Rheological Properties of Wet-Mix Shotcrete Mixtures Made with Crushed Aggregate

The recent depletion of high-quality and well-graded natural-aggregate sources is one of the factors compromising the production of good-quality shotcrete. For this reason, the use of various alternative aggregate sources has been receiving increasing attention as one of the promising solutions for this issue. In this study, the feasibility of using crushed aggregate obtained as a by-product of tunnel-excavation processes in wet-mix shotcrete (WMS) is evaluated based on laboratory tests. To fulfill this aim, efforts have been made to evaluate rheological properties of WMS mixtures incorporating crushed aggregates because shotcrete rheology is recognized as one of the most significant components affecting actual shotcrete behavior such as pumpability and shootability. Other tests performed include air content, slump, and flow. The acceptability of crushed-aggregate WMS mixtures with four standard gradations were evaluated first. Then, allowable gradation ranges for WMS mixtures made with crushed aggregate were suggested based on modified Dinger-Funk gradations and prescribed WMS performance criteria. Results indicate that the use of crushed aggregate may be a suitable measure effectively meeting both industrial demands and shotcrete performance requirements. (C) 2017 American Society of Civil Engineers.