Comparative Grouting Tests with Two Micro-cement Types

Grouting is a technique used to improve the engineering properties of soils and rocks. In this paper two types of micro-cements have been tested: a fast-reacting cement, composed by pure clinker (MasterRoc MP 650) and a slow-reacting cement with 80% slag (MasterRoc MP 680). Injection tests were performed in a column filled with the Hostun sand at a void ratio of 0.7 at a maximum injection pressure of 400 kPa. After curing the samples, at a relative humidity of 98%, a mechanical study was performed: unconfined compressive strength (UCS) tests, Brazilian tests, consolidated-undrained triaxial tests at three different confining pressures. A comparison between samples taken from the upper and lower part of the injected column (670 mm length, 50 mm internal diameter) was performed. Results (both for upper and lower position in the column) are comparable in terms of strength. Mechanical tests showed that both friction angle and cohesion values for the 80% slag cement is higher than for the pure clinker cement. Tests are of valuable interest for both designers and contractors involved in the ground improvement field.