Impact of Confining Pressure on Long-Term Performance of Chemical Grout in Salt Water

This paper describes the results of a six-year laboratory test program to evaluate the performance of chemical-based grouts submerged in a saltwater (brine) environment, simulating a practical application in Saskatchewan, Canada, potash mines. Two types of grout were investigated: (1) Avanti “AV-100 Acrylamide grout;” and (2) Geochem “AC-400 Acrylate grout.” The grouts were prepared underground in a mine at a temperature of approximately 30°C. The specimens were submerged to cure in a nearly saturated NaCl brine solution and transferred to the laboratory for confinement under different pressures of 0, 3.4, and 6.9 MPa (0, 500, and 1,000 psi). The confining pressures were used to simulate different mining conditions and assist in accelerating penetration of brine through the specimens for long-term performance evaluation. Visual inspection and weight loss measurements on each specimen were conducted at ages up to six years. The results of this investigation showed that these chemical grouts deteriorate with time and that this deterioration is dependent on the nature of the grout and on the chemical and the physical environment in which it is placed. The AV-100 grout specimens performed satisfactorily during the first two years of testing. Rapid deterioration associated with large cracks and weight loss up to 82% was observed on specimens subjected to confining pressure of 3.4 and 6.9 MPa during the third to fifth year of testing with no further deterioration in the six years. These specimens shrank to approximately one-fourth of their original volume. In contrast, the AV-100 specimens under atmospheric pressure showed few signs of deterioration after six years of submergence in brine. The AC-400 chemical grout specimens shrank by about 15%–10%, in volume during the first two years of testing. The volume of these grout specimens remained unchanged during the third to the sixth year. However, the AC-400 grout specimens had a total weight loss of 34% during the six years of testing.