Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

Environmental condition affects the property of construction materials. This study gives an initial understanding of Portland cement hydration under low temperatures from the views of laboratory experiments (including electrical resistivity, degree of hydration (DoH), and maturity) as well as thermodynamic calculation. The hydrates of Portland cement at the given period were detected with X-ray diffraction (XRD), and their microstructure was observed by scanning electron microscope (SEM). Experiment result (i.e., DoH and electrical resistivity) indicated that the hydration of Portland cement was delayed by low temperature without hydration stopping at −5°C. Based on a basic kinetics model, the thermodynamic calculation predicted that the final hydrate differs in dependence on environmental temperatures. The mechanical behavior trend of Portland cement paste affected by low temperatures potentially is linked to the appearing of aluminate compounds and reduction of portlandite

Influence of Fineness Levels and Dosages of Light-Burned Dolomite on Portland Cement Performance

The paper aims to understand the effect of light-burned dolomite powders (LBD) on ordinary Portland cement (OPC) and evaluate the influence of LBD dosages and fineness levels on the mechanical properties and hydration properties of OPC. The LBD/OPC pastes were prepared by OPC blended with LBD at various replacement dosages and fineness levels. The mechanical properties were studied by flexural and compressive strength tests, while the hydration properties were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and reaction degree of LBD. Experiment results indicated that the flexural and compressive strength of LBD/OPC samples were higher than reference sample at all ages. The fineness levels of LBD was C (C-LBD) with 0.5–1.5 wt% dosages, and the fineness levels of LBD was B (B-LBD) with 1.5–2.5 wt% dosages can significantly improve the strength of cement-based materials. The main mineral components of LBD are MgO and CaCO3, of which MgO could react with water to form Mg(OH)2 quickly, and CaCO3 could hydrate with C3A to from hydrated calcium carboaluminate (C3A·CaCO3·11H2O), which prevents the conversion of AFt to AFm

Advances and development trends in eco-friendly pavements

The major contemporary in road pavement engineering is related to the creation of green and sustainable infrastructures, e.g., reduction of environmental impacts, increase in traffic safety, and transportation efficiency, etc. This review presents the recent trends in research and the technical solutions developed so far to address these challenges. After the analysis of research status in the past decades, a novel technology system of eco-friendly pavements is proposed considering two solutions, materials modification and structure improvement. The construction of an eco-friendly pavement can be achieved thanks to several different technologies ensuring permeable, noise-reducing, self-luminous, and exhaust-decomposing properties as well as apporting lower heat absorbing and enhanced anti-/de-icing characteristics. A systematic review of these technologies is presented pivoting on four main aspects: technical principle, material and structural composition, performance evaluation, and engineering application. The current trend in road engineering is combining the pavement infrastructure with various eco-friendly functions, e.g., water permeability, noise reduction, low heat absorption, exhaust gas decomposition, and anti-/de-icing. Finally, the review lists the drawbacks of the existing technologies, including high cost, single function, etc., and depicts the future developing direction and architecture of the next generation of eco-friendly pavements in which the road infrastructure should have more environmentally friendly functions than the existing technology