E0317 – Characterization cement pastes degraded in laboratory solutions and physiochemical parameters employed for modeling the process
Previously degradation studies carried out, over a number of different mortars by the research team, have shown that observed degradation does not xclusively depend on the solution equilibrium pH, nor the aggressive anions relative solubility. In our tests no reason was found that could allow us to explain, why same solubility anions with a lower pH are less aggressive than others. The aim of this paper is to study cement pastes behavior in aggressive environments. As
observed in previous research, this cement pastes behaviors are not easily explained only taking into account only usual parameters, pH, solubility etc. Consequently the paper is about studying if solution physicochemical characteristics are more important in certain environments than specific pH values. The paper tries to obtain a degradation model, which starting from solution physicochemical parameters allows us to interpret the different behaviors shown by different composition cements. To that end, the rates of degradation of the solid phases were computed for each considered environment
E0249 – Influence of vermiculite on the formation of porous cordierites
Porous cordierites were prepared from mixtures of talc, kaolinite and vermiculite with alumina or aluminum hydroxide by sintering in an argon atmosphere at 1300 °C for 1 h (porous cordierites of Group I) and 2 h (porous cordierites of Group II). Group I and Group II were different in pore size distribution, quantitative content of mineral phases and cordierite structure parameters. The crystalline phases identified in porous cordierites prepared without vermiculite were cordierite (69–88 vol.%), protoenstatite (25–13 vol.%) and corundum (3–10 vol.%). Vermiculite increased the content of cordierite (84–90 vol.%) and Mg–Al spinel (4–15 vol.%) at the expense of protoenstatite. The calculated unit cell parameters of cordierites were between those of orthogonal and hexagonal cordierites (Group I) and corresponded to disordered orthorhombic rather than hexagonal cordierites (Group II). Group I cordierites had pore size maxima at about ~35 ?m or ~20 ?m, while Group II had maxima at about 35 ?m, 25 ?m and 18 ?m. Porous cordierites prepared fromalumina admixture had slightly lower pore volumes than those prepared fromgibbsite. Cordierites prepared from mixtures rich in vermiculite and gibbsite showed the highest porosity (63% and 57%).
B3353 – Granular Cork Content Dependence of Thermal Diffusivity, Thermal Conductivity and Heat Capacity of the Composite Material/Granular Cork Bound with Plaster
This work is a contribution to understand the thermal behavior of the composite material based on granular cork embedded in plaster. An experimental investigation of its thermal properties was mainly performed using the Flash method and the tiny Hot Plate method in steady state regime. This will allow compare its thermal properties with those of plaster for motivate the proposal that this composite will be used as false ceiling. A comparison of the energy performances of the composite material and plaster was made; it allows deducing a very interesting energy gain. The preliminary findings indicate the composite is better than plaster in term of thermal insulation, energy storage capacity and lightness
B3312 – Hydration kinetics modeling of the effect of curing temperature and pressure on the heat evolution of oil well cement
The heat evolution of Class G and Class H oil well cements cured under different temperatures (25 °C to 60 °C) and pressures (2 MPa to 45 MPa) was examined by isothermal calorimetry. Curing pressure was found to have a similar effect on cement hydration kinetics as curing temperature. Under isothermal and isobaric conditions, the dependency of cement hydration kinetics on curing temperature and pressure can be modeled by a scale factor which is related to the activation energy and the activation volume of the cement. The estimated apparent activation energy of the different cements at 2 MPa varies from 38.7 kJ/mol to 41.4 kJ/mol for the temperature range of 25 °C to 40 °C, which decreases slightly with increasing curing temperature and pressure. The estimated apparent activation volume of the cements at 25 °C varies from ? 23.1 cm3/mol to ? 25.9 cm3/mol for the pressure range studied here, which also decreases slightly in magnitude with increasing curing temperature.
B3259 – Dimensional and ice content changes of hardened concrete at different freezing and
thawing temperatures
Samples of concrete at different water-to-cement ratios and air contents subjected to freeze/thaw cycles with the lowest temperature at about ?80 °C are investigated. By adopting a novel technique, a scanning calorimeter is used to obtain data from which the ice contents at different freeze temperatures can be calculated. The length change caused by temperature and ice content changes during test is measured by a separate experiment using the same types of freeze–thaw cycles as in the calorimetric tests. In this way it was possible to compare the amount of formed ice at different temperatures and the corresponding measured length changes. The development of cracks in the material structure was indicated by an ultra-sonic technique by measuring on the samples before and after the freeze–thaw tests. Further the air void structure was investigated using a microscopic technique in which air ‘bubble’ size distributions and the so-called spacing factor, indicating the mean distance between air bubbles, were measured. By analyzing the experimental result, it is concluded that damages occur in the temperature range of about ?10 °C to ?55 °C, when the air content is lower than about 4% of the total volume. For a totally water-saturated concrete, damages always occur independently of the use of entrained air or low water-to-cement ratios. It is, further, concluded that the length changes of these samples correspond to the calculated ice contents at different temperatures in a linear fashion.
B3257 – Cement–epoxy/water interfaces – Energetic, thermodynamic, and kinetic parameters by means of heat-conduction microcalorimetry
Hydration phenomena at cement/water interfaces drive the characteristics of oil-well cement slurries. In this study, new epoxy-modified cement slurries were synthesized. The slurries characterization has suggested the presence of low amounts of portlandite in the slurry with the higher content of polymerized epoxy resin. The hydration processes of the cement slurries were studied by heat-conduction microcalorimetry. The energetic and enthalpic hydration data were all exothermic in nature. The cumulative heat release curves have shown the presence of multilinearity of the kinetic processes. The hydration microcalorimetric data were well fitted to the multistep Avrami kinetic model. It was found that the epoxy-modified cement slurries present a good potential to be used in environmental-friendly oil-well operations.
B3087 – Impact of aggregate coating with a PEC elastomer on properties of lightweight flax shive concrete
Lightweight concrete becomes an important subject of research because of its insulating properties. The main objective of this research is to present a process improving the flax shive behaviour in a cement matrix. Flax shives stem from flax culture. It is the major product (50% of biomass weight). To be used as aggregates, shives should have a hydrophobization treatment. The aim of this work is the treatment of shives with a biodegradable elastomer: poly(PEG-co-CA). This elastomer is synthesized by the polycondensation of polyethylenglycol (PEG) and citric acid (CA). After their treatment with PEC elastomer, flax shives show a decrease in water absorption. Then, they are incorporated in a cement matrix. Mechanical properties, thermal properties and behaviour towards water (dimensional variations) of concrete are determined. The shive treatment shows an improvement in compressive and flexural strengths but an increase in thermal conductivity. The extreme dimensional variations (EDVs) and drying shrinkage (DS) decrease also with concrete prepared with treated shives compared to the standard. Overall the lightweight concrete obtained exhibits performances close to those of wood concrete.
B2867 – Thermodynamic properties of illite, smectite and beidellite by calorimetric methods: Enthalpies of formation, heat capacities, entropies and Gibbs free energies of formation
The thermodynamic properties of three aluminous 2:1 clay minerals were acquired at 1.013 bars and at temperatures between 5 and 500 K using various calorimetric methods. Calorimetric measurements were performed on hydrated and dehydrated <2 lm clay fractions of smectite MX-80 (Wyoming), illite IMt-2 (Silver Hill) and beidellite SBId-1 (Black Jack Mine). Heat
capacities were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 5 to 500 K. Standard enthalpies of formation were obtained from solution–reaction calorimetry at 298.15 K. The standard Gibbs free energies of formation of the clay minerals were also calculated, together with the equilibrium constants at 25 °C, for anhydrous and hydrated minerals. A comparison between these experimental data and estimated values obtained from prediction models available in the literature, enabled the calculation
method that appears to be the most relevant to be selected, at least for aluminous 2:1 clay minerals.
B2866 – Mechanism of growth of MgO and CaCO3 during a dolomite partial decomposition
The kinetics of the dolomite partial decomposition into MgO and CaCO3 have been investigated using isothermal and isobaric thermogravimetry (T=953 K, CO2 pressure in the range 0.025–0.4 atm). The characterization of the reaction products using XRD, SEM and XPS indicated that fine particles of MgO are formed at the surface of the initial dolomite needles. The elucidation of the mechanism of growth and of the rate-limiting step was based on a series of experiments devoted first to verify the steady-state assumption (by coupling thermogravimetry to
calorimetry), second to verify the existence of a rate-limiting step, and third to determine the variations of the areic growth reactivity, !, in mol m?2 s?1, as a function of CO2 pressure. A growth mechanism in eight elementary steps, involving interface and diffusion steps has been proposed. By comparing the experimental results to the possible rate laws calculated from the mechanism on the assumption of a rate-limiting step, it was found that the growth of MgO and CaCO3 can be controlled by the diffusion of magnesium through the MgO phase surface.
B2764 – Enthalpies of formation of the AgCs(NO3)2 and Ag3Cs(NO3)4 compounds
Molar solution enthalpies of AgNO3, CsNO3, AgCs(NO3)2 and Ag3Cs(NO3)4, were measured in pure water at 298.15 K, using different calorimeters. The corresponding molar solution enthalpies at infinite dilution are then used to derive the enthalpies of formation of the AgCs(NO3)2 and Ag3Cs(NO3)4 compounds referred to the pure nitrates respectively as ?7.34 and ?9.33 kJ mol?1.
B2761 – Microcalorimetric study of the transformation of CaSO4·2H2O in the 40 and 50 wt% P2O5 solutions at 80 °C
A calorimetric study of the transformation of CaSO4·2H2O (gypsum) in 40 and 50 wt% of P2O5 phosphoric acid solutions is undertaken at 80 ?C by dissolving increasing amounts of gypsum in the same volume of liquid. The results show a simple dissolution or its transformation into hemihydrate, CaSO4·1/2H2O, depending on the acid concentration. Kinetic schemes have been developed for these processes. The kinetic and thermochemical parameters were derived iteratively and the enthalpies were compared to experimental values
B2732 – On the interpretation of low temperature calorimetry data
In contrast to most other methods for characterisation of porosity Low Temperature Calorimetry (LTC) can be applied on virgin (undried) samples. This is especially relevant when testing
materials, e.g. cement paste, which is influenced by drying. However, there are a number of factors affecting the interpretation of results obtained by this method. In the present paper, a selection of these has been investigated, in order to determine the possibilities and limitations of using LTC for characterisation of the porosity of cement-based materials. LTC was
carried out on a model material with mono-sized pores of approximately 14 nm saturated with either distilled water or a sodium chloride solution, as well as on water, the salt solution, and an artificial pore solution, alone. It was found that supercooling is unavoidable during the liquid-solid phase transition, and that even at low temperature gradients equilibrium cannot be obtained with the sample size used (1 g liquid). Correcting for non-equilibrium between reference block and sample, the Gibbs–Thomson equation seems applicable for estimation of pore sizes of the investigated size. The estimate may be further improved by taking the effect of ions on freezing point depression into account. It is proposed that the connectivity of pores, e.g. in cementbased materials, may be characterised based on cooling curves, whereas the pore size distribution may be characterised based on the heating curve. Cooling should be undertaken at a high rate to limit transport of liquid, whereas heating should be undertaken at a low rate to limit the effect of nonequilibrium.
B2494 – Conduction Calorimetry and X-Ray Diffraction Investigation of Cement Retardation at 70 – 120°C
Studies on cement retardation in the temperature range of 70 – 120°C using conventional well cementing techniques indicate discontinuities with respect to thickening time. In the temperature range of 70-100°C unexpectedly long thickening times can occur that are not linear but exponential in relation to retarder concentration. At 100-120°C thickening times become shorter again with some retarders showing a notable threshold concentration above which there is minimal increase in thickening time. These discontinuity effects have serious implications in formulating slurries for use in this temperature range.
Conduction calorimetry was used to determine the effects of various retarders on a thermally stable Class G system (Class G cement with 40% silica flour) at a water to cement ratio of 0.4 over the temperature range 70 - 120°C. Retarders included sucrose, dextrose, trehalose, lignosulphonate and glucoheptonate and were chosen for their different retardation effects on cement. Studies were performed in a Setaram C80 conduction calorimeter with a high pressure gas controller. This system allowed the temperature to be ramped from ambient to the test temperature under pressure and more closely simulates well conditions.
B2407 – Some implications of calorimetric ice formation results for frost resistance testing of cement products
The present report focuses on results that are relevant to an understanding of frost damage mechanisms and therefore have implications for frost resistance testing procedures. Low temperature calorimetry is used for such an investigation.
B2406 – Frost durability of high strength concrete: effect of internal cracking on ice formation
Ice formation using low temperature calorimetry were made on non-air entrained high strength concretes before and after exposure to rapid freeze/thaw cycles in water (ASTM C666 proc.A). The purpose was to explore the relation between water absorption during test, changes in ice formation and deterioration, to investigate the deterioration mechanism of non-air entrained HSC in the ASTM C666 Test.
B2363 – Kinetics of interaction of hardened oil-well cement slurries with acidic solutions from isothermal heat-conduction calorimetry
The kinetics of interaction of hydrochloric acid with oil-well cement slurries treated with the silane coupling agents, tetraethyl orthosilicate, 3-(trimethoxysilyl)-1-propanethiol and 3-(chloropropyl)-trimethoxysilane have been investigated isothermal heat-conduction calorimetry at 298.15 K. The Avrami kinetic model gives a better fit to the experimental data than the traditional Lagergren kinetics models. A pore diffusion model suggests acid diffusion only for the standard slurry. The results indicate that isothermal heat-conduction calorimetry is suitable to
evaluate the protective role of silane coupling agents on hardened oil-well cement slurries
B2362 – Use of calorimetry to evaluate cement slurry resistance to the attack of acid solutions
The influence of cement slurry compositions with the silane coupling agents tetraethyl orthosilicate (SiL), 3-(trimethoxysilyl)-1-propanethiol (SH) and 3-(chloropropyl)-trimethoxysilane (CL) on resistance to hydrochloric acid attack has been investigated. Calorimetric results indicate the silanes enhanced the chemical resistance of the slurries. Increasing temperature decreased the time of action of the acid on the slurries. Reactivity follows the sequence: standard slurry > slurry-SiL > slurry-CL ? slurry-SH
B2361 – Studies of early hydration with class G oilwell cement using heatflow conduction calorimetry
Early examination of the hydration of a production class G oilwell cement by heatflow conduction calorimetry under temperature simulated API Schedule 5 and Schedule 8 conditions, using calcium lignosulphonate retarder and doped additions of pure tricalcium silicate and tricalcium aluminate, has demonstrated significant changes in the precise course of hydration if one or more of these additions be present. Reasons for such cahnges are given
B2360 – Cement-Polymer Composites for Oilwell Cementing
The selection of an optimal cementitious material is critical to maintain zonal isolation for the lifetime of oil & gas or gas storage wells not only for primary cementing but also after well abandonment. Polymer powder/cement composites present good mechanical and durability properties since polymer latex promotes improved adhesion and flexibility to the hardened cement paste. So, for well constructions in aggressive environment, polymer powder/cement composites would be good candidates. During the well construction, the cement slurry placement strongly depends on its rheological behaviour. In this paper, we studied rheological properties of polymer powder/cement composite suspensions: they present a transition from a gel to a liquid behaviour in oscillatory shear. The replacement of cement particles by polymer particles induces a decrease of the storage modulus in the gel state. The good quality of the
polymer particle dispersion and their high affinity for cement particles were observed by Scanning Electron Microscopy (SEM). Solid state NMR (29Si and 27Al) and calorimetry allowed to highlight the influence of the polymer addition on both the hydration and hardening of the cement matrix. All these results helped us to understand the relations between the slurry composition, its rheological behaviour and the properties of the hardened materials which allowed us to design new cementing materials.
B2174 – Effect of polysaccharides on the hydration of cement paste at early ages
This work deals with the relative efficiency of polysaccharides and their influence on cement hydration. Several parameters such as the
structure, concentration, average molecular weight, and soluble fraction value of polysaccharides were examined. Cement hydration was
monitored by isothermal calorimetry, thermogravimetry (TGA), and Fourier transform infrared (FTIR) spectroscopy. Results clearly show
that retardation increases with higher polysaccharide-to-cement weight ratio (P/C). Low-molecular-weight starch showed enhanced retarding
effect on the hydration of cement. The retardation effect of polysaccharides is also dependent on the composition of cement.
B1905 – Modification of cement hydration at early ages by natural and heated wood
Heat treatments of wood are widely used for the reduction of wood swelling and dimensional instability of wood-cement composites.
The effect of natural and heated wood on the hydration of cement at early ages was investigated by isothermal calorimetry, thermogravimetry
(TGA) and Fourier transform infrared (FTIR) spectroscopy. The addition of wood strongly delays and inhibits the hydration of
the silicate phases. Consequently, the amount of portlandite is lower in composites than in neat cement. Approximately 30% of the inhibition
of portlandite precipitation is due to an increase of calcium carbonate content in cement paste. The absorption of a part of water
by wood produces a decrease in gypsum consumption. Nevertheless, the ettringite formation is not significantly affected since a diffusion
of sulfate ions from wood occurs.
B1721 – The influence of wood aqueous extractives on the hydration kinetics of plaster
The influence of wood aqueous extractives on the hydration of plaster is discussed in this paper. Two species were chosen: poplar and
forest pine, and the effect of a thermal treatment, which acts as a dimensional stabiliser for wood, was considered. Calorimetric measurements
prove that delays of the setting must be expected, especially for the retified poplar. Conductimetric experiments show that wood extractives
seem to act as a retardant of the nucleation phase of the hydration reaction. The chemical analysis of the extracts reveals the presence of acetic
acid and phenolic molecules, but other experiments prove that their action is not sufficient to explain the retarding effect. Special attention
should be given to the influence of polyphenolic substances known as tannins.
B1701 – Thermokinetic analysis of the hydration process of calcium phosphate cement
A microcalorimeter (Setaram c-80) was used to study the thermokinetics of the hydration process of calcium phosphate cement (CPC), a biocompatible biomaterial used in bone repair. The hydration enthalpy was determined to be 35.8 J g-1 at 37.0°C when up to 80 mg CPC was dissolved in 2 mL of citric buffer. In the present study, parameters related to time constants of the calorimeter were obtained by fitting the recorded thermal curves with the function ?=Ae^(-?1t)(1- e^(-?2t). The real thermogenetic curves were then retrieved with Tian function and the transformation rate of the hydration process of CPC was found to follow the equation alpha=1-[1-(0.0075t)3]3. The microstructures of the hydrated CPC were examined by scanning electron microscopy. The nano-scale flake microstructures are due to crystallization of calcium phosphate and they could contribute to the good biocompatibility and high bioactivity.
B1624 – Kinetics of interaction of hardened oil-well cement slurries with acidic solutions from isothermal heat-conduction calorimetry
The kinetics of interaction of hydrochloric acid with oil-well cement slurries treated with the silane coupling agents, tetraethyl orthosilicate, 3-(trimethoxysilyl)-1-propanethiol and 3-(chloropropyl)-trimethoxysilane have been investigated isothermal heat-conduction calorimetry at 298.15 K. The Avrami kinetic model gives a better fit to the experimental data than the traditional Lagergren kinetics models. A pore diffusion model suggests acid diffusion only for the standard slurry. The results indicate that isothermal heat-conduction calorimetry is suitable to evaluate the protective role of silane coupling agents on hardened oil-well cement slurries.
B1489 – Use of calorimetry to evaluate cement slurry resistance to the attack of acid solutions
The influence of cement slurry compositions with the silane coupling agents tetraethyl orthosilicate (SiL), 3-(trimethoxysilyl)-1-propanethiol (SH) and 3-(chloropropyl)-trimethoxysilane (CL) on resistance to hydrochloric acid attack has been investigated. Calorimetric results indicate the silanes enhanced the chemical resistance of the slurries. Increasing temperature decreased the time of action of the acid on the slurries. Reactivity follows the sequence: standard slurry>slurry-SiL>slurry-CL?slurry-SH.
B1371 – Compatibility of some tropical hardwoods species with portland cement using isothermal calorimetry
Ten Mozambican hardwood species were tested for their compatibility with two classes of Portland cement. Instantaneous heat flux of cement hydration was measured by isothermal calorimetry. Awood-cement compatibility factor was determined. These tests identified species compatible with cement without needing any water treatment (Amblygonocarpus andongensis and Brachystegia speciformis) as well as the species becoming compatible after a simple cold- or hot-water extraction of water-soluble components of wood (Pterocarpus angolensis, Kaya nyasica, Erythrophleum suaveoleuns, Albizia adianthifolia, and Sterculia appendiculata). Millettia stuhlmannii and Julbernadia globiflora showed considerable compatibility improvement following extraction with an NaOH solution (10 g/L). Afzelia quanzenzis, however, appeared to require more treatments to make it sufficiently compatible with Portland cement. Special procedures and treatments must be applied in order to make wood-cement composites from several mixed species.
In Mozambique, the use of synthetic adhesives for the manufacture of wood composites remains an important obstacle to the development of the panel industry. These adhesives are imported and their costs are high. Inorganic binders, especially Portland cement, are extensively used in panel manufacture in various countries. Previous studies have shown that this binder can form an exterior quality panel resistant to termite, fire, and fungal attack [3]. Therefore, substituting cement for synthetic adhesives cement in the manufacture of wood-cement composites would be an economical alternative for the construction industry.
Among the 118 indigenous forest species identified in Mozambique, 75 percent are considered secondary species and are not commercially utilized [12]. In addition, wastes from the wood industry are underutilized and the cement industry is growing.
The literature indicates that not all wood species react favorably with Portland cement. The varying degrees of incompatibility among species are reported to be related to wood extractives [6,11,16]. When Portland cement is used as a binder, such compatibility can be expressed in terms of cement hydration data when mixed with a given wood species [10]. Isothermal calorimetry is a reliable method for investigating cement hydration [2,13]. This technique has the advantage to provide the instantaneous flux of free heat and the total energy of the hydration reactions.
B1009 – Contribution à l’étude physico-chimique des transformations conduisant aux matériaux utilisés dans la confection de béton : L’hydratation des ciments ASMAR.
B0822 – Application of heat flow calorimetry of the study of oilwell cements
The majority of previous studies of the hydration of cements using heat flow calorimetry
have been carried out isothermally. However, with oilwell cements the slurry is mixed
on the surface at ambient temperature and then gradually increases in temperature as it is
pumped down the well. A Setaram C-80 calorimeter has been used to simulate the temperature
ramp in API oilwell cement test schedules. This approach has enabled cementing reactions
to be studied for the first time under conditions approaching those encountered in the
field, and has shown that the results obtained from isothermal experiments may be misleading.
B0798 – Application of thermal analysis to the cement industry
Methods involving heat measurements have been applied in the cement industry for a long time. Differential thermal analysis (DTA) is used to explain the clinkering reactions, but it is a dynamic method which thus does not allow measurements and calculations of the thermal balance of the reactions to be made. In contrast, high temperature microcalorimetry may be used to measure the enthalpy of the clinkering reactions of industrial raw materials. Results obtained by using this technique allow us to determine the thermal profile of clinkering reactions in the kiln and to quantify the heat exchange in the solid material during its burning.
Low temperature conduction microcalorimetry gives information on the hydration mechanism of the cement pastes. In this paper, we review the applications of thermal analysis in the cement industry paying special attention to new methods such as high temperature microcalorimetry.
B0388 – Some aspects of the application of differential scanning calorimetry to cement research.
B0332 – Ice formation in hardened cement paste (II.) Steam-cured pastes with variable moisture contents
B0330 – Low temperature calorimetry as a pore structure probe.
A2360 – High temperature behaviour of self-consolidating concrete. Microstructure and physicochemical properties
This paper presents an experimental study on the properties of self-compacting concrete (SCC) subjected to high temperature. Two SCC mixtures and one vibrated concrete mixture were tested. These concrete mixtures come from the French National Project B@P. The specimens of each concrete mixture were heated at a rate of 1 °C/min up to different temperatures (150, 300, 450 and 600 °C). In order to ensure a uniform temperature throughout the specimens, the temperature was held constant at the maximum temperature for 1 h before cooling. Mechanical properties at ambient temperature and residual mechanical properties after heating have already been determined. In this paper, the physicochemical properties and the microstuctural characteristics are presented. Thermogravimetric analysis, thermodifferential analysis, X-ray diffraction and SEM observations were used. The aim of these studies was in particular to explain the observed residual compressive strength increase between 150 and 300 °C.
A2298 – Effect of thermal pre-treatment conditions of common clays on the performance of clay-based geopolymeric binders
This study focuses on the influence of the thermal pre-treatment conditions on the reactivity of common clays in alkaline and alkaline earth solutions, in respect to form geopolymeric binders. Illite and illite–smectite clays were thermally activated between 550 and 950 °C in oxidizing and reducing atmosphere, respectively. Material and structural changes were characterized by different methods, like thermal analysis, XRD and dissolution tests. Isothermal calorimetric measurements were carried out to characterize the reaction process in alkaline media. The potential of a raw material for the geopolymer reaction by alkaline activation can be derived from the molar ratio of soluble Si/Al in alkaline solutions. Additionally, the standard Chapelle test was executed to determine the pozzolanic reactivity. It could be found that the molar ratio of soluble Si/Al increases with increasing pre-treatment temperature. The presence of 2:1 clay minerals results in a Si/Al ratio between 2 and 3 and indicates a good potential for a geopolymer reaction by alkaline activation. This behavior was remarkably influenced by the atmosphere during the thermal pre-treatment. The maximum pozzolanicity (reactivity) could be obtained at lower temperatures in the case of pre-treatment in reducing atmosphere than in oxidizing atmosphere. Clays calcined in reducing atmosphere result in a more intensive condensation of the aluminosilicates than clays calcined in oxidizing atmosphere at the same temperature. That is possibly caused by the higher ratio of soluble Si/Al after pre-treatment in reducing atmosphere. The performance of the clay-based geopolymer binders was determined by means of bending strength measurements.
A2246 – Study of mechanical behavior of lightweight aggregates concrete of Tunisian clay
In this study, we treated the mechanical behavior of lightweight concrete with Tunisian clay aggregates, shaped and expanded in the laboratory. A method of manufacturing aggregate was followed. The choice of materials was packed and a physical, chemical, mineralogical and thermal (DTA / TGA) characterization of clay and aggregates was performed. For current cement content, we determined the compressive strength at 3, 28 and 90 days for a fixed water-cement ratio E/C. The Young's modulus was determined with empirical formulae. Thus, by SEM observations, we studied the aggregates and the interfacial transition zone (ITZ) between the cement paste and the aggregates at different ages. The obtained constitutes concrete is hence a structure concrete according to the AFNOR norms and the ACI Guide.
A2216 – Technological behaviour and recycling potential of spent foundry sands in clay bricks
The feasibility of recycling spent foundry sand in clay bricks was assessed in laboratory, pilot line and industrial trials, using naturally occurring sand as a reference. Raw materials were analyzed by X-ray fluorescence, X-ray diffraction, particle size distribution, and leaching and combined to produce bodies containing up to 35% wt. sand. The extrusion, drying and firing behaviour (plasticity, drying sensitivity, mechanical strength, bulk density, water absorption, and shrinkage) were determined. The microstructure, phase composition, durability and leaching (EN 12457, granular materials, end-life step, European Waste Landfill Directive; NEN 7345, monolithic materials, use-life step, Dutch Building Material Decree) were evaluated for bricks manufactured at optimal firing temperature. These results demonstrate that spent foundry sand can be recycled in clay bricks. There are no relevant technological drawbacks, but the feasibility strongly depends on the properties of the raw materials. Spent foundry sand may be introduced into bricks up to 30% wt. Most of the hazardous elements from the spent foundry sand are inertized during firing and the concentrations of hazardous components in the leachates are below the standard threshold for inert waste category landfill excepting for chromium and lead; however, their environmental risk during their use-life step can be considered negligible
A2183 – Influence of carbonation on the load dependent deformation of hydraulic lime mortars
The time dependent deformation of natural hydraulic lime mortar (NHL3.5) through creep and shrinkage under load, in the first 63 days after mixing, has been investigated. An apparatus was constructed to measure the dimensional changes of eight individual specimens simultaneously. The influence of load on deformation rate was found to decrease with time during the experiment. The rate of decrease in load dependent deformation, creep, with time was shown to be inversely proportional to the extent of carbonation. This observation supports the theory that deformation can be explained by the dissolution of calcium hydroxide crystals under stress and subsequent re-precipitation of calcite in areas free from stress.
A2071 – Numerical studies of gypsum plaster board panels under standard fire conditions
Gypsum plasterboards are commonly used as a fire safety material in the building industry. Many research studies have been undertaken to investigate the thermal behaviour of plasterboards under standard fire conditions. However, there are many discrepancies in relation to the basic thermal properties of plasterboards while simple equations are not available to predict the ambient surface time–temperature profiles of gypsum plasterboard panels that can be used in simulating the behaviour and strength of steel studs or joists in load bearing LSF wall and floor systems. In this research, suitable thermal properties of plasterboards were proposed based on a series of tests and available results from past research. Finite element models of gypsum plasterboard panels were then developed to simulate their thermal behaviour under standard fire conditions. The accuracy of the proposed thermal properties and the finite element models was validated by comparing the numerical results with available fire test results of plasterboard panels. This paper presents the details of the finite element models of plasterboard panels, the thermal analysis results from finite element analyses under standard fire conditions and their comparisons with experimental results.
A1905 – Systematic analysis of natural pozzolans from Greece suitable for repair mortars
Natural pozzolans were used as pozzolanic cement in concrete mixtures to increase the long-term strength, the concrete durability, and other material properties of Portland cement many centuries ago. The most common pozzolan is the volcanic ash, a siliceous or aluminosiliceous material, which is highly vitreous, coming from volcanic eruptions. In the Greek territory, 39 reactive volcanoes have been recorded both in insular and in terrestrial areas. The reactivity of pozzolans, in the case of lime-based mortars, is attributed to their content in amorphous silica which reacts with Ca(OH)2 from lime, in environmental conditions, and forms C–S–H compounds responsible for the strength gain. Their use in building materials was diachronic. The significant properties of mortars containing pozzolans derive from the mechanism of its gradual strengthening attributed to the reaction of silicates with lime to form secondary cementitious phases which increase the durability and the dense structure of the mortars. In the present paper, two natural pozzolans from Greece are analyzed in order to record their morphological
and analytical microstructure as well as their thermal and physical properties. The results revealed that the pozzolans tested, are materials of high quality and can be used for the production of compatible repair mortars. Also, valuable criteria could be instituted for the selection of reactive pozzolans which could be used for conservation purposes. Among others, crucial parameters for compatibility between old mortars and new ones are the surface features (color, texture, and roughness), the composition (type of binder, granulometry of aggregate), and the pore size distribution.
A1884 – Thermal analysis of dehydroxylation of Algerian kaolinite
Thermal analysis techniques remain important tools amongst the large variety of methods used for analysis of the dehydroxylation of kaolinite. In the present study, the kinetics of dehydroxylation of Algerian kaolinite, wet ball milled for 5 h followed by attrition milling for 1 h, was investigated using differential thermal analysis (DTA) and thermogravimetry (TG). Experiments were carried out between room temperature and 1350 °C at heating rates of 5, 10 and 20 °C min-1. The temperature of dehydroxylation was found to be around 509 °C. The
activation energy and frequency parameter evaluated through isothermal DTA treatment were 174.69 kJ mol-1 and 2.68 9 109 s-1, respectively. The activation energies evaluated through non-isothermal DTA and TG treatments were 177.32 and 177.75 kJ mol-1, respectively. Growth morphology parameters n and m were found to be almost equal to 1.5.
A1869 – Preparation and characterization of photoactive composite kaolinite/TiO2
Preparation of nanocomposite kaolinite/TiO2, using hydrolysis of titanyl sulfate in the presence of kaolin was addressed. A variable (kaolin)/(titanyl sulfate) ratio has been used in order to achieve the desired TiO2 content in prepared nanocomposites. Calcination of the composites at 600 ?C led to the transformation of the kaolinite to metakaolinite and to origination of metakaolinite/TiO2 composites. The prepared samples were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry and diffuse reflectance spectroscopy in the UV–VIS region. Structural ordering of TiO2 on the kaolinite particle surface was modeled using empirical force field atomistic simulations in the Material Studio modeling environment. Photodegradation activity of the composites prepared was evaluated by the discoloration of Acid Orange 7 aqueous solution.
A1819 – Incorporation of fluorophosphate into zinc–aluminium–nitrate layered double hydroxide by ion exchange
The intercalation of fluorophosphate (PO3F2?, FP) in the [Zn–Al] layered double hydroxides (LDHs) was investigated. A nitrate precursor was prepared by coprecipitaion at pH 9. An attempt to intercalate FP by direct coprecipitation reaction led to a poorly crystalline LDH phase. The effects of pH, aging time and anion concentration were studied and allowed to confirm that the best crystalline material, with high exchange extent, was obtained by carrying out the exchange at 25 ?C in 0·1 M FP solution at pH 9 with at least 20 h of aging time.
A1818 – Synthesis and characterization of a new monophosphate (C6H16N2)(H2PO4)2
Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b =7.6942(4), c = 8.1473(5) A ° , a = 114.997(3), b = 92.341(3), c = 113.136(3), V = 329.14(3) A ° 3, Z = 1, and Dx = 1.565g cm–3. The crystal structure has been determined and refined to R = 0.030 and Rw(F2) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H2PO4]n n– chains with (C6H16N2)2+ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, 13C and 31P MAS NMR spectroscopies and Ab initio calculations.
A1817 – Microstructural evolution and phase transformation of different sintered Kaolins powder compacts
Four kinds of Kaolins (K1, K2, K3 and K4) from various originswere studied using Xray diffraction, 29Si and 27Al MAS-NMR spectroscopy and scanning electron microscopy (SEM). Mineralogical and morphological characteristics of these samples are given. Kaolinte is the principal mineral but other minerals are present in small quantities: Illite, Muscovite and Quartz. The thermal behaviour of K1, K2, K3 and K4 was studied. The transformation heats during heating were quantified from DTA measurements and phase changes were followed by Xray
diffraction analyses and 29Si and 27Al MAS-NMR spectroscopy. Results indicated that a series of phase transformations take place as the Kaolin is fired at elevated temperature. Mullite
is first formed at a temperature as low as 1100 ?C. Microstructural evolution of this specimen and their mechanical properties are investigated.
A1816 – Sintering characteristics of kaolin in the presence of phosphoric acid binder
The kaolin–phosphoric acid mixtures with various percentages of phosphoric acid (5 wt%; 10 wt% and 15 wt%) have been investigated at room temperature. During the maturation and the sintering processes, acid reacts with aluminium of kaolin to give a new phase of aluminophosphate. This new phase’s appearance has been confirmed by the thermal analysis, infrared spectroscopy, X-ray diffraction and scanning electron microscopy measurements before and after the sintering processes at different temperatures (800 °C, 1100 °C and 1250 °C). The rupture strength of the body-shaped samples made with the kaolin–phosphoric acid mixtures is higher than that of those made with only kaolin. The porosity decreases with both the sintering temperature rise and the addition of phosphoric acid in the mixture. The addition of 10 wt% of phosphoric acid to the kaolin decreases its calcined temperature by 200 °C.
A1790 – Long-term progressive deterioration following fire exposure of OPC versus slag blended cement pastes
The normal practice of repairing fire-damaged concrete structures is to remove the visibly damaged portions and restore them with new concrete. However, little attention has been given to the
long-term performance of fire exposed concrete which is not removed from the structure. This paper addresses this issue. Ordinary Portland cement (OPC) pastes, when exposed to a critical temperature of 400°C, undergo complete breakdown. This behaviour was attributed to the dehydration of Ca(OH)2, followed by the expansive rehydration of CaO. In contrast, partial replacement of the OPC binder with slag, had a beneficial effect in the mechanical properties of the paste after exposure to high temperatures, as slag significantly reduces the amount of available Ca(OH)2 in the cement paste. The present work provides new data regarding the long-term (after the exposure event) effect of CaO rehydration in the OPC and OPC/slag pastes. After 1 year the ongoing effect of the CaO rehydration was severe in the OPC paste while OPC/slag blends were not affected by rehydration. Compressive strength and thermogravimetric results are presented to explain this behaviour.
A1710 – Thermal study of sandstones from different Czech localities
Thermal analysis is a useful tool for determination of the rock‘s thermal behavior. The thermal behavior of the rock is affected by both its composition and structure. This study presents the application of thermogravimetric, differential thermal, and thermomechanical analyses for the characterization of the selected Czech sandstone samples. The detailed study of mineralogical
composition was carried out by FTIR spectroscopy, X-ray diffraction, and optical microscopy. Thermal expansion during heating up to 1,000 C, together with the coefficient of thermal expansion showed almost the same values for all the studied sandstone samples. Nevertheless, the residual thermal expansion varied depending mainly on the composition. In the case of higher content of quartz, the thermal expansion showed higher values. With increase of carbonate, glauconite, or clay mineral volume, the residual thermal expansion decreased. Factors such as grain size or shape of particles did not significantly influence the observed thermal expansion values.
A1709 – Thermal behavior of selected Czech marble samples
The definition as well as prediction of rock thermal behavior seems to be a quite difficult problem significantly effected by rock composition and structure. Temperature increase causes various changes of rock material (such as decomposition, oxidation, phase and polymorphic transformation, etc.). These changes are connected to thermal expansion with following appearance of tensions and cracks in minerals and rock structure. After consequential temperature decrease, developed tensions and cracks still influence the process. This study presents the application of thermogravimetric analysis, differential thermal analysis and thermomechanical analysis in characterization of selected marble thermal behavior. The texture and morphological orientation of calcite grains for marble samples was determined by optical microscopy. FTIR spectroscopy application along with X-ray diffraction (XRD) extended data about mineralogical composition.
According to optical microscopy, the calcite grains show marked morphological anisotropy in one direction for some samples. Therefore, the thermal expansion had to be measured in three different (perpendicular to each other) directions. It is evident, that the effect of temperature on the final marble properties depends not only on mineralogical composition, but also on structure, texture and morphological orientation of grains. All these facts significantly influence the interpretation of differences in various marble thermal behavior.
A1701 – Alkali-activated metakaolin-slag blends—performance and structure in dependence of their composition
Blast furnace slag and metakaolin were blended together and the combination activated by sodium hydroxide solution. The boundary mixtures were set by the activation of the pure slag and pure metakaolin powders. The type and quantity of the reaction products in the alkaline activated blended binders was determined. It is discussed whether both raw materials react separately and are unaffected by each other or if there is a chemical interaction. The discussion bases on extensive investigations with 29Si and 27Al nuclear magnetic resonance spectroscopy
compared with X-ray diffraction and thermal analysis (DTA/TG). Additionally, the strength performance will be presented and related to structure, composition and the amount of the reaction products.
A1700 – The suitability of thermally activated illite/smectite clay as raw material for geopolymer binders
So called geopolymers or geopolymeric binders and cements are made by means of an alkaline activation of materials reactive in this respect. Such material has to consist of a certain amount of silicate and aluminate phases which can be dissolved by the alkaline medium. In the consequence stable polymeric networks of alumosilicates will be formed. Metakaolins and alumosiliceous fly ashes, in particular, have by now achieved noteworthy significance. The search for alternative low cost or high available materials may lead among other things to “normal clays”. This material is widely available all over the world and may show certain reactivity after a thermal activation process. This investigation focuses on the suitability of illite/smectite clay
to form a geopolymer after thermal and alkaline activation. Therefore clay containing mainly illite was thermally activated between 550 and 950 °C. The degree of dehydroxylation and the reached reactivity were followed by X-ray diffraction, NMR spectroscopy and dissolution techniques. The performance of the geopolymer binder in terms of strength as well as the phase composition was studied.
A1699 – Geopolymeric binders with different fine fillers — Phase transformations at high temperatures
Geopolymers based on metakaolin were synthesised under addition of different fine filler materials. The material properties were measured after hardening and burning; especially strength, porosity and shrinkage. The phase transformation after burning was measured by X-ray diffraction and quantified
A1698 – Thermal and SO2 adsorption properties of some clays from Turkey
Thermal and structural properties of three clays (sepiolite and two kaolinites) from Turkey were studied by thermal analysis (TG–DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR), and surface area measurement techniques The adsorption of sulfur dioxide (SO2) gas by these clays was also investigated. SO2 adsorption values of K1, K2, and S clay samples were measured at 20°C and pressures up to 106 kPa. Sepiolite sample (S) primarily consists of pure sepiolite, only dolomite present as accompanying mineral. Both kaolinite samples, K1 and K2, mainly contain kaolinite as the major clay mineral and quartz as impurity. In K2 sample, muscovite phase is also present. Simultaneous TG–DTA curves of all clay samples were obtained at three different heating rates 10, 15, and 20°C min-1 over the temperature range 30–1200°C. It was found that the retention value of SO2 by S clay (2.744 mmol/g) was higher than those of K1 (0.144 mmol/g) and K2 (0.164 mmol/g) samples.
A1670 – Residual strength properties of sodium silicate alkali activated slag paste exposed to elevated temperatures
The residual compressive strength behavior of alkali activated slag paste (AASP) after temperature exposures up to 1,200°C was investigated. Strength loss of approximately 60% occurred between 100 and 200°Cand a further strength loss in the order of 30% at 800°C. Total loss of strength occurred at 1,200°C. Thermogravimetric studies (TGA/DTG) verified AASP contained no Ca(OH)2 which governs the chemical mechanism of strength loss for ordinary Portland cement (OPC) and blended slag cement pastes. However, the TGA results showed that AASP
had a higher water loss than the other binders between 100 and 200°C and higher thermal shrinkage as indicated by the dilatometry studies. The high thermal shrinkage led to a differential thermal shrinkage gradient within the AASP and induced micro stresses and cracking which was more prominent for larger samples. Differential thermal shrinkage caused by the higher thermal shrinkage of the AAS material was concluded as the mechanism which gives lower residual strength in AASP compared to OPCP.
A1641 – Sulfur dioxide Plasma Treatment of the Clay (Laponite) Particles
Low temperature plasma treatment of the inorganic clay (Laponite) using sulfur dioxide (SO2) as a process gas was carried out in order to graft the functional groups containing sulfur and oxygen (sulfonic acid groups) onto the inert clay surface. Conditions for SO2 plasma modification were optimized by the measurement of the sulfur content as a function of the plasma power, gas flow rate and treatment time. It was found that the sulfur content increased with the increasing of the plasma power as well as the treatment time. Optical emission spectroscopy was presented in order to control the plasma phase and to characterize the different excitation processes of atomic species in SO2 plasma under different discharge conditions. X-ray diffraction spectrometry, X-ray photoelectron spectroscopy, FTIR and thermal analysis measurements of grafted Laponite powder completed the characterization.
A1530 – Study of the hydration of CaO powder by gas–solid reaction
Hydration of CaO powders by reaction with water vapor has been studied in isothermal and isobaric conditions. Experimental tests were performed within the temperature range of 70 °C–420 °C and with a water vapor pressure from 5 to 160 hPa by means of a thermogravimetric device. Two powders, exhibiting slight differences in their physical properties, were studied. However, for one of the powders and under some temperature and pressure conditions, the reaction is not complete. The difference of behavior between both CaO powders was interpreted by considering the effect of the morphological properties on the mechanism of growth of Ca(OH)2.
A1512 – On the hydration of water-entrained cement–silica systems: Combined SEM, XRD and thermal analysis in cement pastes
The work described in this document focuses on the hydration of low water and low porosity SF-modified cement-based materials. The hydration of the clinker compounds was followed by X-ray diffraction (XRD), differential thermal analysis (DTA) and also by means of the thermo-gravimetric technique (TGA). This study was performed in three systems, each with a different composition namely a plain cement paste, a silica fume (SF)-modified cement paste and a water-entrained SF-modified cement paste with superabsorbent polymers (SAPs). In addition to the previous experiments, the microstructure of the systems was accessed by means of the scanning electron microscopy technique (SEM). This was primarily done with the purpose of supporting some ideas that have emerged when determining the hydration of these complex systems using the former techniques. However, in this manuscript only the results found through the TGA/DTA technique will be shown. Thus, in respect to the quantification of the CH phase developing in the system, the results taken by the TGA/DTA technique enable a more feasible description of the hydration of low water and low porosity SF-modified cement systems, including systems with water-entrainment by superabsorbent polymers. The results show that for cement-based materials with the physical nature of the systems that have been studied in this work, the pozzolanic activity is limited due to lack of water and/or space to accommodate additional hydration products, and as a consequence, a surplus of silica fume is to be found in the mature material. Due to either physical or chemical constraints, the system is not able to fully convert the calcium hydroxide into calcium silicate hydrate during the first month of hydration in sealed conditions. Additionally, in systems with water-entrainment by means of superabsorbent polymers, it is possible to observe the internal curing activity being promoted by this addition, which is translated by enhanced hydration of cement reactants. A model has been constructed from the empirical knowledge developed on the previous framework, which may be used in further research activities to study different formulations of SF-modified cement systems and also water-entrained cement-based systems
A1139 – Effect of polysaccharides on the hydration of cement paste at early ages
This work deals with the relative efficiency of polysaccharides and their influence on cement hydration. Several parameters such as the
structure, concentration, average molecular weight, and soluble fraction value of polysaccharides were examined. Cement hydration was
monitored by isothermal calorimetry, thermogravimetry (TGA), and Fourier transform infrared (FTIR) spectroscopy. Results clearly show
that retardation increases with higher polysaccharide-to-cement weight ratio (P/C). Low-molecular-weight starch showed enhanced retarding
effect on the hydration of cement. The retardation effect of polysaccharides is also dependent on the composition of cement.
A0927 – Study of rehabilitation mortars: Construction of a knowledge correlation matrix
In old building rehabilitation practices, the gathering of full knowledge on used mortars is the most difficult task due to their complexity and
variability. At the same time, this necessity of knowledge is critical, since the rehabilitation work must guarantee physical, chemical and
mechanical compatibility between former and restoration mortars, not relinquishing aesthetic details. However, the characterization of old mortars
can be a very complex process, since it involves different techniques and potentially controversial outcomes.
In this work, several mortars were prepared and characterized, in order to improve knowledge that will facilitate the further choice of a suitable
material to replace any old mortar. Analytical techniques like XRD and DTA/TGA were used in the determinations of chemical compositions, and
physical properties determinations (apparent density, open porosity, compression strength, flexural strength, elastic modulus) were important to
understand the mechanical behaviour and durability and to relate it with the prepared formulations composition.
A0794 – Modification of cement hydration at early ages by natural and heated wood
Heat treatments of wood are widely used for the reduction of wood swelling and dimensional instability of wood-cement composites.
The effect of natural and heated wood on the hydration of cement at early ages was investigated by isothermal calorimetry, thermogravimetry
(TGA) and Fourier transform infrared (FTIR) spectroscopy. The addition of wood strongly delays and inhibits the hydration of
the silicate phases. Consequently, the amount of portlandite is lower in composites than in neat cement. Approximately 30% of the inhibition
of portlandite precipitation is due to an increase of calcium carbonate content in cement paste. The absorption of a part of water
by wood produces a decrease in gypsum consumption. Nevertheless, the ettringite formation is not significantly affected since a diffusion
of sulfate ions from wood occurs.
A0637 – Dispersive surface properties of glass-ionomer cements determined by inverse gas chromatography
The surface properties of several glass-ionomer cements (GIC), restorative dental materials, (GC-Fuji, Chemadent G-J,
Ketac Fil and Ketac Molar) were investigated for the first time by means of inverse gas chromatography. This method enables
characterization of surface activity in dispersive (non-polar) and acid-base interactions. The ability of the surface of glassionomers
to participate in dispersive interactions was expressed by the use of the dispersive component of surface free energy gds
.
This parameter was determined with satisfactory precision, meaning that the values of gds
can be further used in the discussion of
the influence of the type of GIC, its preparation and the storage time on the surface properties. The greatest capacity for
dispersive interactions was revealed by Ketac Molar and the lowest by GC-Fuji. Dispersive interactions in the surface activity of
glass-ionomers increased with increasing storage time after cement preparation.
A0527 – Immobilization of heavy metals by calcium sulfoaluminate cement
Two types of calcium sulfoaluminate cement containing 20% and 30% phosphogypsum, respectively, were investigated for their ability in
hazardous waste stabilization. Fourteen series of pastes were prepared, each containing the following soluble salt: Na2CrO4I4H2O;
Na2Cr2O7I2H2O; CrCl3I6H2O; Pb(NO3)2; Zn(NO3)2I6H2O; ZnSO4I7H2O; and CdCl2I5H2O. The level of pollution was 0.069 mol of heavy
metal per Kg of cement.
The study has been carried out by means of X-ray diffraction, thermal analysis, scanning electron microscopy, mercury intrusion
porosimetry, electrical conductivity, and leaching tests. Very good retention of lead, cadmium, zinc and trivalent chromium is observed. The
retention of hexavalent chromium depends upon the nature of the binder: the cement containing 20% gypsum develops the best behaviour.
This is explained by the microstructure of the hydrated paste: in the paste containing 30% gypsum, delayed ettringite precipitates and
damages the hardened paste.
A0507 – Determination of carbonation profiles in non-hydraulic lime mortars using thermogravimetric analysis
The carbonation profile of material taken at various depths in a lime mortar specimen has been determined at different times from manufacture using a novel, high-speed thermogravimetric analysis (TGA) method. While conventional phenolphthalein staining suggests a sharp boundary between carbonated and non-carbonated regions, the new TGA technique shows that up to 15% (w/w) of portlandite remains uncarbonated at the exterior of the mortar and that the extent of carbonation declines linearly over up to 15 mm into the interior. The technique demonstrates the possibility of identifying the presence of Liesegang patterns by measuring variations in the concentration of Ca(OH)2 through the depth profile.
A0477 – Thermal analysis of heritage stones
Many of Sydneys heritage buildings and monuments were built as a result of the first European settlement in the 1800s. These buildings not only display the richness of the Australian culture, but also capture the architectural and historical values of its past. Although many of these buildings still appear to be strong and sound, many signs of deterioration have been detected in recent years. Conservators from various disciplines such as science, architecture and engineering are working closely together to develop suitable solutions to stop or at least slow down the degradation process of these precious buildings. This study demonstrates the usefulness of thermal analysis in determining the weathering mechanisms of marble and sandstone taken from two of Sydneys landmarks, the Captain Arthur Phillips Monument at Sydneys Botanic Gardens and Sydneys St Marys Cathedral. This paper reports the findings of the weathering behaviours of both marble and sandstone samples determined using thermal analysis techniques.
A0332 – The effect of C3S on the early hydration of C3A.
The hydration of C3A, C3S and C3A+C3S mixtures was examined by thermogravimetry, differential
thermogravimetry and ealorimetry. The results showed the early hydration (15 min) of
C3A+C3S is of two types: If the content of C3S<40%, then C3A hydrates as it does alone, but if
the content of C3S>40%, then the hydrate with the lowest temperature and the cubic one do not
appear together up to 15 min.
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