Influence of production systems on the properties of fresh and hardened shotcrete

Abstract In modern shotcrete operations, the mixing and pumping steps are carried out using different production systems and equipment. This adds an element of uncertainty to the process because of variables such as mixer type, rotation speed, mixing time, etc. As a result, this may result in changes to the characteristics and properties of both fresh and hardened sprayed mortar and may ultimately impair the performance of the rendering material. This study assesses the influence of production systems, particularly the mixing process, on the properties of fresh and hardened sprayed mortar. The methods used comprehend the collection and testing of mortar samples produced in wet-mix and dry-mix shotcrete systems, as well as a pre-packaged mortar batched and mixed in a laboratory mixer under controlled conditions according to the manufacturer’s instructions. Results were processed using analysis of variance (ANOVA) and multiple comparison of means using Fisher’s method. A statistically significant difference was observed in the flow table index, water retention, flexural strength and capillarity coefficient of the mortars produced using wet- and dry-mix systems.摘要：在现代喷射混凝土作业中，搅拌与泵送工序采用不同的生产系统及设备完成。由于搅拌机类型、搅拌转速、搅拌时长等变量的存在，该工序引入了不确定性因素。这可能导致新拌与硬化喷射砂浆的各项特征与性能发生变化，最终损害该抹灰材料的使用性能。本研究旨在评估生产系统（尤其是搅拌工序）对新拌与硬化喷射砂浆性能的影响。研究采用的方法包括收集并测试湿拌法与干拌法喷射混凝土系统制备的砂浆试样，以及按照厂商说明书在可控条件下于实验室搅拌机中完成配料与搅拌的预包装砂浆试样。试验结果通过方差分析（ANOVA）以及费希尔法均值多重比较进行统计处理。结果显示，采用湿拌法与干拌法制备的砂浆，其跳桌流动度指数、保水性、抗折强度以及毛细吸水系数均存在统计学意义上的显著差异。