养护制度对粉煤灰基地质聚合物强度影响的研究

Influence of Curing Schedules on the Strength of Fly Ash-Based Geopolymer

以景德镇地区的粉煤灰与炉渣为基础原料,通过添加一定的激发剂压制成型,制备地质聚合物材料,主要研究了养护制度对样品强度的影响,并对样品进行了XRD、SEM、EDS表征。结果表明:80℃养护0. 5 h,可迅速形成大量的钠铝硅酸盐(N-A-S-H);延长80℃的养护时间,Ca^(2+)会取代部分Na^+,形成一定量的钙铝硅酸盐(C-A-SH),抗折强度逐渐升高。继续升至120℃养护时,虽产生的缩聚物(N-A-S-H)较多,但由于水分的快速蒸发,使样品的孔隙率升高,并产生微裂纹,抗折强度下降。180℃养护1. 5 h时,由于形成了无定形的水化硅酸钙(C-S-H),其填充在因失水形成的孔隙中,使抗折强度回升;延长养护时间至3 h,C-S-H遭到破坏,缩聚产物与晶体间受热膨胀不同产生热应力,抗折强度下降。继续升至250℃养护时,随养护时间的延长,玻璃相被进一步侵蚀,缩聚产物进一步增加,桥联于玻璃珠周围,使显微结构致密,抗折强度升高,并保持在40 MPa左右。

Fly ash-based geopolymer materials were pressed by adding certain alkaline agent using fly ash and slag in Jingdezhen area as the original materials. Influence of various curing schedules on the strength of geological polymer materials was studied, and XRD, SEM and EDS were employed to characterize the microstructure and elements of the samples. The results show that a mass of N-A-S-H are formed quickly when the samples are cured at 80 ℃for 0.5 h. A certain amount of C-A-S-H can be formed due to partly replace of Ca^2+ and Na^+ with the extension of curing time at 80 ℃ and the bending strength gradually increased. Rising the curing temperature to 120 ℃, the amount of N-A-S-H increases, but the bending strength decreases because of the rapid evaporation of moisture leaving the porosity of the sample increases and generates micro-cracks. When curing the samples at 180 ℃ for 1.5 h, the bending strength rises again due to the forming of amorphous hydrated calcium silicate (C-S-H) which fill in the pore formed by the water. Extending the curing time to 3 h, the bending strength decreases due to the thermal stress caused by different thermal expansion between the condensation product and the crystal and C-S-H is damaged. Continue to rise the curing temperature to 250 ℃, glass phase is further eroded and condensation products further increase which bridge between glass beads around making the microstructure more compactly. With the extension of curing time the flexural strength increases and the bending strength maintaines at about 40 MPa finally.