基于响应面方法的粉煤灰地质聚合物混凝土制备

Optimization of fly ash geopolymer concrete based on response surface methodology

针对粉煤灰的资源利用和环境保护问题,对粉煤灰地质聚合物混凝土（Fly ash Geopolymer Concrete,FGC）的制备进行了系统研究。为有效解决FGC制备参数的优化问题,在单因素分析的基础之上,采用Box-Behnken Design响应面方法设计并进行了系列研究试验,建立了基于响应面方法的FGC强度预测模型,并对其制备参数进行了优化。结果表明,当FGC水胶比为0.35、用碱量为7.9%、水玻璃模数为1.66时,其28 d抗压强度预测值得到最大值（44.6 MPa）,验证试验证明了响应面方法优化制备FGC的有效性。

Aiming at sufficient resource utilization of the fly ash through environmental protection, the present paper has done a systematic exploration of a new approach to preparing the green geopolymer concrete with the fly ash as the original material. To solve the problem involving all the influential parameters for the fly ash geopolymer concrete （FGC） preparation, we have made a systematic analysis of the single-factor and the changing rule of FGC for the proper regularity of the water-binder ratio, the alkali dosage, the water proportion as well as the sodium silicate modulus respectively so as identify and determinate the Optimal ratio of all the parameters involved. Furthermore, we have also laid out and conducted a series of practical experiments by using the Box- Behnken Design method known as the response surface methodology （RSM） so as establish the strength prediction model of FGC based on the RSM and the optimized preparation parameters of the said model. The single-factor experimental results show that the optimized ratios of all the parameters to guarantee the concrete strength through the water-binder ratio may stand for 0. 32 - 0. 4, with alkali dosage being 7%- 9% and sodium silicate modulus- 1.4 - 1.8, whereas little effect can be found on the strength of FGC to per unit water. Furthermore, we have also conducted the response surface experiments with the water-binder ratio, the alkali dosage, and the sodium silicate modulus, for they have been found significant impact on the strength of FGC along with the single factor test result. In addition, it has been noticed that the influential factors that affect the strength of concrete can be shown in the following descending order ： alkali dosage 〉 the sodium silicate modulus 〉 the water-binder ratio 〉 the interactive items. The optimum calculation with the help of the strength prediction model of FGC based on RSM helps us to confirm that the optimum parameters should be a water-binder ratio of 0.35, an alkali dosage of 7.9% , and a sodium silicate modulus of 1.66. It is just on the aforementioned condition that the compressive strength through a period of 28 d can be predicted to reach the maximum limit of 44. 6 MPa. But, the actual mean 28 d compressive strength of the concrete we have gained through the validation test turns out to be 45.6 MPa under the optimal condition, with the relative prediction error being at about 2.24% , which proves the effectiveness of RSM in optimizing the preparation of FGC. Thus, it can be concluded that this results of this study are in a position to provide a quick and effective method for the green concrete preparation, such as FGC.