Internal curing of high-strength mortar amended with surface-treated coal bottom ash by cold-bonding method

Abstract

The bottom ash which is the one of coal combustion products (CCPs) produced by thermal power plant has low rate of reuse for its irregular shape and large surface pore size. In the advanced research, bottom ash can be effectively utilized in high-strength concrete which can hinder the adverse properties of bottom ash. The cement matrix in high-strength concrete reduces the interlocking among bottom ash particles. Also, bottom ash is beneficial to reduce a self-weight of concrete and to obtain internal curing effect with its highly porous nature. The high-strength concrete which is a effective application way of bottom ash utilization is well known for its large autogenous shrinkage attributed to low water-to-binder ratio. Internal curing can effectively mitigate self-desiccation via extra water supply through cross section. The bottom ash is proven its possibility as an internal curing agent with its highly porous structure, but internal curing efficiency is not as good as commercialized lightweight aggregate such as expanded shale. The large sized pores distributed on the surface of bottom ash causes the reduction of internal curing efficiency. In this study, the surface treatment by cold-bonding method was conducted to improve internal curing efficiency of bottom ash by modifying the surface characteristics. The bonding mechanism of cold-bonding method is pozzolanic reaction among fly ash particles, and it does not undergo the sintering process.. The cold-bonding method possess benefits such as reducing impact on environment, cost to manufacture, and ease of fabrication. The characteristic of surface-treated bottom ash was evaluated mainly for three properties. First, micro-structure of surface-treated bottom ash was observed by BSE image. Second, water transfer properties were investigated. The absorptivity variation by time and desorption properties at the early age using fluorescent material were measured to characterize water transfer properties. Third, ...