This paper is focused on investigating the chemical processes during the carbonation of a gamma dicalcium silicate ( γ -C ₂ S). Isothermal calorimetry, in particular, provides valuable insights into the heat flow associated with the carbonation process under controlled conditions. The carbonation reactivity of γ -C ₂ S under varying CO ₂ pressure and water-to-solid ratio (w/s) using isothermal calorimetry was examined. The influence of these parameters on the extent of the carbonation reaction and the resulting proportions of calcium carbonate polymorphs (calcite, vaterite, and aragonite) was explored. Furthermore, the carbonation products were characterized using X-ray diffraction analysis (XRD), thermogravimetric and differential thermal analysis (TG–DTA), and scanning electron microscopy (SEM) to provide a comprehensive understanding of the reaction mechanism and the properties of the formed products. The results indicated that the partial pressure of CO ₂ had a limited influence on the carbonation degree, whereas the water-to-solid ratio greatly enhanced the extent of the reaction. Aragonite and calcite were identified as the predominant reaction products. Subsequent analyses at high temperatures revealed a transformation of aragonite into calcite at approximately 500 °C, followed by its decomposition into calcium oxide approximately at 800 °C.

This research delves into the potential use of fumed nanosilica in ultra-high performance concrete for ballistic protection. First, the mechanical properties, slump flow, and specific gravity of UHPC with different contents of Aerosil 200 were determined. Then, calorimetric studies were conducted on these cement composites. Lastly, the differential efficiency factor and spalling area of UHPC with fumed nanosilica were determined. It was found out that the slump flow, the mechanical properties, and differential efficiency factor are slightly decreased by the addition of fumed nanosilica. However, the addition of the fumed nanosilica is beneficial in terms of the spalling area decrease and it is highly reactive during the induction period. Some of the results are supported by BSEM imaging.

Geopolymers typically exhibit low yield stress, which is beneficial in most conventional applications but poses limitations for emerging technologies such as 3D printing. This study investigates the use of quaternary ammonium compounds, each differing in the length and number of aliphatic chains, as admixtures to modify the rheological properties of metakaolin-based geopolymers. These admixtures caused a slight increase in the plastic viscosity, but a substantial increase in the yield stress up to 20 times. Time-dependent rheological measurements showed rapid structural recovery of the modified fresh geopolymer paste, which is particularly favourable for 3D printing applications. The dosage and number of long aliphatic chains played a critical role, with double-chained molecules proving more effective than their single-chained counterparts. The interactions of the admixtures with the particles in the fresh geopolymer paste were studied by surface tension and zeta potential measurements, as well as molecular dynamics simulations, which supported the observed rheological behaviour.

This study investigates a non-destructive, compact pulse-echo ultrasonic method that combines an external transmitter with a single receiving sensor to identify different surface treatments applied to cementitious materials. The primary objective was to evaluate whether treatment-induced acoustic changes could be reliably quantified using time-domain signal parameters. Three types of surface conditions were examined: untreated reference specimens (R), specimens treated with a standard lithium silicate solution (A), and those treated with an enriched formulation containing hexylene glycol (B) intended to enhance pore sealing via gelation. A broadband piezoelectric receiver collected the backscattered echoes, from which the maximum amplitude, root mean square (RMS) voltage, signal energy, and effective duration were extracted. Receiver operating characteristic (ROC) analysis was conducted to quantify the discriminative power of each parameter. The results showed excellent classification performance between groups involving the B-treatment (AUC ≥ 0.96), whereas the R vs. A comparison yielded moderate separation (AUC ≈ 0.61). Optimal cut-off values were established using the Youden index, with sensitivity and specificity exceeding 96% in the best-performing scenarios. The results demonstrate that a single-receiver, one-sided pulse-echo arrangement coupled with straightforward amplitude metrics provides a rapid, cost-effective, and field-adaptable tool for the quality control of silicate-surface treatments. By translating laboratory ultrasonics into a practical on-site protocol, this study helps close the gap between the experimental characterisation and real-world implementation of surface-treatment verification.