Muhammad Abubakar, Thienel Karl-Christian, Scherb Sebastian
Institut für Werkstoffe des Bauwesens, Universität der Bundeswehr München, 85577 Neubiberg, Germany.
Materials (Basel). 2023 Mar 28;16(7):2684. doi: 10.3390/ma16072684.
In this work, four naturally occurring (two kaolinite-rich and two smectite-rich) clay samples were collected from different areas around the Ashaka cement production plant, located in Gombe State, Nigeria and calcined in a laboratory. The mineralogical characterization of the clays was carried out by XRD. The hydration kinetics of the calcined clay-cement systems were monitored by isothermal calorimetry. Workability was determined using the flow table method. The reactivity of the calcined clays was determined from the solubility of Si and Al ions and the strength activity index. All calcined clays studied met the requirements of ASTM C618 for the use of natural pozzolans as a partial replacement for hydraulic cement. The metasmectite clays yielded a higher specific surface area, increased water demand, and less reactive Si and Al ions compared to the metakaolin clays. The two calcined clay groups require the addition of superplasticizer to achieve a workability class similar to the Portland cement mortar system. They can be used to replace Portland cement at replacement levels of up to 45%, in combination with limestone powder to form an LC cement, thereby achieving at least a "Level 1" reduction in greenhouse gas emissions.
在这项工作中，从位于尼日利亚贡贝州阿沙卡水泥厂周边不同区域采集了四个天然存在的（两个富含高岭土和两个富含蒙脱石）粘土样本，并在实验室中进行煅烧。通过X射线衍射（XRD）对粘土进行矿物学表征。采用等温量热法监测煅烧粘土 - 水泥体系的水化动力学。使用流动台法测定工作性。根据硅和铝离子的溶解度以及强度活性指数确定煅烧粘土的反应性。所有研究的煅烧粘土均符合美国材料与试验协会（ASTM）C618中关于使用天然火山灰质材料部分替代水硬性水泥的要求。与偏高岭土粘土相比，变蒙脱石粘土具有更高的比表面积、更高的需水量以及活性较低的硅和铝离子。这两组煅烧粘土需要添加高效减水剂才能达到与波特兰水泥砂浆体系相似的工作性等级。它们可用于替代高达45%的波特兰水泥，与石灰石粉混合形成LC水泥，从而实现至少“一级”的温室气体减排。
