Recycling coal bottom ash in construction materials: Technical specifications of bottom ash-based sound absorbing porous concrete applied in highway noise barriers

Abstract

As industrial waste continue to accumulate, they are becoming a major problem for the environment as well as for public health. In addition, European and Spanish waste legislations are promoting the recycling of industrial waste, following the waste hierarchy, instead of landfill disposal.

On the other hand, another environmental problem which is becoming an increasingly significant concern because of its negative impact on human health is noise pollution.

The main scope of the thesis research has been to study the recycling opportunities of coal bottom ash from Spanish coal power stations in construction materials. The objective was focused on developing a material with high content of coal bottom ash which comprises the properties required for the specific applications.

The argumentative line followed in the development of the present work started from the idea of recycling Spanish coal bottom ash as a majority constituent in construction materials for specific applications, such as Portland cement replacement, coarse aggregates replacement in concrete for fire resistance panels, as part of ceramic materials and bricks, and coarse aggregates replacement in porous concrete production with sound absorbing properties.

From the results obtained, bottom ash-based porous concrete for sound absorbing applications has been deeply analysed, enhancing the properties of the final product and describing the technical requirements that could validate its use in highway noise barriers at industrial scale. Besides that, durability and environmental properties have been analysed in order to study the impact of the coal bottom ash-based product on the environment and human health.

Finally, in order to completely analyse the use of coal bottom ash as part of porous concrete for its application as sound absorbing porous material in road traffic noise reducing devices, it has been developed a methodology which accurately predicts the acoustic behaviour of the material without having to manufacture large panels and testing them in a reverberation room at an approved laboratory.

The objectives pursued have been developed from laboratory to semi-industrial scale, which enables to extrapolate the results ensuring the use of bottom ash-based sound absorbing products in road traffic noise reducing devices.