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1.
A. Bakolas E. Aggelakopoulou A. Moropoulou 《Journal of Thermal Analysis and Calorimetry》2008,92(1):345-351
Ceramic powder has been used as an artificial pozzolanic addition, in preparing pozzolanic mortars for the historic/traditional
structures’ construction. In order to evaluate the pozzolanic activity of ceramic powder, several pastes were prepared, by
mixing it with hydrated lime, in different ratios. The pastes were stored in standard conditions (RH=99±1%, T=25±1°C) and evaluated using thermal analysis (DTA/TG), X-ray diffraction (XRD), compressive strength tests and mercury intrusion
porosimetry (MIP), in time. The obtained results revealed that the compounds formed were CSH and C4ACH11 (monocarboaluminate) after 270 days of curing. The calcium hydroxide consumption increases as the initial amount of the ceramic
powder in the paste augments. The maximum strength development is obtained for ceramic powder/hydrated lime ratio 3:1. 相似文献
2.
Barbara Pacewska I. Wilińska M. Bukowska G. Blonkowski Wiesława Nocuń-Wczelik 《Journal of Thermal Analysis and Calorimetry》2004,77(1):133-142
The so-called pozzolanic activity of waste catalysts from fluidised cracking was investigated. For this purpose a series of
cement mixtures with this waste material were prepared and subsequently the pastes and mortars were produced. Waste aluminosilicate
catalyst was used both in raw form and after grinding in a ball mill for 60 min. The hydrating mixtures were subjected to
the calorimetric measurements in a non-isothermal/non-adiabatic calorimeter. After an appointed time of curing the hydrating
materials were studied by thermal analysis methods (TG, DTG, DTA). The pozzolanic activity factors were determined, basing
on the compressive strength data. The increased activity of cement — ground pozzolana systems has been thus proved. An accelerated
Ca(OH)2 consumption as well as higher strength were found for materials containing ground waste catalyst, as compared to those, mixed
with the raw one. Thus grinding was also proved to result in mechanical activation in the case of the waste catalyst from
fluidised cracking.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Effect of metakaolin pozzolanic activity in the early stages of cement type II paste and mortar hydration 总被引:1,自引:1,他引:0
A. L. Cherem da Cunha J. P. Gonçalves P. M. Büchler J. Dweck 《Journal of Thermal Analysis and Calorimetry》2008,92(1):115-119
The cement industry is one which most emits polluting gases to the environment, due to the calcium carbonate calcination,
as well as to the burning of fossil fuels during the manufacturing process. Metakaolin (MK), in partial substitution to cement
in its applications, is having a special worldwide growing role, for the technological increment due to its pozzolanic activity
and mainly to the reduction of those emissions. In the present paper, the effect of pozzolanic activity of metakaolin was
analyzed by thermal analysis in pastes and mortars of type II Portland cement in the first three days of the hydration, during
which, relevant initial stages of the hydration process occur.
By non-conventional differential thermal analysis (NCDTA), paste and mortar samples containing 0, 10, 20, 30 and 40% of metakaolin
in cement mass substitution and using a 0.5 water/(total solids) mass ratio, were evaluated. The NCDTA curves, after normalization
on cement mass basis and considering the heat capacity of each reactant, indicate that the pozzolanic activity behavior of
metakaolin is different in pastes and mortars. Through the deconvolution of the normalized NCDTA curve peaks, it can be seen
that ettringuite formation increases as cement substitution degree (CSD) increases, in both cases. Tobermorite formation is
more enhanced in mortars than in pastes by MK, with a maximum formation at 30% of CSD. In the pastes, tobermorite formation
increases as CSD increases but it is practically the same at 30 and 40% of CSD. 相似文献
4.
Summary The pozzolanic reactivity of thermally treated zeolites was studied on the basis of the Chapelle test combined with X-ray
diffraction (XRD) and Fourier Transform (FTIR) spectroscopy, as well as thermogravimetric analysis (TG/DTG) and differential
thermal analysis (DTA). The raw zeolite samples are from the Pentalofos area, Thrace, NE Greece. Their main mineral constituent
is 'heulandite type-II', an intermediate type of the heulandite-clinoptilolite isomorphous series. Calcination of the samples
was carried out up to 400, 500, 600, 700 and 1000°C for 15 h. The changes were recorded using the above methods. The deformation
of the zeolite crystal lattice starts at about 400°C and proceeds as the temperature of thermal treatment rises. The thermal
treatment of zeolite at 400°C improves its pozzolanic reactivity and accelerates the reaction with Ca(OH)2. 相似文献
5.
Bakolas Asterios Aggelakopoulou Eleni 《Journal of Thermal Analysis and Calorimetry》2019,135(6):2953-2961
Journal of Thermal Analysis and Calorimetry - In order to evaluate the pozzolanic activity of a natural pozzolan (NP) of rhyolitic composition, several pastes were prepared by mixing the pozzolan... 相似文献
6.
The results of pozzolanic activity determination using DTA-TG method are presented. This feature was characterised by Ca(OH)2 residue determination in cement pastes admixtured with siliceous earth, consuming the calcium ions from hydrolysis of cement
clinker minerals. The rate of pozzolanic reaction was thus estimated. Some results for fly ash containing pastes were also
given.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
B. Pacewska G. Blonkowski I. Wilińska 《Journal of Thermal Analysis and Calorimetry》2008,94(2):469-476
In this work, the pozzolanic and hydraulic properties of ashes originating from various sources were studied in model systems
such as ash and ash-lime pastes. The sources of studied ashes were: fluidized combustion of brown coal, pulverized combustion
of brown coal and pulverized combustion of hard coal. This article is a continuation of our previously published studies on
cement pastes with mentioned ashes.
The following experimental techniques were applied: calorimetry, thermal analysis (TG, DTG) and infrared absorption (IR).
Previously drawn conclusions relating to the reactivity of ashes in an environment containing Ca2+ ions were confirmed. According to these conclusions, an ash originating from fluidized combustion of coal exhibited higher
reactivity compared to other ashes from pulverized combustion. Pozzolanic and hydraulic properties of this ash were also confirmed.
Differences in the behaviour of ashes originating from pulverized combustion of various types of coal in the presence of water
and Ca2+ rich environment were demonstrated. 相似文献
8.
Influence of the calcined paper sludge on the development of hydration heat in blended cement mortars 总被引:1,自引:0,他引:1
O. Rodríguez M. Frías Ma I. Sánchez de Rojas 《Journal of Thermal Analysis and Calorimetry》2008,92(3):865-871
The present study is based on the influence of the addition of a pozzolanic material as a result of the activation of an industrial
waste coming from the Spanish paper industry on the heating as well as hydration heat of the cement mortars made with 10 or
20% of active addition.
Once the sludge has been calcined at different temperatures (700–800°C) and stays in furnace (2 and 5 h), the calcined products
showed high pozzolanic activity. The maximum activity corresponded to the paper sludge calcined at 700°C for 2 h (S1). Besides,
it can be proved that there was an increase both of the heating and also of the hydration heat in the first 23–25 h for both
additions (10 and 20% of S1) regarding the reference cement mortar. This behaviour would be related to the influence of different
effects: filler and pozzolanic during the first hours of reaction, and by the dilution effect for longer hydration times,
mainly when 20% of S1 was added. 相似文献
9.
Summary In this paper the optimization of the kaolin calcination is studied, aiming at using the produced metakaolin as supplementary cementitious material. Representative samples of poor Greek kaolin (Milos island) and a high purity commercial kaolin were tested. Samples were heated at different temperatures during different times. The optimization of calcination conditions was studied by DTA-TG and XRD analysis of the raw and thermal treated kaolin samples, by pozzolanic activity analysis of metakaolins and finally by strength development analysis of cement-metakaolin mixtures. This approach showed that heating at 650°C for 3 h is efficient to convert poor kaolins with low alunite content to highly reactive metakaolins. However in the case of kaolin with a high alunite content, thermal treatment at 850°C for 3 h is required in order to remove undesirable SO3. Evidence was found that poor kaolins can be efficiently used for the production of highly reactive metakaolins. 相似文献
10.
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
11.
Pozzolans play an important role in the industry of cement and concrete. They increase the mechanical strength of cement matrices and can be used to decrease the amount of cement in concrete mixtures, thus decreasing the final economic and environmental cost of production; also, as some of them are byproducts of industrial processes (such as silica fume and fly ash) and their use can be seen as a solution for some residues, that otherwise would be disposed as a waste. Pozzolans fixate the Ca(OH)2 generated during cement’s hydration reactions to form calcium silicate hydrates (C–S–H), calcium aluminate hydrates (C–A–H), or calcium aluminosilicate hydrates (C–A–S–H), depending on the nature of the pozzolan. Traditionally, the pozzolanic activity is identified using the Ca(OH)2 fixation percentage which is quantified by thermogravimetric (TG) analysis, using the mass loss due to the Ca(OH)2 dehydroxylation around 500 °C. An alternative method to identify pozzolanic activity at lower temperatures using a standard issue moisture analyzer (MA) is presented in this paper, using the mass loss due to hydrate’s dehydration generated by pozzolans in the pozzolanic reaction. Samples of Ca(OH)2 blended with different pozzolans were prepared and tested at different hydration ages. Using TG analysis and an MA, a good correlation was found between the total mass loss of the same sample, using the two methods at the same temperature. It was concluded that the MA method can be considered a less expensive and less time-consuming alternative to identify pozzolanic activity of siliceous or aluminosiliceous materials. 相似文献
12.
G. Baert S. Hoste G. De Schutter N. De Belie 《Journal of Thermal Analysis and Calorimetry》2008,94(2):485-492
Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the
acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days
increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)2-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic
reaction. A unique relation was found between calcium hydroxide and total heat development. 相似文献
13.
Evaluation of pozzolanic activity of natural and artificial pozzolans by thermal analysis 总被引:2,自引:0,他引:2
In this research, the pozzolanic activity of natural and artificial pozzolan used for preparation of restoration mortars was evaluated. For this purpose, several pastes were prepared, by mixing two artificial pozzolans and a natural one with commercial hydrated lime, in different ratios. The pastes were cured in standard conditions (RH = 98%, T = 25 °C). The pozzolanic activity was evaluated by using simultaneous differential thermal and thermogravimetric analysis (DTA/TG) after curing for 3, 7, 14, 28 days. The obtained results revealed that the various lime/pozzolan pastes displayed different reaction kinetics and therefore the various pozzolans present different reactivity, in proportion to its mineralogical, physical and chemical characteristics. 相似文献
14.
This work focuses on the thermal and mineralogical transformations of
red wall tile pastes. The pastes contain different amounts of calcareous and
are prepared with Brazilian raw materials. Thermal transformations are evaluated
by TG, DTG and DTA, dilatometric analysis, and X-ray diffraction. Four endothermic
transformations were identified and interpreted as the release of physically
adsorbed water, dehydration of hydroxides, dehydroxylation of kaolinite, and
decomposition of carbonate. An exothermic transformation within the 925–950°C
range is associated to crystallization of new phases such as calcium aluminosilicates
and mullite. TG measurements indicate that the total mass loss of the pastes
is dependent on the amount of calcareous addition. Dilatometric analysis indicates
the onset of sintering at around 900°C, leading to shrinkage of the pellets.
The thermal analysis results agree well with the X-ray diffraction. 相似文献
15.
B. E. I. Abdelrazig S. D. Main D. V. Nowell 《Journal of Thermal Analysis and Calorimetry》1992,38(3):495-504
Thermal methods are used extensively in investigating cements and effects of additives on their hydration behaviour. Calcium chloride is the most effective and widely used accelerator for cement hydration, but the result is largely dependent on the rate at which it is added. In this study the influence of calcium chloride dosage on the hydration behaviour of OPC pastes aged for different periods has been investigated by means of differential scanning calorimetry (DSC), thermogravimetry (TG) and X-ray diffraction (XRD) methods. The results are discussed in relation to the relative amounts of calcium hydroxide and total reaction product formed. Chloroaluminate was a product of hydration in the samples dosed with greater than 1% calcium chloride. XRD was unable of itself to differentiate between monochloroaluminate and the calcium aluminate hydrate C4AH13 when present in small amounts. Thermal methods proved effective in characterising the products of hydration in the presence of chloride.
Zusammenfassung Bei der Untersuchung von Zement und des Einflusses von Additiven auf das Hydratationsverhalten von Zement finden thermoanalytische Methoden eine breite Anwendung. Der effektivste und meistbenutzte Beschleuniger für die Hydratation von Zement ist Calciumchlorid, aber die Ergebnisse hängen stark von der Dosiergeschwindigkeit ab. In vorliegender Studie wird mittels DSC-, TG- und Röntgendiffraktionsmethoden der Einflu\ der Dosierung von Calciumchlorid auf das Hydratationsverhalten von verschieden alten OPC-Zementbreiproben untersucht. Die Ergebnisse wurden in Bezug auf die relativen Mengen Calciumhydroxid und das gebildete Gesamtreaktionsprodukt gewertet.Bei Dosen von mehr als 1% Calciumchlorid konnte als Hydratationsprodukt Chloraluminat festgestellt werden. Sind Monochloraluminat und das Calciumaluminathydrat C4AH13 in geringen Mengen vorhanden, kann man zwischen den beiden mittels Röntgendiffraktion nicht unterscheiden. Thermoanalytische Methoden erwiesen sich als effektives Hilfsmittel bei der Charakterisierung der Produkte der Hydratation in Gegenwart von Chlorid.相似文献
16.
R. M. H. Lawrence T. J. Mays P. Walker D. D’Ayala 《Journal of Thermal Analysis and Calorimetry》2006,85(2):377-382
A high speed method of thermal
analysis was developed to allow the carbonation profile of lime mortars to
be followed within a convenient time-frame. The loss in mass on heating, up
to 700°C, of lime/sand mixtures of different proportions was related to
the known quantity of lime in each mixture. It was shown that a heating rate
of 50°C min–1 produced data which had
a very high correlation with known quantities of Ca(OH)2.
Thismethod can be used to measure the extent of carbonation at varying depths
through a limemortar. This can be repeated at intervals to give an insight
into the shape and extent of the carbonation front as it develops over time. 相似文献
17.
Differential thermal analysis and thermogravimetry were used to evaluate the effect of some additives, such as CaSO4, CaCl2 and silica fume amorphous silica from ferrosilicon synthesis on the mechanism and kinetics of reactions occurring in fly
ash-Ca(OH)2 system. The accelerating role of these additives was demonstrated from the data relating to Ca(OH)2 consumption in hydrated pastes, determined by TG measurements.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
19.
Fly ash is the ash precipitated from the exhaust fumes of coal-fired power stations. It consists mainly of active silica and
alumina, with large amounts of glass. The aim of this work was to study the pozzolanic activity of fly ash with lime by means
of DTA as a function of the lime content and the curing time. The curves revealed that the rate of hydration, as indicated
by the residual lime and hydrated compounds, increases with increasing lime content and curing time. It is concluded that
fly ash can be used as a blending material in pozzolanic cement.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献