Non-evaporable Water Research Articles

ChemInform Abstract: EFFECT OF SODIUM CARBONATE ON THE HYDRATION OF TRICALCIUM SILICATE

AbstractWie Be‐ Stimmungen der Gehalte an freiem CaO, nicht verdampfbarem H2O, an Ca"‐ und OH′‐Ionen in der flüssigen Phase sowie calorimetrische Messungen und Messungen des Zeta‐Potentials und der Druckfestigkeit zeigen, läßt sich die beschleunigende Wirkung von 2% Na2OO3 auf die Hydratationsreaktion von C38 auf Ionenadsorption zurückfuhren.

Effect of Sodium Carbonate on the Hydration of Tricalcium Silicate

The effect of sodium carbonate (2%) on the hydration of tricalcium silicate was studied. Free lime, nonevaporable water content, calorimetric measurements, analysis of the liquid phase for Ca2+ and OH− ions, zeta potential measurements, and compressive strength measurements were made. The accelerating action of sodium carbonate can be interpreted in terms of adsorption of ions. Further, since sodium carbonate is a structure breaker for water, more free water will be available in the presence of sodium carbonate, which may accelerate the reaction.

Properties of portland cement paste reinforced with mica flakes

Results of an investigation of the use of high-aspect-ratio mica flakes in hardened portland cement matrices are reported. Increases in flexural strength by a factor of 2 and in fracture toughness by a factor of 4, depending on matrix porosity, are obtained by the addition of small amounts of mica. The dependence of these properties on matrix porosity is determined and the effect of mica flake addition on matrix characteristics discussed, e.g., porosity, surface area, non-evaporable water content.

Properties of polymer latex-cement composites

The effects of water-cement ratio, air content and heat curing on the properties of polymer latex-cement composites were investigated, using saran, styrene-butadiene and acrylic latexes. Load-deflection curves, modulus of rupture (M.O.R.) tensile and compressive strength, void-cement ratio (v/c) and non-evaporable water content (w n) were determined. The latex had only a small effect on w n. Strenght-v/c ratio curves were found to be dependent on polymer type and content and on defoamer type. For the same v/c ratio, all strength values increased with the increase in saran content up to 18% content by weight. With styrene-butadiene and acrylic latexes there was only increase in M.O.R., but not in tensile and compressive strength. For composites of the same workability, increase in strength values by more than a factor of two could be obtained due to the presence of polymer. Strength-polymer content curves of these composites were interpreted in terms of the strength-v/c ratio curves and on the basis of the effect of polymer latex and defoamer on the v/c ratio of the composite. In certain cases, dry heat curing at 40°C to 60°C was found to have beneficial effects on the strength of the saran composites.

Ettringite formation in compressed expansive cement pastes

Type I expansive clinker pastes of w/c=0.25 were compressed at pressures of 50, 200 and 500 Kg/cm 2. Several parameters of the hardened pastes, measured at various curing ages, were compared with those of the non-compressed (control) pastes. Relative values (α values) were developed to express the changes due to compression in total porosity, non-evaporable water, compressive strength, as well as in specific surface area. Surface area changes are due to changes in the size and subsequent growth of the ettringite crystallites. This work is affected by the available pore space. SEM gave direct evidence in favour of a through-solution mechanism at least beyond one day of hydration.

The hydration of a glass‐ionomer (ASPA) cement

AbstractThe hydration of chemical species formed in the cement‐forming reaction has been studied by measuring the evaporable, and non‐evaporable water contents of a glassionomer cement at various stages in its history. Hydration is accompanied by increase in strength and, as loose water is removed from the matrix, a decrease in plasticity. Hydration is attributed to ionisation of the polymeric carboxylic acid and transfer of metal ions from the glass to the polyelectrolyte.

Effect of calcium chloride on the volume contraction, non-evaporable water content and bound chloride content of hydrated portland cement and blast-furnace slag

The change in volume during hydration, Δv, and the water retained at 105°C at ultimate hydration, w n o, have been measured for cement-calcium chloride-water systems in which the cements consisted of portland cement, blastfurnace slag and mixtures of portland cement and blastfurnace slag in equal parts by mass. The results showed that the quantity of chloride bound in the solid phases increased with the initial concentration of chloride in the aqueous phase but the parameters Δv and w n o for a particular system were independent of the initial chloride concentration in the aqueous phase.

Studies on expansive cement II. Hydration kinetics, surface properties and microstructure

Hydration kinetics were followed by measuring non-evaporable water and free sulphate contents. Surface areas, total pore volumes and the microstructure of the hardened expansive cement pastes are discussed. Nitrogen and water vapour were used as adsorbates in the measurement of the surface areas and pore volumes and the results obtained are compared with each other. Scanning electron microscopy was employed to study the microstructures of the hardened pastes.

Studies of the environmental physiology of tropical merinos

Rectal temperature measurements of tropical Merino sheep taken in the sun during summer indicated that there were high and low temperature groups. Animals of low temperature status (e.g. 39.4°C) also exhibited a low respiration rate (e.g. 110/min) in comparison with their less adapted counterparts (40.0° and 190/min). These differences were greatest when ambient temperatures were high. The repeatability of temperature status was 0.46 (P < 0.01). Animals of folds (+) phenotype had significantly higher rectal temperatures than folds (–) animals (P < 0.05). Shearing caused a marked but transient increase in rectal temperature. Compensatory mechanisms apparently involved an increase in cutaneous heat dissipation and/or a decrease in exogenous heat load. Evaporative water loss (80–115 ml/kg/day) greatly exceeded the non-evaporative water loss (40–65 ml/kg/day) of sheep in metabolism cages. Respiratory water loss could account for only 8–10% of the total daily evaporative water loss. Non-respiratory evaporative water loss (as measured by difference) was c. 75–100 ml/kg/day. There were no striking differences between high and low temperature status sheep in this regard. Measurements of respiratory (2 ml/kg/hr) and non-respiratory (5.5 ml/kg/hr) evaporative water loss made in hygrometric tents suggested that the greater non-respiratory water loss was partly due to a higher rate of loss and partly to a longer period of loss per day. This suggestion was supported by the diurnal patterns of rectal temperatures and respiration rates reported here, though no firm conclusions could be made as to the thermotaxic effect of non-respiratory water loss and thermoregulation of tropical Merinos with varying amounts of wool cover.

Study of C 3A - gypsum - Tl 2CO 3 - H 2O system

Effect of thallous carbonate on the hydration of tricalcium aluminate containing 20% gypsum has been studied using isothermal microcalorimeter. The calorimetric results indicate that the hydration reaction is retarded in the presence of Tl 2CO 3. X-ray diffraction and differential thermal analyses indicate the formation of calcium carboaluminate and CaCO 3. The non-evaporable water content of the samples containing Tl 2CO 3 are found to be lower than those without Tl 2CO 3 for the same intervals of time.

Study of Ca 3SiO 5Tl 2CO 3H 2O system

Effects of various concentrations of thallous carbonate on the hydration of tricalcium silicate have been studied using an isothermal microcalorimeter. The calorimetric results indicate that the hydration reaction is accelerated in the presence of Tl 2CO 3. X-ray diffraction analysis shows that the concentration of C 3S decreases rapidly in the presence of Tl 2CO 3. Differential thermal analysis of C 3S hydrated in the presence of Tl 2CO 3 indicates the presence of CaCO 3. Non-evaporable water content and the degree of hydration of C 3S show that the accelerating action of Tl 2CO 3 is more pronounced only during the early period of hydration. Analysis of the liquid phase in contact with the C 3S paste indicates that the concentration of Ca ++ and OH − ions are changed considerably in the presence of Tl 2CO 3.

Hydration of low porosity slag-lime pastes

Slag-lime pastes of low porosity (water/solid ratio of 0.20) were hydrated from 6 hours to 180 days at 20°C. The kinetics and mechanisms of the hydration process were studied from the results obtained in this investigation. The depth of the hydrated layer on the slag particles is found to be thin indicating that the hydration reaction is very slow. The molar compositions of the formed hydrates could also be calculated from the free lime, nonevaporable water and uncombined slag contents. A high lime product (molar C/S+A ratio of 2.5–2.6) is formed during the early stage of the hydration process, then the molar C/S+A ratio drops to a value of 1.5 and finally rises to a value of 1.7 at 180 days. The surface areas and pore volumes of hydrates were determined from water and nitrogen adsorption measurements. For water vapor adsorption, the water molecules in the adsorbed phase seem to be highly oriented in an ordered array. This effect might be associated with the polar character of water molecule, when adsorbed on an ionic surface like high lime hydrate. The results of x-ray diffraction and SEM observations indicate only the formation of ill-cyrstallised hydration products.

Hydration of Ca 3SiO 5K 2C0 3 system

A thermal analysis study of the effect of various levels of K 2C0 3 upon the hydration reaction of tricalcium orthosilicate, Ca 3SiO 5 or 3CaO· SiO 2, was performed using a Mettler 1 thermoanalyzer. Data obtained by combined differential and gravimetric thermal analyses of nonevaporable water and free-lime contents were used to determine kinetics of Ca 3SiO 5 hydration influenced by the addition of l and 5% K 2CO 3. Attempts were made to study the activation energies of decompositions of hydrates formed by Ca 3SiO 5H 2OCO 2 reaction. Calorimetry, scanning electron microscopy, and energy dispersive X-ray analysis were used to support the model derived from thermoanalytical studies.

Pore structure of hydrated calcium silicates. III. Influence of temperature on the pore structure of hydrated tricalcium silicate

Water vapor adsorption isotherms were obtained for samples of tricalcium silicate hydrated for from 1 hr to 28 days at temperatures of 25, 50, 75, and 100°C. The isotherms were used for determination of the BET and S t surface areas and for calculation of pore volume and surface area distributions in both micropores and wide pores. The analytical modification of the “corrected modelless” method was used in the analysis of the wide pores. Micropores were analyzed by the “MP method” using the t-curves of Mikhail and co-workers. At early stages of hydration both the amount of nonevaporable water and the surface area of the samples, per unit of nonevaporable water, increased with the temperature. However, after froml to 3 days, the samples hydrated at lower temperatures had higher nonevaporable water contents and surface areas. The rate of hydration decreased rapidly and, for samples hydrated at 75 and 100°C, the reaction had apparently ceased in less than 28 days. Results of micropore and wide pore analysis were in line with the above findings. However, due probably to the simultaneous occurrence of micropore filling and capillary condensation, no micropores were detected in some of the samples.

Studies on a Method to Determine the Amount of Granulated Blastfurnace Slag and the Rate of Hydration of Slag in Cements

A method of quantitative determination of granulated blastfurnace slag not only in unhydrated slag cement but also in hydrated paste as an unreacted part was established by using a salicylic acid, aceton-methanol solution. In this solution slag hardly dissolves, but most of the hydrated slag, clinker minerals and their hydrates dissolve. Utilizing this principle, with some corrections if necessary, it is possible to determine the amount of unreacted slag.The experiment to determine the amount of unhydrated slag on the hydration of various types of slag cement pastes were carried out.The amount of unreacted slag contained in these cement pastes was determined by using the salicylic acid, aceton-methanol solution. The accuracy of this measurement was found to be satisfactory. Unreacted C3S was quantified and the hydration products were detected by X-ray diffraction. Non-evaporable water, free Ca(OH)2, and free CaSO4 were also determined by chemical analysis, and the hydrated phases were observed under a microscope.The chemical compositions of the products and the rate of reaction of each component such as slag, C3S and CaSO4, and the depths of the reacted layer on the particles of slag and C3S were calculated from the experimental data.In every type of slag cement, the rate of reaction of slag contained was unexpectedly slow. Further, after hydration for about 3-7 days, the rate of reaction of slag and C3S showed a remarkable decrease.