Development of a MgO-metakaolin binder system

Dhakal, Milap; Scott, Allan; Shah, Vineet; Dhakal, Rajesh; Clucas, Don

doi:10.1016/j.conbuildmat.2021.122736

Cited by 28 publications

(12 citation statements)

References 43 publications

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“…A linear trend is observed for CC and MK mixes, with an increase in the compressive strength a reduction in porosity is observed while for SF mixes at same porosity level a range of compressive strength is observed. Dhakal et al [36] also reported a similar trend between strength and porosity for a range of MgO-MK mixes.…”

Section: Volume Of Permeable Voidsmentioning

confidence: 61%

Long-term performance of MgO–SiO2 binder

2022

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Magnesium silicate hydrate (M–S–H) formed on reaction of MgO and reactive SiO2 imparts binding characteristics similar to Portland cement (PC). Limited knowledge is available on the long-term mechanical and durability performance of M–S–H binder systems. In this study, the performance of MgO–SiO2 binder was assessed up to 365 days. In addition to silica fume (SF), the most widely used silica source with MgO, calcined clay (CC) with kaolinite content of ~ 40–50% and industrial grade metakaolin (MK) were also investigated. Mortar specimens were prepared with all the three silica sources at three different proportion levels of MgO and silica source. Thermodynamic modelling was carried out to further understand the changes occurring in the phase assemblage during hydration for the adopted proportions. Concrete mixes comprising of MgO and MK or SF in a ratio of 1:1 and PC as a control mix were cast a water to binder ratio of 0.4. The compressive strength and porosity were measured at 7, 28, 90 and 365 days on mortar and concrete specimens. In addition, elastic modulus and electrical resistivity was also measured on the concrete samples at all the above-mentioned ages. MgO mixes with CC and MK showed a continual increase in compressive strength until 365 days whereas strength retrogression was observed in MgO–SF mixes after 90 days. The durability indicators for MgO–MK concrete showed better or similar performance as compared to PC. The aluminum present in the CC and MK helps to improve the overall characteristics of the MgO–SiO2 binder.

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Section: Volume Of Permeable Voidsmentioning

confidence: 61%

Long-term performance of MgO–SiO2 binder

2022

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“…The performance of HMC cement may also be improved by adding Al, which has received little attention so far. The combination of MgO with metakaolin leads to comparable compressive strength as MgO plus silica fume [13,53]. For sodium-carbonate activated Mg-cements a significant increase in compressive strength is observed in the presence of Al (Figure 7, [13]) confirming that Al in fact plays an important role in HMC cements.…”

Section: Effect Of Al2o3 and Sio2mentioning

confidence: 82%

MgO‐based binders

Lothenbach,

Bernard,

German

et al. 2023

ce papers

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To limit global temperature rise to below 2°C, we need to radically and rapidly change the way we build and use materials, since construction is responsible for 20‐40% of industrial CO2 emissions. Magnesium carbonate‐based cements have the potential to become a major carbon sink in construction industry, as CO2 will not be emitted during their production, but CO2 will rather be bound during hardening. Two different reaction mechanisms lead to setting and hardening of such HMC cements: i) hydration of MgO‐Mg‐carbonate, also in blends with silica and other mineral additions, in the presence of water or salt solutions (such as sodium bicarbonate solution) at ambient conditions or ii) carbonation hardening of MgO‐based systems at increased CO2 partial pressure and/or at increased temperatures.However, the utilization of hydrated magnesium carbonate and magnesium silicate cements is currently hampered by the lack of systematic experiments and of fundamental understanding of the factors affecting the hardening process, mechanical properties, long‐term behavior and durability. In particular, the role of temperature, relative humidity and addition of supplementary cementitious materials and/or industrial by‐products has not been systematically investigated. We need knowledge both on the practical side through systematic experiments with pastes, mortars and concretes as well as on a fundamental level through solubility and sorption experiments and thermodynamic modelling. In addition, reaction kinetics need to be optimized as well as the early formation of the preferred phases (stability enhancement) to develop efficient HMC cements for construction. Due to the socio‐economic relevance of cement and concrete, the impact of such “carbon”‐negative cements may go beyond a purely scientific one and lead to technological breakthroughs to the benefit of environment and society.

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“…The use of calcined clay instead of micro silica could decrease the price of such building materials. Additionally, the combination of MgO with a reactive aluminosilicate, such a calcined clays, has been recently considered as an alternative binder [46,[88][89][90][91][92]. Clays are widely available in the Earth's crust [93] compared to the availability of silica fume [94,95] and they can be activated to produce large amount of reactive aluminosilicates.…”

Section: Conclusion and Opportunitiesmentioning

confidence: 99%

Research progress on magnesium silicate hydrate phases and future opportunities

Bernard

2022

RILEM Tech Lett

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This short letter summaries the latest research on the structure and thermodynamic modelling of the magnesium silicate hydrates (M-S-H) phases. M-S-H structure is comparable to hydrated clays, with a smaller and rounder microstructures compared to clay platelets. Similar to clay minerals, M-S-H can incorporate ions such as aluminium and hydrated exchangeable cations to compensate the negative surface charge. This fundamental understanding of M-S-H structure allowed to develop structure-based thermodynamic models, which can further help to optimise the conditions for M-S-H formation and its use as cementitious materials. Optimized binders containing M-S-H have the advantages of presenting: i) good mechanical properties, ii) dense microstructure and potentially good resistances to leaching and iii) low pH values. These types of binders could therefore be used for cement products with non-steel reinforcement, for the encapsulation of specific wastes, for products containing natural fibres or for the clay stabilisation, etc.

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Development of a MgO-metakaolin binder system

Cited by 28 publications

References 43 publications

Long-term performance of MgO–SiO2 binder

Long-term performance of MgO–SiO2 binder

MgO‐based binders

Research progress on magnesium silicate hydrate phases and future opportunities

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