Abstract
This paper presents the results of an experimental study aimed at determining the influence of wood fly ash (WFA) from three Croatian power plants on the properties of concrete. First, the chemical and physical properties of WFA’s were determined. It was found that these properties are highly influenced by combustion technology, the type and parts of wood used as fuel, and the local operating conditions. Subsequently, workability, heat of hydration, stiffness development, 28-day compressive strength, apparent porosity, and capillary absorption were determined on concrete mixes prepared with WFA as cement replacement from 5–45% by weight. Cement replacement up to 15% with the finest WFA accelerated hydration, stiffness development, and increased compressive strength of concrete up to 18%, while replacement with coarser WFA’s led to a decrease in compressive strength of up to 5% and had more gradual heat liberation. The dominant effect that could explain these findings is attributed to the filler and filling effect mechanisms. At the same time replacement content of up to 45% had very little effect on capillary absorption and could give concrete with sufficiently high compressive strength to be suitable for construction purposes.
Highlights
The need to reduce greenhouse gas emissions accelerates the transition to renewable energy sources
For ashes F4 and F5, the density slightly decreased with increasing wood fly ash (WFA) content, while for ash F6, the density increased with increasing ash content
The results indicate that the compressive strength of concrete made with F4 and F5 ashes could be improved at a cement replacement level of less than 15%
Summary
The need to reduce greenhouse gas emissions accelerates the transition to renewable energy sources. Biomass is the largest source of renewable energy in the European Union (EU), of which 60% comes directly or indirectly from forests [1,2]. The most common way of producing energy from biomass is combustion, and this process yields on average a quantity of ash between 2.7% and 3.5% of the original weight of wood biomass [3]. 7.3 million tons of ash were produced from wood biomass in the EU-28 countries in 2015 [4]. Assuming that the combustion of 1 PJ of primary biomass produces about 2000 tons of ash [6], it follows that about 95 million tons of ash were produced globally and about 11 million tons of ash were produced in the EU-28 countries, most of which is wood biomass ash (WBA)
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