Effect of Wood Biomass Ash Storage on the Properties of Cement Composites.

Since ash from wood biomass mostly ends up in landfills, recent research has focused on finding its economic and environmental added value as a potential new raw material in the construction industry. However, for wood ash to be used on an industrial scale in construction, a strategy for its proper storage must be defined. Proper storage of WBA is important to ensure quality control for applications in cementitious composites. This work investigated the aging of wood biomass ash (WBA) collected from five different power plants in Croatia and its influence on the performance of cementitious composites. WBA and cement pastes were investigated at different aging times (up to one year) using thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), isothermal calorimetry and initial and final setting times. The results showed that storage of WBA in closed and open containers resulted in carbonation and hydration of mainly free lime and periclase, respectively, which affected the reactivity and setting times of WBA cement pastes.

Influence of Wood Fly Ash on Concrete Properties through Filling Effect Mechanism.

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.

Pilot Scale Production of Precast Concrete Elements with Wood Biomass Ash.

Downsizing fossil fuel dependence and greenhouse gas emissions is at the forefront of a sustainable future. The expansion of renewable energy while striving to minimize dependence on fossil fuels has led to biomass taking the lead among renewable energy sources, with wood having the broadest application. Along with the growing trend of using biomass as a renewable energy source, the combustion of wood biomass results in wood biomass ash (WBA), leading to compelling amounts of waste. In this study, the technical feasibility of fly WBA from different Croatian power plants was analyzed to evaluate its potential use in precast concrete drainage elements and curb units. By implementing a performance-based design, the influence of various factors in thermal processing of wood biomass was investigated, together with a detailed characterization of WBA in order to assess the feasibility of using WBA as a secondary raw material in a large-scale industrial batching plant. The compressive strength and durability properties (water absorption, permeability, and freeze-thaw resistance) of concrete mixtures with WBA as a replacement for 15 wt% cement were evaluated and compared with the precast concrete manufacturer's technical requirements. The main concerns identified were compositional inconsistency of WBA, workability downturn, delay in initial reactivity rate, and increased water absorption. Concrete with WBA based on a circular design has been found to be a viable solution to cement depletion, stepping up from recycling to reuse of industrial waste.

Potential of Using Wood Biomass Ash in Low-Strength Composites.

Reducing greenhouse gas emissions and dependence on fossil fuels is the cornerstone of all European climate and energy strategies. Consequently, renewable energy sources are becoming more competitive with fossil fuels. The largest source of bioenergy in the European Union is biomass-fired power plants. Therefore, the European coal phase-out strategy led to an increased use of wood biomass as a sustainable fuel, generating large amounts of wood biomass ash (WBA). In the research studies reported so far, WBA has been mainly used in cementitious composites. However, given the similarities between the chemical composition of WBA and hydraulic lime (HL), this research focused on its potential classification as a building lime. Overall, three different sources of fly WBA were considered for the preparation of binders as mixtures of WBA and coal fly ash (CFA) in different ratios. The contribution of each binder mixture on the paste and mortar properties was analyzed based on the chemical composition, setting time, volume stability, and contribution to the mortar strength (compressive and flexural). In general, it can be concluded that the studied binders can meet the criteria of EN 459-1. However, special attention should be paid to the volume deformations and the setting time.

Residual Mechanical Properties of Concrete Made with Crushed Clay Bricks and Roof Tiles Aggregate after Exposure to High Temperatures.

This paper presents the residual mechanical properties of concrete made with crushed bricks and clay roof tile aggregates after exposure to high temperatures. One referent mixture and eight mixtures with different percentages of replacement of natural aggregate by crushed bricks and roof tiles are experimentally tested. The properties of the concrete were measured before and after exposure to 200, 400, 600 and 800 °C. In order to evaluate the basic residual mechanical properties of concrete with crushed bricks and roof tiles after exposure to high temperatures, ultrasonic pulse velocity is used as a non-destructive test method and the results are compared with those of a destructive method for validation. The mixture with the highest percentage of replacement of natural aggregate by crushed brick and roof tile aggregate has the best physical, mechanical, and thermal properties for application of such concrete in precast concrete elements exposed to high temperatures.