Experiments on the Use of Gunite with Resins in the Maintenance of Dam Facings

Abstract

The replacement and repair of deteriorated surfaces with gunite is one of the most common operations of facing maintenance for hydraulic works (dams, canals, etc.). However, a certain number of cracking and deteriorated phenomena occurred during these last years, mainly due to temperature and shrinkage problems, to a poor adhesion to the base and, generally, to an objective difficulty of quality control, has lead the Research Center on Hydraulics and Structures (CRIS) of the Italian Electricity Board (ENEL) to study any possible improvement for gunite. For this purpose, the possibility was considered of adding acrylic resins in water dispersion to the gunite, during spraying, and its effectiveness was tested through a series of experimental investigations. Besides a small experimental application on a dam facing, a set of specimens of gunite, with and without resins, was prepared on site, under normal operating conditions. Laboratory tests concerned the following properties: compression and bending strength, adhesion, water absorption, porosity and water permeability. The results obtained do not seem to indicate, however, in the specimens with resins, improvements in the physical-mechanical characteristics such as expected.