高强无收缩地聚物的研制与性能研究

Study on the Development and Property of High Strength Geopolymers Without Shrinkage

当今碱激发工业固废制备的地聚物胶凝材料是最具潜力替代普通硅酸盐水泥的绿色胶凝材料之一。筛选粉煤灰、矿渣和偏高岭土为前驱体,NaOH-水玻璃的混合液体为碱激发剂,高分子吸水性树脂(polymer absorbent resin,SAP)与复合膨胀剂为补偿收缩材料,制备了一种力学性能优异且体积无收缩的地聚物,并通过扫描电子显微镜(Scanning Electron Microscope,SEM)和X-射线衍射(X-Ray Diffraction,XRD)等手段进行微观分析。结果表明,当水固比为0.32、碱含量为12%、水玻璃模数为1.3及复合型膨胀剂掺量为6%时,所制备的地聚物力学性能最好,具备高早期强度的功能;硬化24 h后体积无收缩,膨胀率为0.02%;此时地聚物浆体流动性较大,无泌水现象,结石率高。究其原因在于水化产物中网络状的N-A-S-H凝胶与C-A-S-H凝胶以及少量CaCO_(3)晶体相互交织,形成致密的结构提高了体系的力学性能,而膨胀剂生成的针棒状AFt和少量Ca(OH)_(2)晶体补偿收缩的同时,也具有增强功能。本工作可为绿色新型建筑材料的推广和应用提供一定的理论支持。

Currently,geopolymer cementing materials prepared from alkali-activated industrial solid waste are considered one of the most promising green cementing alternatives to Portland cement.By utilizing fly ash,slag and metakaolin as precursors,the mixture of sodium hydroxide-sodium silicate as alkali activator,polymer absorbent resin(SAP)and composite expansion agent as shrinkage compensating materials,a geopolymer with exceptional mechanical properties and non-shrinkage volume was prepared.Scanning Electron Microscopy(SEM)and X-Ray Diffraction(XRD)were conducted for microscopic analysis.The results show that when the water-solid ratio was 0.32,the alkali content was 12%,the sodium silicate modulus was 1.3 and the compound expansion agent content was 6%,the polymer exhibits the optimal mechanical properties and high early strength.After hardening for 24 h,no shrinkage occurred in the volume while exhibiting an expansion rate of only 0.02%.At this time,the geopolymer slurry demonstrates excellent fluidity without any bleeding phenomenon while maintaining a high stone rate.This can be attributed to the interweaving of network N-A-S-H gel and C-A-S-H gel with a small amount of CaCO_(3) crystals in the hydration products,which form a dense structure improving the mechanical properties of the system.Additionally,needle-rod Aft generated by the expansion agent with a small amount of Ca(OH)_(2) crystals contribute to compensate shrinkage and strengthen simultaneously.This work provides valuable theoretical support for the promotion and application of new green building materials.