Development of cement based materials for grouting of rock at Olkiluoto

The objective of the work was to develop grouting mixes that met two separate sets of given requirements at the temperature of 12 °C. The grouts were based on four different commercially available grouting cements: two which were relatively slow reacting sulfate resistant (SR) cements and the other two Portland cements. Grouting properties were improved by varying the mix composition with water-to-cement (w/c) ratio, superplasticiser, silica slurry, retarder, accelerator and mixing order. The mixes were first modified to meet the preliminary (bleeding, setting and flow properties) requirements and then tested for penetrability in a filter test with 1 bar (0.1 MPa) pressure and for rheology. With the SR cements, the problem was their slow strength development at the ambient temperature. It was accelerated by lowering the w/c and by CaCl2 addition, which was added at the end of the open time period. Consequently, the penetrability became low and the yield value large. The coarser SR cement (Injektering 30) behaved better in the penetrability test than the finer one (Ultrafin 12). With all cements, higher w/c ratios could be used and bleeding avoided by using silica slurry, but setting properties changed: with both SR cements and Mikrodur P-U the setting became too slow. Surprisingly, with Rheocem 900 the open time became too short with a w/c up to 3.0, but those mixes showed poor penetrability.