4) the economic and technical benefit is remarkable for the fly ash-cement concrete mixed with alkali excitant.

水利部公益性行业科研专项经费项目(201301033)