高钙粉煤灰CO_(2)矿化预处理及其对地聚物力学性能的影响研究

CO2-mineralized pretreatment of high-calcium fly ash and its effect on mechanical properties of geopolymers

为提高高钙粉煤灰在混凝土中的水化活性和体积安定性,分别以原状、CO_(2)矿化预处理6、24 h的3种高钙粉煤灰为单一前驱体制备了地聚物,研究了矿化程度对高钙粉煤灰理化特性的影响,并分析其作用机理。结果表明,经6、24 h CO_(2)矿化预处理的高钙粉煤灰中f-CaO含量比原状高钙粉煤灰降低了2.64、2.80个百分点。采用6 h CO_(2)矿化预处理高钙粉煤灰制备的地聚物1 d抗压强度可达29.7 MPa,比原状高钙粉煤灰制备的提高了34.4%。经6 h CO_(2)矿化预处理可以促进水化产物的生成和成核结晶。但CO_(2)矿化预处理时间过长(24 h)时,不利于高钙粉煤灰基地聚物的强度发展。

To improve the hydration activity and volume stability of high-calcium fly ash(HCFA)in concrete,geopolymers were prepared using three types of high calcium fly ash as a single precursor,subjected to intact state and CO_(2)mineralization pretreatment for 6 and 24 hours,respectively,and the influence of mineralization degree on the physicochemical properties of HCFA was investigated,and its mechanism of action was analyzed.The results showed that with the increasing degree of mineralization,the free calcium oxide content in the samples decreased by 2.64 percent point and 2.80 percent point,and the 1-day compressive strength of the geopolymer prepared from HCFA pretreated with 6 h of CO_(2)mineralization could reach 29.7 MPa,which was improved by 34.4%.This was because the 6 h of carbonation pretreatment for HCFA could promote the generation of hydration products and nucleation and crystallization.However,if the carbonation pretreatment time was long(24 h),it was detrimental to the strength development of the HCFA-based geopolymer.