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Zhao S, Zhang D, Li Y, Gao H, Meng X. Physical and Mechanical Properties of Novel Porous Ecological Concrete Based on Magnesium Phosphate Cement. MATERIALS (BASEL, SWITZERLAND) 2022; 15:7521. [PMID: 36363112 PMCID: PMC9655557 DOI: 10.3390/ma15217521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/19/2022] [Accepted: 10/24/2022] [Indexed: 06/16/2023]
Abstract
Ecological concrete could reduce the environment impacts of the tremendous construction of infrastructures due to its favorability to plant growth. Nonetheless, the alkalinity of the ecological concrete is usually too high when using ordinary Portland cement (OPC). To solve this problem, the magnesium ammonium phosphate cement (MPC) was used to prepare a novel porous ecological concrete instead of OPC. The pH value and compressive strength of MPC were analyzed and the pore structure was evaluated. The chemical composition and morphology were investigated by an X-ray diffraction test and scanning electron microscope observation. In addition, the void ratio, compressive strength and planting-growing characteristic of MPC-based porous ecological concrete were also studied. The pH value of the MPC suspension ranged from 6.8 to 8.5, which was much lower than that of OPC. The pH value of MPC gradually increased with the increment of phosphorus/magnesium molar ratio (P/M) and the compressive strength reached a maximum value of 49.2 MPa when the P/M value was 1/4. Fly ash (FA) and ground blast furnace slag (GBFS) could improve the pore structure and compressive strength; however, the pH value was slightly increased. As the paste-to-aggregate ratio increased, the void ratio of concrete gradually decreased, while the compressive strength gradually increased. The meadow grass was planted in the MPC-based ecological concrete, and the seeds germinated in one week and showed a better growth status than those planted in the OPC-based ecological concrete.
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Hoyos-Montilla AA, Puertas F, Molina Mosquera J, Tobón JI. Infrared spectra experimental analyses on alkali-activated fly ash-based binders. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 269:120698. [PMID: 34942413 DOI: 10.1016/j.saa.2021.120698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/06/2021] [Accepted: 11/30/2021] [Indexed: 06/14/2023]
Abstract
One of the most used characterization techniques in the field of alkaline activated cements studies is infrared spectroscopy. Its prominence lies in that it allows characterizing mixtures during the alkaline activation by providing information about the vibrations of the chemical bonds in the molecular units, both of amorphous and crystalline products. This research paper is aimed at examining the influence of the concentration of calcium hydroxide (CH), sodium hydroxide (SH), temperature and curing time on the structure of alkaline activated cements, based on coal fly ash, from the deconvolution of the infrared spectrum between 4000 and 400 cm-1. 9 mixtures were analyzed by infrared spectroscopy at 3 and 28 days after curing, based on a surface's response experimental design by varying the amount of SH (5.17-10.83 M), CH (2.93-17.07% ash's wt.) and the curing temperature (25, 35 and 45 °C). The results show significant variations in the frequency and area of the deconvolved bands in the functional groups: O-H (2600-3800 cm-1), C-O (1580 and 1350 cm-1) and T-O (T: Si (Al), 1300-400 cm -1). Such variations are due to the reorganization of the forming elements (present in the ash) network and modifiers (present in CH and SH) for the formation of cementing gels C-(A) -S-H (970 cm-1) and N-A-S-H (1009 cm-1).
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Affiliation(s)
| | - F Puertas
- Eduardo Torroja Institute for Construction Sciences (IETcc - CSIC), Madrid, Spain
| | - Jarol Molina Mosquera
- Grupo de Investigación e Inovación en Energía - GIIEN, Institución Universitaria Pascual Bravo, Medellin, Colombia
| | - Jorge I Tobón
- Cement and Construction Materials Group, Department of Materials and Minerals at Universidad Nacional de Colombia, Medellin, Colombia
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Barzgar S, Lothenbach B, Tarik M, Di Giacomo A, Ludwig C. The effect of sodium hydroxide on Al uptake by calcium silicate hydrates (CSH). J Colloid Interface Sci 2020; 572:246-256. [PMID: 32247198 DOI: 10.1016/j.jcis.2020.03.057] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 02/25/2020] [Accepted: 03/16/2020] [Indexed: 10/24/2022]
Abstract
To reduce the CO2 emissions from cement production, Portland cement (PC) is partially replaced by supplementary cementitious materials (SCM). Reactions of SCM with PC during hydration leads to the formation of CSH with more silicon and aluminum than in PC, which affects the stability and durability of such concrete. Therefore, it is crucial to determine the role of aluminum on CSH properties to predict the formed hydrate phase assemblages and their effects on durability. Aluminum sorption isotherms including very low Al concentrations have been determined for CSH with Ca/Si ratios from 0.6 to 1.4. Elemental measurements were performed with ICP-MS and ICP-OES. The presence of secondary phases was investigated by using thermogravimetric analysis and XRD. Higher dissolved concentrations of Al were observed at increased alkali hydroxide concentrations and thus higher pH values. High alkali hydroxide led to an increased Al(OH)4- formation, which reduced the Al uptake in CSH. This comparable behavior of Al and Si towards changes in pH values, points toward the uptake of aluminum within the silica chain both at low and high Ca/Si ratios. A higher Al uptake in CSH was observed at higher Ca/Si ratios, which indicates a stabilizing effect of calcium in the interlayer on Al uptake.
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Affiliation(s)
- Sonya Barzgar
- Empa, Laboratory for Concrete / Construction Chemistry, CH-8610 Dübendorf, Switzerland; École Polytechnique Fédéral de Lausanne (EPFL), ENAC IIE GR-LUD, CH-1015 Lausanne, Switzerland.
| | - Barbara Lothenbach
- Empa, Laboratory for Concrete / Construction Chemistry, CH-8610 Dübendorf, Switzerland; NTNU, Department of Structural Engineering, Trondheim, Norway.
| | - Mohamed Tarik
- Paul Scherrer Institute (PSI), ENE LBK CPM, 5232 Villigen PSI, Switzerland.
| | - Alessio Di Giacomo
- Empa, Laboratory for Concrete / Construction Chemistry, CH-8610 Dübendorf, Switzerland.
| | - Christian Ludwig
- École Polytechnique Fédéral de Lausanne (EPFL), ENAC IIE GR-LUD, CH-1015 Lausanne, Switzerland; Paul Scherrer Institute (PSI), ENE LBK CPM, 5232 Villigen PSI, Switzerland.
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Hughes CE, Walkley B, Gardner LJ, Walling SA, Bernal SA, Iuga D, Provis JL, Harris KDM. Exploiting in-situ solid-state NMR spectroscopy to probe the early stages of hydration of calcium aluminate cement. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2019. [PMID: 30772677 DOI: 10.1016/j.mtadv.2019.100007] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We report a high-field in-situ solid-state NMR study of the hydration of CaAl2O4 (the most important hydraulic phase in calcium aluminate cement), based on time-resolved measurements of solid-state 27Al NMR spectra during the early stages of the reaction. A variant of the CLASSIC NMR methodology, involving alternate recording of direct-excitation and MQMAS 27Al NMR spectra, was used to monitor the 27Al species present in both the solid and liquid phases as a function of time. Our results provide quantitative information on the changes in the relative amounts of 27Al sites with tetrahedral coordination (the anhydrous reactant phase) and octahedral coordination (the hydrated product phases) as a function of time, and reveal significantly different kinetic and mechanistic behaviour of the hydration reaction at the different temperatures (20 °C and 60 °C) studied.
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Affiliation(s)
- Colan E Hughes
- School of Chemistry, Cardiff University, Park Place, Cardiff, Wales, CF10 3AT, UK
| | - Brant Walkley
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK
| | - Laura J Gardner
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK
| | - Samuel A Walling
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK
| | - Susan A Bernal
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK; School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - Dinu Iuga
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - John L Provis
- Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, UK.
| | - Kenneth D M Harris
- School of Chemistry, Cardiff University, Park Place, Cardiff, Wales, CF10 3AT, UK.
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Okoronkwo MU, Balonis M, Katz L, Juenger M, Sant G. A thermodynamics-based approach for examining the suitability of cementitious formulations for solidifying and stabilizing coal-combustion wastes. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2018; 217:278-287. [PMID: 29609144 DOI: 10.1016/j.jenvman.2018.02.095] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 02/22/2018] [Accepted: 02/27/2018] [Indexed: 06/08/2023]
Abstract
Cementitious binders are often used to immobilize industrial wastes such as residues of coal combustion. Such immobilization stabilizes wastes that contain contaminants by chemical containment, i.e., by uptake of contaminants into the cementitious reaction products. Expectedly, the release ("leachability") of contaminants is linked to: (i) the stability of the matrix (i.e., its resistance to decomposition on exposure to water), and, (ii) its porosity, which offers a pathway for the intrusion of water and egress of contaminant species. To examine the effects of the matrix chemistry on its suitability for immobilization, an equilibrium thermodynamics-based approach is demonstrated for cementitious formulations based on: ordinary portland cement (OPC), calcium aluminate cement (CAC) and alkali activated fly ash (AFA) binding agents. First, special focus is placed on computing the equilibrium phase assemblages using the bulk reactant compositions as an input. Second, the matrix's stability is assessed by simulating leaching that is controlled by progressive dissolution and precipitation of solids across a range of liquid (leachant)-to-(reaction product) solid (l/s) ratios and leachant pH's; e.g., following the LEAF 1313 and 1316 protocols. The performance of each binding formulation is evaluated based on the: (i) relative ability of the reaction products to chemically bind the contaminant(s), (ii) porosity of the matrix which correlates to its hydraulic conductivity, and, (iii) the extent of matrix degradation that follows leaching and which impact the rate and extent of release of potential contaminants. In this manner, the approach enables rapid, parametric assessment of a wide-range of stabilization solutions with due consideration of the matrix's mineralogy, porosity, and the leaching (exposure) conditions.
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Affiliation(s)
- Monday Uchenna Okoronkwo
- Laboratory for the Chemistry of Construction Materials (LC(2)), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA.
| | - Magdalena Balonis
- Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA; Institute for Technology Advancement, University of California, Los Angeles, CA 90095, United States.
| | - Lynn Katz
- Department of Civil, Architectural and Environmental Engineering, University of Texas, Austin, TX 78712, USA.
| | - Maria Juenger
- Department of Civil, Architectural and Environmental Engineering, University of Texas, Austin, TX 78712, USA.
| | - Gaurav Sant
- Laboratory for the Chemistry of Construction Materials (LC(2)), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA; Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA; California Nanosystems Institute, University of California, Los Angeles, CA, USA.
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Park SM, Jang JG, Lee HK. Unlocking the role of MgO in the carbonation of alkali-activated slag cement. Inorg Chem Front 2018. [DOI: 10.1039/c7qi00754j] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
MgO incorporation into alkali-activated slag cement reduces the rate of carbonation.
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Affiliation(s)
- S. M. Park
- Department of Civil and Environmental Engineering
- Korea Advanced Institute of Science and Technology
- Daejeon 34141
- Republic of Korea
| | - J. G. Jang
- Division of Architecture and Urban Design
- Incheon National University
- Incheon
- Republic of Korea
| | - H. K. Lee
- Department of Civil and Environmental Engineering
- Korea Advanced Institute of Science and Technology
- Daejeon 34141
- Republic of Korea
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Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate. Sci Rep 2017; 7:44032. [PMID: 28281635 PMCID: PMC5345016 DOI: 10.1038/srep44032] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 01/31/2017] [Indexed: 11/10/2022] Open
Abstract
The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as ‘columns’ to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a ‘bottom-up’ approach.
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Walkley B, San Nicolas R, Sani MA, Gehman JD, van Deventer JSJ, Provis JL. Phase evolution of Na2O-Al2O3-SiO2-H2O gels in synthetic aluminosilicate binders. Dalton Trans 2016; 45:5521-35. [PMID: 26911317 DOI: 10.1039/c5dt04878h] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This study demonstrates the production of stoichiometrically controlled alkali-aluminosilicate gels ('geopolymers') via alkali-activation of high-purity synthetic amorphous aluminosilicate powders. This method provides for the first time a process by which the chemistry of aluminosilicate-based cementitious materials may be accurately simulated by pure synthetic systems, allowing elucidation of physicochemical phenomena controlling alkali-aluminosilicate gel formation which has until now been impeded by the inability to isolate and control key variables. Phase evolution and nanostructural development of these materials are examined using advanced characterisation techniques, including solid state MAS NMR spectroscopy probing (29)Si, (27)Al and (23)Na nuclei. Gel stoichiometry and the reaction kinetics which control phase evolution are shown to be strongly dependent on the chemical composition of the reaction mix, while the main reaction product is a Na2O-Al2O3-SiO2-H2O type gel comprised of aluminium and silicon tetrahedra linked via oxygen bridges, with sodium taking on a charge balancing function. The alkali-aluminosilicate gels produced in this study constitute a chemically simplified model system which provides a novel research tool for the study of phase evolution and microstructural development in these systems. Novel insight of physicochemical phenomena governing geopolymer gel formation suggests that intricate control over time-dependent geopolymer physical properties can be attained through a careful precursor mix design. Chemical composition of the main N-A-S-H type gel reaction product as well as the reaction kinetics governing its formation are closely related to the Si/Al ratio of the precursor, with increased Al content leading to an increased rate of reaction and a decreased Si/Al ratio in the N-A-S-H type gel. This has significant implications for geopolymer mix design for industrial applications.
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Affiliation(s)
- Brant Walkley
- Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
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