Pub Date : 2024-11-28DOI: 10.1016/j.cemconcomp.2024.105873
Tian Li , Rita Nogueira , Jorge de Brito , Paulina Faria , Jiaping Liu
<div><div>Recycled concrete powder (RCP) influences cement paste's rheology, but the mechanisms remain unclear. This paper intends to fill this gap by employing a new method for measuring water absorption, the minimum water requirement method, an organic carbon analyser, and a laser particle size analyser. The cementitious material's water absorption (<span><math><mrow><mi>W</mi></mrow></math></span>), packing density (<span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span>), water reducer adsorption (<span><math><mrow><msub><mi>Q</mi><mrow><mi>a</mi><mi>d</mi></mrow></msub></mrow></math></span>), and particle size distribution are determined. Results show that, as the RCP's content increases from 0 % to 25 %, the cementitious material's <span><math><mrow><mi>W</mi></mrow></math></span>, <span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span>, <span><math><mrow><msub><mi>Q</mi><mrow><mi>a</mi><mi>d</mi></mrow></msub></mrow></math></span>, volume fraction, and average particle size increase by 21.7 %, 0.9 %, 26.2 %, 1.4 %, and 30.6 %, respectively. Consequently, the particle's surface covered by the water reducer (<span><math><mrow><mi>θ</mi></mrow></math></span>) and distance (<span><math><mrow><mi>H</mi></mrow></math></span>) decrease by 26.5 % and 32.6 %, respectively, resulting in an increase in the paste's yield stress (<span><math><mrow><msub><mi>τ</mi><mn>0</mn></msub></mrow></math></span>) and plastic viscosity (<span><math><mrow><msub><mi>η</mi><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></math></span>) by 1946.6 % and 45.3 %, respectively. Based on an existing yield stress model, RCP affecting <span><math><mrow><msub><mi>τ</mi><mn>0</mn></msub></mrow></math></span> can be attributed to changes in the particle system's colloidal and contact interactions. A decrease in <span><math><mrow><mi>H</mi></mrow></math></span> increases colloidal interactions. Conversely, an increase in <span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span> and a decrease in fine particle content reduce contact interactions. Colloidal interactions are more significant, thus <span><math><mrow><msub><mi>τ</mi><mn>0</mn></msub></mrow></math></span> increases. Based on the functional expression for the <span><math><mrow><msub><mi>η</mi><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></math></span> developed here, RCP affecting <span><math><mrow><msub><mi>η</mi><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></math></span> can be attributed to changes in hydrodynamic interactions and contact interactions. A decrease in <span><math><mrow><mi>H</mi></mrow></math></span> increases hydrodynamic interactions. An increase in <span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span> combined with a decrease in fine particle content decrease contact interactions. Additionally, an increase in <span><math><mrow><msub><mi>Q</mi><mrow><mi>a</mi><mi>d</mi></mrow></msub></mrow></math></span> reduces pore solution's v
{"title":"Effect of recycled concrete powder on the rheological properties of cement paste: New findings","authors":"Tian Li , Rita Nogueira , Jorge de Brito , Paulina Faria , Jiaping Liu","doi":"10.1016/j.cemconcomp.2024.105873","DOIUrl":"10.1016/j.cemconcomp.2024.105873","url":null,"abstract":"<div><div>Recycled concrete powder (RCP) influences cement paste's rheology, but the mechanisms remain unclear. This paper intends to fill this gap by employing a new method for measuring water absorption, the minimum water requirement method, an organic carbon analyser, and a laser particle size analyser. The cementitious material's water absorption (<span><math><mrow><mi>W</mi></mrow></math></span>), packing density (<span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span>), water reducer adsorption (<span><math><mrow><msub><mi>Q</mi><mrow><mi>a</mi><mi>d</mi></mrow></msub></mrow></math></span>), and particle size distribution are determined. Results show that, as the RCP's content increases from 0 % to 25 %, the cementitious material's <span><math><mrow><mi>W</mi></mrow></math></span>, <span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span>, <span><math><mrow><msub><mi>Q</mi><mrow><mi>a</mi><mi>d</mi></mrow></msub></mrow></math></span>, volume fraction, and average particle size increase by 21.7 %, 0.9 %, 26.2 %, 1.4 %, and 30.6 %, respectively. Consequently, the particle's surface covered by the water reducer (<span><math><mrow><mi>θ</mi></mrow></math></span>) and distance (<span><math><mrow><mi>H</mi></mrow></math></span>) decrease by 26.5 % and 32.6 %, respectively, resulting in an increase in the paste's yield stress (<span><math><mrow><msub><mi>τ</mi><mn>0</mn></msub></mrow></math></span>) and plastic viscosity (<span><math><mrow><msub><mi>η</mi><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></math></span>) by 1946.6 % and 45.3 %, respectively. Based on an existing yield stress model, RCP affecting <span><math><mrow><msub><mi>τ</mi><mn>0</mn></msub></mrow></math></span> can be attributed to changes in the particle system's colloidal and contact interactions. A decrease in <span><math><mrow><mi>H</mi></mrow></math></span> increases colloidal interactions. Conversely, an increase in <span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span> and a decrease in fine particle content reduce contact interactions. Colloidal interactions are more significant, thus <span><math><mrow><msub><mi>τ</mi><mn>0</mn></msub></mrow></math></span> increases. Based on the functional expression for the <span><math><mrow><msub><mi>η</mi><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></math></span> developed here, RCP affecting <span><math><mrow><msub><mi>η</mi><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></math></span> can be attributed to changes in hydrodynamic interactions and contact interactions. A decrease in <span><math><mrow><mi>H</mi></mrow></math></span> increases hydrodynamic interactions. An increase in <span><math><mrow><msub><mi>φ</mi><mi>m</mi></msub></mrow></math></span> combined with a decrease in fine particle content decrease contact interactions. Additionally, an increase in <span><math><mrow><msub><mi>Q</mi><mrow><mi>a</mi><mi>d</mi></mrow></msub></mrow></math></span> reduces pore solution's v","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105873"},"PeriodicalIF":10.8,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142735676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.cemconcomp.2024.105868
Jingjie Wei, Kamal H. Khayat
While self-consolidating concrete (SCC) has emerged as a highly effective approach for the repair of concrete structures, there have been few investigations regarding the effect of the combination of different fiber and shrinkage-mitigating material types (shrinkage-reducing admixture, SRA; superabsorbent polymer, SAP; and expansive agent, EA) on the flexural behavior of repaired structures. This study aims to explore the influence of three different shrinkage-mitigating materials (1.25%–2.5 % SRA, 4%–8% EA, and 0.2%–0.4 % SAP), four fiber types (two macro synthetic fibers, MSFA and MSFB; 5D hooked steel fibers, 5D; a combination of 80 % 3D hooked steel +20 % short steel fibers STST) on fresh and hardened properties, cement hydration, and drying shrinkage of fiber-reinforced self-consolidating concrete (FR-SCC). Specifically, the effect of different shrinkage-mitigating materials, fiber types, and two repair thicknesses corresponding to 1/3 and 2/3 of the total height of prismatic element on the flexural performance of composite specimens repaired using FR-SCC was studied. The bond strength between existing concrete and FR-SCC was also investigated to reveal the flexural behavior of the composite beams. The results indicate that prismatic specimens repaired with FR-SCC made with 1.25 % SRA showed excellent flexural performance compared to those repaired using FR-SCC made with 4%–8% EA and 0.2%-0.4%SAP. The adverse effect of the incorporation of 4%–8% EA and 0.2%–0.4 % SAP on flexural behavior of repair specimens can be attributed to a lower existing concrete-FR-SCC interfacial and fiber-matrix bond strengths. Using SRA, EA, or SAP in FR-SCC improved bond strength with substrate by 10%–60 % compared to FR-SCC without any shrinkage-mitigating materials. The use of 1.25 % SRA showed the highest bond strength, which increased by 10%–37 % and 33%–44 %, respectively, compared to that made with SAP and EA. As the increase in the repair thickness of specimens, the incorporation of SRA, EA, or SAP had different efficiencies to enhance the flexural toughness and residual strength of the repair specimens. Furthermore, the incorporation of 5D fiber and 1.25 % SRA in SCC showed excellent flexural performance, followed by MSFA, STST, and MSFB fibers. The increase in the repair thickness from 1/3 to 2/3 of the total height of the composite beam enhanced the flexural toughness and residual strength by a maximum of 133 % and 160 %, respectively, attributing to fiber type and the increase in fiber volume at the cross-section of specimens.
自密实混凝土（SCC）已成为修复混凝土结构的一种高效方法，但有关不同纤维和减缩材料（减缩外加剂，SRA；超吸收聚合物，SAP；膨胀剂，EA）的组合对修复结构抗弯行为影响的研究却很少。本研究旨在探讨三种不同的减缩材料（1.25%-2.5% SRA、4%-8% EA 和 0.2%-0.4% SAP）、四种纤维类型（两种大合成纤维 MSFA 和 MSFB；5D 钩状钢纤维 5D；80% 3D 钩状钢纤维 + 20% 短钢纤维 STST 组合）对纤维增强自密实混凝土（FR-SCC）的新拌和硬化性能、水泥水化和干燥收缩的影响。具体而言，研究了不同的减缩材料、纤维类型和两种修复厚度（分别相当于棱柱构件总高度的 1/3 和 2/3）对使用 FR-SCC 修复的复合试件抗弯性能的影响。此外，还研究了现有混凝土与 FR-SCC 之间的粘结强度，以揭示复合梁的抗弯行为。结果表明，与使用含 4%-8% EA 和 0.2%-0.4%SAP 的 FR-SCC 修补的棱柱试样相比，使用含 1.25% SRA 的 FR-SCC 修补的棱柱试样表现出优异的抗弯性能。掺入 4%-8% EA 和 0.2%-0.4% SAP 会对修复试样的抗弯性能产生不利影响，这是因为现有混凝土-FR-SCC 的界面强度和纤维-基质粘结强度较低。与不使用任何减缩材料的 FR-SCC 相比，在 FR-SCC 中使用 SRA、EA 或 SAP 可将与基材的粘结强度提高 10%-60%。使用 1.25% SRA 的粘结强度最高，与使用 SAP 和 EA 的粘结强度相比，分别提高了 10%-37%和 33%-44%。随着试样修复厚度的增加，加入 SRA、EA 或 SAP 对提高修复试样的弯曲韧性和残余强度有不同的效果。此外，在 SCC 中掺入 5D 纤维和 1.25% SRA 表现出优异的抗弯性能，其次是 MSFA、STST 和 MSFB 纤维。将修复厚度从复合梁总高度的 1/3 增加到 2/3，可使弯曲韧度和残余强度分别提高 133% 和 160%，这与纤维类型和试样横截面上纤维体积的增加有关。
{"title":"Effect of shrinkage-mitigating materials, fiber type, and repair thickness on flexural behavior of beams repaired with fiber-reinforced self-consolidating concrete","authors":"Jingjie Wei, Kamal H. Khayat","doi":"10.1016/j.cemconcomp.2024.105868","DOIUrl":"10.1016/j.cemconcomp.2024.105868","url":null,"abstract":"<div><div>While self-consolidating concrete (SCC) has emerged as a highly effective approach for the repair of concrete structures, there have been few investigations regarding the effect of the combination of different fiber and shrinkage-mitigating material types (shrinkage-reducing admixture, SRA; superabsorbent polymer, SAP; and expansive agent, EA) on the flexural behavior of repaired structures. This study aims to explore the influence of three different shrinkage-mitigating materials (1.25%–2.5 % SRA, 4%–8% EA, and 0.2%–0.4 % SAP), four fiber types (two macro synthetic fibers, MSF<sub>A</sub> and MSF<sub>B</sub>; 5D hooked steel fibers, 5D; a combination of 80 % 3D hooked steel +20 % short steel fibers STST) on fresh and hardened properties, cement hydration, and drying shrinkage of fiber-reinforced self-consolidating concrete (FR-SCC). Specifically, the effect of different shrinkage-mitigating materials, fiber types, and two repair thicknesses corresponding to 1/3 and 2/3 of the total height of prismatic element on the flexural performance of composite specimens repaired using FR-SCC was studied. The bond strength between existing concrete and FR-SCC was also investigated to reveal the flexural behavior of the composite beams. The results indicate that prismatic specimens repaired with FR-SCC made with 1.25 % SRA showed excellent flexural performance compared to those repaired using FR-SCC made with 4%–8% EA and 0.2%-0.4%SAP. The adverse effect of the incorporation of 4%–8% EA and 0.2%–0.4 % SAP on flexural behavior of repair specimens can be attributed to a lower existing concrete-FR-SCC interfacial and fiber-matrix bond strengths. Using SRA, EA, or SAP in FR-SCC improved bond strength with substrate by 10%–60 % compared to FR-SCC without any shrinkage-mitigating materials. The use of 1.25 % SRA showed the highest bond strength, which increased by 10%–37 % and 33%–44 %, respectively, compared to that made with SAP and EA. As the increase in the repair thickness of specimens, the incorporation of SRA, EA, or SAP had different efficiencies to enhance the flexural toughness and residual strength of the repair specimens. Furthermore, the incorporation of 5D fiber and 1.25 % SRA in SCC showed excellent flexural performance, followed by MSF<sub>A</sub>, STST, and MSF<sub>B</sub> fibers. The increase in the repair thickness from 1/3 to 2/3 of the total height of the composite beam enhanced the flexural toughness and residual strength by a maximum of 133 % and 160 %, respectively, attributing to fiber type and the increase in fiber volume at the cross-section of specimens.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105868"},"PeriodicalIF":10.8,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.cemconcomp.2024.105870
Xiaodi Dai , Sharu Bhagavathi Kandy , Narayanan Neithalath , Aditya Kumar , Mathieu Bauchy , Edward Garboczi , Torben Gaedt , Samanvaya Srivastava , Gaurav Sant
3D-printing could offer substantial benefits to the construction industry including the fabrication of customized/bespoke components, eliminating formwork, and reducing material waste. Despite these advantages, control of the pumpability, extrudability, and buildability of 3D-printed concrete (3DPC) remains challenging. This study demonstrates how the use of fly ash (FA) enables enhanced thermal stiffening, and rapid alkali-activation in the presence of portlandite (Ca(OH)2, CH). In general, blends of CH and FA exhibit less structural build-up at low temperatures, but upon reaching a trigger temperature of 75 °C, these blends achieve rapid stiffening, at rates of ∼800 Pa/s. The rapid stiffening arises from the flocculation of CH particles, and the onset of the pozzolanic/alkali-activation reactions between CH and FA, resulting in the formation of C-A-S-H and N-A-S-H during stiffening. Careful selection of the FA-CH blend ratio, which displays an optimum at ∼20 mass % CH, enables the composition of cement-free formulations for 3D-printing applications. The outcomes have important implications on alternate feedstock pathways to compose carbon-efficient formulations for construction.
三维打印技术可为建筑行业带来巨大的好处，包括制造定制部件、消除模板和减少材料浪费。尽管有这些优势，但控制三维打印混凝土（3DPC）的可泵性、可挤出性和可施工性仍具有挑战性。本研究展示了粉煤灰（FA）如何在存在波长石（Ca(OH)2，CH）的情况下增强热刚度和快速碱活化。一般来说，CH 和 FA 的混合物在低温下的结构形成较少，但当达到 75 °C 的触发温度时，这些混合物会以 ∼800 Pa/s 的速度快速硬化。快速硬化的原因是 CH 颗粒的絮凝，以及 CH 和 FA 之间开始发生热固性/碱激活反应，从而在硬化过程中形成 C-A-S-H 和 N-A-S-H。对 FA-CH 混合比的精心选择（CH 质量百分比在 20 ∼ 20% 时为最佳）可为 3D 打印应用提供无水泥配方。这些成果对建筑用碳效率配方的替代原料途径具有重要意义。
{"title":"Thermally stimulated stiffening and fly ash's alkaline activation by Ca(OH)2 addition facilitates 3D-printing","authors":"Xiaodi Dai , Sharu Bhagavathi Kandy , Narayanan Neithalath , Aditya Kumar , Mathieu Bauchy , Edward Garboczi , Torben Gaedt , Samanvaya Srivastava , Gaurav Sant","doi":"10.1016/j.cemconcomp.2024.105870","DOIUrl":"10.1016/j.cemconcomp.2024.105870","url":null,"abstract":"<div><div>3D-printing could offer substantial benefits to the construction industry including the fabrication of customized/bespoke components, eliminating formwork, and reducing material waste. Despite these advantages, control of the pumpability, extrudability, and buildability of 3D-printed concrete (3DPC) remains challenging. This study demonstrates how the use of fly ash (FA) enables enhanced thermal stiffening, and rapid alkali-activation in the presence of portlandite (Ca(OH)<sub>2</sub>, CH). In general, blends of CH and FA exhibit less structural build-up at low temperatures, but upon reaching a trigger temperature of 75 °C, these blends achieve rapid stiffening, at rates of ∼800 Pa/s. The rapid stiffening arises from the flocculation of CH particles, and the onset of the pozzolanic/alkali-activation reactions between CH and FA, resulting in the formation of C-A-S-H and N-A-S-H during stiffening. Careful selection of the FA-CH blend ratio, which displays an optimum at ∼20 mass % CH, enables the composition of cement-free formulations for 3D-printing applications. The outcomes have important implications on alternate feedstock pathways to compose carbon-efficient formulations for construction.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105870"},"PeriodicalIF":10.8,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142718892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Interest in the use of graphene to enhance the properties of cementitious materials is growing, but major impediments in implementation are the cost of graphene and changes in binder rheology attributable to these nanomaterials. This study explores the influence of novel, cost-effective, environment-friendly, and mass-producible graphene on the rheology and early-age structure development of cementitious binders. Two novel graphene types—fractal graphene (FG) and reactive graphene (RG)—are used in plain cement mixtures as well as those containing 30 % (by mass) of fly ash and/or limestone powder, at low dosages of ≤0.02 % by mass of binder. The early- and later-age compressive strengths are higher (by ∼5–35 %) for the graphene-modified mixtures, and they more-than-compensate for early strength reduction induced by higher cement replacement levels. Yield stress, plastic viscosity, storage modulus, and short-term thixotropy are found to be significantly higher (up to 2 times or more for yield stress, plastic viscosity, and storage modulus, and up to 3 times for short-term thixotropy) for the FG- and RG-modified pastes, with a dominant enhancement noted for the RG-modified pastes. Time-dependent storage modulus evolution using small amplitude oscillatory shear tests, supplemented with associated models indicate faster structural buildup for the FG- and RG-modified pastes due to the contributions of FG and RG to inter-particle interactions and hydration. Storage modulus evolution beyond the onset of acceleration is found to be well-related to adjusted cumulative heat of hydration and electrical conductivity values, providing rapid and inexpensive means of reliably estimating early-age structure development in cementitious systems. It is determined that ultra-low dosages (≤0.02 % by mass of binder) of FG and RG can aid in tuning the rheological and structure-development parameters, which will be beneficial towards unique applications such as 3D concrete printing and ultra-high performance concretes.
{"title":"Rheology and early-age structure development in binary and ternary blends modified with novel graphene types","authors":"Sahil Surehali , Collin Gustafson , Sayee Srikarah Volaity , Ranjith Divigalpitiya , Aditya Kumar , Narayanan Neithalath","doi":"10.1016/j.cemconcomp.2024.105869","DOIUrl":"10.1016/j.cemconcomp.2024.105869","url":null,"abstract":"<div><div>Interest in the use of graphene to enhance the properties of cementitious materials is growing, but major impediments in implementation are the cost of graphene and changes in binder rheology attributable to these nanomaterials. This study explores the influence of novel, cost-effective, environment-friendly, and mass-producible graphene on the rheology and early-age structure development of cementitious binders. Two novel graphene types—fractal graphene (FG) and reactive graphene (RG)—are used in plain cement mixtures as well as those containing 30 % (by mass) of fly ash and/or limestone powder, at low dosages of ≤0.02 % by mass of binder. The early- and later-age compressive strengths are higher (by ∼5–35 %) for the graphene-modified mixtures, and they more-than-compensate for early strength reduction induced by higher cement replacement levels. Yield stress, plastic viscosity, storage modulus, and short-term thixotropy are found to be significantly higher (up to 2 times or more for yield stress, plastic viscosity, and storage modulus, and up to 3 times for short-term thixotropy) for the FG- and RG-modified pastes, with a dominant enhancement noted for the RG-modified pastes. Time-dependent storage modulus evolution using small amplitude oscillatory shear tests, supplemented with associated models indicate faster structural buildup for the FG- and RG-modified pastes due to the contributions of FG and RG to inter-particle interactions and hydration. Storage modulus evolution beyond the onset of acceleration is found to be well-related to adjusted cumulative heat of hydration and electrical conductivity values, providing rapid and inexpensive means of reliably estimating early-age structure development in cementitious systems. It is determined that ultra-low dosages (≤0.02 % by mass of binder) of FG and RG can aid in tuning the rheological and structure-development parameters, which will be beneficial towards unique applications such as 3D concrete printing and ultra-high performance concretes.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105869"},"PeriodicalIF":10.8,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1016/j.cemconcomp.2024.105865
Tong Zhang , Jiaze Cui , Meng Chen , Jinlai Yang , Zhiguo Yan , Mingzhong Zhang
The utilisation of carbonated recycled aggregates in concrete has been increasingly considered as an effective strategy for CO2 sequestration in the built environment and enhancement of concrete sustainability. Following up a pervious review on the role of carbonated recycled concrete aggregates in the mechanical properties of concrete, this paper presents a comprehensive review on the effects of carbonation treatment on the chemical compositions and physical properties of recycled concrete aggregates, as well as the role of carbonated recycled concrete aggregates in microstructure and durability-related properties including volume deformation, transport properties, chemical resistance, freeze-thaw resistance and fire resistance of concrete. A special focus is placed on the relationship between microstructure and durability-related properties of carbonated recycled aggregate concrete considering the effects of pre-treatment method, replacement level, curing age, water-to-binder ratio and quality of the original aggregates. The insights into the deterioration mechanism and strategies for improving the durability of carbonated recycled aggregate concrete are provided. This review summarises the recent advances in the field, followed by a discussion on the remaining challenges and opportunities for future research.
{"title":"Durability of concrete containing carbonated recycled aggregates: A comprehensive review","authors":"Tong Zhang , Jiaze Cui , Meng Chen , Jinlai Yang , Zhiguo Yan , Mingzhong Zhang","doi":"10.1016/j.cemconcomp.2024.105865","DOIUrl":"10.1016/j.cemconcomp.2024.105865","url":null,"abstract":"<div><div>The utilisation of carbonated recycled aggregates in concrete has been increasingly considered as an effective strategy for CO<sub>2</sub> sequestration in the built environment and enhancement of concrete sustainability. Following up a pervious review on the role of carbonated recycled concrete aggregates in the mechanical properties of concrete, this paper presents a comprehensive review on the effects of carbonation treatment on the chemical compositions and physical properties of recycled concrete aggregates, as well as the role of carbonated recycled concrete aggregates in microstructure and durability-related properties including volume deformation, transport properties, chemical resistance, freeze-thaw resistance and fire resistance of concrete. A special focus is placed on the relationship between microstructure and durability-related properties of carbonated recycled aggregate concrete considering the effects of pre-treatment method, replacement level, curing age, water-to-binder ratio and quality of the original aggregates. The insights into the deterioration mechanism and strategies for improving the durability of carbonated recycled aggregate concrete are provided. This review summarises the recent advances in the field, followed by a discussion on the remaining challenges and opportunities for future research.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105865"},"PeriodicalIF":10.8,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142696508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1016/j.cemconcomp.2024.105861
Pitabash Sahoo, Souradeep Gupta
Excavated soil from widescale tunneling and excavation can be used in 3D-printed constructions. This research investigates the feasibility of 3D printing using geopolymer stabilized excavated soil (GP-E) containing 42% clay rich in kaolinite minerals. At dosages 0.50–1.5 wt%, sucrose is added to control the hydration and time-dependent rheological properties, enabling adequate open printing time (OPT) for large-scale printing. Experimental findings show that 1% and 1.5% sucrose addition to GP-E offers OPT of 130 min and 170 min respectively compared to 32 min for GP-E. By enabling better dispersion, the addition of sucrose allows smooth extrusion with shape retention of 90 – 92% at a lower NaOH solution-to-binder ratio (0.68) than GP-E (0.75). Sucrose and clay (in the soil) act synergistically to reduce the time-dependent static yield stress but maintain it at an adequate level of 5–8 kPa required for stacking up the layers without collapse. Flow retention and thixotropy are maintained at 100% during the printing window, which balances extrusion and buildability. As a result, the sucrose-GP-E mix could be built up to a height of 1.05 m compared to 0.19 m for GP-E. 1 % sucrose-added GP-E possesses 28 – 40% and 70% higher wet compressive strength and inter-layer bonding respectively compared to GP-E depending on the loading direction. These are linked to the refinement of capillary porosity and a 13–15% reduction in shrinkage. In summary, the findings present a potential route for controlling the printing time of geopolymer-stabilized earthen materials while reducing the embodied carbon and enhancing the mechanical performance.
{"title":"3D printing with geopolymer-stabilized excavated earth: Enhancement of printability and engineering performance through controlled retardation","authors":"Pitabash Sahoo, Souradeep Gupta","doi":"10.1016/j.cemconcomp.2024.105861","DOIUrl":"10.1016/j.cemconcomp.2024.105861","url":null,"abstract":"<div><div>Excavated soil from widescale tunneling and excavation can be used in 3D-printed constructions. This research investigates the feasibility of 3D printing using geopolymer stabilized excavated soil (GP-E) containing 42% clay rich in kaolinite minerals. At dosages 0.50–1.5 wt%, sucrose is added to control the hydration and time-dependent rheological properties, enabling adequate open printing time (OPT) for large-scale printing. Experimental findings show that 1% and 1.5% sucrose addition to GP-E offers OPT of 130 min and 170 min respectively compared to 32 min for GP-E. By enabling better dispersion, the addition of sucrose allows smooth extrusion with shape retention of 90 – 92% at a lower NaOH solution-to-binder ratio (0.68) than GP-E (0.75). Sucrose and clay (in the soil) act synergistically to reduce the time-dependent static yield stress but maintain it at an adequate level of 5–8 kPa required for stacking up the layers without collapse. Flow retention and thixotropy are maintained at 100% during the printing window, which balances extrusion and buildability. As a result, the sucrose-GP-E mix could be built up to a height of 1.05 m compared to 0.19 m for GP-E. 1 % sucrose-added GP-E possesses 28 – 40% and 70% higher wet compressive strength and inter-layer bonding respectively compared to GP-E depending on the loading direction. These are linked to the refinement of capillary porosity and a 13–15% reduction in shrinkage. In summary, the findings present a potential route for controlling the printing time of geopolymer-stabilized earthen materials while reducing the embodied carbon and enhancing the mechanical performance.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105861"},"PeriodicalIF":10.8,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142696509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.cemconcomp.2024.105866
Miao Lu , Yan Xia , Jianhua Yan, Lei Wang
The high alkalinity, chlorine, and potentially toxic elements (PTEs) content of municipal solid waste incineration fly ash (MSWI FA) hindered its potential application in construction materials. This study proposed the recovery of MSWI FA via wet carbonation and developed a novel sustainable carbonated-MSWI FA-based binder. Experimental results showed that MSWI FA achieved 12 wt% CO2 capture through wet carbonation. Besides, wet carbonation removed 82 % of chlorine from MSWI FA and reduced the leaching risk of PTEs in both pretreatment leachate and carbonated-MSWI FA. The designed sustainable paste exhibited an outstanding 28-day compressive strength of 45.6 MPa. The chloride and sulfate salts in the carbonated-MSWI FA played an important role in hydration kinetics of pastes. Sulfate in carbonated-MSWI FA reacted with aluminate to form ettringite, and the residual chloride was captured by CO3-Cl-AFm. The proposed wet carbonation route provided a promising and sustainable way for CO2 capture and facilitating the application of MSWI FA in construction materials.
城市固体废物焚烧飞灰（MSWI FA）的碱度、氯和潜在有毒元素（PTEs）含量较高，阻碍了其在建筑材料中的潜在应用。本研究提出了通过湿法碳化回收 MSWI FA 的方法，并开发了一种新型的可持续碳化-MSWI FA 粘合剂。实验结果表明，通过湿法碳化，MSWI FA 实现了 12 wt% 的二氧化碳捕集。此外，湿法碳化还能去除 MSWI FA 中 82% 的氯，并降低预处理渗滤液和碳化-MSWI FA 中 PTEs 的浸出风险。所设计的可持续浆料 28 天抗压强度高达 45.6 兆帕。碳化-MSWI FA 中的氯盐和硫酸盐对浆料的水化动力学起着重要作用。碳化-MSWI FA 中的硫酸盐与铝酸盐反应生成乙丁睛石，残余氯化物被 CO3-Cl-AFm 捕获。所提出的湿法碳化路线为二氧化碳捕集提供了一种有前景且可持续的方法，并促进了 MSWI FA 在建筑材料中的应用。
{"title":"Wet carbonation of MSWI fly ash for sustainable limestone calcined clay cement-type composites","authors":"Miao Lu , Yan Xia , Jianhua Yan, Lei Wang","doi":"10.1016/j.cemconcomp.2024.105866","DOIUrl":"10.1016/j.cemconcomp.2024.105866","url":null,"abstract":"<div><div>The high alkalinity, chlorine, and potentially toxic elements (PTEs) content of municipal solid waste incineration fly ash (MSWI FA) hindered its potential application in construction materials. This study proposed the recovery of MSWI FA via wet carbonation and developed a novel sustainable carbonated-MSWI FA-based binder. Experimental results showed that MSWI FA achieved 12 wt% CO<sub>2</sub> capture through wet carbonation. Besides, wet carbonation removed 82 % of chlorine from MSWI FA and reduced the leaching risk of PTEs in both pretreatment leachate and carbonated-MSWI FA. The designed sustainable paste exhibited an outstanding 28-day compressive strength of 45.6 MPa. The chloride and sulfate salts in the carbonated-MSWI FA played an important role in hydration kinetics of pastes. Sulfate in carbonated-MSWI FA reacted with aluminate to form ettringite, and the residual chloride was captured by CO<sub>3</sub>-Cl-AFm. The proposed wet carbonation route provided a promising and sustainable way for CO<sub>2</sub> capture and facilitating the application of MSWI FA in construction materials.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105866"},"PeriodicalIF":10.8,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142685074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.cemconcomp.2024.105867
Tadi Sunil Bhagat , Rathish Kumar Pancharathi
This study is aimed at assessing the synergy of the biochar utilization and early age CO2 curing on the mechanical performance, hydration and CO2 uptake in cementitious materials. Three different biochars Bamboo biochar (BBC), Peanut Husk Biochar (PHBC) and Rice Husk Biochar (RHBC) were utilized with dosages up to 5 % by mass of cement and their influence under water curing and early age CO2 curing was studied. Analytical studies using FTIR, XRD, TGA, SEM-EDS were extended on optimum biochar mixes for characterizing the microstructure, hydration, carbonation and CO2 uptake of various biochar based mixes. The optimum dosage was found to be 1 % for BBC & PHBC while it is 2 % in RHBC from a strength perspective. Calcium carbonate polymorphs – amorphous CaCO3 and aragonite are found to be dominant products besides other hydration products. The biochars porous surface ability to enable hydration products precipitation is revealed. Early age CO2 curing resulted in 23 % improved degree of hydration and 19 % improved CO2 uptake with 2 % rice husk biochar based mix compared to control mix without biochar. The improved early age strength with 48 h CO2 curing at flue gas CO2 concentration of 17 % and under ambient conditions were found to be promising aspects for implementation of this method in an industrial set up for production of carbon sinking cementitious products.
{"title":"Performance, microstructure and carbon sequestration potential of agro biochar based cement mortars","authors":"Tadi Sunil Bhagat , Rathish Kumar Pancharathi","doi":"10.1016/j.cemconcomp.2024.105867","DOIUrl":"10.1016/j.cemconcomp.2024.105867","url":null,"abstract":"<div><div>This study is aimed at assessing the synergy of the biochar utilization and early age CO<sub>2</sub> curing on the mechanical performance, hydration and CO<sub>2</sub> uptake in cementitious materials. Three different biochars Bamboo biochar (BBC), Peanut Husk Biochar (PHBC) and Rice Husk Biochar (RHBC) were utilized with dosages up to 5 % by mass of cement and their influence under water curing and early age CO<sub>2</sub> curing was studied. Analytical studies using FTIR, XRD, TGA, SEM-EDS were extended on optimum biochar mixes for characterizing the microstructure, hydration, carbonation and CO<sub>2</sub> uptake of various biochar based mixes. The optimum dosage was found to be 1 % for BBC & PHBC while it is 2 % in RHBC from a strength perspective. Calcium carbonate polymorphs – amorphous CaCO<sub>3</sub> and aragonite are found to be dominant products besides other hydration products. The biochars porous surface ability to enable hydration products precipitation is revealed. Early age CO<sub>2</sub> curing resulted in 23 % improved degree of hydration and 19 % improved CO<sub>2</sub> uptake with 2 % rice husk biochar based mix compared to control mix without biochar. The improved early age strength with 48 h CO<sub>2</sub> curing at flue gas CO<sub>2</sub> concentration of 17 % and under ambient conditions were found to be promising aspects for implementation of this method in an industrial set up for production of carbon sinking cementitious products.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105867"},"PeriodicalIF":10.8,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.cemconcomp.2024.105863
Liwu Mo , Peng Liu , Yahui Gu , Jiahua Kuang
The use of argon oxygen decarbonization slag (AODS) is restricted due to its volume unsoundness and low hydration reactivity. In this study, the feasibility of transforming AODS toward a highly reactive mineral admixture with appreciable CO2 sequestration was investigated, the hydration behavior, evolution of the compositions and microstructures of AODS with carbonation time were systematically studied, and CO2 footprint of carbonated AODS was elucidated. Results indicated that γ-C2S in AODS could quickly react with CO2 to form CaCO3. MgO and bredigite dissolved significantly when the pH value of the slurry dropped to 7.0, leading to a significant increase in the Mg2+ concentration of the slurry, and promoting the conversion of calcite to monohydrocalcite. However, due to the lower Ca/Si and Ca/Mg ratios, calcium silicate (CS) and akermanite exhibited extremely low carbonation reactivity. As the carbonation time increased, the particle size of CaCO3 gradually increased, from approximately 150 nm at 5min to approximately 400 nm at 20min, [SiO4] gradually transited from the Q0, Q1 and Q2 structures to the Q3 and Q4 structures, ultimately forming a large amount of amorphous SiO2 gel, which led to an obvious increase in specific surface area of AODS. The compressive strength of cement mortar mixed with 20 wt% carbonated AODS (CAODS) was increased by 25.8 % compared with that of the mortar incorporating AODS. The CO2 sequestration capacity of AODS can reach approximately 200 kg/t, and 193.4 kg CO2 can be cut when 1 ton of CAODS-based composite cement with excellent cementitious properties is produced.
{"title":"Transforming AOD slag toward a highly reactive mineral admixture with appreciable CO2 sequestration: Hydration behavior, microstructure evolution, and CO2 footprint","authors":"Liwu Mo , Peng Liu , Yahui Gu , Jiahua Kuang","doi":"10.1016/j.cemconcomp.2024.105863","DOIUrl":"10.1016/j.cemconcomp.2024.105863","url":null,"abstract":"<div><div>The use of argon oxygen decarbonization slag (AODS) is restricted due to its volume unsoundness and low hydration reactivity. In this study, the feasibility of transforming AODS toward a highly reactive mineral admixture with appreciable CO<sub>2</sub> sequestration was investigated, the hydration behavior, evolution of the compositions and microstructures of AODS with carbonation time were systematically studied, and CO<sub>2</sub> footprint of carbonated AODS was elucidated. Results indicated that γ-C<sub>2</sub>S in AODS could quickly react with CO<sub>2</sub> to form CaCO<sub>3</sub>. MgO and bredigite dissolved significantly when the pH value of the slurry dropped to 7.0, leading to a significant increase in the Mg<sup>2+</sup> concentration of the slurry, and promoting the conversion of calcite to monohydrocalcite. However, due to the lower Ca/Si and Ca/Mg ratios, calcium silicate (CS) and akermanite exhibited extremely low carbonation reactivity. As the carbonation time increased, the particle size of CaCO<sub>3</sub> gradually increased, from approximately 150 nm at 5min to approximately 400 nm at 20min, [SiO<sub>4</sub>] gradually transited from the Q<sup>0</sup>, Q<sup>1</sup> and Q<sup>2</sup> structures to the Q<sup>3</sup> and Q<sup>4</sup> structures, ultimately forming a large amount of amorphous SiO<sub>2</sub> gel, which led to an obvious increase in specific surface area of AODS. The compressive strength of cement mortar mixed with 20 wt% carbonated AODS (CAODS) was increased by 25.8 % compared with that of the mortar incorporating AODS. The CO<sub>2</sub> sequestration capacity of AODS can reach approximately 200 kg/t, and 193.4 kg CO<sub>2</sub> can be cut when 1 ton of CAODS-based composite cement with excellent cementitious properties is produced.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105863"},"PeriodicalIF":10.8,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.cemconcomp.2024.105851
Bei He , Xinping Zhu , Hongen Zhang , Aiguo Wang , Daosheng Sun , Nemkumar Banthia , Zhengwu Jiang
The interfacial bonding between steel fibers and Ultra-High Performance Concrete (UHPC) matrix is pivotal for the mechanical properties in extreme environments. Herein, a surface nanoengineering approach using the sol-gel method was reported to enhance the resistance of fiber bonding to varying cryogenic and elevated exposures (−170 °C ∼ 200 °C). Additionally, the interfacial bonding and failure of the steel fiber-matrix interface were evaluated by in-situ acoustic emission (AE) monitoring and a series of microscopic characterizations. The result indicated that the deposition of a nano-SiO2 coating with a film structure thickness of approximately 150 nm on fiber surface could be achieved. The coating exhibited excellent cryogenic resistance but inferior elevated resistance, as elevated temperatures caused the coating to crack and corrode. After modification, the interfacial bonding stability exposed to thermal variations was enhanced. At ambient temperature, the bond strength of the modified fibers increased by 44.68 % compared to before modification, while that increased by 1.54 %–13.49 % in a single thermal-variations cycle compared to the ambient modified group. Interface enhancement arises from imbalances in nanocoating thermal stability, moisture phase changes, properties of three-phase interface transition zone, and thermal expansion coefficient disparities. Those findings provide new insight into the attempts to improve the mechanical and durability properties of concrete under extreme temperature environments.
{"title":"Nano-engineering steel fiber for UHPC: Implication for varying cryogenic and elevated exposure","authors":"Bei He , Xinping Zhu , Hongen Zhang , Aiguo Wang , Daosheng Sun , Nemkumar Banthia , Zhengwu Jiang","doi":"10.1016/j.cemconcomp.2024.105851","DOIUrl":"10.1016/j.cemconcomp.2024.105851","url":null,"abstract":"<div><div>The interfacial bonding between steel fibers and Ultra-High Performance Concrete (UHPC) matrix is pivotal for the mechanical properties in extreme environments. Herein, a surface nanoengineering approach using the sol-gel method was reported to enhance the resistance of fiber bonding to varying cryogenic and elevated exposures (−170 °C ∼ 200 °C). Additionally, the interfacial bonding and failure of the steel fiber-matrix interface were evaluated by in-situ acoustic emission (AE) monitoring and a series of microscopic characterizations. The result indicated that the deposition of a nano-SiO<sub>2</sub> coating with a film structure thickness of approximately 150 nm on fiber surface could be achieved. The coating exhibited excellent cryogenic resistance but inferior elevated resistance, as elevated temperatures caused the coating to crack and corrode. After modification, the interfacial bonding stability exposed to thermal variations was enhanced. At ambient temperature, the bond strength of the modified fibers increased by 44.68 % compared to before modification, while that increased by 1.54 %–13.49 % in a single thermal-variations cycle compared to the ambient modified group. Interface enhancement arises from imbalances in nanocoating thermal stability, moisture phase changes, properties of three-phase interface transition zone, and thermal expansion coefficient disparities. Those findings provide new insight into the attempts to improve the mechanical and durability properties of concrete under extreme temperature environments.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"156 ","pages":"Article 105851"},"PeriodicalIF":10.8,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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