Irreversible Changes in the Grouting Industry Caused by Polyurethane Grouting: An Overview of 30 Years of Polyurethane Grouting

Water reactive polyurethane grouts were introduced into the grouting industry during the late sixties by the Takenaka company in Japan under the trade name TACSS. It became possible to inject "one component" grouts without potlife that do not easily wash out and react with the ground water. Because of environmental scrutiny, the first series of TACCS were replaced by solvent-free, hydrophobic, MDI based polyurethane prepolymers. Whilst remarkable successes were booked in mining and geotechnical engineering projects, more and more these products were used for permanent seepage control for sealing concrete structures. Hydrophilic polyurethanes were also introduced in Japan predominantly for the latter application. They contained solvents and were TDI based. Their high reactivity and high dilution ratio with water made them attractive to practitioners. In 1980, the N.V. DeNeef Chemie obtained the exclusive rights for TACSS for most places on earth and the successes in stopping major leaks in tunnels changed classic grouting (sodium silicate cement combinations) and seepage control grouting (acrylamide grouting) because of practical and environmental considerations. After the N.V. Denys brought similar products to the industry in 1980, more manufacturers jumped on the bandwagon. By the mid-eighties there were more than 10 manufacturers of polyurethane grouts. Several new and improved hydrophobic water reactive urethanes were developed during the eighties as a result of this new trend. A few manufacturers created closed cell, water reactive hydrophobic polyurethanes. The era of custom-made formulations, tailored to the project, started. Water reactive hydrophilic polyurethanes came under close scrutiny because of longevity problems. The classic two-component polyurethane foams, used in mining were gradually introduced in geotechnical engineering. For permanent seepage control, in concrete structures two-component polyurethane elastomers became popular. The introduction of hydro-block in France for major inflow control was another remarkable development. Extensive research was performed, especially in Scandinavia to establish life time expectancy of hydrophobic water reactive polyurethane. Pioneering research was done to establish mathematical models to understand the flow of P.U. through fine fissures. This paper focuses on the engineering aspects of polyurethane grouting with in the background the history of these fascinating products. It elaborates on the various types of applications illustrated with case histories for each type.