Conceptualization, development and design of a mortar spraying machine

Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m²/hour. However, with the mortar spraying machine, an area of 30m²/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence and compaction of plastering compared to the manual method.