This study investigates the hydration, microstructure, autogenous shrinkage, electrical resistivity, and mechanical properties of Portland cement pastes modified with PEG-PPG triblock copolymers with varied molecular weights. The early age properties including setting time and hydration heat were examined using the Vicat test and isothermal calorimetry. The hydration products and pore size distribution were analyzed using thermogravimetric analysis (TGA) and nitrogen adsorption, respectively. Mechanical properties and electrical resistivity were evaluated using the compressive strength test and electrochemical impedance spectroscopy (EIS). It was shown that the addition of the copolymers reduced the surface tension of the cement paste pore solution due to the presence of a hydrophobic block (PPG) in the molecular structure of the copolymers. The setting time and hydration heat were relatively similar in the control paste as well as the pastes modified with the copolymers. The results showed that copolymers were able to reduce the autogenous shrinkage in the paste due primarily to a reduction in pore solution surface tension. TGA showed a slight increase in the hydration degree of the paste modified with the copolymers. The compressive strength was reduced in the pastes modified with the copolymers that showed an increased volume of air voids. The addition of copolymers did not affect the electrical resistivity of the pastes except in the case where there was a large volume of air voids, which acted as electrical insulators.

Marine carbonate production and dissolution are important components of the global carbon cycle and the marine alkalinity budget. Global carbonate production by marine fish (ichthyocarbonate) has been estimated to be as high as 9.03 Pg CaCO₃ yr⁻¹; however, the fate of ichthyocarbonate is poorly understood. High magnesium concentrations in ichthyocarbonate would traditionally suggest rapid dissolution under current marine conditions, but a correlation between dissolution rate and mol%MgCO₃ has not been observed. Here, we aim to determine the role of organic coatings on dissolution rates of ichthyocarbonate in marine environments. We applied a combination of petrographic, geochemical, and microCT approaches to assess the quantity and distribution of organic matter in ichthyocarbonate produced by two species of marine fish, the Gulf toadfish (Opsanus beta) and the Olive flounder (Paralichthys olivaceus). We show that organic matter, including external coatings and embedded organic material, is volumetrically significant, ranging from 8.5% to 32.3% of ichthyocarbonate by volume. Bleach oxidation of external organic matter coatings increased the dissolution rate of ichthyocarbonate by more than an order of magnitude, suggesting these coatings serve to reduce reactive surface area of the mineral fraction in ichthyocarbonate. Assuming that organic coatings do not influence sinking rates, external coatings extend the depth of ichthyocarbonate persistence in the water column by ∼12–15×. Therefore, organic coatings are an important determinant of the role of ichthyocarbonate in the marine carbon cycle.

The novelty of this study is to present a multilayer framework for predicting the air‐entrained porosity of cement paste based on the molecular characteristics of nonionic surfactants. Air‐entraining agents enhance concrete durability against freeze–thaw damage; however, their development is labor‐intensive and cost‐prohibitive. This research implements a multilayer approach by incorporating three hierarchical layers: the molecular properties of nonionic surfactants (Layer 1), their physicochemical characteristics (Layer 2), and the air‐entrained microstructural porosity of hardened cement paste (Layer 3). By integrating key molecular parameters—such as hydrocarbon chain length, hydrophobicity, and molecular weight—this model effectively predicts the air‐entrained porosity of cement paste. An extensive experimental study was conducted to characterize the physicochemical and microstructural properties of 59 distinct nonionic surfactants. To the best of our knowledge, this represents the first comprehensive dataset of molecular and physicochemical properties of air‐entraining agents reported in the literature. Moreover, no prior study has established such a detailed link between the molecular characteristics of nonionic surfactants and cement microstructure. This dataset served as the foundation for developing the predictive model, which demonstrated the feasibility of this approach in predicting the air‐entraining performance of nonionic admixtures. The developed model facilitates the rapid screening of candidate surfactants and the optimization of their molecular structure while minimizing the need for extensive experimentation. Furthermore, distinct trends emerged from the dataset, offering new insights into the interdependent properties that govern air entrainment in cementitious materials.

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.