AbstractsEarth & Environmental Science

Hydraulic structures play an important role in regulation and transport of water in reservoirs as well as open channels. They are also useful for flow measurement. Examples of such structures include spillways, stilling basins, weirs, gates, and culverts. These structures commonly have concrete surfaces. Under the impacts of water flow, the concrete surfaces suffer inevitably from abrasive erosion. This is particularly problematic for ageing structures under the impacts of flowing water with suspended sediment in high concentrations. Severe abrasion can cause structural deterioration, leading to a shortened service life. It may not be possible to completely prevent abrasion in hydraulic structures. However, it is possible to reduce abrasion by using proper repairing materials. This study is aimed at investigating different types of repairing materials, with respect to their suitability as a protective layer on existing concrete surfaces. This study takes the experimental approach. Concrete specimens of cylindrical shape were cast using four types of materials: 1) a premium quality concrete mix of Portland cement, 2) latex modified repair material, 3) silica fume fibre-reinforced repair material, and 4) fly ash fibre-reinforced repair material. The concrete specimens were allowed to harden for a period of up to 28 days. A series of laboratory experiments were carried out, where the flat circular surface at the top of the concrete cylinders was subject to direct impact (for 3 to 9 hours) from a high-speed jet of a sand and water mixture from a nozzle. Material mass loss was determined as well as the depth of jet-induced abrasion on the top surface, abraded surface topography and abraded material volume, were measured using 3D scan technology. These measurements were analyzed using ArcGIS tools, and MATLAB functions. Evaluations of how well the concrete specimens resisted abrasive erosion were determined through comparisons. The results show that in terms of abrasion resistance, the silica fume material is the best among the four types of materials, whereas the concrete mix is the poorest. The results also show that abrasion resistance of the concrete specimens increases when they have had sufficient time to age to their maximum structural integrity. A longer exposure to jet flow leads to higher abrasion. This study is perhaps the first to combine 3D scan and ArcGIS technologies to investigate abrasion depth and volume of different concrete materials. This study has led to the development of effective methods for data analysis and interpretation.