The influence of SO3 content of portland cement on the creep and other physical properties of concrete

It is shown that the creep of concrete is very sensitive to the SO₃ content of cement. Examples are given in which creep doubles when SO₃ is reduced from 3.7 to 1.6%. The SO₃ requirement for minimum creep is high, and can exceed 4.0% even when the C₃A¹ and alkali contents of the cement are low to medium and fineness is moderate. It is also demonstrated that the dependence of creep on the SO₃ contents of the cement does not vary with the duration of the creep test. Compressive strength to 1 year, modulus of elasticity, drying shrinkage and 3-year expansion in water were measured and the relationships between these properties of concrete and the SO₃ content of cement were determined.     

Studies on delayed ettringite formation in heat-cured mortars: II. Characteristics of cement that may be susceptible to DEF

Expansions of mortar bars, stored over (but not in) water after simulated steam curing to 85 °C, were related to certain cement compositional parameters. The relationship is expressed in the form of a “delayed ettringite formation (DEF) index.” The DEF index is computed as the joint product of the SO₃/Al₂O₃ molar ratio of the cement, the sum of its SO₃ and Bogue C₃A percentages divided by 10 and the square root of the alkali content expressed as equivalent % Na₂O. The mortars studied were made with 18 different cements, prepared from a set of six representative clinkers by incorporating Terra Alba gypsum to total SO₃ contents that were 1% below optimum, at optimum and 1% above optimum (as defined in ASTM C 563). Measurements of expansion were recorded at intervals for up to 1400 days. Severe cracking and prominent DEF-induced expansions were observed in mortar bars derived from four of the six ‘oversulfated’ cements and lesser expansions from three of the six cements prepared at optimum SO₃ contents. No expansion was found for cements of DEF index below a threshold value; above this value expansions were approximately proportional to the difference between DEF index and its threshold value. The relationship confirms the significance of all three compositional parameters making up the index, e.g., the SO₃/Al₂O₃ molar ratio, the joint contents of SO₃ and C₃A, and the alkali content, in influencing the extent of DEF-induced expansion. In these measurements, the apparent pessimum effect for SO₃ content previously reported by others was not found, although SO₃ contents examined spanned the supposed pessimum value of 4%. Rather, expansion increased with increasing SO₃ content for mortars made with all clinkers exhibiting expansion.     

A 4:1 range in concrete creep when cement SO3 content,curing temperature and fly ash content are varied

It is shown that by varying three factors a 4:1 range in creep after two years can be obtained with concretes that are of the same strength grade and slump, and which attain the specified strength before the load is applied. The factors are the temperature at which the concrete is maintained whilst it gains the specified strength, the SO₃ content of the cement, and whether or not fly ash is used. For a creep range as wide as 4:1 the SO₃ and fly ash contents need only change within the usual limits encountered in practice, and the temperature change need only be comparable with that between winter and summer in a temperate climate. The extreme magnitude of this effect is emphasized by the observation that changes in paste content sufficient to cause slump to drop from 160 mm to zero produce a creep range of only 1.6:1.     

Management of fatty acid methyl ester (fame) wastewater by a combined two stage chemical recovery and coagulation process

A two‐step treatment process for fatty acid methyl ester (FAME) wastewater was carried out at a laboratory scale and ambient temperature. In the first step, FAME was chemically recovered from the wastewater using three types of acid (H₂SO₄, HNO₃, and HCl) at different pH values ranging from 1.0 to 8.0. Optimally, approximately 15–30 mL/L of FAME was recovered when using H₂SO₄ at a final wastewater pH of 1–2.5 and a reaction time of 7 min. The properties of the recovered FAME were within the acceptable ranges for both community and methyl ester standards, except for the viscosity and the quantity of methyl ester. In the second treatment step, the aqueous phase discharged from the first step was adjusted to within the favourable pH range for chemical coagulation by either Al₂(SO₄)₃ (pH 4.5–10) or poly‐aluminum chloride (PAC; pH 2.5–7.0) by the addition of CaO, and then subjected to chemical coagulation with either Al₂(SO₄)₃ or PAC, as appropriate dose at 0–10 g/L. Under optimum conditions, >98.3%, 97.7%, and 99.2% of COD, BOD₅, and oil and grease were respectively removed using Al₂(SO₄)₃ at 2 g/L, whilst that achieved by PAC coagulation (at 1 g/L) was slightly lower at 98.2%, 96.5%, and 98.6%, respectively. The calculated operating cost of this management system was significantly cheaper than those using conventional management procedures, but will require an additional treatment stage such as biological remediation in sedimentation ponds to reduce the pollutant levels to acceptable limits.     

Effect of H3PO4 on the PbSO4/PbO2 electrode in H2SO4 solutions

The influence of H₃Po₄ small additions on the polarization behaviour of the PbSO₄/PbO₂ electrode, in H₂SO₄ solutions of different concentrations, was studied using the microelectrode technique and the coulometric method. The reference electrode was the Hg/Hg₂SO₄/H₂SO₄ electrode. The potentiogram analysis and the coulometric measurements show that the main effect of the H₃PO₄ is the drastic passivation of the electrode processes, within the potential range under study, ie the +800 mV to +1650 mV potential range. The Q_a and Q_c electricity amounts are of about 5–10 times smaller in the H₂SO₄ solution with H₃PO₄ addition, compared with the H₂SO₄ solution free of H₃PO₄ addition. A high increase of the oxygen evolution overvoltage could also be seen. Taking into account the ratio between the H₃PO₄ addition amount, in % (w/o) and the PbO₂ active mass per unit surface area, from the lead acid batteries, we can conclude that the small H₃PO₄ additions do not decrease the capacity of the active mass of the battery, but they hinder the insulator film formation between the active mass and the grid.     

Thermodynamic equilibrium of organic-electrolyte mixtures in aerosol particles

This thermodynamic model describes the phase equilibria of mixtures of electrolytes and organic species in aqueous solutions existing as aerosol particles. The activity coefficient of each species in solution is explicitly related to the chemical composition by treating the (inorganic) ion–water, organic–water and ion-organic interactions with a combined Pitzer–UNIFAC thermodynamic approach. It was parameterized with a new type of multifunctional “meta-group” to better represent measured properties of long-chain monofunctional compounds and short-chain multifunctional compounds. Interactions between dissolved electrolytes and organic species are modeled using the “salting-out” effect of NaCl with organic compounds to predict the hygroscopic growth of particles composed of a salt and diacid. The predicted growth agrees well with laboratory measurements. The presence of 50% malonic acid decreases the growth of pure (NH₄)₂SO₄ by 20% at high relative humidities, while mixtures with 50% succinic acid and 50% glutaric acid cause decreases of 35% and 38%, respectively. The mixing of organic compounds with solubility higher than 4 mol·L⁻¹ with salt can decrease the observed DRH. The mixture of malonic acid and (NH₄)₂SO₄ is predicted to start taking up water at 58%, much lower than the DRH of pure (NH₄)₂SO₄ (80%). Insoluble compounds do not change the observed DRH, while reducing the amount of water taken up. The predicted water contents for internal and external mixtures are largely similar, with small differences predicted for mixtures of soluble organic species. The largest deviation of 10% between the water contents of internal and external mixtures occurs for 50% malonic acid with 50% (NH₄)₂SO₄. For less soluble compounds such as succinic acid and glutaric acid, the two types of growth generally agree within 3%.     

Melt flow and fiber properties of copolyesters

The effect of modifying monomer [sodium 3,5-di(carbonethoxy)benzene sulfonate] contents range from 1.5 to 4.5 mol % on the melt flow and fiber properties of copolyesters (COPET) dyeable with basic dyes was investigated. An Instron capillary rheometer was used to obtain data over shear rates ranging from 10 to 10⁴ s^?1 at 265, 275, and 285°C. The COPET's flow properties as a function of temperature, inherent viscosity, melting point, and modifying monomer content were determined. The drawn fibers annealed in oil and air at 80, 110, 130, 150, 175, and 200°C were studied by means of measurements of shrinkage ratio, crystallinity, birefringence, long period, sonic rate, and static state flexibility of molecular chain. All these showed that the large side group, ? SO₃Na in COPET molecular chains causes an increase in chain rigidity and melt viscosity, and a decrease in crystallinity and orientation.     

Effects of NaCl on the capture of SO2 by CaCO3 during coal combustion

The effects of NaCl on the capture of SO₂ by CaCO₃ during coal combustion were studied using a thermogravimetric analyzer. All experiments were carried out in a flowing air atmosphere at a heating rate of 10, 20 or 30 °C/min. The experimental results showed that more SO₂ reduction was achieved as long as NaCl was added together with CaCO₃ to coal. It indicated that NaCl improved the behavior of CaCO₃ capturing SO₂. NaCl alone reduced SO₂ emission within the range from 300 to 700 °C in the experiments, while the capture of SO₂ by NaCl alone would be reemitted when temperature was raised over 700 °C. Adding sorbents such as CaCO₃ together with NaCl was necessary for a reliable SO₂ reduction.     

Photochemical Oxidation of Sulfur Dioxide in Air in the Presence of Ozone

The photochemical conversion of small amounts of SO₂ into SO₃ and, finally, H₂SO₄ aerosol in an atmospheric air flow with small admixtures of ozone has been studied experimentally. Ozone admixtures increase the SO₂ oxidation rate by a factor of 2.5 to 3.0 when the SO₂ concentration in air is 0.07 mol %. Theoretical estimations predict a stronger effect of ozone. This discrepancy between the observed and calculated data may be due to the flow temperature rise caused by irradiation.     

Structural changes and dyeability of silk fibroin fiber following shrinkage in neutral salt solution

The fine structural changes of Bombyx mori silk fibroin fibers, induced by shrinking with concentrated calcium chloride aqueous solution at elevated temperature were investigated as a function of shrinking rate. Tensile strength decreased and elongation at break increased in the shrinkage range 13–67%, the shape of the stress–strain curve changing from rubberlike to brittle at high shrinkage values (70–90%). The birefringence gradually decreased over the entire shrinking range examined, the curve becoming steep as the shrinkage exceeded about 67%. The behavior of isotropic refractive index (n_iso) closely resembled that of birefringence (Δn) in the shrinking range 13–67%. Beyond shrinkage of 67%, the n_iso showed a tendency to increase, especially for the sample with 80% shrinkage. Dichroism measurements showed that the molecular orientation within the amorphous regions decreased sharply at the beginning of the shrinking treatment, within the range 0–13%, then attained a saturation at about 55%. The position and intensity of the major X-ray diffraction peak at 20.5° remained essentially unchanged regardless of the shrinking treatment. The results of dyeing behavior showed that the saturation value attained by shrunk silk fibers was significantly larger than that of the untreated control sample. Both standard affinity and the heat of dyeing increased slightly for the shrunk silk fibroin fiber, suggesting that a larger number of reactive sites became available for the interaction between dye molecules and fibroin chains. A schematic model is proposed for explaining the relation between structural changes and enhanced dyeability of the silk fibers following shrinkage in neutral salt solution. © 1994 John Wiley & Sons, Inc.     

Effect of dye auxiliaries on the kinetics of advanced oxidation UV/H2O2 of Acid Orange 7 (AO7)

BACKGROUND: The effect of four dye‐auxiliary chemicals, typically employed in acid dyeing, on the performance of UV/H₂O₂ decolouration of the model non‐biodegradable dye C.I. Acid Orange 7 (AO7) was investigated. The initial concentration of AO7 was 0.150 g L^?1, while the concentration of the auxiliary compounds (NaCl, Na₂SO₄, Na₂CO₃ and CH₃COOH) was varied in the range 1–10 g L^?1. RESULTS: The negative influence of the presence of the dye‐auxiliary compounds studied on the decolouration rate of AO7 decreased in the following order: CH₃COOH > Na₂SO₄ > NaCl > Na₂CO₃. Results were quantified in terms of the observed kinetic rate constant, k_obs (s^?1), of AO7 decolouration as a function of dye auxiliary chemical concentration. The decolouration rate of AO7 decreased as the concentration of dye‐auxiliary compound increased in the range 1–5 g L^?1, while higher concentrations had a minor effect. Upon addition of 5 g L^?1 of CH₃COOH, NaCl and Na₂SO₄, the kinetic rate constant decreased by 39%, 30% and 12%, respectively. CONCLUSIONS: It was concluded that the presence of NaCl, Na₂SO₄ and above all of CH₃COOH should be considered in the design of the treatment of real dye‐bath effluents by UV/H₂O₂. Copyright © 2008 Society of Chemical Industry     

The use of GA-ANNs in the modelling of compressive strength of cement mortar

In this paper, results of a project aimed at modelling the compressive strength of cement mortar under standard curing conditions are reported. Plant data were collected for 6 months for the chemical and physical properties of the cement that were used in model construction and testing. The training and testing data were separated from the complete original data set by the use of genetic algorithms (GAs). A GA-artificial neural network (ANN) model based on the training data of the cement strength was created. Testing of the model was also done within low average error levels (2.24%). The model was subjected to sensitivity analysis to predict the response of the system to different values of the factors affecting the strength. The plots obtained after sensitivity analysis indicated that increasing the amount of C₃S, SO₃ and surface area led to increased strength within the limits of the model. C₂S decreased the strength whereas C₃A decreased or increased the strength depending on the SO₃ level. Because of the limited data range used for training, the prediction results were good only within the same range. The utility of the model is in the potential ability to control processing parameters to yield the desired strength levels and in providing information regarding the most favourable experimental conditions to obtain maximum compressive strength.     

Oxidation of SO2 in a Trickle Bed Reactor Packed with Activated Carbon at Low Liquid Flow Rates

In this study, the oxidation of SO₂ on activated carbon (AcC) by using distilled water and air was carried out in a laboratory scale trickle bed reactor (TBR). Distilled water and air containing 1.7 % (v/v) SO₂ were fed co‐currently downward through a fixed bed of AcC particles in a range of 1–7 cm³/s and 10–27 cm³/s respectively. H₂SO₃/H₂SO₄ solutions were the products obtained in the liquid phase. Steady‐state experiments were performed in a column of 0.15 m packing height and 0.047 m column diameter at 20 °C and atmospheric pressure. Experimental reaction rates of this study were compared with those of other studies on the basis of plug flow model of Mata‐Smith given in literature.     

Radiolysis of Fremy's Salt in the Presence of Some Hydrated Electron Scavengers in Alkaline Aqueous Solution

Fremy's salt, ON(SO₃)₂^2?, was irradiated with γ-rays in deaerated alkaline aqueous solutions in the presence of NO₃^?, N₂O. In the presence of N₂O an increase of the G(-ON(SO₃)₂^2? = G from 6.1 to about 6.7 was observed within a limited range of concentration, while with NO₃^? the change is gradual. This is consistent with NO₂ and OH produced, respectively, in the reaction of e_aq^? with Fremy's salt, taking place in one-electron-equivalent processes, and with the assumption that pairs of radicals may originate from water molecules.     

Granulation of finely crystalline ammonium sulphate using calcium oxide and sulphuric acid

Two types of finely crystalline ammonium sulphate (particle size distributions: white type 7% 2–3 mm, 45% 1–2 mm, 48% <1 mm; blue type 1% 2–3 mm, 8% 1–2 mm, 91% <1 mm) were granulated by adding calcium oxide and concentrated sulphuric acid using a rotating drum in the laboratory and pilot plant. The granules had satisfactory physical and chemical properties.The granules made in the pilot plant with 25 kg ammonium sulphate, 0.5 kg CaO, 1.26 litres of water and 0.9 to 1.125 litres of 98.5% H₂SO₄ had 80 to 97% of the granules within the size range of 1–3 mm, abrasion resistance of 0.4 to 0.8% <1 mm, crushing strength of 1.4 to 2.3 kg, critical relative humidity of 65–70%, pH 1.8 to 1.9 and N, S and Ca contents of 19, 24 and 1%. The quality of the granules when stored for 6 months alone or blended together with common fertilizers did not change.A glass house trial using barley demonstrated that the agronomic values of 4 prototype ammonium sulphate granules produced in the laboratory were similar to 3 standard granular ammonium sulphate fertilizers.The process of granulation which could easily be adopted in superphosphate manufacturing plants is recommended for plant scale testing.Provisional New Zealand Patent (No 236,025) applied for.     

The electrochemical oxidation of lead in various H2OH2SO4 mixtures—II. Ring-disc electrode study

The rotating ring-disc electrode technique was used to study the generation of soluble Pb(II) species during the anodic oxidation of the lead electrode in various H₂OSO₄ media. The concentration range extended from 0.06 to 10.3 M H₂SO₄. For every concentration it was possible to detect a small cathodic ring current variation which was attributable to the reduction of Pb(II) to Pb. Quantitative measurements of the collection efficiency showed that the small cycle life of the lead-acid battery in 5.6 M H₂SO₄ cannot be ascribed to the dissolution step.     

Application of the Pseudo-Deterministic Receptor Model to Resolve Power Plant Influences on Air Quality in Pittsburgh

A multivariate pseudo-deterministic receptor model was applied to determine emission and ambient source contributions rates of SO₂ and elements from four small coal-fired boilers influencing air quality at the Carnegie Mellon University (CMU) Supersite. The model was applied to ambient SO₂ and particle measurements, the latter, made every 30-min for 10 elements (Al, As, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) during a 12.5-h period on April 1, when winds blew from between 290–330° in which the four coal boilers are situated. Agreement between predicted and observed SO₂ concentrations was excellent (r of 0.92; and their ratio, 1.09 ± 0.22) when 4 emission sources were used in the model. Average ratios of predicted and observed concentrations for As, Cr, Cu, Ni, Pb, Se, and Zn varied from 0.97 ± 0.20 for Cr to 1.07 ± 0.44 for As. Performance indices for these elements were all well within acceptable ranges. Emission rate ratios of various metal species to Se predicted are similar for the three of the coal boilers, but differed substantially for the fourth, as expected for a boiler with minimal particle control technology. All are within the range derived from previous PDRM results and in-stack measurements (except Al) at 7 Eastern U.S. coal-fired power plants. The results suggest that the PDRM approach is applicable to a city encompassing complex topography and may successfully be applied using commonly available meteorological data.     

Adsorption of chlorophyll-a from acetone solution on natural and activated bentonite

The adsorption of chlorophyll-a on bentonite desiccated at 110°C, untreated and acid-treated with H₂SO₄ solutions over a concentration range between 0·25 and 2·50 mol dm^?3, from acetone solution at 25°C has been studied. The adsorption isotherms may be classified as using Giles' classification, as type S (untreated sample and 0·25 mol dm^?3 H₂SO₄-treated sample), type H (0·50 mol dm^?3 H₂SO₄-treated sample) and type L (1·00 and 2·50 mol dm^?3 H₂SO₄-treated samples). This fact suggests that the bentonite surfaces (low, high and medium affinity, respectively) behave in differently relation to the adsorption of the chlorophyll-a molecules. The experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K_f) of the samples; K_f values range from 0·43 mg kg^?1 for the untreated bentonite up to 108·89 mg kg^?1 for the 0·50 M H₂SO₄-treated bentonite. The removal efficiencies (R) have also been calculated and range from 5·71% for the untreated bentonite up to 85·18% for the 0·50 M H₂SO₄-treated bentonite.     

Electrochemical behavior of magnesium alloys AZ91D,AZCe2, and AZLa1 in chloride and sulfate solutions

The influence of Cl⁻ and SO₄²⁻ on the electrochemical behavior of AZ91D, AZCe2, and AZLa1 was studied. For all alloys, there was a current plateau in the anodic polarization curves in Na₂SO₄ solutions. In 0.5% NaCl solution, there was a small current plateau, whereas there was none in the 3.5% and 5% NaCl solutions. This indicated that SO₄²⁻ is less aggressive than Cl⁻. The range of the current plateau decreased with increasing SO₄²⁻ concentration. For all alloys, the high frequency capacitive loop in the Nyquist plots decreased with increasing concentration consistent with the decrease in corrosion resistance with increasing Cl⁻ and SO₄²⁻ concentration.     

Influence of the physical-chemistry properties of an acid-activated bentonite in the bleaching of olive oil

The bleaching process at 90°C of an olive oil from Jaen (Spain) using natural bentonite and bentonite acid treated with H₂SO₄ (over a concentration range between 0.50 M and 5.00 M) has been studied. The bleaching capacities of the bentonite samples were calculated by applying the Freundlich equation to the experimental data points corresponding to the bleaching process. The bleaching capacities (K_F parameter) range from 2.5 × 10^?7 for non-treated bentonite up to 0.85 for 2.50 M H₂SO₄ treated bentonite. The bleaching capacity of the 5.00 M H₂SO₄ treated bentonite (K_F = 0.81) is less than that of the 2.50 M H₂SO₄ treated bentonite.