基于DIC方法的地聚合物混凝土断裂过程分析

为了量化研究地聚合物混凝土断裂过程参数的演化过程,采用数字图像相关(digital image correlation,DIC)方法及夹持引伸计法对含初始缺口粉煤灰基地聚合物混凝土试样在三点弯曲加载过程中的裂缝口张开位移(CMOD)、裂尖张开位移(CTOD)及裂缝扩展长度进行测试与计算分析.结果表明:DIC测试的裂缝口张开位移与夹持引伸计测试值吻合较好,试样经历了起裂、裂缝的稳态和亚稳态扩展及失稳破坏阶段;基于DIC测试的裂尖张开位移与基于弹性等效的理论计算吻合较好,但基于DIC裂缝扩展长度的测试值与弹性等效裂缝扩展长度的计算值之间存在较大偏差,导致这一差别的主要原因是由于地聚合物混凝土与水泥混凝土一样存在断裂过程区.     

地聚合物凝胶结构特性的分子动力学研究

通过分子动力学模拟的方法,在参照实验数据构建起的初始结构模型的基础上,根据N-A-S-H凝胶体系的结构特点,选取Na原子、H2O分子及Si2Al O10基团作为基本单元的组成,构建了地聚合物凝胶结构模型。根据模拟过程中体系的运动轨迹,进行多次优化模拟操作,计算出N-A-S-H凝胶体系的径向分布函数(RDF)、XRD模拟图谱及力学性能等有关参数,并结合实验数据对所建结构模型的准确性进行了验证。结果表明,分子动力学模拟值与实验值吻合较好,不仅验证了所建结构模型的有效性,也为其在N-A-S-H凝胶体系的进一步深入研究提供了可能。     

高温短期养护对低钙粉煤灰地质聚合物性能的影响

以低钙粉煤灰为硅铝原料,NaOH和钠水玻璃为激发剂,粉煤灰和NaOH混合后加水玻璃并在50℃、60℃、70℃、80℃和90℃的烘箱内养护6h、12h和18h制备地质聚合物。探讨了高温短期养护对地质聚合物力学性能的影响,并对在80℃下养护18 h的地质聚合物进行了XRD和TG分析,表明形成了具有耐高温性能的低钙粉煤灰地质聚合物。在较低温度下只有经较长时间养护才能获得较高抗压强度的地质聚合物;而在较高温度下可以在较短时间内获得较高抗压强度。     

Synthesis of heat and ambient cured one-part geopolymer mixes with different grades of sodium silicate

The use of solid activators in the manufacture of geopolymer enhances its commercial viability as it aids the development of a one-part “just add water” geopolymer mixture, similar to the conventional Portland cement-based materials. This study is aimed to synthesize heat and ambient cured one-part geopolymer mixes. Appropriate combinations of low calcium (Class F) fly ash, slag and hydrated lime as the aluminosilicate source materials were activated by three different grades of sodium silicate and a combination of sodium silicate and sodium hydroxide powders. A conventional two-part geopolymer mix with the commonly used sodium hydroxide and sodium silicate solutions was also made for comparison. Effects of the type and amount of the solid activator, the amount of fly ash replacement with slag and hydrated lime and water content on short term mechanical properties of the heat cured one-part geopolymer mixtures including workability of the fresh mix, hardened density and compressive strength were evaluated. Subsequently, effects of ambient curing on the properties of the developed one-part geopolymer mixes were also investigated. Moderate to high compressive strength of over 37 MPa developed for the heat and ambient cured one-part geopolymer mixes. The 28-days compressive strengths of the ambient cured one-part geopolymer mixtures, regardless of the type of activator and geopolymer source materials, were comparable to those of the counterpart heat cured one-part geopolymer mixes. Such one-part geopolymer mixes could enhance the commercial viability and large-scale applications of the geopolymer in the construction industry.     

地聚合物的早期反应过程及表征技术

地聚合物因其高强、耐久性好等优点而得到迅速发展。早期地聚合反应过程直接影响其强度的发展及后期的耐久性能。介绍了量热法、动态流变测试法等常规测试技术与电子顺磁共振、X射线小角度散射等测试表征技术在地聚合物早期反应过程中的研究与应用,并展望了低场核磁共振、计算机模拟等其他研究方法在地聚合物体系中的应用潜力与前景,以期推动地聚合物早期反应研究的进步,促进地聚合物胶凝材料在实际工程中的应用与发展。     

早期地聚合反应过程的~1H低场核磁共振

在地聚合物体系中,浆体的组成及微观结构对于其硬化后的性能有着重要的影响。利用1H低场核磁共振仪对比研究了纯偏高岭土基(MK-100)及掺高钙粉煤灰(MK-85)的地聚合物的早期反应过程,探测了不同结合状态的水分子的质子信号,获得了水的纵向弛豫时间(T1)和横向弛豫时间(T2)。研究表明:1H低场核磁共振法适宜于研究地聚合物的早期反应过程,根据浆体纵向弛豫时间T1的加权平均值,可以将早期地聚合反应过程划分为加速期、减速期和稳定期3个阶段;高钙粉煤灰的加入使地聚合物浆体加速期缩短,减速期延长。早期地聚合反应过程中水的横向弛豫时间T2可以很好地表征毛细水或凝胶水的变化趋势。高钙粉煤灰的加入会延缓毛细水向凝胶水的转变过程。     

矿物聚合物的合成及其对Cr(Ⅵ)的解毒与固化

以煤矸石为原料、水玻璃和NaOH为碱性激发剂合成矿物聚合物,以添加硫化物的矿物聚合物对Cr(Ⅵ)进行解毒与固化,对固化体进行了检测.结果表明,当硫化物与Cr(Ⅵ)的摩尔比大于3∶1时,矿物聚合物中总铬的浸出浓度小于1 mg/L时,铬固化率大于99％,对Cr(Ⅵ)的最大固化量为1.2％.添加硫化物的矿物聚合物对Cr(Ⅵ)的解毒与固化是基于氧化还原反应,S2-被氧化为S2+(平均化合价),Cr(Ⅵ)被还原为Cr(Ⅲ),Cr(Ⅲ)被矿物聚合物中的-OAl(-)(OH)3吸引并固化在非晶质结构中.     

3D打印地质聚合物的研究进展和应用探索

地质聚合物是一种以铝硅酸盐为原料与碱激发剂反应而成的绿色建筑材料,将该材料应用于增材制造(3D打印)中有助于环境的可持续发展。本文介绍了挤出成型地质聚合物砂浆的研究进展,着重比较了3D打印样品与铸模成型地质聚合物样品的力学性能,此外,简述了粉煤灰基地质聚合物水泥在大型建筑构件增材制造中的应用潜力,及其在金属矿和高价值矿物矿渣(宝石矿等)回收利用方面的应用可行性。     

Evaluation of the potential of geopolymer mortar in the rehabilitation of buried infrastructure

Concrete pipes represent the backbone of the wastewater collection systems in many cities across North America. These pipes are in various stages of deterioration, generally due to microbiological induced corrosion and/or mechanical loading. A common method of rehabilitating these structures is the use of cementitious coatings. This paper describes the development and testing of three novel geopolymer mix designs prepared using metakaolin and fly ash (class C and F) precursors. Specimens prepared using Portland cement-silica fume blend were also tested for comparison purposes. The specimens were placed in several concentrations of sulphuric acid for a period of eight weeks. The corrosion resistance and remaining compressive strength of geopolymer mortar made from class F fly ash precursor were found to be substantially higher compared with the enhanced OPC formulation. The other geopolymer mix designs were found to perform equally or better compared with the OPC binary blend.     

水玻璃激发矿渣制备纳米地质聚合物研究

采用扫描电镜(SEM)、结合能量散射X-射线能谱分析(EDXA)、场发射扫描电镜(FESEM),对水玻璃激发矿渣细粉水化产物的生成及发展进程中的微观形貌进行了系统的研究.在水化早期,矿渣玻璃体快速解体,形成大量的硅溶胶和铝溶胶覆盖于矿渣表面;随着龄期的延长,硅铝溶胶之间发生缩聚反应,生成相互搭接的树枝状网络结构的地质聚合物凝胶体,表明矿渣玻璃体的解体是一个形成溶胶的过程.而缩聚反应是一个形成凝胶的胶凝过程.纳米地质聚合物结构密实,抗压强度从1d的26.5MPa增至28d的60.IMPa.地质聚合物是由20nm左右的颗粒搭建成的网络结构所组成.