Polymer-Based Emulsion (PBE) grout was developed in the 1970s and initially used to seal high pressure-high rate water inflows into deep subsurface South African mines. PBE use broadened over the decades to include water-sealing in mines in other countries and in underground tunnels for subway systems and other municipal infrastructure. Because of its radiation tolerance, PBE has been evaluated and used for water-sealing at nuclear facilities.
PBE is a suspension of colloidal polymer emulsoids dispersed in a solution of additives promoting flow and adhesion. PBE is injected in a fluid state and remains fluid until activated. PBE is a non-Newtonian, dilatant fluid; it sets by internal shear as the grout passes through fractures or other voids in water-bearing media. Set time may also be controlled chemically with the use of activator or inhibitor. Still, PBE is differentiated from solution grouts, because it is a single-part grout whose set does not require a chemical reaction.
After successful application in South Africa, PBE use for sealing mine leaks broadened geographically to the UK, Australia, Namibia, Zambia, USA, Canada and Russia. The grout has successfully sealed discrete inflows higher than 9800 liters per minute at pressures up to 17,000 kilopascals. PBE use broadened, because it is significantly less vulnerable to washout than commonly used cementitious grouts. Furthermore, unlike acrylamides and acrylates, PBE does not contain hazardous constituents in either liquid or solid form.
PBE has been successfully used to seal underground tunnel leaks in North America, Africa, Australia, Singapore and Hong Kong. Because of its low viscosity, small particle size and, hence, significant spread behind liner systems, PBE allows for drilling of fewer, more widely-spaced injection points than commonly used solution grouts, thereby decreasing drilling and labor costs for grouting programs. PBE bonds strongly to concrete and rock; it does not get pushed out of fractures in tunnel linings in response to recovering positive-side water pressure.
PBE has also been applied at a nuclear power facility in Canada, has been considered for use at Fukushima, Japan and is planned for use at a research facility in the United States. Laboratory testing has demonstrated that PBE is radiation-tolerant and can survive exposure levels up to 100 MRad without adverse changes to its physical properties and sealing capabilities. Based on studies for nuclear applications, PBE life has been estimated to be greater than 125 years.
