Abstracts Category : Other

Cold-bonded lightweight aggregate concrete-filled steel tubular stub column under axial compression

by Neelam Bajracharya

Consumption of concrete as a construction material is ever growing and billions of tonnes of concrete are consumed in the world annually. Concrete manufacturing requires a large amount of aggregates of which the volumetric fraction normally ranges from 60% to 80%. By far the most widely used aggregates for concrete are natural minerals, including river sand, quarry sand, limestone, gravel, basalt and granite. Alarmingly, growing consumption of concrete is depleting the natural resources of these aggregates, and consequently the sustainability of the environment is threatened. Therefore, suitable alternatives to natural aggregates must be found. Meanwhile, traditional coal-fired power plants are still the major source of energy generation, and the demand for energy, as well as concrete, is also ever growing. Fly ash and bottom ash, as a by-product of coal-fired power plants, put a strain on waste management that is very costly as the ash threatens not only the environment but also the quality of the agricultural land. Currently, fly ash is mainly used as a supplementary cementitious material in the production of concrete, whereas bottom ash is mainly used in embankment and road construction. Recent research shows the potential use of fly ash in manufacturing aggregate for concrete production. Using fly ash aggregate to make one cubic meter of concrete would increase the fly ash usage of up to approximately 12 times higher than that in fly ash blended cement. Therefore, using fly ash and bottom ash aggregate in concrete would significantly promote the use of fly ash and bottom ash in the construction industry. In Australia, fly ash and bottom ash are abundantly available from numerous coal-fired power plants. Extensive studies have proven that fly ash can be used to manufacture concrete aggregates. The most economical way of producing aggregates from fly ash and/or bottom ash is the palletisation of ash and cement powder/other binders with a spray of water. The bottom ash and fly ash aggregate formed by this economical method is called cold-bonded lightweight aggregate. Research on cold-bonded lightweight aggregate has been conducted to characterise the aggregate and the concrete made from this aggregate. The focus of these studies was the strength of the aggregate and that of the concrete made from it, proving that cold-bonded lightweight aggregate can be utilised to produce structural concrete. However, little research has been conducted to understand its stressstrain relationship, which is vital for structural analysis and design. This research aims to fill this knowledge gap. In this research, the characterisation of cold-bonded lightweight aggregate was performed. Cold-bonded lightweight aggregate was produced using 70% bottom ash and 30% fly ash. This cold-bonded lightweight aggregate was supplied by Nu-Rock Australia Pty. Ltd. The water absorption, density, and crushing value of the aggregate were measured. The cold-bonded lightweight aggregate was well graded to ensure the production of good qualityAdvisors/Committee Members: Western Sydney University. School of Computing, Engineering and Mathematics (Host institution).