CONSTRUCTION AND BUILDING MATERIALS
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2020
·
IF 4.419
Jinfeng Sun,Liang Tian,Zhuqing Yu,Yu Zhang,Chengdong Li,Guihua Hou,Xiaodong Shen
The effects of using different sizes of nano-TiO 2 (NT) on the hydration characteristics of Portland cement with different water to solid ratios (w/s, solid: cement + NT) were investigated in this study. Cement was partially replaced by NT with two sizes, 5 nm and 25 nm, at weight fractions of 0, 0.5%, 1.0%, 1.5% and 2.0%. The compressive strength, hydration products, hydration degree, pore structures and morphologies of the modified cement pastes were systematically evaluated. The experimental results showed that a suitable NT content effectively enhanced the compressive strength of the cement paste, and this enhancement directly depended on the NT particle size. Cement paste mixed with 5-nm NT resulted in a higher compressive strength than 25-nm NT, irrespective of the w/s ratio. The cement paste with a maximum compressive strength at all the curing ages was obtained using a 0.3 w/s ratio and 0.5 wt% of 5-nm NT (which were therefore identified as the optimal NT parameters). The compressive strength of this cement paste increased by 41.4%, 15.9%, 18.7% and 24.35% at 1, 3, 7 and 28 days, respectively, compared to a control sample. For both NT sizes, the w/s ratio and the NT content controlled the compressive strength development of the paste during the early and late ages, respectively. Compared with 25-nm NT, replacing cement by 5-nm NT within the optimum content range was more effective in accelerating cement hydration, increasing the hydration degree, decreasing the crystal size of Ca(OH) 2 , refining the pore structure and densifying the cement paste at the microscale, all of which increased the compressive strength at the macroscale.
研究领域:
土木工程
·
材料科学
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DOI
高影响因子
CONSTRUCTION AND BUILDING MATERIALS
·
2025
·
IF 8
Bin Xu,Zhaoyang Sun,Ming Sun,Binmeng Chen
Employing a high water-to-cement ratio (w/c) represents an effective strategy for mitigating the carbon footprint associated with the 3D concrete printing (3DCP) process. Here, we propose a novel method for achieving targeted rheological control for 3DCP via adjusting initiator concentrations for in-situ polymerization of sodium acrylate (SA) with a high w/c ratio of 0.55. Results indicate that the slower polymerization rate in the in-situ polymerization-modified cement paste (IPC) with lower initiator concentrations leads to inadequate dynamic and static yield stress during the extrusion and early stacking stages, potentially causing the flow-out of the printed filament. Conversely, more rapid polymerization occurs in IPC with higher initiator concentrations, resulting in the formation of extensive polymer bridges between cement particles. Consequently, their rheological properties are optimized for both the extrusion and stacking stages, with the static yield stress reaching the build strength of 100 kPa within 45 min, thereby ensuring stability during multi-layer stacking. Furthermore, in-situ formed polymers refine the pore structure and establish polymer networks within the cement matrix, enhancing the mechanical performance of IPC. As a result, IPC demonstrates adequate compressive strength and a significant increase in flexural strength, meeting the requirements for non-load-bearing elements even at a high water-to-cement ratio of 0.55. These findings highlight the potential of initiator concentration tuning in in-situ polymerization as a viable approach to optimize both rheological and mechanical properties in 3DCP, thereby improving printability and structural integrity in 3D printed cementitious materials.
研究领域:
土木工程
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材料科学
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增材制造
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建筑技术
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流变学
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DOI
高影响因子
MATERIALS AND STRUCTURES
·
2025
·Vol. 58
·期 7
·1-25
·
IF 3.9
Xue Lutao,Li Yubiao,Li Rui,Yu Wenqiang
The mismatch in physical properties between traditional mortar and the porous substrate of foam concrete (FC) leads to poor adhesion and cracking, limiting the wider application of FC. In order to address this issue and alleviate the storage pressure of low silica iron tailings (LSIT), this study developed an advanced plastering mortar system for foam concrete blocks through systematic optimization of LSIT. A comprehensive evaluation was conducted on six critical parameters, including the water-cement ratio, the aggregate ratio of LSIT to sand, the content of cement, hydroxypropyl methyl cellulose (HPMC), re-dispersible latex powder (RDP), and polypropylene fiber (PPF), establishing their quantitative impacts on mortar performance. The optimal performance was achieved with a water-cement ratio of 0.84, aggregate ratio of 11:3, cement content of 30%, HPMC content of 0.4%, RDP content of 1.5%, and PPF content of 0.15%, yielding a mortar density of 1447.9 kg/m 3 , 28 d compressive strength of 8.21 MPa, and 104 mm consistency, parameters fully compliant with the M8 grade specifications in JC/T 890-2017. Advanced microstructural characterization (XRD, SEM, and hydration heat analysis) demonstrated that LSIT particles refined the granulometric distribution through microaggregate effects. In addition, C 3 S dissociation was retarded by HPMC through Ca 2+ chelation, extending the induction period of hydration. Moreover, the RDP facilitated interfacial cross-linking via transesterification, forming the core–shell structures of C–S–H and polymer, compared with the control sample, the portlandite content was slightly reduced. Furthermore, the PPF reinforcement is achieved through crack-deflection and bridging mechanisms. The modification system of multi-component materials therefore exhibits a three-fold synergistic action, including the gradation optimization of particles, the regulation of hydration kinetics, and the toughening of the interfacial. These findings establish a viable pathway for high-value utilization of iron tailings in construction materials and simultaneously elucidate the physicochemical mechanisms underlying the interactions of composite modifiers in cementitious systems. Furthermore, the modified additive system serves as a viable template for valorizing diverse solid wastes. Graphical abstract
研究领域:
土木工程
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建筑材料
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固废资源化利用
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水泥基材料
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微观结构分析
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DOI
高影响因子
危险品化学品经营许可证（带存储）