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1.
Effect of polycarboxylate type of super plasticizer on the hydration properties of composite cements
The work aims to study the effect of polycarboxylate type of super plasticizer on the hydration of composite cements. In this
paper we have studied the hydration of 20 wt% fly ash (FA) blended Portland cement in the presence of 0.1 wt% super plasticizer
(SP). Water consistency, setting times, non-evaporable water contents, compressive strength, water percolation, and air content
measurements were carried out. In addition, X-ray diffraction studies were carried out to understand the hydration process.
The results indicated the increase in compressive strength of the FA blended Portland cement in the presence of SP and with
the increase of the hydration time. 相似文献
2.
Tongsheng Zhang Qijun Yu Jiangxiong Wei Jianxin Li 《Journal of Thermal Analysis and Calorimetry》2012,110(2):633-639
To improve the properties of steel slag blended cements, a chemical activator was added into blended cements, the mechanical properties and durability of steel slag blended cements were investigated. The results show that steel slag in blended cement pastes presents low hydraulic activity and makes practically no contribution to strength development. After the addition of chemical activator, the mechanical properties and durability of ternary blended cements are increased significantly. The hydration process and micro-structural development of blended cement was investigated by isothermal calorimeter and scanning electric microscope, respectively. Steel slag started hydration in the first 3?days in the presence of chemical activator, steel slag and granulate blast furnace slag reacted with Ca(OH)2 to form a dense microstructure as curing proceeded. Therefore, both early and late compressive strengths of steel slag blended cement with 35% cement clinker and 30% steel slag can be comparable with those of Portland cement. 相似文献
3.
The properties of high-strength concrete under standard curing condition (20 °C, 95% RH), high-temperature curing condition (50 °C) and temperature match curing condition were comparatively investigated. The cumulative hydration heat of composite binder containing fly ash and silica fume is lower than that of composite binder containing the same amount of slag. Addition of fly ash and silica fume clearly reduces the adiabatic temperature rise of concrete, but adding slag leads to higher adiabatic temperature rise than Portland cement concrete. High-temperature curing condition and temperature match curing condition lead to the sustainable increase in compressive strength of concrete containing mineral admixture, but they hinder the later-age strength development of Portland cement concrete. For cement–slag paste and cement–fly ash–silica fume paste, the non-evaporable water contents increase significantly and the pore structures are much finer under high-temperature curing condition and temperature match curing condition, which negatively affect the pore structure of Portland cement paste. The differences in properties of concrete among three curing conditions become smaller with time. The properties obtained under standard curing condition can approximately reflect the long-term properties of high-strength concrete in the real structure. The concrete prepared with cement–fly ash–silica fume composite binder has the highest compressive strength, finest pore structure and best resistance to chloride permeability under any curing condition. This composite binder is very suitable to prepare the high-strength concrete with large volume. 相似文献
4.
Esperanza Menéndez Carmen Andrade Luis Vega 《Journal of Thermal Analysis and Calorimetry》2012,110(1):443-450
The hydration process of the cements induces the formation of different kinds of hydration products. The main products of hydration are C?CS?CH gel and portlandite [Ca(OH)2]. The C?CS?CH gel is an amorphous compound that is discomposed progressivity with the temperature until approximately 1,000?°C, while the portlandite is discomposed between 450 and 550?°C. Also, calcium carbonate can be formed as a consequence of the portlandite carbonation. All of these processes can be analysed and quantified by simultaneous differential thermal analysis and thermogravimetric analysis. And by X-ray diffraction it is possible to identify the crystalline phases. Some authors have corroborated that the portlandite can be rehydrated, after dehydration processes due to thermal exposition of the cement paste. But all of these experiments have been made with young cement pastes or at temperatures lower than 650?°C. In this work the behaviour of young and mature cement pastes have been studied in relation with the portlandite decomposition and the possibility of the rehydration of it in water presence. We found that young pastes and old pastes, stored at laboratory conditions, and later burned, show a certain grade of rehydration, specially the pastes burned at 650?°C (with ??80% of reformation of portlandite) with respect to the pastes burned at 1,000?°C (between 20 and 40%). It is corroborate that the rehydration process is directly related to the formation of CaO during the burning. Also, a formation of unstable portlandite is detected in young pastes burned at 650?°C, which can be rehydrated easily. Although, the mature pastes that have been burned initially and stored under laboratory conditions cannot be rehydrated, due to the formation of stable products during the storage. 相似文献
5.
In this paper the effect of limestone, fly ash, slag and natural pozzolana on the cement hydration products is studied. Four
composite cements containing limestone, natural pozzolana from the Milos Island, slag and fly ash have been produced by intergrinding
clinker (85%), the above main constituent (15%) and gypsum. The grinding process was designed in order to produce cements
of the same 28d compressive strength. The hydrated products, formed after 1–28 days, were studied by means of X-ray diffraction.
Unhydrated calcium silicate compounds of clinker and hydration products such as C*H, C*S*H and ettringite are clearly observed.
Although there is not significant differentiation among samples hydrated for the same period of time, modifications of calcium
aluminate hydrates as well as sulfoaluminate hydrates, are indicated by the XRD patterns. In samples of limestone cement,
monocarboaluminate is formed in the first 24 hours and is still present after 28 days. 相似文献
6.
In this study a calorimeter was applied to investigate the hydration of cements with fly ash (pulverised fuel ash – PFA) admixture.
Four cements were used to produce the binders containing from 5 to 60% fly ash. The process of hydration in cementitious systems
with fly ashes is slower than in reference pastes without admixtures. However, the calorimetric calculations and the shape
of heat evolution curves seem to indicate a complex interaction between the components of cement and ash resulting in the
increasing total heat evolved values per unit of cement. At higher fly ash content the accelerating effect of alkalis and
alumina should be taken into account and discussed in terms of the composition of initial cement. The modifications of hydration
kinetics and mechanism in this case is very well visualised by means of calorimetry.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Ghosh Kousiki Choudhury Dibyasree Lahiri Susanta 《Journal of Radioanalytical and Nuclear Chemistry》2019,319(1):91-99
The viability of ground coal bottom ash as a potential Portland cement constituent to be used in building materials is assessed. Currently, coal fly ash is used to produce Portland cements and concretes. However, coal bottom ash is mainly landfilled. Gamma spectrometry analysis, compressive strength, physical and chemical testing were performed. The ground coal bottom ash activity concentration index (I = 1.03) was compared to that of the coal fly ash (I = 1.11) provided from the same thermo-electrical power plant. Ground coal bottom ash could be used in building materials in the same way as coal fly ash as a Portland cement constituent.
相似文献8.
F. S. Hashem M. S. Amin S. M. A. El-Gamal 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1391-1398
This paper represents a laboratory study on the acid resistance of hardened ordinary Portland cement (OPC) and blended OPC pastes at two different curing temperatures. The blended materials used are rice husk ash (RHA) and cement kiln dust (CKD). The blended cement pastes were prepared using a water/solid (W/S) ratio of 0.3. The effects of immersion in deionized water (pH 7) and sulfuric acid solutions (pH 1, 2 and 3) at two temperatures (20 and 50 °C) on the compressive strength and phase composition of the various hardened blended cement pastes were studied. The results of compressive strength revealed that the increase of curing temperature from 20 to 50 °C resulted in increase the reduction of compressive strength due to acid attack up 2 months, but the resistance to sulfuric acid attack increases after that time due to the formation of crystalline calcium silicate hydrates (CSH) which have higher resistance to acid attack than the amorphous CSH formed at the early ages of hydration. The presence of RHA and CKD improves the resistance to sulfuric acid attack at both curing conditions. From the results of X-ray diffraction analysis and differential scanning calorimetric technique curves, the main hydration products identified are CSH, portlandite, and calcium sulfoaluminate hydrates. 相似文献
9.
This paper analyzes the effect of fly ash chemical character on early Portland cement hydration and the possible adverse effects
generated by the addition of gypsum. Behaviour was analyzed for pure Portland cements with varying mineralogical compositions
and two types of fly ash, likewise differing in chemical composition, which were previously characterized under sulphate attack
as: silicic-ferric-aluminic or aluminic-silicic ash in chemical character, irrespective if they are in nature, siliceous or
siliceous and aluminous materials according to the ASTM C 618-94a.
The experimental results showed that water demand for paste with a normal consistency increased with the replacement ratio
in fly ash with a more aluminic than silicic chemical character, whereas it declined when silicic-ferric-aluminic ash was
used. On the other hand, the differences between the total heat of hydration released at the first valley and the second peak
also clearly differentiated the two types of ash. While the relative differences increased in the more aluminic than silicic
ash, they declined in the more silicic than aluminic. In another vein, the findings indicate that within a comparable Blaine
fineness range, the reactive alumina (Al2O3r−) content in pozzolanic additions has a greater effect on mortar strength than the reactive silica (SiO2r−) content, at least in early ages up to 28 days. Finally, the adverse effect generated in the presence of excess gypsum is
due primarily to the chemical interaction between the gypsum and the C3A in the Portland cement and the reactive alumina (Al2O3r−) in the fly ash. 相似文献
10.
Jihui Zhao Duanle Li Shucong Liao Dongmin Wang Hao Wang Peiyu Yan 《Journal of Thermal Analysis and Calorimetry》2018,132(3):1459-1470
This paper investigates the influence of mechanical grinding on pozzolanic characteristics of circulating fluidized bed fly ash (CFA) from the dissolution characteristics, paste strength, hydration heat and reaction degree. Further, the hydration and hardening properties of blended cement containing different ground CFA are also compared and analyzed from hydration heat, non-evaporable water content, hydration products, pore structure, setting time and mortar strength. The results show that the ground CFA has a relatively higher dissolution rate of Al2O3 and SiO2 under the alkaline environment compared with that of raw CFA, and the pozzolanic reaction activity of ground CFA is gradually improved with the increase of grinding time. At the grinding time of 60 min, the pozzolanic reaction degree of CFA paste is improved from 6.32% (raw CFA) to 13.71% at 7 days and from 13.65 to 28.44% at 28 days, respectively. The relationships of pozzolanic reaction degree and grinding time of CFA also conform to a quadratic function. For ground CFA after a long-time grinding such as 60 min, the hydration heat and non-evaporable water content of blended cement containing CFA are significantly improved. Owing to relatively smaller particle size and higher activity of ground CFA, the blended cement paste has more hydration products, narrower pore size distribution and lower porosity. For macroscopic properties, with increase in grinding time of CFA, the setting time and strength of blended cement are gradually shortened and improved, respectively. 相似文献
11.
Effect of nano-metakaolin addition on the hydration characteristics of fly ash blended cement mortar
M. S. Morsy Y. Al-Salloum T. Almusallam H. Abbas 《Journal of Thermal Analysis and Calorimetry》2014,116(2):845-852
The effect of nano-metakaolin (NMK) addition on hydration characteristics of fly ash (FA) blended cement mortar was experimentally investigated. The amorphous or glassy silica, which is the major component of a pozzolan, reacts with the calcium hydroxide liberated during calcium silicate hydration. It is believable to add FA and NMK particles in order to make high performance concrete. The physico-mechanical properties of FA blended cement mortars made with different percentages of NMK were investigated. The experimental results showed that the compressive and flexural strengths of mortars containing NMK are higher than those of FA blended cement mortar at 60 days of hydration age. It is demonstrated that the nanoparticles enhances strength than FA. In addition, the hydration process was monitored using scanning electron microscopy and thermal gravimetric analysis (TG). The results of these examinations indicate that NMK behaves not only as a filler to improve microstructure, but also as an activator to promote the pozzolanic reaction. 相似文献
12.
Fly ashes from the combustion of coal thermal power stations are commonly incorporated into portland cements and/or concretes
and mortars. The chemical and morphological composition of fly ashes, together with their particle size, make them suitable
as pozzolanic(non-calcic) or pozzolanic/hydraulic(highly calcic) additions to manufacture such building materials. This work
focuses on the incorporation of two different fly ashes (non-calcic but of very different Fe2O3(%) contents, fineness and morphology) to two ordinary portland cements (of very different mineralogical composition as well),
to determine the effects those have and the interactions they produce in the hydration reactions of portland cement. The main
techniques employed for this study have been: conduction calorimetry and Frattini test; secondary techniques applied have
also been: determination of setting times and analysis by X-ray diffraction and SEM. Analysis of the results obtained permitted
to find different effects of fly ash addition on the hydration reactions of portland cements. Thus, dilution and stimulation
effects augment with the increased fly ash percentage. Delay and acceleration of the reactions depend mainly on the type of
portland cement and are accentuated with increased fly ash contents. Their behaviour as concerns heat dissipation mainly,
depends on the type of fly ash used and is more pronounced with increased cement replacement. On the other hand, the pozzolanic
activity of these fly ashes has been revealed at 7 and 28 days, but not at 2 days. Finally, pozzolanic cements can be manufactured
using different portland cements and/or types of fly ashes, in the appropriate proportions and compatible qualities, depending
on the effect(s) one wish to enhance at a specific age, which is according to previous general conclusions drew out of sulphate
attack and chloride attack researches.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Yu S. J. Wang S. X. Tan Z. C. Liao C. Q. Li Y. S. 《Journal of Thermal Analysis and Calorimetry》2009,96(3):993-998
In this work, the hydration rate and products of blended zeolite cements were studied for periods up to 360 days. Thermoanalytical
methods (TG/DTG and DTA) were applied in order to evaluate the hydration rate of blended cements, while. X-ray diffraction
and FTIR spectroscopy were used in order to identify the hydrated products. As it is concluded the incorporation of zeolite
in cement contributes to the consumption of Ca(OH)2 formed during the cement hydration and the formation of cement-like hydrated products. The pozzolanic reaction of the zeolite
is rather slow during the first days of hydration but it is accelerated after the 28 days. 相似文献
14.
Hydration of shrinkage-compensating binders with different compositions and water-binder ratios 总被引:1,自引:0,他引:1
The calorimetric data of blended shrinkage-compensating binders with different compositions were measured at 25°C at different
water-binder ratios using an isothermal calorimeter. The hydration characteristics of shrinkage-compensating binders were
evaluated and their influence on the expansive properties of blended shrinkage-compensating binders was determined. Composition
and w/b ratio significantly affect the hydration rate and degree of shrinkage-compensating binders, as well as their expansive
and mechanical properties. The total heat of hydration of binders decreases with w/c ratios. Its final hydration degree also
decreases with w/c ratio. The ternary binders composed with Portland cement, mineral admixture and expansive agent show low
hydration heat and rate of heat evolution, but their total heat of hydration increases continuously and surpasses that of
binary binder in later period at low w/b ratio.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Ximena Gaviria María Victoria Borrachero Jordi Payá José María Monzó Jorge Iván Tobón 《Journal of Thermal Analysis and Calorimetry》2018,132(1):39-46
Ordinary thermogravimetric analysis (TG) and high-resolution TG tests were carried out on three different Portland cement pastes to study the phases present during the first day of hydration. Tests were run at 1, 6, 12 and 24 h of hydration, in order to determine the phases at these ages. High-resolution TG tests were used to separate decompositions presented in the 100–200 °C interval. The non-evaporable water determined by TG was used to determine hydration degree for the different ages. The effect of particle size distribution (PSD) on mineralogical evolution was established, as well as the addition of calcite as mineralogical filler. Finer PSD and calcite addition accelerate the hydration process, increasing the hydration degree on the first day of reaction between water and cement. According to high-resolution TG results, it was demonstrated that ettringite was the only decomposed phase in the 100–200 °C interval during the first 6 h of hydration for all studied cements. C-S-H phase starts to appear in all cements after 12 h of hydration. 相似文献
16.
Sanjay Kumar Ankur Jain Yoshitsugu Kojima 《Journal of Thermal Analysis and Calorimetry》2017,128(2):721-733
This paper studies the addition (0–40% w/w) of natural zeolite (NZ, 84% clinoptilolite) in blended cements made with Portland cement (PC) with low and medium C3A content. The isothermal calorimetry was used to understand the effect of NZ on the early cement hydration. For low C3A cement, the addition of NZ produces mainly a dilution effect and then the heat released curve is similar to plain cement with lower intensity. For medium C3A cement, the curve shows the C3S peak in advance and a high intensity of third peak attributed to C3A hydration. The high cation fixed of NZ reduces the ions concentration (especially alkalis) in the mixing water stimulating the PC hydration. The flowability decreases when the NZ replacement level increases. Results of Fratini’s test show that NZ with both PCs used presents slow pozzolanic activity. At early age, XRD and FTIR analyses confirm that hydration products are the same as that of the corresponding PC and the CH is progressively reduced after 28 days and some AFm phases (hemi- and monocarboaluminate) appear depending on the NZ percentage and the PC used. For low replacement levels, the compressive strength is higher than the corresponding PC from 2 to 28 days. For high replacement levels, the early compressive strength is lower than that of corresponding plain PC and the pozzolanic reaction improves the later compressive strength of blended cements. 相似文献
17.
M. Komljenović Lj. Petrašinović-Stojkanović Z. Baščarević N. Jovanović A. Rosić 《Journal of Thermal Analysis and Calorimetry》2009,96(2):363-368
This paper presents the results of investigation of properties of fly ash from four major thermal power plants in Serbia.
Chemical, mineralogical and thermal characterization of fly ash has been performed in order to determine the possibility of
its use as the raw material for the construction material industry, primarily the cement industry. Thermal properties of the
raw mixtures for Portland cement clinker production based on fly ash were also investigated. The conclusion was reached that
the use of fly ash as a component of the raw mixture components for the production of cement clinker not only enables substitution
of natural raw materials, but could also have a positive influence on reduction of the sintering temperature of Portland cement
clinker. 相似文献
18.
K. Wieczorek-Ciurowa P. Dulian A. Nosal J. Domagała 《Journal of Thermal Analysis and Calorimetry》2010,101(2):471-477
The effect of alkaline hydrothermal activation of class-C fly ash belite cement was studied using thermal analysis (TG/DTG)
by determining the increase in the combined water during a period of hydration of 180 days. The results were compared with
those obtained for a belite cement hydrothermally activated in water. The two belite cements were fabricated via the hydrothermal-calcination
route of class-C fly ash in 1 M NaOH solution (FABC-2-N) or demineralised water (FABC-2-W). From the results, the effect of
the alkaline hydrothermal activation of belite cement (FABC-2-N) was clearly differentiated, mainly at early ages of hydration,
for which the increase in the combined water was markedly higher than that of the belite cement that was hydrothermally activated
in water. Important direct quantitative correlations were obtained among physicochemical parameters, such as the combined
water, the BET surface area, the volume of nano-pores, and macro structural engineering properties such as the compressive
mechanical strength. 相似文献
19.
K. Vessalas P. S. Thomas A. S. Ray J. -P. Guerbois P. Joyce J. Haggman 《Journal of Thermal Analysis and Calorimetry》2009,97(1):71-76
Thermogravimetric (TG) analysis was applied to the characterisation of the pozzolanic reaction in mortars containing the supplementary
cementitious materials (SCMs) pitchstone fines (PF) and fly ash (FA) as partial replacements for Portland cement (PC). TG
analysis was used to determine the proportion of calcium hydroxide (CH) present from the hydration of the PC based on the
dehydroxylation of the CH present in the blended PC-SCM mortars. The consumption of CH indicated that both SCMs underwent
the pozzolanic reaction and that PF was found to compare favourably in its pozzolanic reactivity of FA, the industry and globally
accepted standard artificial pozzolan. 相似文献
20.
B. Pacewska G. Blonkowski I. Wilińska 《Journal of Thermal Analysis and Calorimetry》2006,86(1):179-186
Investigations of physico-chemical properties
of three kinds of fly ash and their influence on cement hydration were performed
in this work. Thermal analysis, microcalorimetry, infrared absorption and
others were used. It was confirmed that the kind of coal and combustion conditions
essentially influence physico-chemical properties of fly ash and in consequence
influence cement hydration. Investigated fly ashes show in cement system so-called
pozzolanic activity. Fly ash from combustion of brown coal in fluidized furnace
revealed better activity compared to other investigated ones. This work is
an introduction to more extensive investigation of fly ash activation. 相似文献