Belite-rich Cement Research Articles

Influence on compressive strength and CO2 capture after accelerated carbonation of combination β-C2S with γ-C2S

In order to deal with the current global climate crisis, it is urgent to reduce greenhouse gas emissions and store CO2 in the atmosphere through Carbon Capture and Storage (CCS) technology. Both C3S and C2S are the main mineral components of Ordinary Portland Cement; through accelerated carbonation reaction, C2S could sequestrate more CO2 and gain a rapid development of early strength. β-C2S and γ-C2S, as two stable crystallines of C2S, can both capture CO2. Compared to β-C2S, the γ-C2S essentially shows no hydration activity, but γ-C2S shows higher reactivity to CO2 during the carbonation process. The conversion of β-C2S to γ-C2S would cause volume expansion, saving electricity during the grinding process and reducing CO2 emissions. To synthetic different proportions of β and γ polymorphic of C2 S, the different weight content of B2O3 (B2O3 wt%) was mixed with the analytical pure chemical reagent of CaCO3 and SiO2, and different cooling rates were used. The synthetic C2S (F1, S1, F2, S2) were exposed to pure CO2 gas with 2 bar pressure for 2 h. After carbonation, compressive strength was tested, carbonation degree was calculated. The synthetic C2S (S2) containing 57.8 wt% β-C2S and 42.2 wt% γ-C2S showed the highest compressive strength and the higher CO2 sequestration capacity, with the compressive strength of 46.3 MPa and the 14.14% CO2 uptake. The XRD results and TG-DTG analysis have proved that different calcium carbonates, including calcite, aragonite, vaterite, and ACC (amorphous calcium carbonate), were formed after carbonation. FT-IR observed the characteristic vibration of calcium carbonate, the microstructure of different calcium carbonate crystals was observed by FE-SEM. The calcite in the S2-C group showed more thermodynamic stability, confirmed by TG analysis at the temperature stage of 680℃～820℃. The mechanical bond force of rhombic calcite contributed to the high compressive strength. And S2-C group had the lowest porosity, which contained the highest volume of capillary pores and the lowest volume of macropores among the 4 groups. The combination of β-C2S with γ-C2S exhibited rapid strength development and high sequestration of CO2 after carbonation. The carbonation of combination of β-C2S and γ-C2S was able to devote to the rapid development of compressive strength and rather a high capacity of capturing CO2, and the proper proportions of β-C2S and γ-C2S were beneficial to develop belite-rich cement, as well as speed up the absorption and storage of CO2 in the atmosphere.

Effects of cement types and addition of quartz and limestone on the normal and carbonation curing of cement paste

Belite-rich cement (BRC) and carbonation curing are vital in the cement and construction industries for reducing carbon emissions and achieving carbon neutrality. In this study, the effects of quartz, limestone, and the type of cement (BRC and ordinary Portland cement) on the carbonation curing and normal curing of cement paste were systematically studied. The water/binder ratio was 0.5, and the replacement ratio of quartz/limestone was 20%. The experimental results showed that adding 20% quartz/limestone to BRC effectively accelerated the carbonation curing process, and the acceleration effect of quartz was more obvious than that of limestone. The compressive strength of the samples with 20% quartz and limestone added to BRC was 72 MPa and 69 MPa, respectively, after 28 days of carbonation curing. These are respectively 1.7 times and 1.6 times higher than the compressive strength of the samples under normal curing. The late-age strength mainly depended on the amount of cement and marginally depended on the addition of quartz/limestone. Quartz improved carbonation efficiency by increasing the porosity of the cement paste and providing nucleation sites for the silica gel formed during carbonation. Moreover, CH, ettringite, monocarboaluminate, and hemicarboaluminate were fully carbonated, and large amounts of alite and belite were carbonated during carbonation curing. The electrical resistivity after 28 days of carbonation curing was 38–72 times higher than its electrical resistivity after 28 days of normal curing. After carbonation curing, the quartz-blended BRC had a high resistivity of 1562 kΩ·cm. Thus, quartz is an effective supplementary material for the carbonation curing of concrete. Moreover, the combination of quartz and BRC has a greater impact on carbonation curing than the combination of limestone and BRC.

Effects of the Curing Conditions on the Carbonation Curing Efficiency of Ordinary Portland Cement and a Belite-Rich Cement Mortar

In the present study, the efficiency of five different carbonation and/or water curing conditions on the properties of belite-rich cement mortar and ordinary Portland cement mortar was investigated. The hybrid curing of samples was carried out by submerging samples at different levels in water or in a lime-saturated solution kept under carbonation curing conditions. The compressive strength was measured to compare the physical properties of the cement mortars, and X-ray diffraction and thermogravimetric analysis results were analyzed to compare the physicochemical properties. The results revealed that the supply of additional moisture during carbonation curing tends to decrease carbonation curing efficiency and that the hydration products of cement paste are predominantly affected by the depth at which the specimen was immersed in the liquid rather than the type of liquid used.

Belite hydration at high temperature and pressure by in situ synchrotron powder diffraction

Portland cements are currently used as Oil‐Well‐Cements for the sheath between the metal casing and the borehole. At high pressures and temperatures, the resulting C–S–H gel(s) is partly unstable and it can react to give different crystalline phases and changing microstructure which increases porosity. It is known that the addition of silica-rich materials to Portland cements, used to decrease the overall Ca/Si molar ratio, avoids/minimises the early strength retrogression experienced by neat cement slurries. Alternatively, belite-rich cement could be used but belite reactivity in these conditions is largely unexplored. Here, belite-rich mixtures have been quantitatively studied at 180 bars and of 160 °C by in situ synchrotron powder diffraction using a tailored-designed spinning capillary cell. For model alite/belite mixtures, alite strongly accelerates belite hydration in these conditions. At 10 h of hydration, β-C2S shows a reaction degree of 30 and 80% for 20 wt%C3S-80 wt%C2S and 50 wt%C3S-50 wt%C2S mixtures, respectively. Furthermore, the 50 wt%C3S mixture hydrates yielding significant amounts of Jaffeite and α-C2SH and the 20 wt%C3S mixture gave no Jaffeite and much lower amount of α-C2SH. Finally, a belite cement has also been hydrated in these conditions and the reaction degree of belite was 50% at 10 h. The hydration of this cement did not yield Jaffeite neither α-C2SH in the studied experimental conditions.

Influence of water to cement ratio on CO2 uptake capacity of belite-rich cement upon exposure to carbonation curing

The present study investigates the effect of water to cement ratio on the physiochemical and microstructural properties of carbonation cured belite-rich cement. Five varying water to cement ratio for belite-rich cement were carbonation cured for 28 days. It is observed that distinct form of behavior is exhibited on variation of water to cement ratio and its relation to the strength development in carbonation curing. The results demonstrated that higher water to cement ratio led to greater uptake of CO2 which enhanced the consumption of belite phase leading to increased production of calcite. The microstructural analysis showed that the varying water to cement ratio allowed for refinement of pore structure for belite-rich cement with reduced interconnection between pores. In particular, the relationship between water to cement ratio and formation of carbonation product is kept in focus along with the porosity distribution.

Rheological properties of belite-rich cement doped with sulfur

Reactive belite cement based on clinker doped with sulfur is a new type of low-energy cement that is still in the laboratory testing phase. In terms of application, one of the desired properties of new cement is its well-defined rheological behavior in fresh state. The chemical composition of the belite cement was determined by wet chemistry analysis, the phase composition of the belite cement clinker by quantitative X-ray powder diffraction analysis and microscopic point counting and specific surface by Blaine method. Rheological properties were determined by rotational rheometer in flow and oscillation regime. Shear and time dependent rheological parameters were calculated from flow curves. Stability of belite cement paste was judged based on the critical strain determination in amplitude sweep test. Setting was evaluated by Tussenbrock needle penetration test and oscillation time test on rheometer. The properties of the laboratory belite cement were correlated to industrial cement CEM I, CEM II/A-LL and CEM III/A. Reactive belite cement pastes show good flow properties both due to small amount of alite and larger amount of rounded belite grains and clusters. Belite rich cement show decent stability comparable to CEM III and very good dispersing efficiency of PCE based HRWR.

Early Hydration of Activated Belite-Rich Cement

Implementation of high belite cement in cement production would have strong environmental impact in reduction CO2 emissions and saving of pure limestone deposits. The goal of the study is to describe the role of alkali and C-S-H activators on hydration of high belite cement. Analytical approach for early hydration is based on combination of isothermal calorimetry, X-ray powder diffraction in-situ, DTA-TG, FT-IR.

Synthesis and Characterization of Belite-rich Cement by Exploiting Alumina Sludge

Alumina sludge from drinking water treatment plants raises serious environmental concerns. In order to address these concerns, the present study aims at exploiting the alumina sludge generated by water purification unit as a raw material substitute in the production of belite clinkers. The chemical composition, morphology and nature of mineralogical phases in the alumina sludge-based clinkers/ cements are assessed respectively by Fluorescence-X (F-X), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analyses. Afterwards, the mechanical testing on the synthesized clinker/belite cements is carried out by employing compressive/ flexural strength analysis. The obtained results show that the best clinker is obtained at 1300°C with a lime saturation factor of raw meal in the order of 85.37% without any chemical stabilizers. In addition, we find a compressive strength value of the mentioned clinker in the order of 18.2 MPa during 28 days curing. With these results, the synthesized alumina sludge-based belite-rich cement shows significant potential to be commercialized.

Effect of early-strength-enhancing agents on setting time and early mechanical strength of belite–barium calcium sulfoaluminate cement

Belite–barium calcium sulfoaluminate (C2.75B1.25A3$) cement is a new type of belite-rich cement with great long-term mechanical performance and good durability. Its early-age mechanical property was found to be comparable to that of Grade 32.5 ordinary Portland cement. In order to further improve its early hydration activity, the effect of two known early-strength agents on the performance of the belite–barium calcium sulfoaluminate cement was investigated by means of XRD, pore structure and TGA. It was found that Na2SO4 and Ca(HCOO)2 can be used as an early-strength-enhancing agents for this type of cement with the best dosage of 0.5 and 2.0% by weight, respectively. Ca(HCOO)2 was preferable to this type of cement from the durability point of view.

Effect of waste gypsum on the setting and early mechanical properties of belite-C2.75B1.25A3$ cement

Belite-barium calcium sulfoaluminate (C2.75B1.25A3$) cement was belite-rich cement containing C2.75B1.25A3$ mineral of 9 mass%. Due to the differences in dissolution velocity and element sulfur content, the effects of citro-, phosphor- and FGD gypsum on the setting and early mechanical properties of belite-C2.75B1.25A3$ cement were investigated. The experimental results showed that citrogypsum had the fastest dissolution velocity among all the waste gypsum. This resulted in the short initial and final setting time of belite-C2.75B1.25A3$ cement with citrogypsum. Moreover, the early compressive strength of belite-C2.75B1.25A3$ cement with citrogypsum was high, owing to that much content of AFt and C–S–H gel was formed at an early age. In summary, the later compressive strength of belite-C2.75B1.25A3$ cement with any type of waste gypsum was superior to that of cement with reference natural gypsum. Also, the early compressive strength of cement with any type of waste gypsum was comparable to that of cement with reference gypsum. Therefore, citro-, phosphor- and FGD gypsum all could replace natural gypsum as an adjusting agent of belite-C2.75B1.25A3$ cement.

Polymer-modified cement using belite-rich cement and carbonation reaction

This paper describes the hardening mechanisms and mechanical properties of a new polymer-modified cement (PMC), produced by carbonation of belite-rich cement. A PMC containing carbonated belite-rich cement and ethylene vinyl acetate (EVA) copolymer has high bending strength, and carbonation improves the toughness. The reaction rate of the cement is related to the amounts of CO2 in carbonated samples with or without EVA. The reaction of belite is accelerated by carbonation and the addition of EVA. The pore volumes of carbonated samples containing EVA are smaller than those of EVA-free samples.

Active low-energy belite cement

The term ‘low-energy cement’ is used for cements that can be in some applications used instead of OPC, and which are produced with less energy. A more extensive utilization of these cements would lead to the lowering of expenses on production of binders as well as a reduction of undesirable emissions. The belite-rich cement belongs to this group. Pure belite clinkers with interstitial matter consisting of C3A and C4AF have not been produced, as they have insufficient strength. This work describes the results of hydraulic activation of belite-rich clinkers with sulfate anions. The principle of activation is used for the preparation of belite-rich clinkers with an increased Ca:Si ratio in the structure of dicalcium silicate and partial substitution of SiO44− by SO42−. Cements, prepared from these belite-rich clinkers, containing up to 20% of alite, which are burned at 1350°C, have the same technological properties, including early strengths, as OPC.

Performances of Belite-Rich Cement Concrete with Fly Ash and Phosphorous Slag Powder

This paper presents the results of laboratory and outdoor exposure site studies on belite-rich cement concrete with phosphorous slag powder and fly ash. The parameters studied included strength, hydration heat, ultimate elongation, Young’s modulus, and adiabatic in temperature. The experimental results showed that belite-rich cement resulted in a higher rate of strength development of mortar and concrete at later ages when compared with that of moderate-heat Portland cement. And the hydration heat of belite-rich cement is lower than that of reference. This is due to the different phase composition of the two cements. Belite-rich cement contains less C3S but more C2S than moderate-heat Portland cement. In addition, belite-rich cement concrete with phosphorous slag powder and fly ash exhibited better performances than those of moderate-heat Portland cement concrete.

Hydration and leaching characteristics of cement pastes made from electroplating sludge

The purpose of this study was to investigate the hydration and leaching characteristics of the pastes of belite-rich cements made from electroplating sludge. The compressive strength of the pastes cured for 1, 3, 7, 28, and 90 days was determined, and the condensation of silicate anions in hydrates was examined with the 29Si nuclear magnetic resonance (NMR) technology. The leachabilities of the electroplating sludge and the hardened pastes were studied with the multiple toxicity characteristic leaching procedure (MTCLP) and the tank leaching test (NEN 7345), respectively. The results showed that the electroplating sludge continued to leach heavy metals, including nickel, copper, and zinc, and posed a serious threat to the environment. The belite-rich cement made from the electroplating sludge was abundant in hydraulic β-dicalcium silicate, and it performed well with regard to compressive-strength development when properly blended with ordinary Portland cements. The blended cement containing up to 40% the belite-rich cement can still satisfy the compressive-strength requirements of ASTM standards, and the pastes cured for 90 days had comparable compressive strength to an ordinary Portland cement paste. It was also found that the later hydration reaction of the blended cements was relatively more active, and high fractions of belite-rich cement increased the chain length of silicate hydrates. In addition, by converting the sludge into belite-rich cements, the heavy metals became stable in the hardened cement pastes. This study thus indicates a viable alternative approach to dealing with heavy metal bearing wastes, and the resulting products show good compressive strength and heavy-metal stability.

Solutionizing of additional ions in belite-rich clinkers and the properties of the resulting cement

Belite-rich cement (BRC) can be made at lower temperature, but it has unsatisfactory reactivity. The crystal structure of dicalcium silicate (C2S) was modified by solutionizing some additional irons. By adding barium sulfate (BaSO4) in the raw meals, the clinkers were easier to be burnt, and the compressive strength of BaSO4-modified BRC was considerably improved. The distortion of the crystal structure of C2S was confirmed by the interplanar distance change and nuclear magnetic resonance (NMR) of 29Si in C2S. An effective way was found to activate C2S and to broaden the application field of Belite-rich cement.

결합재와 혼화재 종류에 따른 콘크리트의 수화반응 특성

Recently, owing to the development of industry and improvement of building techniques, concrete structures are becoming larger and higher. This study was performed to analyze hydration reation properties of concrete with binders and admixtures, such as OPC, low heat cement, belite rich cement, slag powder, lime powder and fly ash. To investigate effects of PC type superplasticizer on the hydration, experiments involving FT-IR, XRD, DSC, SEM were analyzed at the curing age 1day, 3days and 28days. The hydration reaction rate of OPC concrete slightly delayed at the curing age 1day, blast furnace slag powder and fly ash were more effective. BRC and LHC concretes can be used for concrete structures in winter season.

Steelmaking slags as raw material for sulphoaluminate belite cement

In the present study, slags from the steelmaking industry are described and considered as a potential raw material within the field of sulphoaluminate belite cement. The objective of the study was to investigate the possibility of using a substantial amount of steelmaking slags as raw meal in the manufacture of a sulphobelitic clinker. A further aim was to compare the influence of different slags in relation to the formation of sulphoaluminate and the other clinker phases required. The behaviour of high temperature reactions was investigated by using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out through X-ray powder diffraction, and scanning electron microscopy. Three different mixtures and a single ladle slag were prepared using modified Bogue calculations, which are characterised by the assessment of a potential phase composition in order to produce belite-rich cement activated with sulphoaluminate. The results so far prove that steelmaking slags have the potential to be used as raw material, since sulphoaluminate along with polymorphs of dicalcium silicate and ferrite phases were detected after firing at 1200°C in an air atmosphere.

결합재 조건에 따른 콘크리트의 수화발열 특성에 관한 연구

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 실험 계획 및 방법3. 실험 결과 및 분석4. 결론참고문헌요약

High durability cementitious material with mineral admixtures and carbonation curing

Nuclear waste repositories need highly durable cementitious materials to function for over thousands of years while resisting leaching and degradation. The durability of cementitious material can be effectively improved by reducing permeability and by changing cement hydrates to a less soluble matrix. This paper describes the properties of carbonated new cementitious materials containing belite-rich cement and γ-2CaO · SiO 2 as main components. In addition, the long-term leaching properties are investigated and compared with ordinary Portland cement by using a predictive leaching model.

Recent Progress in Crystal Chemistry of Belite. Intracrystalline Microtextures Induced by Phase Transformations and Application of Remelting Reaction to Improvement of Hydration Reactivity.

The microtextures of belite induced by a remelting reaction and other transformations (e.g., the polymorphic phase transitions of α→α′→β) have been reviewed. The remelting reaction, in which the α-phase belite decomposes into a liquid and the α′-phase during cooling, is necessarily preceded by the phase transition of α→α′; the α′-phase nucleates as lamellae within the parent α-phase so that there is good lattice matching across the interface. The resulting lamella boundaries provide heterogeneous nucleation sites for the exsolving liquid by the remelting reaction. A variety of microtextures results depending on the wettability of the belite lamellae by the exsolved liquid as well as on the cooling rate. The belite in which the remelting reaction occurred to a large extent showed higher hydration reactivity and better grindability than the quenched material. Recent years have seen developments in a new application for the remelting reaction that involves modifying belite-rich cement.