The rheological performance of wet-process sprayed mortars
This paper, which reports on part of a three year research project into wet-process sprayed concrete for repair, examines the influence of rheology on the pumping and spraying of mortars. The performance of seven commercially available pre-packaged repair mortars and six laboratory designed fine mortars was examined using the Tattersall two-point and Viskomat rotational viscometers, the pressure bleed test, the slump test, a build test and a vane shear strength test. These tests were used to form a rheological audit of each mortar. The two-point apparatus was successful with low-workability mortars and their flow resistance and torque viscosities were determined. These parameters were also obtained with the Viskomat, although problems were encountered due to their low workability. The pressure bleed test measured both the rate and the total volume of liquid emitted from the mixes whilst the vane shear strength test provided an instantaneous reading of the shear strength of the mortars and is compared with their slump. The mortars were pumped and sprayed through a worm pump to assess their suitability and to measure their adhesion to a substrate by build thickness. This value is a measure of sprayability and is converted into values of maximum shear and bending stress which are then compared with the workability parameters in order to determine their inter-relationship.
- Architecture, Building and Civil Engineering