Cesium immobilization of high pH and low pH belite-rich cement under varying temperature.

Low-pH cement is being studied in radioactive waste repositories. The belite-rich cement (BRC) recently gained attention due to its higher CO sequestration and low pH attainment under carbonation exposure. Therefore, this study evaluated the effects of pH and temperature on cesium immobilization of BRC.

Phase-Change Materials in Concrete: Opportunities and Challenges for Sustainable Construction and Building Materials.

The use of phase-change materials (PCM) in concrete has revealed promising results in terms of clean energy storage. However, the negative impact of the interaction between PCM and concrete on the mechanical and durability properties limits field applications, leading to a shift of the research to incorporate PCM into concrete using different techniques to overcome these issues. The storage of clean energy via PCM significantly supports the UN SDG 7 target of affordable and clean energy.

Influence of the Precursor, Molarity and Temperature on the Rheology and Structural Buildup of Alkali-Activated Materials.

This study presents an investigation of the effects of the precursor, alkalinity and temperature on the rheology and structural buildup of alkali activated materials. Here, 100% fly ash, 100% slag and blended mixes of fly ash and slag were activated by 4 M, 6 M, 8 M or 10 M (only for sodium hydroxide) solutions at 25 °C, 35 °C, 45 °C and 55 °C. The rheological properties were investigated to obtain the flow curves, viscosity, storage modulus, and loss factor of these materials.

Special Issue: "Microstructures and Durability of Cement-Based Materials".

Cement-based materials play an irreplaceable role in building and sustaining our society by meeting the performance demand imposed on structures and sustainability. Cement-based materials are no longer limited to derivatives of Portland cement, and appreciate a wider range of binders that come from various origins. It is therefore of utmost importance for understanding and expanding the relevant knowledge on their microstructure and likely durability performance.

Characteristics of Preplaced Aggregate Concrete Fabricated with Alkali-Activated Slag/Fly Ash Cements.

This study assesses the characteristics of preplaced aggregate concrete prepared with alkali-activated cement grout as an adhesive binder. Various binary blends of slag and fly ash without fine aggregate as a filler material were considered along with different solution-to-solid ratios. The properties of fresh and hardened grout along with the properties of hardened preplaced concrete were investigated, as were the compressive strength, ultrasonic pulse velocity, density, water absorption and total voids of the preplaced concrete.

Mechanical Properties, Microstructure, and Chloride Content of Alkali-Activated Fly Ash Paste Made with Sea Water.

The aim of the present study is to investigate the potential of sea water as a feasible alternative to produce alkali-activated fly ash material. The alkali-activated fly ash binder was fabricated by employing conventional pure water, tap water, and sea water based alkali activating solution. The characteristics of alkali-activated materials were examined by employing compressive strength, mercury intrusion porosimetry, XRD, FT-IR, and Si NMR along with ion chromatography for chloride immobilization.

Structural evolution of binder gel in alkali-activated cements exposed to electrically accelerated leaching conditions.

The structural evolution of a binder gel in alkali-activated cements exposed to accelerated leaching conditions is investigated for the first time. Samples incorporating fly ash and/or slag were synthesized and were exposed to electrically accelerated leaching by applying a current density of 5 A/m. The leaching behavior of the samples greatly depended on the binder gel formed in the samples.

Utilization of Calcium Carbide Residue Using Granulated Blast Furnace Slag.

The solidification and stabilization of calcium carbide residue (CCR) using granulated blast furnace slag was investigated in this study. CCR binding in hydrated slag was explored by X-ray diffraction, Si and Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, and thermodynamic calculations. Mercury intrusion porosimetry and and compressive strength tests assessed the microstructure and mechanical properties of the mixtures of slag and CCR.

Effect of Carbonation on Abrasion Resistance of Alkali-Activated Slag with Various Activators.

The effect of carbonation on the abrasion resistance of alkali-activated slag (AAS) was investigated. Various activator sets were selected for synthesizing AAS specimens, and the compressive strength was measured before and after carbonation. The abrasion resistance of the specimens was measured in accordance with the ASTM C944 test method.

Calcined Oyster Shell Powder as an Expansive Additive in Cement Mortar.

The present study prepared calcined oyster shell powder having chemical composition and crystal structure of calcium oxide and lime, respectively, and investigated the fresh and hardened properties of cement mortar incorporating calcined oyster shell powder as an additive. The test results indicated that the hydration of calcined oyster shell powder promoted the additional formation of Ca(OH) at the initial reaction stage, thereby increasing the heat of hydration. In particular, the volumetric increase of calcined oyster shell powder during hydration compensated the autogenous shrinkage of mortar at early ages, ultimately leading to a clear difference in the shrinkage values at final readings.

Cesium and Strontium Retentions Governed by Aluminosilicate Gel in Alkali-Activated Cements.

The present study investigates the retention mechanisms of cesium and strontium for alkali-activated cements. Retention mechanisms such as adsorption and precipitation were examined in light of chemical interactions. Batch adsorption experiments and multi-technical characterizations by using X-ray diffraction, zeta potential measurements, and the N₂ gas adsorption/desorption methods were conducted for this purpose.

An NMR Spectroscopic Investigation of Aluminosilicate Gel in Alkali-Activated Fly Ash in a CO₂-Rich Environment.

The present study investigated aluminosilicate gel in alkali-activated fly ash exposed to a CO₂-rich environment by means of NMR spectroscopy. The alkali-activated fly ash was exposed to an atmospheric CO₂ concentration of 10% after curing at 80 °C initially for 24 h. Under high concentrations of CO₂, highly reactive components Na and Al, which completely reacted within the first few hours, were unaffected by carbonation, while Si, with relatively slower reactivity, behaved differently.