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Graphene nanoribbons (GNRs) possess superior electrical properties due to their unique structures, making them increasingly valuable in composite materials. This study investigated the ability of GNRs to serve as nano-reinforcing agents that modify the electrical and self-sensing properties of cementitious composites compared to conventional nanomaterials such as carbon nanotubes (CNTs). Because they are highly dispersible in alkaline environments, GNRs can form effective conductive networks within a cement matrix. Incorporating 0.05 wt% GNRs into a cementitious composite significantly reduced the electrical resistivity of the sample after 28 d of curing by 64.61 % compared to the control sample. After drying, its electrical resistivity was still 42.82 % lower than that of the control sample. Furthermore, the GNRs-incorporated sample (dry state) exhibited a remarkable 63.65 % fractional change in resistivity when subjected to cyclic compressive stress. These results suggest that GNRs hold significant potential for enhancing the electrical and self-sensing properties of cementitious composites. [Display omitted] ● GNRs are compared with those of conventional conductive nanofiller CNTs. ● GNRs significantly improve the electrical conductivities and self-sensing properties of cementitious composites. ● Dispersion of nanomaterials determines the electrical behavior of cementitious composites. ● An overly dense microstructure does not benefit from forming conductive pathways. [ABSTRACT FROM AUTHOR]

This study investigated the effectiveness of graphene nanoribbons (GNRs) as nanoadditives for enhancing fire resistance of cementitious composites and compared their performance with conventional carbon nanotubes (CNTs). First, GNRs with striped structures exhibited superior dispersion stability compared to CNTs. Second, GNRs demonstrated excellent thermal stability, remaining structurally intact at 800 °C, while CNTs began decomposing above 450 °C. At room temperature, the GNRs significantly promoted the hydration reaction of cement clinkers, reduced the porosity, and refined the pore structure, thereby enhancing the mechanical properties of the cementitious composites. In high-temperature environments, GNRs act as bridges for cracks, effectively mitigating the deterioration of the mechanical strength caused by the dehydration and decomposition of hydration products. Moreover, the GNRs inhibited pore development and elongation, improving fire resistance. Overall, this study highlights the potential of GNRs as promising nanomaterials for enhancing the performance of cementitious composites under high-temperature conditions. [Display omitted] • GNRs possess superior thermal stability, and their structure remains undamaged even at a temperature of 800 °C. • GNRs improve the mechanical properties of cementitious composites by promoting the hydration reaction and providing a bridging and filling effect. • GNRs can effectively inhibit the development and elongation of pores and improve the microstructure of cementitious composites subjected to heating. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of graphene nanoribbons (GNRs) on the mechanical and electrical properties of cementitious composites was investigated by compared to carbon nanotubes (CNTs). • GNRs presented better dispersion and effectively promoted the hydration reaction of cement particles. • GNRs could notably decrease the resistivity of cementitious composites owing to their excellent electrical properties. Several functional fillers have been used to modify the mechanical and electrical properties of cement-based materials. Graphene nanoribbons (GNRs) have attracted considerable attention as the next generation of carbon-based nanomaterials owing to their excellent properties. This paper aims to assess the influence of GNRs with varying incorporation amounts (0.05, 0.10, and 0.15 wt% of cement) on the mechanical properties, hydration behavior, and electrical properties of ordinary Portland cement paste via mechanical strength test, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, and alternating current electrochemical impedance spectroscopy. The enhanced performance of GNRs in cementitious composites was compared with that of carbon nanotubes (CNTs), which are one of the most popular and conventional nano-reinforcing agents for cement-based materials. The results of this study show that, compared to CNTs, GNRs significantly decrease the resistivity of cementitious composites owing to their excellent electrical properties. Furthermore, after the exfoliation of CNTs, GNRs possess a larger specific surface area and exhibit improved dispersibility. Thus, GNRs provide better nucleation and filling effects for cementitious composites to promote the hydration reaction of cement clinkers and modify the microstructure of the cement matrix, resulting in enhanced mechanical properties of the cementitious composites. [ABSTRACT FROM AUTHOR]

• Eggshell powder as an alternative to limestone was used to produce cement clinker. • Eggshell cement clinker possesses the same anhydrous clinker phases as OPC. • Strength development and hydration kinetics of eggshell cement were evaluated. • Morphologic observation on hydration products of cement pastes was assessed. • Eggshell is a suitable limestone substitute for cement clinker production. In the Portland cement industry, the reuse of industrial by-products as raw materials for cement clinker production has been increasing. Eggshell waste, which is discharged in large volumes by households and the food industry, consists of a trigonal-calcite (CaCO 3) structure, and it possesses characteristics analogous to limestone. In this study, eggshell cement (ESC) was synthesized at 1470 °C using pulverized eggshell waste as a raw material for cement clinker production, as an alternative to limestone. Limestone cement (LPC) clinker was also produced under identical conditions to ESC. The anhydrous phases in the synthesized cements and hydrated cement pastes were characterized using X-ray diffraction with Rietveld refinement, field emission scanning electron microscopy, isothermal calorimetry, compressive strength tests, and thermogravimetry analysis. The results indicated that ESC exhibited four main cement clinker phases, namely C 3 S, C 2 S, C 3 A, and C 4 AF, identical to commercial ordinary Portland cement (OPC). Moreover, the strength development and hydration characteristics of ESCs are similar to those of LPC. As a consequence, this study illustrated that recycling eggshell waste to partially substitute limestone in raw materials for OPC production is feasible. [ABSTRACT FROM AUTHOR]

This study explored the influence of alumina type and gypsum content on the hydration, mechanical properties, and chemical changes of Portland–limestone cement (PLC) using isothermal calorimetry, inductively coupled plasma-optical emission spectroscopy (ICP-OES), ionic chromatography (IC), compressive strength testing, X-ray diffraction (XRD), 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR) spectroscopy, and mercury intrusion porosimetry (MIP) testing. The addition of alumina shortened the induction period, accelerated the acceleration period, and increased the mechanical strength of the PLC pastes with 3 and 7 wt% gypsum. The acceleration effect and strength enhancement were not distinct in the PLC pastes with less gypsum (0.1 wt%). The addition of γ-alumina led to the greatest accelerating effect and strength improvement in the PLC pastes with 3 and 7 wt% gypsum, and the compressive strength achieved was comparable to those of pure Ordinary Portland cement (OPC) pastes without limestone. The addition of γ-alumina induced the rapid dissolution of gypsum and consumption of sulfate ions. The chemical change affected by the addition of alumina varied greatly depending on the gypsum content, and trends in AFt and AFm formation in the PLC pastes with different gypsum contents were confirmed. Finally, pore size refinement was observed through the addition of alumina to PLC pastes with 3 and 7 wt% gypsum. • Incorporation of alumina accelerates the hydration of the PLC with 3 wt% and 7 wt% of gypsum. • Addition of alumina rapidly consumed gypsum in the PLC pastes and depletes the sulfate ions in its pore solution. • Addition of γ-alumina led the greatest strength increase in the PLC. • Addition of alumina promoted the formation of carboaluminate phase. • Pore size refinement was observed through the addition of alumina in the PLC. [ABSTRACT FROM AUTHOR]

Low-lime calcium silicate cement (CSC) is a CO 2 -reactive cement that utilizes the carbonation products of low- or non-hydraulic C 2 S, C 3 S 2 , and CS phases under H 2 O- and CO 2 -rich conditions. However, the reactivity and compressive strength of the CSC require further improvement. Therefore, this study aims to investigate the effects of blending ordinary Portland cement (OPC) as a reactive source into CSC on the initial reaction kinetics, phase evolution, and compressive strength development during carbonation curing. To assess the effects of blending CSC and OPC, CSC was substituted by OPC with the incremental ratio of 20 wt%. Notably, the CSC sample with 20 wt% OPC incorporation exhibited the highest compressive strength, which increased by up to 2.5 times compared to the pure CSC paste. Analysis of the microstructural phase evolution revealed that this significant increase in compressive strength was attributed to the strong mechanical interlocks between the rhombic CaCO 3 crystals, which were reinforced by a substantial amount of vaterite. [Display omitted] • Microstructure of blended CSC and OPC pastes under carbonation curing was studied. • Incorporation of OPC enhanced the initial reaction and Ca leaching of the cement paste. • Blending ratio of CSC:OPC= 8:2 was the most favorable for the formation of vaterite. • Vaterite generated on the calcite crystals reinforced the mechanical interlock. • Reinforced mechanical interlock significantly enhanced the compressive strength. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergistic effects of hybrid graphene oxide, nanosilica, and functionalized carbon nanotube were investigated. • Triple-hybrid nanomaterials demonstrated improved dispersion stability. • Triple-hybrid composites had improved thermal resistance and pore structures. • The pore structure demonstrated the high dispersity of the triple-hybrid nanomaterials within the cementitious composites. This study aimed to reveal the synergistic effects of graphene oxide (GO)/nanosilica (NS)/functionalized carbon nanotube (FCNT) hybrid nanomaterials on the thermal resistance and pore refinement of cementitious composites. The dispersion states and sizes of the nanomaterials in distilled water and Ca2+-rich solutions were assessed. In addition, the pore characteristics and thermal resistance of the nanomaterial-incorporated cementitious composites were analyzed. In the GO/NS/FCNT hybrid solution, a reinforcing effect of FCNT on the GO plate resulted in high resistance to wrinkling and agglomeration of GO; therefore, the stretched GO plate structure was advantageous for long-term dispersion maintenance, and well-dispersed NS enabled a more active pozzolanic reaction in cement paste. As a result, the triple-hybrid GO/NS/FCNT-reinforced cementitious composites demonstrated improved thermal resistance owing to their high residual strength after heating as well as homogenized pore structures with less elongated pore shapes and lower porosity than control specimens without nanomaterials. [ABSTRACT FROM AUTHOR]