Abstract
ABSTRACT Cenosphere is a coal combustion by-product that presents interesting properties to be used in the production of cementitious materials, such as hollow structure, low density, low thermal conductivity and notably thermal stability. In addition, it displays pozzolanic reactivity under thermal curing. However, the cenosphere potential for the development of unique construction materials has not been fully investigated, remaining obscure for both power plants and the construction field. This study investigated the employment of waste cenosphere in partial substitution to sand for the obtainment of high-strength lightweight concrete materials. Cenosphere from a Brazilian power plant was chemically and physically characterized and the feasibility of its use in concretes was investigated. It was discovered that the power plant’s fly ash is composed of approximately 0.2% of cenosphere. In addition, the cenosphere displayed size ranging from 30 to 300 µm and were suitable for use as fine aggregate in concrete. Concrete with 33, 67, and 100% fine aggregate replacement by the waste cenosphere was produced. Cenosphere-based high strength concrete presented strength higher than 70 MPa and density as low as 1500 kg • m-3. Compared to mixes of reference, cenosphere application as fine aggregate improved the specific strength of high-strength concrete while maintaining equivalent mechanical properties.
Highlights
In the past few decades, great efforts have been made to reduce the amount of greenhouse gases (GHG) emission to the atmosphere with new alternatives for energy production
It is estimated that 8 tonnes per day of cenosphere are lost in the evaluated power plant
Using waste cenosphere collected at a thermoelectric power plant, high-strength lightweight concrete with equivalent mechanical properties of the conventional density ones were produced
Summary
In the past few decades, great efforts have been made to reduce the amount of greenhouse gases (GHG) emission to the atmosphere with new alternatives for energy production. Besides all investment on renewable solutions, the coal shares on global energy production is still significant [1]. Recycling of byproducts from the coal industry, such as fly ash, is crucial. Around 0.2 to 2 wt% of fly ash entrap large volume of air from the gas stream, causing the formation of hollow spherical-shaped particles called cenospheres [3-5]. Due to the hollow structure, they present low density (ranging from 400 to 900 kg · m-3 [6]) and low thermal conductivity. Cenospheres, to fly ash, are aluminosilicates with Si/Al ratio ranging from 1.5 to 3.5 [4]. The yield of cenosphere is governed by the combustion temperature, fall distance, cooling rate and viscosity of the melt [5,8]
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