室温碱激发低钙粉煤灰地质聚合物配比试验研究

为得到室温下粉煤灰与碱激发剂质量比、水玻璃与氢氧化钠溶液质量比和氢氧化钠溶液摩尔浓度对粉煤灰地质聚合物力学性能的影响,以低钙粉煤灰为原料,制备了地质聚合物胶凝材料。采用正交试验方法,分析粉煤灰地质聚合物抗压强度,探讨碱激发剂配比对粉煤灰地质聚合物力学性能的影响,结合SEM、XRD和FTIR对试样进行表征,并对该材料的应力-应变曲线进行了研究。结果表明:粉煤灰地质聚合物的抗压强度随着激发剂掺量的减少而增大,水玻璃在激发剂中的比值与粉煤灰地质聚合物的抗压强度呈现正相关,其中粉煤灰与碱激发剂质量比为1.8,水玻璃与氢氧化钠溶液质量比为2.5且氢氧化钠溶液的浓度为10 mol/L时,120 d龄期的抗压强度可达51.98 MPa。对应力-应变曲线分析得出,在一定程度上,激发剂的掺入量对粉煤灰地质聚合物的破坏应变和弹性模量有较大影响。SEM、XRD和FTIR分析表明随着养护时间增长,胶凝材料体系内结构更致密,生成了更多的硅铝酸盐凝胶。

Experimental Study on Proportion of Room Temperature Alkali-Activated Low-Calcium Fly Ash Geopolymer

In order to investigate the influence of the mass ratio of fly ash to alkali activator, the mass ratio of water glass to sodium hydroxide solution, and the molar concentration of sodium hydroxide solution on the mechanical properties of fly ash geopolymer at room temperature, low-calcium fly ash were used as raw material to prepare geopolymer cementing material. Orthogonal test method was used to analyze the compressive strength of fly ash geopolymers and to discuss the influence of the ratio of alkali activator on the mechanical properties of fly ash geopolymers. SEM, XRD and FTIR were also carried out to characterize the geopolymer samples, and the stress-strain relationship of the material was studied. The results show that the compressive strength of fly ash geopolymer increases with the decrease of activator content, and the ratio of water glass in activator is positively correlated with the compressive strength. When the mass ratio of fly ash to alkali activator is 1.8, the mass ratio of water glass to sodium hydroxide solution is 2.5, and the concentration of sodium hydroxide solution is 10 mol/L, the compressive strength of the obtained geopolymer after curing for 120 d reaches to 51.98 MPa. The stress-strain curves show that the amount of activator has a greater impact on the failure strain and elastic modulus of fly ash geopolymer to some extent. Moreover, the results of SEM, XRD and FTIR show that the structure of the cementitious material system become denser with the increase of curing time, and more aluminosilicate gels are mainly generated.