Koen Van Balen

Bio: Koen Van Balen is an academic researcher from Katholieke Universiteit Leuven. The author has contributed to research in topics: Masonry & Cultural heritage management. The author has an hindex of 13, co-authored 64 publications receiving 825 citations.

Competition between Hydration and Carbonation in Hydraulic Lime and Lime-Pozzolana Mortars

Abstract: A combined reaction of hydration and carbonation takes place in hydraulic lime and lime-pozzolana mortars. Hydration reactions are the first reaction and carbonation of lime is the complementary reaction in the strength gain. Competition between these two reactions can occur in lime-pozzolana mortars if the pozzolanic material has low reactivity with lime, leading to the consumption of lime by carbonation reaction. The degree and the order of these reactions are strongly influenced by the moisture content. Hydration reactions are enhanced under moist conditions while carbonation is delayed. Curing under dry conditions does not sufficiently increase their strength because the hydration reactions are slowed down or even terminated by the full carbonation of lime in lime-pozzolana mortars. The consequence of this on the mechanical properties of the mortars is remarkable while the same impact is not observed in their porosity. Such mortars require moist conditions to ensure sufficient strength development.

Characteristics of steel slags and their use in cement and concrete—A review

Abstract: Steel slags are industrial by-products of steel manufacturing, characterized as highly calcareous, siliceous and ferrous. They can be categorized into basic oxygen furnace (BOF) slag, electric arc furnace (EAF) slag, and ladle furnace (LF) slag. They are found to be useful in many fields, such as road construction, asphalt concrete, agricultural fertilizer, and soil improvement. However, better utilization for value-added purposes in cement and concrete products can be achieved. In this paper, an overview of the recent achievements and challenges of using steel slags (BOF, EAF and LF slag) as cement replacement (usually ground into powder form with the size of 400–500 m2/kg) and aggregate in cement concrete is presented. The results suggest that the cementitious ability of all steel slags in concrete is low and requires activation. For the incorporation of steel slags as aggregate in concrete, special attention needs to be paid due to the potential volumetric instability associated with the hydration of free CaO and/or MgO in the slags. Studies have indicated that adequate aging/weathering and treatments can enhance the hydrolyses of free-CaO and -MgO to mitigate the instability. Considering the environmental and economic aspects, steel slags are also considered to have a potential use as the raw meal in cement clinker production.

Biomass waste utilisation in low-carbon products: harnessing a major potential resource

Abstract: The increasing demand for food and other basic resources from a growing population has resulted in the intensification of agricultural and industrial activities. The wastes generated from agriculture are a burgeoning problem, as their disposal, utilisation and management practices are not efficient or universally applied. Particularly in developing countries, most biomass residues are left in the field to decompose or are burned in the open, resulting in significant environmental impacts. Similarly, with rapid global urbanisation and the rising demand for construction products, alternative sustainable energy sources and raw material supplies are required. Biomass wastes are an under-utilised source of material (for both energy and material generation), and to date, there has been little activity focussing on a ‘low-carbon’ route for their valorisation. Thus, the present paper attempts to address this by reviewing the global availability of biomass wastes and their potential for use as a feedstock for the manufacture of high-volume construction materials. Although targeted at practitioners in the field of sustainable biomass waste management, this work may also be of interest to those active in the field of carbon emission reductions. We summarise the potential of mitigating CO2 in a mineralisation step involving biomass residues, and the implications for CO2 capture and utilisation (CCU) to produce construction products from both solid and gaseous wastes. This work contributes to the development of sustainable value-added lower embodied carbon products from solid waste. The approach will offer reduced carbon emissions and lower pressure on natural resources (virgin stone, soil etc.).