A Japanese energy company has developed a concrete spray mix that, it claims, reduces waste and cuts cost.
Up to 30% of conventional concrete can be lost in splash-back. Chugoku Electric Power claims that the viscosity of the mix is improved if between a third and a half of the fine aggregate is substituted with coal ash, therefore decreasing the size of rebound. Using this method in either dry or wet spraying, costs can be reduced by about 5%.
The new method was first used on the Yamaguchi Prefecture tunnel project, with the next likely to be in a Shimane Prefecture tunnel.
About 300,000 tonnes of coal ash are produced for every million kW of electricity generated. Other uses for it include using it as a ground stabiliser, a cavity filler and in roadbed material.
