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1. Improving the early reactivity of activated basic oxygen furnace slag – The influence of particle fineness and grinding aids

Author

J.C.O. Zepper, S. de Bruin, X. Ling, K. Schollbach, S.R. van der Laan, and H.J.H. Brouwers

Subjects
Basic oxygen furnace slag, Activation, Grinding aids, Reactivity, Particle fineness, Technology
Abstract

Basic oxygen furnace slag (BOF slag), also known as Linz-Donauwitz slag, is an industrially by-product of the steel industry and produced during the converter process. In this research we have investigated the effect of grinding aids and particle fineness on the hydration of potassium citrate activated BOF slag. It was investigated the effects of five different grinding aids on the grindability and hydration of activated BOF slag in laboratory batch milling experiments. The grinding aids generally improve the grindability of BOF slag and therefore increase the particle fineness of BOF slag. This had the consequence that the hydration of activated BOF slag was improved. Only one grinding aid, triethanolamine (TEA) also improved the hydration of BOF slag besides providing higher particle fineness. The combination of the higher particle fineness and additional effect of TEA on the hydration improved the compressive strength to 60 and 78 MPa of activated BOF slag. An additional important of this research is that the hydration of BOF slag is significantly more sensitive on particle fineness compared to ordinary Portland cement.

Published
2024
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2. Scalable cooling cementitious Composites: Synergy between Reflective, Radiative, and Evaporative cooling

Author

Daoru Liu, Anna Kaja, J.C.O. Zepper, Daiwei Fan, Dongyu Zhang, H.J.H. Brouwers, Qingliang Yu, Building Materials, Building Physics and Services, Mechanical Engineering, Stimuli-responsive Funct. Materials & Dev., and EIRES Systems for Sustainable Heat

Subjects
Cementitious cooling composites, Calcium silicate hydrates, Solar spectral reflectivity, Mechanical Engineering, SDG 13 – Klimaatactie, SDG 13 - Climate Action, Atmospheric window, Building and Construction, Electrical and Electronic Engineering, Radiative cooling, Moisture, Civil and Structural Engineering
Abstract

Promoting the sustainability of the building industry is one of the major approaches to addressing energy depletion and climate change. Here, we developed scalable cementitious cooling composites (CCCs) with superior energy-free cooling performance and environmental applicability. Optical properties, phase composition, microstructure, and silica reactivity of composites are characterized and analyzed. Onsite measurements are conducted to evaluate the surface/internal cooling capacities and validate the cooling principles and such composites’ climatic applicability. Results show that calcite, C[sbnd]S[sbnd]H phases (especially tobermorite), and a higher water-to-powder ratio can increase the solar reflectivity (Rsun). Meanwhile, C[sbnd]S[sbnd]H and calcite can also increase the spectral emissivity in the atmospheric window (εaw). Optimal sizes of 0.5 μm (particles) and 1.0 μm (pore size) for Mie scattering are determined by Finite-Difference Time-Domain simulations. The Rsun of 0.90 and εaw of 0.88 are simultaneously achieved, which are comparable to exquisitely designed polymer-based coatings, metamaterials, and multi-layer composites. The surface cooling of 17.3 ℃, internal cooling of 9.2 ℃ by solar reflection, internal cooling of 4.8 ℃ by evaporative cooling, and internal cooling above 2.8 ℃ by mid-infrared (MIR) emission are observed. CCCs are proven to provide efficient cooling in different conditions, with low investment, facile production, and high environmental resistance.

Published
2023

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