Erich Schönian and Alex Naudts
Urban –Verlag Hamburg/Wien, 2003
Abstract
Hot bitumen grouting technology has continually evolved since its early applications almost a century ago in the USA, in France and Germany, to seal persistent leaks in and below dams, in tunnels and for erosion protection along canals.
Advancement in the industry especially in the field of monitoring and grouting equipment has made the injection of hot bitumen, often applied in conjunction with cement based suspension grout, the most economical, practical and sure solution to stop major inflows through, below or around structures. Hot bitumen remedial grouting was successfully applied in projects such as the Stewartville Dam and the Lower Baker Dam in the USA, a potash mine in Canada, a quarry in West Virginia, a large mine in Asia, a dam in Brazil, and a tunnel in Milwaukee. These applications proved the effectiveness of the hot bitumen grouting technique to stop major water inflows and stabilize water bearing, cohesionless soils, in a fast, predictable and economical way.
Hot bitumen is the ideal grout to stop major inflows due to its temperature dependent viscosity. At high temperatures, the dynamic viscosity of bitumen is typically in the range of 15 to 100 cP (1 cP = 10-3 Pa s), wich allows the bitumen grout to flow and permeate very small fissures and sore channels. The steam created during contact of the hot bitumen with the water enhances the penetrability of the bitumen grout.
The first report on the penetrability and behaviour of soft-graded hot bitumen as a single grout by van Asbeck/Schonian (4), documented remarkable finding regarding bitumen penetration in cracks. As the bitumen grout comes in contact with water (colder temperatures), the viscosity of the grout drastically increases resulting in a lava-like flow. A hard insulating crust is formed at the interface between water and bitumen and shelters the low viscosity, hot bitumen behind it. The “crust” is re-melted from within and facilitates the bitumen to penetrate the medium to be grouted.
The cement based suspension grout injected in conjunction with the hot bitumen sets up on contact with the hot bitumen creating a more competent “creep-free” end product able to resist the hydrostatic pressures. The purpose of the cement based suspension grout is also to compensate for the shrinkage of the bitumen as it cools. The hot bitumen and cement based suspension grout combination form a stable, chemical-resistant, environmentally friendly solution. This paper elaborates on a few remarkable field applications, one of which probably was one of the largest grouting efforts every undertaken.