Board of the Swiss Federal Institutes of Technology

MgO can be sourced from magnesium silicates or desalination brines with no direct CO2 emissions from the raw materials. This paper critically reviews available literature on magnesium carbonate cements prepared from MgO, water and magnesium carbonates such as nesquehonite or hydromagnesite. Such MgO - magnesium carbonate cements develop high early strength due to the formation of hydrous carbonate-containing brucite (HCB), which incorporates both carbonate and H2O into its structure. Hydrated magnesium carbonate cements have a high potential to bind additional CO2. In the presence of SiO2, magnesium silicate hydrates (M-S-H) also form, which exhibit a high resistance to carbonation. The Mg/Si ratio governs the phase assemblage, as silica can react with HCB to form M-S-H. Magnesium carbonate and silicate hydrate cements have a pH value ranging from 10 to 11, demonstrate a high resistance to leaching, while the corrosion rate of steel rebars is comparable to PC.

Clay-based, low-COQ cement-stabilized materials offer a sustainable alternative to conventional building materials. This study examines the impact of various admixtures (Na-hexametaphosphate, Na-carbonate, Na-silicate, Na-citrate, and Na-oxalate) on the rheological behavior of poured systems containing a MgO-metakaolin cement as stabilizer. The yield stress reduction follows the order Na-hexametaphosphate > Na-silicate > Na-citrate > Naoxalate >= Na-carbonate > no admixture. The zeta potential data with the solution analysis of the suspensions show that the adsorption of admixtures and/or a change in pH leads to a more negative surface, enhancing dispersion through electrostatic repulsion. Silicate and phosphate are not found in the suspension, 29Si ssNMR indicates that silicate precipitates and polymerizes most likely as M-S-H. The phosphates are most likely adsorbed onto particles with opening of the phosphate rings observed by 31P NMR. The anionic charge density of adsorbed polyphosphates was calculated and linked to the decreased colloid sizes observed with increasing Nahexametaphosphate concentration.

We test and simulate the mesoscopic cracking behavior of specimens made of a standard concrete mixture. To this end, we combine stable wedge-splitting fracture experiments performed during X-ray tomography, their analysis with digital volume correlation providing the full three-dimensional displacement field, and phase-field cohesive fracture modeling. In our computations, we apply the measured boundary conditions and model the actual heterogeneous material structure at the mesoscopic scale. Within the phase-field model, we explicitly distinguish among (thus individually represent) the mesostructural features of distinct material phases with size above a threshold of 1 mm, while we homogenize pores and finer aggregates below this threshold within the cementitious mortar matrix, with material parameters characterized accordingly. We compare experimental and numerical results in terms of both local and global quantities.

Buildings represent a promising flexibility source to support the integration of renewable energy sources, as they may shift their heating energy consumption over time without impacting users’ comfort. However, the predicted flexibility potential of a building’s Heating, Ventilation, and Air Conditioning (HVAC) system is based on uncertain ambient weather forecasts and a typically inaccurate building thermal model. This paper presents an uncertainty-aware flexibility quantifier using a chance-constrained formulation. Because such a quantifier may be conservative, we additionally model real-time feedback in the quantification, in the form of affine feedback policies. Such adaptation can take the form of intra-day trades or rebound around the flexibility provision period. To assess the flexibility quantification formulations, we further assume that flexible buildings participate in secondary frequency control markets. The results show some increase in flexibility and revenues when introducing affine feedback policies. Additionally, we demonstrate that accounting for uncertainties in the flexibility quantification is necessary, especially when intra-day trades are not available. Even though an uncertainty-ignorant potential may seem financially profitable in secondary frequency control markets, it comes at the cost of significant thermal discomfort for inhabitants. Hence, we suggest a comfort-preserving approach, aiming to truly reflect thermal discomfort on the economic flexibility revenue, to obtain a fairer comparison.

Chronic exposure to environmental stressors, like road traffic noise, is linked to negative health impacts. This cross-sectional field study investigates the associations between road traffic noise exposure at home, residential green, and stress biomarkers (cortisol and cortisone) among residents in the city of Zurich, Switzerland. The study involved 224 participants exposed to varying levels of noise at home and varying access to green spaces in the vicinity of home. Data collection included 3 cm near-scalp hair samples for cortisol and cortisone as biomarkers for chronic stress, residential environment assessments, and questionnaires. Exposure to road traffic noise at home was quantified through modelled L-den and residential green through the normalized difference vegetation index (NDVI) and percentage of public green spaces. Multiple linear regression models were used to study the association of the long-term physiological stress biomarkers with the exposure to road traffic noise at home and residential green. There was no association between noise exposure and stress biomarkers, while a significant negative association of cortisone (beta = -0.0084; 95 % CI: -0.0162 to -0.0006; p < 0.05) and the sum of cortisol and cortisone (beta = -0.0086; 95 % CI: -0.0165 to -0.0008; p < 0.05) was found with green space area in the neighborhood. These findings highlight the importance of public green spaces contributing to public health in urban settings.