An evaluation of repair mortars installed by worm-pump spraying

This paper examines the fresh and hardened performance of wet-process sprayed mortars and the influence of rheology on the pumping and spraying of these mortars. Seven commercially available preblended repair mortars designed for hand application, together with a laboratory-designed fine mortar, were investigated using the Tattersall two-point rotational viscometer, the pressure bleed test, the slump test, and a vane shear strength test. The mortars were pumped and sprayed with a small diameter worm pump and the build thickness determined. Hardened properties measured include compressive strength, tensile bond strength, hardened density and drying shrinkage. Tests were conducted on cast and in-situ specimens and, where possible, on specimens produced by spraying directly into a cube or beam mould. Initial findings for predicting the pumpability and sprayability of the mortars are presented and this is linked together with the hardened performance. These results show that the majority of proprietary pre-blended repair mortars designed for hand application are suitable for wet-process application with a worm pump.