A molecular formalism of the hydraulic cement deterioration stored at different temperatures and its impact on the mechanical behavior

Abstract

The different temperatures associated with the climatic conditions of each continent and each biome directly influence the exposure properties of each material used in each region, including hydraulic cement, an important material widely employed in bridges, viaducts, and buildings worldwide. Despite being prepared at elevated temperatures, hydraulic cement is often stored and used under ambient conditions, posing challenges, particularly in tropical environments. The present work investigates the effects of different temperatures (10 °C, 30 °C, and 50 °C) on the deterioration of hydraulic cement and microstructural and mechanical behaviors. Kinect investigations were carried out to advance a chemical formalism of the deterioration of cement stored at different temperatures in a tropical climate. Signs of chemical deterioration of cement samples were investigated by XRD and SEM analyses, which revealed the presence of essential phases on the surface of the mortars, such as Portlandite, CSH, and Ettringite. The study incorporated gray residue into the mortar mixtures in two forms: addition (type B mortar) and substitution (type C mortar). For type B, 10 % of gray residue was added as an additive without reducing the cement content, while for type C, 10 % of the cement was replaced with gray residue to lower environmental impact. The presence of gray residue contributed to the hydration kinetics and microstructure, enhancing the formation of CSH phases, which are critical for mechanical strength. Mechanical performance revealed that type A (reference mortar) suffered a 6 % reduction in compressive strength after 90 days of storage at ambient conditions, while type B showed a 23 % increase due to the addition of ash residue, and type C, although with a 33 % reduction, balanced lower cement use with environmental benefits and mitigated losses related to chemical deterioration. Finally, sustainable mortars showed better mechanical performance than traditional ones, especially when the cement was stored at 50 °C, as predicted by the kinetic formalism (R² = 0.99 across storage conditions).