This study investigates the influence of high-entropy oxide (HEO) fine powder with submicron agglomerates (Mg₀.₂Ni₀.₂Co₀.₂Cu₀.₂Zn₀.₂O) on the mechanical performance, microstructural development, and durability characteristics of cement-based mortars. HEO was synthesized via a modified sol–gel method and incorporated into mortar mixtures as an additional additive at dosages of 0–1.0 wt% relative to the cement content. The experimental results demonstrate a strong dosage-dependent behavior. The optimum performance was obtained at 0.25 wt% HEO, where compressive and flexural strengths increased by up to approximately 3–4% compared to the control sample. In contrast, higher dosages (≥ 0.75 wt%) resulted in a gradual reduction in mechanical performance, indicating a threshold beyond which HEO begins to negatively affect hydration-related processes. Microstructural analysis (XRD and SEM–EDS) revealed that HEO particles contribute to matrix densification through a filler effect and act as nucleation sites for hydration products, leading to a more compact cementitious structure at optimal content. However, excessive incorporation appears to disrupt hydration continuity due to particle agglomeration and dilution effects. Durability tests showed improved resistance to water absorption, chloride ion penetration, and corrosion current with increasing HEO content, attributed to pore refinement and reduced ion transport pathways. The most balanced performance in both mechanical and durability properties was achieved at low HEO dosage. Overall, high-entropy oxides demonstrate significant potential as nano-scale additives for cementitious systems; however, their effectiveness is highly dependent on dosage, with low replacement levels providing the most beneficial performance balance.
Grouting materials used in water-rich and chloride-exposed environments require adequate workability, mechanical performance, and durability. To optimize the formulation, a series of orthogonal tests was conducted to assess how fly ash (10–30%), rust inhibitor (1–3%), and anti-corrosion agent (2–6%) affect the fresh and hardened properties of cement grouts at a constant water-to-binder ratio of 0.5. Setting behaviour, mechanical properties, chloride ion penetration resistance, pore structure, and hydration products were investigated. Fly ash and the anti-corrosion admixture prolonged the setting time. The highest 28-day compressive and flexural strengths were obtained at 20% fly ash. At 30%, the dilution effect outweighed the later-age pozzolanic contribution and slowed strength development. Within the investigated range, 6% anti-corrosion admixture provided the greatest improvement in strength and chloride ion penetration resistance, whereas the rust inhibitor had a smaller effect on the charge passed. Mixtures containing 20% fly ash and 4–6% anti-corrosion admixture exhibited lower porosity and a refined pore-size distribution. By contrast, 30% fly ash resulted in a less favourable pore structure. SEM and XRD results indicated a denser matrix at 28 days, consistent with continued cement hydration and the later-age pozzolanic reaction of fly ash. Previous studies have mainly focused on individual mineral or chemical admixtures, whereas the combined effects of fly ash, rust inhibitors, and anti-corrosion admixtures under fixed workability conditions remain insufficiently understood. This study reveals their distinct and complementary roles, providing a basis for the multi-objective optimisation of grouting materials in chloride-rich and water-saturated environments. Overall, 20% fly ash, 4–6% anti-corrosion admixture, and 1–2% rust inhibitor provided the best performance balance under the investigated conditions.
Rui Xu, Jing Xue, Tianlei Wang et al.· Applied Sciences· 0 citations
Red mud (RM), a highly alkaline by-product of the alumina refining process, poses significant environmental challenges due to its large-scale accumulation. This study systematically investigates the mechanical performance, thermal resistance, and durability of RM-based cement mortar, evaluating the individual effects of fly ash (FA), basalt fibers (BF), and nano zinc oxide (NZO) as separate modifying constituents introduced independently into the RM matrix. Fourteen mortar mixtures were prepared with RM replacement levels of 10–35%, a constant FA content of 15%, BF dosages of 0.5–1.5%, and NZO dosages of 0.5–2.0%. Workability, 28-day compressive and flexural strengths, residual mechanical properties after exposure to 600 °C and 800 °C, sulfate resistance, and microstructural characteristics were evaluated. Increasing RM content reduced workability and mechanical strength, with compressive and flexural reductions reaching 35.5% and 29.0% at 30% RM, respectively. FA partially compensated through its ball-bearing effect and pozzolanic reactivity. The optimal 1.5% BF dosage increased the compressive and flexural strengths by 14.7% and 37.5%, respectively, and significantly enhanced the residual performance at elevated temperatures. The optimal 0.5% NZO improved the compressive and flexural strengths by 13.2% and 18.3%, respectively; however, 2.0% NZO caused complete strength loss, which may be associated with severe nanoparticle agglomeration and possible zinc-containing reaction products reported in previous studies. The formation of specific crystalline phases was not experimentally verified in the present study. Sulfate resistance deteriorated with increasing RM, whereas 1.5% BF and 1.0% NZO reduced mass loss by 58.9% and 59.7%, respectively. SEM confirmed that RM15 + FA15 exhibited the densest microstructure with minimal voids. The results demonstrate that RM can be effectively utilized as a sustainable cement replacement, with FA, BF, and NZO each independently identified as effective performance-enhancing constituents at their respective optimal dosages; their combined quaternary application remains untested and is proposed as a direction for future validation.
Sultan Almuaythir, Mousa Shhabat, Ahmed M. Ashteyat et al.· Sustainability· 0 citations
This research explores the usability of reactive MgO (RM)-based materials as sustainable, low-carbon alternative binders for 3D concrete printing. Specifically, RM was substituted with 25 wt% of diverse silica sources to assess their potential: micro-silica (MS), metakaolin (MK), fly ash (FA), and basalt powder (Bst). By evaluating rheology, buildability, and 28-day compressive strength under a constant initial consistency, results reveal that the MK blend exhibited optimal rheological behavior. It combined low initial dynamic yield stress for smooth extrusion with substantial time-dependent viscosity build-up, completely preventing filament deformation. All mixtures demonstrated excellent buildability, successfully sustaining 20-layer structures without collapse. Furthermore, XRD analysis confirmed that highly amorphous silica in MS and MK facilitated extensive precipitation of magnesium silicate hydrate (M-S-H) gels. This microstructural improvement yielded the highest compressive strengths of 16.5 MPa and 13.9 MPa, respectively. Ultimately, RM-SiO₂ systems emerge as highly promising, low-carbon materials for digital construction.
B. Akturk, S. Ulukaya, T. Yazar· Materiales de Construccion· 0 citations
Traditional portland cement (PC)-based ultrahigh-performance concrete (UHPC) is prone to spalling under fire temperatures due to its dense microstructure, accompanied by severe performance degradation, which hinders its widespread application in engineering. Therefore, this study developed an aluminate cement-based UHPC (AUHPC) with excellent high-temperature resistance and antispalling performance, and systematically investigated the effects of steel fiber type, content, and exposure temperature on the compressive and splitting tensile properties. The results indicate that steam and dry-heat curing effectively inhibit the strength retrogression caused by the transformation of
CAH
10
to
C
3
AH
6
. Meanwhile, with the increase in temperature, recycled brick powder (RBP) participates in the hydration reaction and forms stable
C
2
ASH
8
. At 400°C, the compressive and splitting tensile strengths of AUHPC specimens containing 5% RBP reach the maximum, with the strength of RSF2 specimens increasing by 37.2% and 46.3%, respectively, compared with that at room temperature. When the temperature exceeds 600°C, the number of pores on the specimen surface decreases gradually, while the cracks increase and widen. At 800°C, the splitting tensile strength of NSF2 and RSF2 series specimens decreases by 44.6% and 7.9%, respectively, compared with that at 20°C. At 1,200°C, the holes and channels left by the complete melting of normal steel fibers (NSF) aggravate the high-temperature damage, and the strength decreases with the increase of NSF content, while refractory steel fibers (RSF) exhibit better compatibility with AUHPC matrix.
Wei Ma, Danying Gao, Jiyu Tang et al.· Journal of materials in civi...· 0 citations
Substituting aluminosilicate pozzolans for cement offers a stable and environmentally sustainable mixture. The primary innovation lies in incorporating polypropylene and steel fibers into self-compacting mixtures to enhance mechanical properties and durability, coupled with artificial intelligence modeling (artificial neural networks and decision trees) for compressive strength prediction. This integrated experimental and computational methodology enables more precise optimization of mix designs.The methodology involved producing 16 mix designs with alkaline concentrations of 8 and 12 M, variations in pozzolan quantities, and fiber volumes (0.5 to 1% by volume). Samples underwent ambient and heat curing, with evaluations of fresh properties (slump flow, L-box, V-funnel), mechanical properties (compressive and tensile strength), water absorption, shrinkage, and microstructure (SEM and XRD). Modeling was performed using experimental data to predict compressive strength. Results indicated that increasing molarity from 8 to 12 densifies the concrete microstructure, boosting compressive strength by up to 25% (from 40 to 96.83 MPa at 28 days), although alkaline solution costs may rise. Steel fibers, by forming resilient internal networks, improved tensile and flexural strength by up to 30% and reduced drying shrinkage by 11% . Hybrid fiber combinations enhanced high-temperature durability, retaining 80% strength at 600°C. The AI models achieved accuracies exceeding 88% , positioning this concrete as a sustainable and efficient alternative to Portland cement concrete.
Meysam Rostami, Vahid Rostami, A. Lork· Journal of Resource Manageme...· 0 citations
A multi-scale reinforced cement mortar was developed by combining 0.05% multi-walled carbon nanotubes (MWCNTs) with hybrid polyethylene fibre (PEF) and basalt fibre (BF). A total of 12 mixtures were prepared and evaluated for flexural and compressive strengths, rapid chloride migration, sulfate resistance (up to 120 days) and microstructure. Compared with the reference mixture without fibres or MWCNTs, mix P20B30 (0.20% PEF + 0.30% BF) showed an increase of 27% in 28-day flexural strength, an increase of 10% in 28-day compressive strength, a reduction in the non-steady-state chloride migration coefficient of 68% and a 72% decrease in sulfate-induced mass loss. These results identified P20B30 as the best-performing mixture on the basis of combined mechanical and durability indicators. The improvements are attributed to matrix/interfacial transition zone densification by MWCNTs and multi-scale crack bridging by hybrid fibres, which jointly restricted transport pathways and damage evolution.
Zhengfa Chen, Jiahua Yan, Xiwen Hua et al.· Magazine of Concrete Researc...· 0 citations
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