Ageing of cement grouted joint by water and acidic flows for assessing dam foundation quality

ABSTRACT: Cement grouting is widely used to maintain the safety of dams by reducing the water pressure in rock foundations and by improving its quality. However, little is known about the ageing of grouted joints. Some studies have suggested that erosion and dissolution caused by water flow are the main factors of degradation. This paper deals with a laboratory study assessing the performance of cement grout injection in rock or mortar test samples and submitted to a constant water (or acid) flow. Each sample was kept in a sealed box where a pump induced a flow at constant pressure. The degradation time ranged from two weeks to two months. The main decrease occurred on the cement grout surface, showing a modification on Barton's JRC and a global variation of the shear strength indeed. Finally, the study adds a new dimension to the grout degradation of dams, which offer an accelerated system of deterioration by flow.