bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of temperature on the early hydration of Portland cement and blended cements
Authors: Escalante-Garcia J. I. , Sharp J. H.
Published: October 2009

The effect of temperature, in the range 10–60°C, on the early hydration of two Portland cements from Mexico and three blended cements has been investigated by means of isothermal conduction calorimetry. The blended cements were based on the two Portland cements with partial replacement by ground granulated blast furnace slag, GGBFS (60%), pulverized fuel ash, PFA (30%) and blast and a Mexican volcanic ash (22%). An increase in the temperature of hydration brought about initial acceleration of all five cement systems, as indicated by the increased magnitude of the maximum of peak II and shifts to earlier times. There was a clear contribution from the GGBFS to the heat evolution curves of the blended cement incorporating GGBFS, which increased with increasing temperature. By way of contrast, there was no enhancement of the cement hydration in the early stages of hydration in the case of the PFA blended cement, and the appearance of peak II was slightly retarded. The incorporation of volcanic ash had little effect on the initial hydration, but gave an additional peak after peak II, similar to that observed in the GGBFS system. At this stage, the total heat evolved was greater than that in the corresponding neat cement, especially at 20°C. It has also been demonstrated that alkali activation of GGBFS and volcanic ash was readily brought about by NaOH at 40°C. The enhanced activity observed in the Portland cement–volcanic ash system is attributed to activation of the ash by the portlandite liberated during the early hydration of alite.
The formation of ettringite from tricalcium aluminate and magnesium sulphate
Authors: Clark B. A. , Brown P. W.
Published: October 2009

Isothermal calorimetry and X-ray diffraction analyses were used to investigate the hydration of tricalcium aluminate (3CaO·Al2O3) in 0·5, 1·0 and 3·0 M magnesium sulphate solutions. Hydration was carried out isothermally at temperatures ranging from 30 to 80°C. Monosulphate (Ca4Al2(OH)12·(SO4)·6H2O), ettringite ([Ca3Al(OH)6·12H2O]2·(SO4)3·2H2O), gypsum (CaSO4·2H2O) and a hydrogarnet phase (Ca3[Al(OH)6]; C3AH6) were all observed as hydration products. Monosulphate and C3AH6 were the only phases observed for hydration in 0·5 and 1·0 M magnesium sulphate solutions. Ettringite was the dominant crystalline phase after hydration in 3·0 M solution, regardless of temperature. Gypsum was the only other crystalline phase observed after hydration in 3·0 M solutions. Hydration rates are faster than those observed in previous studies using similar sources of tricalcium aluminate and calcium sulphate. This indicates the hydration rate of tricalcium aluminate is enhanced by the presence of magnesium in solution. No crystalline magnesium containing phases were detected, regardless of temperature or magnesium sulphate concentration.
A review of cement–superplasticizer interactions and their models
Authors: Mollah M. Y. A. , Adams W. J. , Schennach R. , Cocke D. L.
Published: October 2009

This paper presents a focused review of cement–superplasticizer interactions. It has been concluded from the survey of the literature that cement–superplasticizer interactions are generally preceded by the adsorption of superplasticizers on the hydrating cement particles. However, the mechanisms of such adsorptive interactions have not been adequately addressed experimentally or discussed in the literature. The reason for this appears to be the lack of a conceptual model that can delineate the results to date and project needed experiments. A charge-controlled-reaction mechanism model involving Ca2+ ions from initial hydration is proposed to explain the adsorption characteristics of superplasticizers and other organic additives and their effects. The calcium ions released by hydration form a bilayer immediately upon contact of water with the cement, which is followed by adsorption of superplasticizer anions on the Ca2+ ion side of the bilayer. The interfacial structures and their influence on electrical characteristics, hydration reactions and phase growth in the hydrating cement are discussed in terms of the proposed model.
Alkali-activated slag: hydration process and development of microstructure
Authors: Wang S.-D.
Published: October 2009

This paper presents the results of an investigation into the hydration process and development of the microstructure of alkali-activated slag. Samples were examined by X-ray diffraction, scanning electron microscope, X-ray microanalysis of energy dispersive spectrum, and solid-state nuclear magnetic resonance. Hydration products have been identified as calcium-silica-hydrate (C–S–H) gel of low Ca/Si ratio, hydrotalcite, AFm phases and CH. It has been found that two types of AFm phase exist, depending on the exposure conditions. The initial AFm phase is formed through the transformation of CH and, upon exposure to air, it transforms into a carbonated form, hemicarbonate. It has been proposed that aluminium plays a key role in enhancing silicate polymerization. Slag compositional effects are discussed on the formation of hydration products and the development of microstructure.
Zinc oxide in Portland cement. Part II: hydration, strength gain and hydrate mineralogy
Authors: Bolio-Arceo H. , Glasser F. P.
Published: October 2009

Soluble zinc salts added to cement mix water are generally agreed to retard hydration. The role of zinc in clinker is, however, less well-established. Experiments are reported on clinker stimulants and real industrial clinker meals, the latter doped with 1·5 wt% ZnO. Contrary to findings in the literature, relatively little zinc goes into solid solution in the main clinker phases: much is present in the interstitial phases as a solid solution based on 6CaO·3ZnO·2Al2O3. Supplementary studies of the CZA system disclose the existence of two ternary phases: C6Z3A2 and C3ZA2. Both are cementitious in combination with Ca(OH)2 or gypsum, or with both. ZnO at 1·5 wt% clinkered in industrial meal, does not affect set times but enhances the rate of strength gain. Zinc remains relatively insoluble, with aqueous Zn concentrations of stimulants not exceeding 2·2 ppm.
Hot acid resistance of polymer-modified calcium aluminate/fly ash/polyphosphate cements
Authors: Sugama T. , Weber L. , Brothers L. E.
Published: October 2009

To confirm the resistance of sodium polyphosphate-modified class F fly ash/calcium aluminate blend (SFCB) cements to an H2SO4 solution (pH 1·6) at 90°C, various different organic polymer dispersions were incorporated into the cements. It was found that acrylic-styrene copolymer (ASC), with a pH ∼4, was the most effective in mitigating acid erosion of the cements. The reasons for making them less susceptible to acid attack are due to the following two major roles of ASC. The first is ASC's chemical affinity for the Ca2+ ions liberated from monocalcium aluminate (CA) and calcium dialuminate (CA2) in the calcium aluminate cement (CAC) reactant, so forming Ca-complexed carboxylate compounds in the interfacial contact zone between ASC and CAC. The other role is related to the coverage of the reaction products by the ASC film and the unreacted CAC and fly ash particles, generating a network structure. These roles significantly restrain the formation of gypsum yielded by the reaction between H2SO4 and CAC. Gypsum is detrimental to the cements because it expands, making them vulnerable to acid erosion, because of its expansion nature. The loss in weight of ASC-modified SFCB cements after exposure for 25 days to hot acid was only 2·6%, compared with 27·3% in unmodified cements after the same exposure time.
Properties of cement compacts produced by isostatic compaction
Authors: Vanis P. , Odler I.
Published: October 2009

This paper describes a method of producing compacts from cement mixes with extremely low water-cement ratios by isostatic compaction. The main advantage of this procedure is the fact that such compacts exhibit a greater uniformity in the degree of compaction than those produced by unidirectional pressing. The resultant strength increases with increasing pressure of compaction and is higher if high-strength, rather than ordinary Portland cement, is used as a starting material. The strength also increases if silica fume or natural wollastonite with acicular crystal morphology is added to the starting mix
Chemical kinetics of C-S-H decomposition in hardened cement paste subjected to elevated temperatures up to 800°C
Authors: Peng G. F. , Chan S. Y. N. , Anson M.
Published: October 2009

To achieve both qualitative and quantitative understanding of the decomposition of hardened cement paste (HCP) at elevated temperatures, X-ray diffraction (XRD) tests were conducted on HCP samples after exposure to various peak temperatures from 400 to 800°C. The kinetic equations of C-S-H decomposition at 600, 700 and 800°C are proposed. The quantitative measurement using α-Al2O3 as a reference phase, revealed that the decomposition of C-S-H started at 560°C but became significant only above 600°C. The C-S-H decomposition rate increased dramatically with temperatures above 600°C. The decomposition of C-S-H influenced the strength loss of high-performance concrete (HPC) exposed to temperatures above 600°C but had little or no effect on the occurrence of explosive spalling. This test result confirms the vapour pressure mechanism for explosive spalling of HPC. It is also postulated that the strength loss of concrete exposed to temperatures below 600°C must be mainly caused by the HCP pore-structure coarsening.
Concrete rheometer
Authors: Struble L. J. , Puri U. , Ji X.
Published: October 2009

This paper describes a concrete rheometer based on the BTRHEOM design and presents equations to compute shear stress and strain rate from the measured values of torque and angular velocity. The influence of the boundary layer at the outer wall of the rheometer on the measured concrete flow behaviour is assessed. Different materials at the wall are shown to have significant effects on the values of yield stress and plastic viscosity, and results show it is reasonable to presume that the boundary layer is paste. It was found experimentally that the height of the gap between the top and bottom plates affects the measured torque and measured strain rate but has little effect on apparent viscosity.
Structural changes during thermal dehydration of ettringite
Authors: Shimada Y. , Young J. F.
Published: October 2009

Changes in crystal structure of ettringite on dehydration in normal atmosphere have been re-examined by means of thermogravimetry, X-ray diffraction, and 27Al nuclear magnetic resonance spectroscopy. Synthetic ettringite crystals were heated at various temperatures up to 200°C for durations of up to 7 h. The ettringite structure maintains some long-range order until the coordination number of calcium changes to 5 by dehydration of twelve water molecules from channels and columns with heat treatment at 70°C. When the coordination number of calcium decreases to 5, the short-range order of the structure is disrupted and ettringite becomes X-ray-amorophous. Subsequently, the rest of the water molecules in the columns and bridging OH groups in calcium polyhedra are removed, essentially destroying the framework of the columns. This is accompanied by changes in the coordination number of aluminium from 6 to 4.
Neural network modelling of the effects of inorganic impurities on calcium aluminate cement setting
Authors: Stegemann J. A. , Buenfeld N. R.
Published: October 2009

Neural network analysis was used to construct models of setting time as a function of mix composition and addition concentration using existing data for calcium aluminate cements. The models were able to represent the non-linear temperature dependency of setting times and generalised from the literature data to find exponential relationships between setting time and addition concentration. An induction time estimated from the results of different types of setting measurements was used in modelling to determine the following ranking of induction times: Ba > Ca ≥ Sr ≥ Mg ≥ K ≈ Na ≥ control ≫ Li and citrate ≥ Br−≫ [Formula: see text] > C1−> control ≈ [Formula: see text] ≥ OH−> [Formula: see text] ≈ [Formula: see text] > [Formula: see text] High variability of the results reported in the literature resulted in a root-mean-square error of 174% for the best model, which may provide a method-independent estimate of the interlaboratory reproducibility for setting time measurement.
Setting of alkali-activated slag cement. Influence of activator nature
Authors: Fernández-Jiménez A. , Puertas F.
Published: October 2009

The objective of this work was to determine the mechanisms that govern the setting times of alkali-activated slag (AAS) cement pastes, as a function of the nature of the alkaline activator used. For this purpose three different activators were used: waterglass (Na2SiO2.nHaOH with a SiO2/NaO ratio equal 1·5), NaOH and Na2CO3. The concentration of all solutions was constant = 3% of Na2O by mass of the slag. The pastes were studied through isothermal conduction calorimetry, FTIR and 29Si and 27Al MAS-NMR. Results indicate that pastes activated with waterglass develop faster setting due to the formation of an initial calcium silicate hydrate. Setting, in pastes activated with NaOH is due to the formation of a more polymerised calcium silicate hydrate. Pastes activated with Na2CO3 show longer setting times due to the initial formation of a sodium calcium carbonate which retard the reaction processes.
Scanning electron micrographs and their interpretation in the context of a theory proposed for the hardening behaviour of cementitious materials
Authors: Abyaneh M. Y. , Keedwell M. J. , Leppard C.
Published: October 2009

The results of scanning electron micrographs (SEM) obtained from samples of Pulverised Fuel Ash (PFA)-lime, PFA-lime-gypsum and PFA-cement mixtures subjected to various curing times are presented and interpreted in the context of a mechanism previously developed for the hardening behaviour of cementitious materials. Additionally energy dispersive X-ray analysis (EDAX) has also been carried out on the same samples. The micrographs suggest that the strength of the materials increase with time, partly as a result of the growth of cementitious materials in places where PFA particles are in contact with each other, and partly due to the needle-like growths which eventually link the PFA particles. Using EDAX it is found that when the beam of electrons is focused on the cementitious material a higher proportion of aluminium, potassium and silicon ions is found compared with that in a more overall field of view. The results suggest that the rate of hardening of these materials would be, in ascending order, PFA-lime, PFA-lime gypsum and PFA-cement.
The kinetics of the hydration of cement, investigated by an electrical resistance method
Authors: Wiegman-Ho L.
Published: October 2009

Various methods of measuring the initial and final setting time of cements have been proposed and widely used. None of these, however, is satisfactory for a more scientific and fundamental investigation of the hydration process, since the hardening process could not be followed continuously. These indirect and empirical measurements led to many misconceptions on the hydration process and on the effect of accelerators and retarders, etc. The measurement of conductance provides a non-destructive and continuous method for studying the hydration of cements. The kinetics can be described by two parameters: an induction period, t0, and one or two first-order reaction rate constants, k and k′, for the decrease of conductance. The influence of additives on both parameters has been studied extensively.
Ceramic fibre-reinforced calcium aluminate/flyash/polyphosphate cements at a hydrothermal temperature of 280°C
Authors: Sugama T. , Weber L. , Brothers L. E.
Published: October 2009

The usefulness was assessed of two ceramic fibres, α-Al2O3 and α-Al2O3/mullite mixture, for improving the toughness of sodium polyphosphate-modified fly ash/calcium aluminate blended (SFCB) cement, which is used for completing geothermal wells. At the hydrothermal temperature of 280°C, the reaction between the α-Al2O3 phase-based fibre's surfaces and silicate in the cement slurry was responsible for the development of a moderate bonding at the interfaces between the fibres and the SFCB cement matrix. This development improved fracture toughness to 2·7 times more than that of non-reinforced cements. In contrast, adding α-Al2O3/mullite mixed phase-based fibres did little to improve the fracture toughness because of the transformation of the mullite into Na-P type zeolite. This mullite → zeolite phase transition was caused by the hydrothermal reaction of mullite with the Na in the cement. This transition generated a strong linkage between the fibres and the matrix; however, it also converted the strong, flexible and tough fibres into fragile, brittle fibres. Correspondingly, cracks generated in the cement composites propagated through the fibres, but not at the fibre/matrix interfaces.
A new leaching test based in a running water system to evaluate long-term water resistance of concretes
Authors: Vernet C. , Alonso C. , Andrade C. , Castellote M. , Llorente I. , Hidalgo A.
Published: October 2009

The results of leaching tests are one of the criteria used to evaluate the performance of cementitious materials for stabilisation/solidification of hazardous wastes. The action of water is of special importance due to its effect on the integrity of the cement solid phases. Likewise, the degraded material originated by the water action may facilitate the transport of toxic components from the material to the environment. Therefore, there is an interest in determining the material behaviour under the long-term action of water in representative conditions of a real storage scenario, in particular where radioactive waste storage times of 300 years or more are needed. During this time, the stabilised waste should maintain its properties. In the present paper a new leaching method to test the performance of concretes for long-term behaviour under natural water interaction is presented. An open system and a system of continuous running of natural water flowing at a fixed rate have been used. The system has been applied to test high- and ultra-high performance concretes for over a year. It gives different results to those previously reported using demineralised water or acid solutions. The method was developed to represent real scenarios in contact with granitic groundwater.
Elastic modulus changes in cementitious materials submitted to thermal treatments up to 1000°C
Authors: Masse S. , Vetter G. , Boch F. , Haehnel C.
Published: October 2009

Three categories of cementitious materials (Portland cement pastes, siliceous and calcareous sand mortars, and microconcretes with siliceous sand and silica fume) were subjected to cumulative thermal treatments at temperatures (T) up to 1000°C. Changes in room-temperature elastic modulus E*(T) of heat treated materials were followed by a non-destructive ultrasonic technique at 10 MHz. Each category exhibits specific changes in E*(T)/E*0 plotted against T, where E*0 was the value before heat treatment, irrespective of the water:binder ratio.
Properties and development of the microstructure in cement pastes modified by a styrene–butadiene co-polymer
Authors: Odler I. , Liang N.
Published: October 2009

This paper considers the effects on properties and texture of adding a styrene-butadiene co-polymer dispersion to Portland cement pastes. In studying the rheology of fresh pastes it was found that their flow characteristics decreased at lower levels of polymer addition, yet improved when the level of polymer added was increased. The rate of hydration was significantly reduced by the presence of the polymer. In the hardened paste the polymer was distributed as a continuous three-dimensional network, interlocked with the cement hydration products. As to the physico-mechanical properties of the hardened pastes, the addition of the polymer – at a constant water/solid ratio – increased the flexural strength and work of fracture of the material and at the same time lowered its compressive strength, modulus of elasticity and hardness.
The influences of ultra-fine powders on the compatibility of cement and superplasticiser with very low water/binder ratio
Authors: Long G. , Wang X. Y. , Xiao R. , Xie Y.
Published: October 2009

The effects of ultra-fine powders such as pulverised fly ash (PFA), granulated blast furnace slag (GBFS) and silica fume (SF) on the compatibility of grade 525 ordinary Portland cement and superplasticiser (DFS-2) are studied in detail. The results indicate that the addition of PFA or GBFS into cement mixture with water/binder ratio of 0·22 can improve compatibility of mixtures and superplasticiser (DFS-2), while adding a large amount of SF into cement mixture will degrade it. At the same time, the influence of PFA, GBFS and SF on the fluidity of paste, as well as on the compactness of paste with very low water/binder ratio, is also investigated.
Effect of superplasticisers on the behaviour and properties of alkaline cements
Authors: Puertas F. , Palomo A. , Fernández-Jiménez A. , Izquierdo J. D. , Granizo M. L.
Published: October 2009

This paper examines the effect of the latest generation of superplasticiser admixtures (based upon vinyl and polyacrylate copolymers) on certain properties and characteristics of alkaline cement pastes and mortars obtained by the alkaline activation of a blast-furnace slag and by the activation of a Class F fly ash. In the case of pastes and mortars derived from the slag subjected to an alkaline activation process, the nature of the admixture affects the activation process and the way in which the strength develops. However, this effect is much less marked in materials that have been obtained from the alkaline activation of fly ash.
Effect of applied hydrostatic stress on the hydration of Portland cement and C3S
Authors: Zhou Q. , Beaudoin J. J.
Published: October 2009

The hydration behaviour of Portland cement and C3S with and without stress applied were studied at water to solid (w/s) ratios of 0·35 and 0·50. A greater degree of hydration and denser microstructure were obtained with hydration under stress at an early stage of the hydration process, normally within 48 h. This observation was confirmed by the determination and comparison of CH content, TGA results, surface area and pore-size distribution of samples hydrated with and without applied stress. Environmental SEM examination provided the evidence that microcracking occurred only in samples hydrated under applied stress. It is suggested that this facilitated the migration of water into the protective layers (around cement grains) that form in the early stages of hydration accelerating the reaction with the unreacted cores of the particles.
Effect of complex admixtures on cement properties and the development of a test procedure for the evaluation of high-strength cements
Authors: Sobolev K.
Published: October 2009

Recent research has shown that a state-of-the-art process for high-performance (HP) cement adds a new dimension to ‘classical’ cement technology. The key idea of the process involves the mechano-chemical activation of cement at the grinding stage. A silica-based complex admixture is used for the activation of the cement imparting high strength and improved durability to mortars and concrete. This paper describes the effect of different complex admixtures on the strength of HP cement. According to the available results, mortars based on HP cement possess a compressive strength of up to 148 MPa. A comparison of alternative evaluation methods helps to recommend the test procedure for HP and high-strength cement.
Hydration of Portland cement in the presence of clay minerals studied by 29Si and 27Al MAS NMR spectroscopy
Authors: Krøyer H. , Lindgreen H. , Jakobsen H.J. , Skibsted J.
Published: October 2009

The effects of the addition of clay minerals on the hydration reactions and kinetics of alite and belite are investigated for a white Portland cement (WPC)–kaolinite (20 wt%) blend and a mixture of 90 wt% WPC and 10 wt% bentonite using 29Si MAS NMR spectroscopy. 29Si MAS NMR spectra, used to follow the hydration from 12 h to one year, demonstrates that the two clay minerals have an accelerating effect on the hydration of both alite and belite. The relative intensities for the resonances from the calcium–silicate–hydrate (C–S–H) phase in these spectra show that addition of kaolinite results in a C–S–H phase that on average has longer chains of SiO4 tetrahedra as compared to the results for pure WPC. On the other hand, addition of bentonite results in a C–S–H with slightly shorter average SiO4 chain lengths. Furthermore, the 29Si MAS NMR spectra demonstrate that the basic structure of the kaolinite admixture is not affected by the hydrating cement and that kaolinite is not consumed during hydration. This observation is supported by 27Al MAS NMR which also shows that the rate of formation of ettringite is very similar for the pure WPC and the WPC–kaolinite mixture. Finally, the 27Al quadrupole coupling parameters and isotropic chemical shift are reported for octahedrally coordinated aluminum in kaolinite.
Chloride diffusion measured by a modified permeability test in normal and blended cements
Authors: Mejía R. , Delvasto S. , Gutiérrez C. , Talero R.
Published: October 2009

Chloride permeability was determined using a modified version of the ASTM Standard Method. A current passing through a mortar was monitored at regular one minute intervals over a 72 h period for each sample and the ionic flux calculated. This RTC (rapid test coefficient) method was used to determine the chloride diffusion coefficient for normal and blended Portland cement mortars containing silica fume, fly ash, natural pozzolan, activated clay, and granulated blast slag, respectively. The RTC method was applied to determine chloride permeability when silica fume is incorporated into cement mixes. Also, the porosity and absorptivity of these mortars and the corrosion activity of embedded reinforced specimens were measured. A good correlation was found between the coefficient obtained by the RTC method and that determined from the increased chloride concentration, and on the other hand, a good correlation was also found between pozzolanic characteristics and this last chemical parameter and/or its direct and indirect related parameters. The proposed method can be used as a quick tool to evaluate chloride diffusion.
Use of lithium compounds to prevent expansive alkali—silica reactivity in concrete
Authors: Berra M. , Mangialardi T. , Paolini A. E.
Published: October 2009

The effectiveness of Li2CO3 and LiNO3 in preventing expansive alkali–silica reactivity in concrete mixes made with two natural siliceous aggregates and different alkali contents was investigated using both the expansion test at 38°C and 100% RH and the ultra-accelerated expansion test in alkaline solutions at 150°C. LiNO3 proves to be always effective while Li2CO3 is effective only when the difference between the concrete alkali content (Lac) and the threshold alkali level of the aggregate (TAL) does not exceed 1.7 kg Na2Oeq/m3 and the concrete mixes are stored at 38°C and 100% RH. The ultra-accelerated test methods proves to be appropriate for determining the effective dosages of LiNO3 in concrete mixes made with different alkali contents. There exists a linear relationship between the effective dosage of LiNO3 in terms of Li2O/Na2Oeq molar ratio and the difference Lac-TAL, indicating a remarkable increase of Li2O/Na2Oeq with Lac.
Concrete carbonation tests in natural and accelerated conditions
Authors: Sanjuán M. A. , Andrade C. , Cheyrezy M.
Published: October 2009

Concrete carbonation is one of the main causes of reinforcement corrosion. Determination of the rate of concrete carbonation can be made by exposing specimens in natural atmospheres; however, as this results in too slow a process, testing is usually made by accelerating the process using atmospheres of relatively high CO2 concentration. No general validation exists on how to extrapolate these testing conditions to real performance. This paper tries to contribute to the understanding of accelerated carbonation testing, by making comparisons between natural and accelerated (5 and 100% CO2) conditions in a set of concretes. The results indicate that accelerated testing changes the ranking of concrete resistance towards carbonation and that therefore, the comparison has to be made among concrete with the same additions. The use of calculation methods (service life models) if properly adjusted with natural tests may be a useful complementary tool. The carbonation velocity, VCO2 derived from the square root law is a very useful parameter to compare concretes in any testing conditions.
On the formation of thaumasite CaSiO3·CaSO4·CaCO3·15H2O: Part I
Authors: Bellmann F.
Published: October 2009

Thaumasite from a geological source was dissolved in distilled water at 8°C. The ionic concentrations in solution were measured after equilibration and a solubility product was calculated. The corresponding Gibbs free energy for the formation of thaumasite from the constituting elements at 8°C was calculated to be −7638 kJ/mol from the solubility product. The obtained datum allows a simulation of the formation of thaumasite in concrete. Results of the simulation are presented in part II and compared to experimental observations in part III of this report.
Fourier transform infrared evaluation of autoclaved cellulose fibre pulps used in cement-based building materials
Authors: Liu B. , Thomas P. S. , Klimesch D. S. , Ray A.
Published: October 2009

Preliminary studies on the effects of autoclaving cellulose fibre pulp used in fibre-cement building materials were conducted by Fourier transform infrared. Autoclaving at 180°C at different times in tap water showed little spectral differences. The use of lime solution under the same condition showed significant spectral differences in the regions of 3020 to 3800 cm−1 and 800 to 1600 cm−1. The former is the region corresponding to O—H stretch where the differences are the result of variations in the hydrogen bonding. The differences in the latter region correspond mainly to C—O stretching modes in COH and the acetal O—C—O—C groups. These results are rationalised in terms of susceptibility of the cellulose fibres to alkaline hydrolysis and oxidative alkaline hydrolysis under high temperature autoclaving conditions. Results from differential scanning calorimetry and environmental scanning electron microscopy also showed similar trends, confirming that only under the adverse alkaline and autoclave environment does the cellulose undergo significant degradation.
Studies on chloride fixing in concrete with lead oxide admixture
Authors: Thilagavathi S. , Das A. , Manoharan K.
Published: October 2009

Day by day the increase in environmental pollution is playing a major role in the corrosion of concrete reinforcement, requiring researchers to focus on its prevention. Among the various corrosives, chloride ions produce major impact by virtue of their small size, high penetrating power, mobility and low activation energy for depassivation. The present research work is aimed at reducing the free chloride content in concrete using lead oxide as an admixture. Different proportions of admixture, varying between 5% and 20% (by weight), with regular increments of 5%, were adopted for concretes with varying curing times (3–28 days). An optimum percentage of chloride reduction was arrived at based on these proportions. The experiments revealed a 13% reduction of free chloride in cement grout and a 35% reduction in concrete with the lead oxide admixture. An increase of 30–60% in compressive strength was also observed for varying curing periods. This admixture, being economical compared with other admixtures such as zirconium oxide and titanium oxide, was found to reduce a higher amount of free chlorides, making it a feasible admixture to adopt. It can be concluded that lead oxide may effectively reduce the free chloride content in concrete, thereby reducing the risk of reinforcement corrosion.
Effect of magnesium and sulphate ions on the sulphate resistance of blended cements in low and medium-strength concretes
Authors: Vedalakshmi R. , Raj A. Sundara , Srinivasan S. , Babu K. Ganesh
Published: October 2009

Structural concrete components undergo degradation when exposed to sulphate-bearing environments. Diffusion of sulphate ions through concrete pores causes the formation of expansive products such as gypsum and ettringite in the internal microstructure of concrete. This chemical change leads to a significant reduction of strength in structural components. In the literature it has been reported that in blended cements, because of the reduction of calcium hydroxide, magnesium sulphate ions directly react with the cementitious calcium—silicate—hydrate (C—S—H) gel and convert this into non-cementititous magnesium—silicate—hydrate (M—S—H) gel. However, in the present investigation it was observed that, in low-strength concrete (20 MPa), blended cements show more resistance than ordinary Portland cement (OPC) because of the pozzolanic and dilution effect of added fly ash and slag. In this concrete, the expansive product, namely gypsum, densifies the porous pore structure and does not cause any cracking. In the case of medium-strength concretes (30 and 40 MPa), the pozzolanic and dilution effects of blended cements are not very significant and hence they did not show any increase in sulphate resistance compared with OPC cement. In these medium-strength concretes because of their pore structure, the expansive products cause micro-cracks. The inferior performance of concretes with blended cements due to magnesium ion attack is mainly attributed to the formation of ettringite and gypsum, as in the case of sodium sulphate, and these cause more micro-cracks in comparison with OPC cement. Thermal analysis also confirms this.
Long term durability at 40°C of ecoefficient belite cement-mortar exposed to sulfate attack
Authors: Guerrero A. , Goñi S. , Lorenzo M. P.
Published: October 2009

The durability of cement-based materials with respect to exterior aggressions is one of the current priorities in civil engineering. Depending on their use, the cement-based materials can be exposed to different types of aggressive environments. For instance, damage to concrete structures in contact with a sulfate and saline environment are of most importance. Belite cements have excellent durability against determined expansive attacks and lower heat of hydration than that of Portland cements. These properties convert belite cements into good candidates for the immobilisation of low-level liquid waste and medium-level liquid waste. In this work, the authors present a long-term durability study at 40°C of a kind of belite cement from coal fly ash class C as alternative raw material. The aggressive was a 0·5 mol/l sodium sulfate (Na2SO4) solution, which is common in some evaporator concentrate solutions of medium-level liquid waste and low-level liquid waste. The attack was evaluated by means of flexural strength changes of mortars over 180 days. Furthermore, the changes in microstructure were followed by mercury intrusion porosimetry and mineralogy by X-ray diffraction.
Factors influencing the properties of a steel slag composite cement
Authors: Zhang T.-S. , Liu F.-T. , Liu S.-Q. , Zhou Z.-H. , Cheng X.
Published: October 2009

To examine the feasibility of a possible application of a steel slag that is locally available in large quantities, for the preparation of steel slag composite cement (SSCC), the effects of the granularity of the steel slag and of varying the amounts of clinker, steel slag, and activators on the properties of SSCC were investigated. An optimal composition, which generated a cement that was comparable with 42·5R cement, was obtained. The hydration products of the SSCC and micro-structure of hardened paste were analysed by X-ray diffraction and scanning electron microscopy. The results show that the 3 day compressive strength of SSCC was increased by 119·7% by the addition of a compound activator. The large amount of hydration products generated in the early hydration period contributed to the significant increase in the early strength of the prepared SSCC.
Very high early strength of ultra-high performance concrete containing nanoscale pozzolans using the microwave heat curing method
Authors: Korpa A. , Trettin R.
Published: October 2009

This paper deals mainly with the application of a microwave heat curing method to ultra-high strength and performance concrete specimens made up of combinations of micro and nanoscale pozzolans. The application of this curing method enables very high early strength, as high as 420 MPa to be obtained after 1 day by a total microwave curing duration of 2 h. In addition it was observed that the achieved strength depended on the kind of nanoscale pozzolan (oxide) used and on the microwave energy, time of treatment and treatment duration. In comparison with the oven curing method this method has the advantages of much shorter curing times and better curing efficiency. The microwave curing of ultra-high performance concrete seems to be very advantageous for applications where extreme concrete strength in very short time is required.
Ahead of the game—masonry dam design in the British colonies 1800–1900, part 1: 1800–1872
Authors: Chrimes Michael
Published: October 2009

British dam practice in the nineteenth century was dominated by the use of earth embankments with puddle clay cores. Theoretical approaches to masonry dam design developed in France in the mid-nineteenth century, therefore had little immediate impact on British practice (although they were commented on by Rankine). However, British engineers working overseas often benefited from advanced academic training, at the military colleges, the East India Company's seminary, Addiscombe, and later the Cooper's Hill College, and made more widespread use of masonry structures. Differing geological conditions, geography and cost all played their part, but the overall impression is one of innovation that at times astounded the UK engineering establishment. This paper chronicles the work of the pioneers of colonial dam design in the context of the history of masonry dams. Part one describes developments owing to the discovery of the ‘rational method’.
An innovative new spillway for Bruton flood storage reservoir
Authors: Pether Rachel , Marsh Peter , Cartwright Paul
Published: October 2009

The Environment Agency implemented a programme of remedial and improvement works at Bruton flood storage reservoir in 2008. As part of the works, an upgrade to the existing spillway was required and this was achieved using a stepped block system designed in accordance with a Construction Industry Research and Information Association special publication. A total of 1869 blocks weighing 900 kg each were needed, presenting a number of challenges, which were overcome through close liaison between the designer, contractor and manufacturer. Despite a tight programme and poor weather conditions over the summer, installation of the blocks commenced in April 2008 and was completed on schedule in September 2008.
British Waterways reservoirs safety works: remedial works for Whitemoor Reservoir
Authors: Spasic-Gril Ljiljana
Published: October 2009

This paper describes the safety remedial works that have been undertaken on five British Waterways reservoirs built in Victorian times. The paper also presents a detailed description of options studied to ensure that the spillway at Whitemoor reservoir can pass the design flood without any threat to the integrity of the embankment.
Queen Mary and King George V emergency draw down schemes
Authors: Philpott Bryn , Oyeyemi Yinka , Sawyer John
Published: October 2009

Thames Water owns a large number of non-impounding reservoirs. These have unusually long embankments with narrow clay cores and gravel shoulders, which could be susceptible to piping failure and erosion. They are typically located in urban areas. Thames Water has therefore reviewed its policy regarding emergency draw down capacity and started an improvement programme on the most critical reservoirs. The Queen Mary and King George V reservoirs are two of these critical non-impounding reservoirs with continuous embankment lengths of 6·3 km and 6·5 km and storage volumes of 30 Mm3 and 12 Mm3 respectively. Following the statutory inspection of these reservoirs, a safety recommendation was made that required a significant increase to the existing emergency draw down capacity of each reservoir. This required Queen Mary reservoir to achieve 0·75 m emergency draw down from top water level within 24 h and King George V reservoir to achieve 1 m draw down in 24 h. Studies instigated as a result looked at various options of achieving the draw down, with the final solution involving the design and construction of twin siphon pipes fitted with submerged discharge valves. It is believed that a number of UK reservoirs may require additional emergency draw down capacity over the next few years, as measures in the interest of safety, defined within the terms of the Reservoirs Act 1975. This paper looks at the options considered before arriving at the final solution and discusses challenges in the design and construction of the schemes.
ICOLD symposium in Sofia
Authors: Hinks Jonathan , Wood Robin
Published: October 2009

The International Commission on Large Dams (ICOLD) holds a conference and annual meeting every three years, including one in Brasilia in May 2009. In intermediate years there is an annual meeting and symposium. The symposium held in Sofia, Bulgaria, in June 2008 was entitled ‘Operation, rehabilitation and upgrading of dams’. A total of 160 papers were published; this article offers comments on a rather subjective selection of those papers. Papers are available on request (within reason) from the first author (hinksjl@halcrow.com).
Engineering ‘the aerodrome of democracy’, Canada 1939–1944
Authors: MacKenzie A
Published: October 2009

The British Commonwealth air training plan was created to address the critical shortage of trained flyers that existed at the outbreak of World War II. As the expansion of existing training facilities in areas likely to be subject to enemy attack was unlikely to be satisfactory, an agreement was reached between Great Britain, Canada, Australia and New Zealand to provide training facilities in Canada. Initial requirements were for 58 airfields, one to be complete by May 1940, 37 by the end of 1941 and the remaining 20 by April 1942. The extent of this civil engineering challenge is highlighted by the fact that, in 1939, the Royal Canadian Air Force possessed only five airfields. However, not only were the original targets achieved, they were surpassed in both scope and time. On completion, 88 ‘main’ airfields were in use; as most of these airfields required at least one ‘satellite’ field with many of the facilities of the main fields, the grand total was 176 airfields. In the words of President Roosevelt, Canada had become ‘the aerodrome of democracy’. As airfields were constructed in every province of Canada, planning and logistical problems were immense. Standardisation of design for airfield layout, prefabrication of components for hangars and other airfield structures, a centralised management organisation and the application of what, today, we would describe as modern construction project management techniques all helped Canada's civil engineers to successfully complete this Herculean task.
St Pancras station: Victorian ‘cathedral of the railways’
Authors: Roberts G
Published: October 2009

Completed in October 1868, St Pancras station was among the last of London's rail termini to be constructed. The superstructure inspired the designers of other railway termini being planned at the time, including those in New York, Glasgow, Manchester and Paris. This paper describes the construction of the terminus and the adjacent Midland Grand Hotel, together with their decline and recent regeneration so as to again become the ‘cathedral of the railways’.
The viscoplastic behaviour of a geogrid-reinforced model wall
Authors: Simonini P. , Gottardi G.
Published: October 2009

The paper deals with the time-dependent behaviour of retaining walls reinforced with polypropylene geogrids and subjected to increasing loads applied to the soil surface behind the wall. The experimental programme involved fully automatic small-scale 1g physical models of a geogrid-reinforced wall. Long-term model tests were carried out using different plate loading rates in order to investigate the time-dependent response of the reinforced walls. The paper presents details of the physical model, testing procedure and principal test results. An analytical interpretation of the time-dependent viscoplastic behaviour using a simple three-parameter time-rate equation is shown to fit the experimental data, and is then proposed to predict the long-term displacements of the reinforced walls.
Finite element parametric study of the behavior of segmental block reinforced-soil retaining walls
Authors: Ling H. I. , Leshchinsky D.
Published: October 2009

Geosynthetic-reinforced-soil retaining walls with modular-block (segmental) facing have gained wide popularity because of their satisfactory performance and aesthetic appearance. A better understanding of the deformation of this wall system requires an analytical tool that is capable of considering the properties of soils, geosynthetic reinforcement, and soil–structure interactions in a realistic manner. In this paper, a validated finite element procedure was used with a hyperbolic soil model for conducting a series of analysis under working-stress conditions. The effects of the length, spacing and stiffness of reinforcement, the width, interaction and connection strength of the modular block, and the backfill and foundation soil properties were investigated. The deformation and lateral stress at the wall face, vertical stress along the base of the wall and the strains developed in the geosynthetic reinforcement are discussed. All design parameters were found to affect the wall performance with a certain degree of sensitivity.
Long-term filtration performance of nonwoven geotextile-sludge systems
Authors: Aydilek A. H. , Edil T. B.
Published: October 2009

A study of the filtration behaviour of contaminated wastewater treatment sludges was conducted. The laboratory portion of the study included a series of filtration tests with different nonwoven geotextiles. Filtration performance of the sludge–nonwoven-geotextile systems was also observed in field test cells by exhuming geotextile samples from the cells after exposure followed by analysis. The results indicated that the sludges could be filtered with nonwoven geotextiles selected on the basis of geotextile permittivity. The standard gradient ratio test did not always reflect the filtration performance, and therefore other clogging ratios should be considered. Two commonly used geotextile constriction sizes, O95 and O50, could not be related to either clogging or piping. Additionally, ratios of geotextile constriction size to soil particle size in the existing filter criteria did not always predict the observed filtration performance.
Analysis of geotextile tube behaviour by large-scale field model tests
Authors: Shin E. C. , Oh Y. I.
Published: October 2009

This paper presents the geotechnical behaviour of geotextile tubes based on the results of two field model tests. The tests were performed on two types of dredged material (sand and silty clay) at the Songdo land reclamation site in the Bay of Incheon, Republic of Korea. The dredged materials were hydraulically pumped into the geotextile tubes by dredging ship. The shape variations of geotextile tubes with the two different dredged materials are also presented. The field test results show that, when dredged sand is pumped in to fill the geotextile tube, the tube drops about 40% in height within 2 days after completion of drainage. By contrast, if the clayey filling material is used, after drainage the height of the geotextile tube reduces by approximately 50% within a month.