scholarly journals Hydration behaviour of limestone-calcined clay and limestone-slag blends in ternary cement

2021 ◽  
Vol 6 ◽  
pp. 17-24
Author(s):  
Anuj Parashar ◽  
Shashank Bishnoi
Keyword(s):  
Bound Water ◽  
Heat Of Hydration ◽  
Cement Clinker ◽  
Strength Development ◽  
Gravimetric Analysis ◽  
Calcined Clay ◽  
X Ray ◽  
Blended Cements ◽  
Degree Of Hydration ◽  
Hydration Behaviour

The effect of kaolinitic calcined clay and slag on the hydration of limestone-containing ternary blended cements was investigated. The effect of alumina from different sources of SCMs was considered to activate the formation of carboaluminates. Ternary blends with 50% ordinary portland cement clinker, 45% blends of limestone calcined clay (LC2) in 1:2 blend and slag limestone blend (SLS) in 2:1 mix proportion with 5% of gypsum were studied. The hydration behaviour was analysed based on cement mortar compressive strength, heat of hydration using an isothermal calorimeter and bound water measured using thermal gravimetric analysis (TGA). In addition, the degree of hydration of clinker phases and the composition of calcium - alumino - silicate - hydrate (C-A-S-H) gels forming in two different systems were compared on 90 days hydrated samples analysed using X-Ray diffractometry (XRD) and scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDX) respectively. The results show a rapid early strength development in limestone calcined clay cement blend (LC3) but a lower clinker hydration in comparison with slag limestone cement blend (SLSC) at later ages. In both the cement blends the formation of hemicarboaluminate (Hc) and monocarboaluminate (Mc) was confirmed at 90 days, but the conversion of Hc to Mc was higher in SLSC. Results further confirmed a lower degree of hydration and higher alumina incorporation in the C-A-S-H gel in the LC3 comparison to SLSC. The presence of calcium hydroxide was also confirmed in the SLSC blend due to the hydraulic nature of slag that supported the later age conversion of Hc to Mc as not seen in LC3.

scholarly journals Effect of sulfur on the polymorphism and reactivity of dicalcium silicate of Portland clinker

Cerâmica ◽  
2011 ◽  
Vol 57 (341) ◽  
pp. 129-135 ◽  
Author(s):  
F. R. D Andrade ◽  
S. D Gomes ◽  
M Pecchio ◽  
Y Kihara ◽  
F. M. S Carvalho ◽  
...  
Keyword(s):  
Large Scale ◽  
Mineralogical Composition ◽  
Tricalcium Silicate ◽  
Heat Of Hydration ◽  
Dicalcium Silicate ◽  
Cement Clinker ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Cell Parameters ◽  
Starting Mixture

The present study regards the effect of sulfur in dicalcium silicate (Ca2SiO4), a major crystalline phase (20 to 40 wt.%) of the ordinary Portland cement clinker. Dicalcium silicate is also known as C2S (2CaO.SiO2) or belite. The synthesis of the C2S samples was made with high purity reactants with addition of sulfur as CaSO4.2H2O, mixed according to the stoichiometric proportion 2Ca:(1-x)Si:xS, in which x corresponds to the cationic proportion of sulfur, with values ranging from 0 to 20%. Added amounts of SO3 in the samples were 0.23, 1.39, 2.77, 4.60 and 9.71wt.%. Chemical composition of the samples was determined by X-ray fluorescence before and after sintering. Large-scale sulfur loss by volatilization leads to an excess in calcium and consequently to formation of increasing amounts of tricalcium silicate with increasing sulfur content in the starting mixture. Mineralogical composition of the samples and cell parameters of C2S polymorphs were determined by X-ray diffraction and Rietveld refinements. Structural analysis of diffraction data indicates that the presence of sulfur stabilizes the intermediate temperature polymorph β C2S, with increasing unit cell volume. The reactivity with water (heat of hydration) of the samples was measured by differential scanning calorimetry, which was strongly influenced by the highly reactive tricalcium silicate.

Preparation and Composition Optimization of Low-CO2-Emission Cement Containing Belite, Calcium Sulfoaluminate and Ferrite

2017 ◽  
Vol 727 ◽  
pp. 1067-1073 ◽  
Author(s):  
Wu Yao ◽  
Qiao Ling ◽  
Meng Xue Wu
Keyword(s):  
Compressive Strength ◽  
Cement Clinker ◽  
Strength Development ◽  
Optimal Composition ◽  
X Ray Diffraction ◽  
Scattered Electron ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Compressive Strength Development ◽  
Composition Optimization

Cement clinker with low CO2 emission was prepared in laboratory, which mainly consist of belite (C2S), calcium sulfoaluminate (C4A3S), and ferrite (C4AF). The mineral composition of clinker was optimized for better compressive strength development. The chemical and physical properties of this prepared cement were characterized through X-ray diffraction (XRD), back scattered electron-scanning electron microscopy (BSE-SEM) and differential thermal analysis (DTA). The results reveal that C4A3S governs most of the compressive strength at early ages, while C2S contributes to the later strength development. C4AF is in liquid when fired to 1300°C, beneficial to the mass transfer but causing high crystallinity of C2S when excessive. Finally the results of experiments suggest that the optimal composition of clinker is 50wt. % C2S, 40wt. % C4A3S and 10wt. % C4AF.

scholarly journals Study on Corrosion Mechanism of Different Concentrations of Na2SO4 Solution on Early-Age Cast-In-Situ Concrete

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2018
Author(s):  
Fei Zhang ◽  
Zhiping Hu ◽  
Li Dai ◽  
Xin Wen ◽  
Rui Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Of Hydration ◽  
Strength Development ◽  
Early Age ◽  
Corrosion Mechanism ◽  
Concrete Durability ◽  
Internal Corrosion ◽  
X Ray ◽  
Hydration Rate

The deterioration of early-age concrete performance caused by SO42− internal diffusion in concrete is a critical factor of concrete durability. In this study, the mechanical properties, heat of hydration, and pore structure of early-age cast-in-situ concrete with different sodium sulfate (Na2SO4) concentrations were studied. The mechanism of SO42− internal corrosion was evaluated by measuring the dynamic elastic modulus, compressive strength, and heat of hydration rate. Scanning electron microscopy, energy dispersive spectroscopy, X-ray computed tomography, X-ray diffraction, thermogravimetry-derivative thermogravimetry, and differential scanning calorimetry were applied to analyze microstructural variations and complex mineral assemblages of concrete samples. The results indicated that during the hardening process of cast-in-situ concrete, Na2SO4 first promoted and then hindered the hydration rate of cement, and also hindered the early strength development of the cement. As the concentration of Na2SO4 solution increases, the corrosion products of ettringite (AFt) and gypsum (Gyp) gradually increase, causing cross cracks in the concrete. The proportion of small and medium pores first increases and then decreases, and the large pores first decrease and then increase. The mechanical properties of concrete gradually decrease and diminish the mechanical properties of the concrete (thereby accelerating the damage to the concrete).

scholarly journals Characteristics of Blended Cements Produced from Selected Hardwood Ashes

2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Akeem A Raheem ◽  
Blessing O Orogbade
Keyword(s):  
Chemical Composition ◽  
Wood Ash ◽  
Heat Of Hydration ◽  
Cement Clinker ◽  
Potassium Oxide ◽  
Cassia Siamea ◽  
Suitable Material ◽  
Blended Cements ◽  
Setting Times ◽  
Portland Cement Clinker

In an attempt to find an alternative binding material for construction industry, this study considered the use of wood ash from three different hardwoods namely: Tectonagrandis, Cassia siamea and Vitellariaparadoxa as a pozzolan in cement production. The study investigates the chemical composition (silica (SiO2), aluminum oxide (Al2O3), ferric oxide (Fe2O3), calcium oxide (CaO), magnesium oxide (MgO), sulphur trioxide (SO3), sodium oxide (Na2O) and potassium Oxide (K2O)) of the ashes and the clinker. The production of blended cements were carried out in the factory by replacing 5- 50% by weight of Ordinary Portland Cement Clinker with the ashes during the manufacturing process. The cement without wood ash serves as the control. The physical characteristic (fineness, initial and final setting times, heat of hydration and residue on 45µm sieve), and the chemical composition of the blended cements were also investigated. The results showed that all the wood ashes (Tectonagrandis ash (TGA), Cassia siamea ash (CSA) and Vitellariaparadoxa ash (VPA)) were suitable material for use as pozzolan since they satisfied the requirement for such a material by having a combined SiO2, Fe2O3 and Al2O3 of more than 70%. The TGA, CSA and VPA blended cements satisfied standard requirements for up to 20% replacement level. It was concluded that all the wood ashes were suitable for use in the production of blended cements.

scholarly journals The effects of seawater and nanosilica on the performance of blended cements and composites

2020 ◽  
Vol 10 (12) ◽  
pp. 5009-5026 ◽  
Author(s):  
Pawel Sikora ◽  
Didier Lootens ◽  
Maxime Liard ◽  
Dietmar Stephan
Keyword(s):  
Transport Properties ◽  
Reaction Rate ◽  
Mechanical Performance ◽  
Setting Time ◽  
Blended Cement ◽  
Heat Of Hydration ◽  
Strength Development ◽  
Cement Pastes ◽  
Blended Cements ◽  
Setting Times

AbstractThis study investigates the effects of seawater and nanosilica (3% by weight of cement), on the fresh and hardened properties of cement pastes and mortars produced with two types of low heat cements: Portland pozzolana cement (CEM II) and blast furnace cement (CEM III). The heat of hydration, initial and final setting times, rheological properties, strength development, sorptivity and water accessible porosity of the cement pastes and mortars were determined. The data reveal that cement type has a significant effect on the reaction rate of cement with seawater and nanosilica (NS). Specimens produced with slag-blended cement exhibited a higher cement reaction rate and the composite produced exhibited better mechanical performance, as a result of the additional reaction of alumina rich phases in slag, with seawater. Replacement of freshwater with seawater contributes mostly to a significant improvement of early strength. However, in the case of slag-blended cement, 28 day strength also improved. The incorporation of NS results in additional acceleration of hydration processes, as well as to a decrease in cement setting time. In contrast, the addition of NS results in a noticeable increment in the yield-stress of pastes, with this effect being pronounced when NS is mixed along with seawater. Moreover, the use of seawater and NS has a beneficial effect on microstructure refinement, thus improving the transport properties of cement mortars. Overall, the study has showed that both seawater and NS can be successfully used to accelerate the hydration process of low heat blended cements and to improve the mechanical and transport properties of cement-based composites.

scholarly journals Chemical and Physical Characteristics of Blended Cements Produced from Softwood Ash

2018 ◽  
Vol 1 (March 2018) ◽  
pp. 1-7
Author(s):  
B.O Orogbade ◽  
A.A Raheem
Keyword(s):  
Chemical Composition ◽  
Wood Ash ◽  
Heat Of Hydration ◽  
Cement Clinker ◽  
Potassium Oxide ◽  
Agricultural Residue ◽  
Suitable Material ◽  
Blended Cements ◽  
Setting Times ◽  
Portland Cement Clinker

In an attempt to convert agricultural residue to alternative binding material for use in construction industry, this research considered the use of wood ash from Anacardium- occidentale (kaju) wood which is softwood as a pozzolan in cement production. In this study, the chemical composition (silica (SiO.), aluminum oxide (AI,O,), ferric oxide (Fe,O,), calcium oxide (CaQ), magnesium oxide (MgO), sulphur trioxide (SO,), sodium oxide (Na,O) and potassium Oxide (K,O)) of the ashes and the clinker was investigated. The production of blended cements were carried out in the factory by replacing 5- 50% by weight of Ordinary Portland Cement Clinker with the ashes during the manufacturing process. The cement without wood ash serves as the control. The physical characteristic (fineness, initial and final setting times, heat of hydration and residue on 45um sieve), and the chemical composition of the blended cements were also investigated. The results showed that Anacardiumoccidentale ash (AOA) was a suitable material for use as pozzolan since it satisfied the requirement for such a material by having a combined SiO, Fe,O,and Al,O,of more than 70% according to ASTM C 618. The AOA blended cements satisfied standard requirements for up to 20% replacement level. It was concluded that the wood ash was suitable for use in the production of blended cements.

scholarly journals Effects of Quartz Powder on the Microstructure and Key Properties of Cement Paste

2018 ◽  
Vol 10 (10) ◽  
pp. 3369 ◽  
Author(s):  
Run-Sheng Lin ◽  
Xiao-Yong Wang ◽  
Gui-Yu Zhang
Keyword(s):  
Compressive Strength ◽  
Linear Relationship ◽  
Cement Hydration ◽  
Isothermal Calorimetry ◽  
Bound Water ◽  
Heat Of Hydration ◽  
Crystal Nucleation ◽  
Partial Replacement ◽  
Quartz Powder ◽  
X Ray

This paper compares the effects of the water-to-binder (w/b) ratio and quartz contents on the properties of cement–quartz paste. The w/b ratios of the paste mixtures specimens are 0.5 and 0.2, and the quartz powder contents are 0, 10, and 20%. At the age of 1, 3, 7, and 28 days, compressive strength test, X-ray fluorescence (XRF) spectroscopy, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), isothermal calorimetry, and thermogravimetric (TG) analysis were performed. The experimental results show that the quartz powder mainly has the dilution effect and crystal nucleation effect on cement hydration, and the addition of quartz powder does not change the type of hydration product. The effect of quartz powder on cement hydration is closely related to the w/b ratio. In the case of a low w/b ratio of 0.2, the addition of quartz powder did not impair the compressive strength of paste. For different w/b ratios (0.5 and 0.2) and various quartz powder contents (0, 10, and 20%) at different ages (1, 3, 7, and 28 days), there is a uniform linear relationship between strength and porosity. Similarly, there is a uniform linear relationship between chemically bound water and calcium hydroxide, between heat of hydration and compressive strength, and between chemically bound water and compressive strength. At the same time, the effect of the partial replacement of cement by quartz powder on sustainability is considered in this paper.

Properties of Mortar with Recycled-Cement

2012 ◽  
Vol 193-194 ◽  
pp. 397-401
Author(s):  
Hong Zheng Lu ◽  
Hong Mei Ai ◽  
Fang Yan ◽  
Li Dong Han
Keyword(s):  
Mechanical Property ◽  
Compressive Strength ◽  
Chemical Composition ◽  
Cement Mortar ◽  
Cement Clinker ◽  
Strength Development ◽  
X Ray Diffraction ◽  
X Ray ◽  
Strength Grade ◽  
Waste Concrete

Waste concrete as the main object of the study, was proved to be capable of producing recycled-cement. The chemical composition of recycled-cement was analyzed by X-ray diffraction and compared with industrial clinker from Onoda Company. The result of comparison showed that the minerals in recycled-cement were almost the same as the industrial clinker, except a little MgO and CA. The amount of four main minerals in cement clinker was reasonable. The mechanical property of mortar produced with recycled-cement was measured. The results showed that the compressive strength of recycled-cement mortar can reach the standard of mortar with P.O 32.5. The excess MgO and the strength grade of waste concrete we used in the research were identified as the restriction of the strength development of recycled-cement.

Scanning Electron Microscopy and x-ray analysis of microparticles and early hydration effects

1995 ◽  
Vol 53 ◽  
pp. 692-693
Author(s):  
Yun Lu ◽  
David C. Joy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Morphological Development ◽  
Early Hydration ◽  
X Ray ◽  
Blended Cements ◽  
Powder Particles ◽  
Chemical Wastes ◽  
Scanning Electron

High resolution scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDXA) were performed to investigate microparticles in blended cements and their hydration products containing sodium-rich chemical wastes. The physical appearance of powder particles and the morphological development at different hydration stages were characterized by using high resolution SEM Hitachi S-900 and by SEM S-800 with a EDX spectrometer. Microparticles were dispersed on the sample holder and glued by 1% palomino solution. Hydrated bulk samples were dehydrated by acetone and mounted on the holder by silver paste. Both fracture surfaces and flat cutting sections of hydrating samples were prepared and examined. Some specimens were coated with an 3 nm thick Au-Pd or Cr layer to provide good conducting surfaces. For high resolution SEM S-900 observations the accelerating voltage of electrons was 1-2 KeV to protect the electron charging. Microchemical analyses were carried out by S800/EDS equipped with a LINK detector of take-off angle =40°.

scholarly journals Description of the concrete carbonation process with adjusted depth-resolved thermogravimetric analysis

2021 ◽  
Author(s):  
Nico Vogler ◽  
Philipp Drabetzki ◽  
Mathias Lindemann ◽  
Hans-Carsten Kühne
Keyword(s):  
Calcium Hydroxide ◽  
Bound Water ◽  
Reference Method ◽  
Microscopic Analysis ◽  
Limestone Powder ◽  
Gravimetric Analysis ◽  
Sample Material ◽  
Accelerated Carbonation ◽  
Temperature Range ◽  
Carbonation Process

AbstractThe thermal gravimetric analysis (TG) is a common method for the examination of the carbonation progress of cement-based materials. Unfortunately, the thermal properties of some components complicate the evaluation of TG results. Various hydrate phases, such as ettringite (AFt), C–S–H and AFm, decompose almost simultaneously in the temperature range up to 200 °C. Additionally, physically bound water is released in the same temperature range. In the temperature range between 450 °C and 600 °C, the decomposition of calcium hydroxide and amorphous or weakly bound carbonates takes place simultaneously. Carbonates, like calcite, from limestone powder or other additives may be already contained in the noncarbonated sample material. For this research, an attempt was made to minimise the influence of these effects. Therefore, differential curves from DTG results of noncarbonated areas and areas with various states of carbonation of the same sample material were calculated and evaluated. Concretes based on three different types of cement were produced and stored under accelerated carbonation conditions (1% CO2 in air). The required sample material was obtained by cutting slices from various depths of previously CO2-treated specimen and subsequent grinding. During the sample preparation, a special attention was paid that no additional carbonation processes took place. As reference method for the determination of the carbonation depth, the sprayed application of phenolphthalein solution was carried out. Microscopic analysis was examined to confirm the assumptions made previously. Furthermore, the observed effect of encapsulation of calcium hydroxide by carbonates caused by the accelerated carbonation conditions was examined more closely.

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