Spray-applied waterproofing membranes in tunnelling: A construction perspective

Abstract

Spray-applied waterproofing membranes have received a lot of press and attention in recent years, but the coverage has in large either been design focussed or driven by the material suppliers of such membranes or opponents of the approach. This paper aims to provide a comprehensive overview of the limitations and advantages of spray-applied waterproofing membranes from a practical construction perspective. It discusses the logistic benefits compared to traditional sheet membranes, but also highlights the hidden complexities and impacting factors that are often not fully transparent. The paper covers activities that need to be considered when scheduling or costing such works and provides a general basis for the preparation of Work Method Statements. It also covers contractual constraints, requirements under current international and national standards and regulations, pre-production trials, and quality testing requirements. OH&M considerations are also addressed. Additionally, the paper identifies complementary tasks that are often overlooked but are necessary for a successful membrane installation. These tasks include pre-production trials and quality testing requirements, as well as other activities that need to be considered when choosing a sprayed waterproofing solution. The paper concludes by summarizing the requirements stated by different material manufacturers. All of this is complemented by the authors own experience and observations, and a summary of the consequences drawn from the reviewed data. Consequently, an overview on the aspects of usage of a sprayed-applied membrane material is presented, which the author hopes will provide some practical guidance for the evaluation of the suitability and application of such a product.