bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of large steelmaking slag blocks using a new carbonation process
Authors: Isoo T. , Takahashi T. , Okamoto N. , Fukuhara M.
Published: October 2009

Porous slag blocks (1 m3) were produced by carbonation of steelmaking slag over a period of 12 days. The compressive strength and bulk density of the blocks were 18·4 ± 3·3 MPa and 2·4 g/cm3, respectively. To make a large block, the optimum amount of water and bulk density of the compact were 5·3–6·3 mass% and 2·30–2·37 g/cm3, respectively. The carbonation reaction occurred homogeneously in the blocks, and the amount of CO2 that reacted with the slag was approximately 6 mass% at all depths from the surface of the block. When left exposed to various weather conditions for 1 year, the blocks showed no cracks or destruction.
Hydration of high alumina cement in the presence of alkalis
Authors: Fernández-Carrasco L. , Blanco-Varela M. T. , Puertas F. , Vázquez T. , Glasser F. P. , Lachowski E.
Published: October 2009

Some degradation processes in aluminous cement concretes are related to the presence of alkalis contained in aggregates or other external sources. Carbonation of aluminous cement in the presence of alkalis is sometimes called ‘alkaline hydrolysis’ and has been described by some authors as a catalytic-like process which leads to the total destruction of the affected element (concrete). The minimum parameters required for this hypothetical alkaline hydrolysis to occur have been established. However, despite several attempts made in specialized laboratories, the process has not yet been proven. The role played by K+, in particular, is still unknown. This paper attempts to investigate the hydration process of aluminous cement in the presence of high concentrations of K+ (1 and 3M). The influence of reaction temperature in the evolution of phases and the resistant development is also investigated.
Effect of solvent exchange on length change and creep of D-dried hydrated C3S paste
Authors: Tamtsia B. T. , Beaudoin J. J.
Published: October 2009

The results of a study on creep of D-dried hydrated C3S paste after exchange of water in saturated samples with organic solvent are presented. Length and mass changes were also measured when saturated C3S paste prepared at a water-solid ratio of 0·4 was immersed in both methanol and isopropanol. A differential thermogravimetric technique was used in order to determine the effect of solvent treatment on dehydration of C3S paste, and its correlation with pore structure, modulus of elasticity and microhardness. Methanol and isopropanol exchanges prior to drying reduce the magnitude of creep in the dry state, suggesting an irreversible interaction of solvent with C-S-H.
Nanostructural investigations of hydrating cement pastes produced from cement with different fineness levels
Authors: Häußler F. , Hempel M. , Baumbach H. , Tritthart J.
Published: October 2009

Small angle neutron scattering (SANS) represents a powerful tool for the characterisation of the inner structure of technically relevant porous materials, e.g. hydrating cement pastes. Various parameters can be obtained by this non-destructive method, allowing repeated measurements as well as long term investigations, such as particle size distribution, specific inner surface, the scattering curve parameter A(2), etc. The latter describes the power law behaviour and can be correlated with fractality. It was shown that the observation window (size range of observable structures) can be modulated by the choice of the SANS instrument (observable Q-range). This paper describes and discusses the results of SANS investigations to study, first, the time dependent behaviour of the microstructural changes within the first 68 days of hydration, i.e. the scattering curve parameter A(2), and second, the influence of the different granulometric characteristics, i.e. particle size distribution of the pastes after one year of hydration. The time dependent changes (a) of the specific inner surface and (b) of the scattering curve parameter A(2) were quantified.
Investigation of utilization of amorphous silica residues as supplementary cementing materials
Authors: Wang L. , Seals R. K. , Roy A.
Published: October 2009

This paper presents the results of a study on the use of amorphous silica (AS) residues as supplementary cementing materials. Standard ASTM tests on setting time and compressive strength development of cement paste and mortar with up to 30% AS residues were carried out. With increasing amounts of AS residue, the setting time of the pastes shortened and the compressive strength of the mortar increased at all ages. The hydrated phases in pastes were determined using X-ray diffractometry and scanning electron microscopy. Observations indicated that Ca(OH)2 decreased or disappeared and C-S-H gel appeared in large quantity at early ages due to the addition of AS residue. The results obtained from the research confirmed that AS residue has a remarkable pozzolanic activity. It can be used as a supplementary cementing material and will significantly improve some basic properties of cement.
OPC hydration with highly alkaline solutions
Authors: Martinez-Ramirez S. , Palomo A.
Published: October 2009

Hydration of an ordinary Portland cement (OPC) with highly concentrated alkaline solutions has been carried out. Two different alkaline solutions were used: NaOH (10 M) and Na2CO3 (3·8 M). Mineralogical composition of the compounds formed after hydration process were determined by FTIR; XRD; DTA/TG. Soluble salts in water and in methanol–salicyclic acid were extracted and the amount of sodium fixed by the CSH gel was deduced. The main conclusion of this work is that if high concentration of NaOH is present in the hydrating solution, CSH gel breakdown is produced. Additionally, it has been showed that gypsum reacts with sodium producing Na2SO4. Finally, in the carbonation process a calcium±sodium carbonate is formed.
Effects of silica reactivity on the nature and formation of Al-substituted 1·1 nm tobermorite
Authors: Klimesch D. S. , Ray A. S.
Published: October 2009

The effects of the reactivity of the silica source on the formation and morphology of Al-substituted 1·1 nm tobermorite in a hydrothermally treated CaO-Al2O3-SiO2-H2O system were studied. Colloidal silica and fine quartz were used as the silica source and gibbsite, containing only octahedrally coordinated Al, was the aluminous source used in this investigation. From a combination of solid-state 27Al MAS NMR, XRD, DTA-TGA and SEM, unequivocal evidence can be found that, with increasing silica reactivity, tetrahedrally coordinated Al in Al-substituted 1·1 nm tobermorite prevails over octahedrally coordinated Al species. Reaction sequences in this system as a function of the reactivity of the silica source are presented.
Influence of chemical and phase composition of mineral admixtures on their pozzolanic activity
Authors: Shvarzman A. , Kovler K. , Schamban I. , Grader G. S. , Shter G. E.
Published: October 2009

The influence of the chemical and phase composition of different mineral admixtures on pozzolanic activity was studied. Local kaolin clay, activated kaolin clay, porcellanite, activated porcellanite, pumice, fly ash, silica fume and ground quartz were used as components of blended binders for various mortars. Thermal treatments were performed as a means for activation of the minerals. The phase transformations during heat treatment were studied by X-ray diffraction services (XRD) and differential thermal analysis/thermogravimetric analyses (DTA/TGA). The pozzolanic activity of these materials as a function of heat treatment parameters was investigated.
Activated fly ash cements: tolerable limit of replacement for durable steel reinforced concrete
Authors: Saraswathy V. , Muralidharan S. , Thangavel K. , Srinivasan S.
Published: October 2009

At present the utilisaton of fly ash in cement and concrete in India is very minimal. Therefore, enhancing the activity of fly ash is the critical key to large scale applications. Physical, thermal and chemical activation methods have been effected and their performance characteristics tested by aggressive macro cell corrosion technique. The salient features of the investigations were: steel embedded in ordinary Portland cement (OPC) and unprocessed fly ash incorporated cements suffered severe corrosion under macro cell corrosion conditions. But OPC containing treated fly ashes improved the corrosion resistant properties to a greater extent. Chemically treated fly ashes showed superior performance when compared to thermally treated and physically treated systems. The tolerable limit of replacement level for various treated fly ashes under aggressive macro cell corrosion condition is found to be 20%–30%. Under 30% replacement level, chemically activated fly ash (CFA) system showed lowest corrosion rate, highest durability factor and lowest macro cell current under accelerated macro cell corrosion conditions.
Hydration of calcium sulfoaluminate cement at less than 24 h
Authors: Zhang L. , Glasser F. P.
Published: October 2009

Calorimetry, X-ray diffraction, scanning electron microscopy, microprobe and porosimetry were used to investigate hydration processes occurring at 25°C, 55°C and 85°C for commercial calcium sulfoaluminate (CSA) cement during the first 24 h. CSA cement pastes harden through the formation of an initial ettringite skeleton and its subsequent infilling by mixtures of ettringite, AFm and C-S-H. At low water/cement ratios these yield a dense, rather featureless paste. The formation rate of ettringite is significantly increased at elevated temperatures. A ‘shrinking sphere’ model is proposed to explain the competitive kinetics of hydration processes with formation of inner and outer products which are shown to differ significantly in mineralogy.
Acid-resistant polydimethylsiloxane additive for geothermal well cement in 150°C H2SO4 solution
Authors: Sugama T. , Brothers L. E. , Weber L.
Published: October 2009

The resistance of sodium polyphosphate-modified fly ash/calcium aluminate blend (SFCB) geothermal cement to H2SO4 solution (pH 1·2) at 150°C is enhanced by incorporating an emulsion of silanol-terminated polydimethylsiloxane (PDMS) into slurries. The crystalline phase composition of both 150°C-autoclaved PDMS-modified and unmodified cements consisted of three hydration reaction products: hydroxyapatite (HOAp), boehmite, and Na-P type zeolite; one carbonation product, calcite; and three unconsumed reactants: monocalcium aluminate, perovskite and quartz from calcium aluminate cement and fly ash. When unmodified cement was exposed for 20 days to hot acid, its surface was covered with the crystalline bassanite (CaSO4:1/2H2O) phase as the acid corrosion product of cement. Bassanite was formed not only by reactions between H2SO4 and calcite or monocalcium aluminate, but also by reaction of HOAp with acid. In contrast, PDMS protected the cement against acid corrosion in two ways: it considerably reduced the formation of calcite and it abated the rate of reaction of HOAp with acid.
Fingerprinting of South African cement clinkers and gypsum as a tool for cement identification purposes
Authors: Potgieter J. H. , Potgieter S. S. , McCrindle R. I. , Tamas F. D.
Published: October 2009

The final composition of cement is of great importance for both the manufacturer and the consumer, since the behaviour of the cement and its application depend largely on it's composition. The composition of cement in turn, depends heavily on the raw materials, the geological origin thereof and the manufacturing process. In previous research, the major element composition of cement has been well-characterised, but the minor and trace element composition in many cases has not. This investigation is an attempt to analyse some of the materials comprising cement, cement clinker and gypsum, for a suite of trace elements that will provide a unique fingerprint of the final product. It was found that for both the clinker and the gypsum a suite of trace elements can be successfully employed to uniquely characterise the materials. The contribution of such a fingerprint is that it can provide valuable information in the case of a forensic analysis for discrimination purposes and also predict the behaviour of these species with regard to their immobilisation in a cementitious matrix.
Early age strain recovery of hardened cement paste—microstructural factors
Authors: Beaudoin J. J. , Tamtsia B. T.
Published: October 2009

The total strain and strain recovery-time response of hardened cement paste subjected to a sustained load was followed using impedance spectroscopy. An immediate increase in the high-frequency arc diameter on removal of the load was interpreted in terms of microstructural behaviour. The nature of the strain recovery characteristics was observed to be strongly dependent on the water=cement ratio. Aspects of a strain recovery mechanism based on readsorption of water on unloading are discussed.
Corrosion resistance of alkali-activated slag cement
Authors: Shi C.
Published: October 2009

This paper examines the corrosion of alkali-activated blast furnace slag cement in pH 3 nitric acid, pH 3 acetic acid, 30% CaCl2 solution and 15% CO2 atmosphere at relative humidity of 52%. ASTM Type I Portland cement is used as a reference. Experimental results indicate that alkali-activated slag pastes are corroded more slowly than Portland cement pastes in these acid and salt solutions. Alkali-activated slag pastes are carbonated very quickly during an accelerated carbonation test because of shrinkage cracking, while no carbonation can be detected on Portland cement pastes after 75 days of exposure to 15% CO2 at a relative humidity of 52%. Detailed analyses indicate that all these differences can be attributed to the difference in hydration products in the two types of hardened cement pastes.
A comparative study of steel- and carbon-fibre cement as piezoresistive strain sensors
Authors: Wen Sihai , Chung D.D.L.
Published: October 2009

Carbon-fibre (15 μm diameter) cement is a better piezoresistive strain sensor than stainless steel-fibre (8 μm diameter) cement at a similar fibre volume fraction, as shown by a higher signal-to-noise ratio and better reversibility upon unloading, albeit having a lower gauge factor (particularly under tension). Steel-fibre cement containing 0·36 vol% fibres is a better piezoresistive strain sensor than that containing 0·72 vol% fibres, as shown by better reversibility upon unloading and the higher gauge factor under compression. The difference in performance of carbon- and steel-fibre cement is attributed to a difference in piezoresistivity mechanism.
Influence of silicate ratio and additives on the sulphate resistance of Portland cement
Authors: Moon H.-Y. , Lee S.-T.
Published: October 2009

The role of the silicate ratio in determining the content of calcium hydroxide liberated in the hydration process and the effect of additives on sulphate attack was evaluated. The resistance of Portland cements with varying silicate ratios and blended cements with ground granulated blast-furnace slag (GGBFS) or fly ash (FA) to sulphate attack was assessed by determining the deterioration factor (DF) and length change caused in mortar specimens with immersion to a 5% sodium sulphate solution. Additionally, microstructural investigations were performed by instrumental analysis (XRD, ESEM, EDS, MIP and DTA). Results of this study indicate that the silicate ratio is more influential than C3A content on sulphate attack resistance. The performance of blended cements was better than that of parent cements and is attributed to the lower calcium hydroxide content of blended cements resultant from pozzolanic reaction.
Alkali releases from crushed minerals and thermally activated constituents of metakaolin
Authors: Dow C. , Glasser F. P.
Published: October 2009

Metakaolin is a valuable pozzolanic material. It is obtained by heating kaolin, nominally Al4[Si4O10](OH)8, at 450–800°C. However kaolin from natural sources may be notably impure, even after beneficiation. During heating, essential to convert unreactive kaolin to reactive metakaolin, impurities present in the precursor kaolin may become activated with respect to dissolution in alkaline cement pore fluid. The most important impurities in this context are muscovite and potassium-rich felspar. Potassium felspar and muscovite, heated and unheated, were slurried with Ca(OH)2 and water at ∼22°C for up to 28 days. Significant alkali releases were obtained even from unheated minerals. However, the extent of release increased with increasing calcination temperatures in the range 500–700°C. The results indicate that supposedly ‘inert’ aggregate minerals may become reactive towards cement. In cement–metakaolin mixes, much of the alkali liberated from mineral impurities is probably incorporated into cement solids but the overall effectiveness of metakaolin in decreasing the alkali contents of cement pore fluid is reduced. However, alkali release may also be beneficial: metakaolin may release sufficient alkali to enhance slag hydration in slag–Ca(OH)2–metakaolin blends.
Measurement of the water retentivity of cement mortars
Authors: Carter M. A. , Green K. M. , Wilson M. A. , Hoff W. D.
Published: October 2009

This paper describes techniques to measure how well a soft mortar mix retains water when it is in contact with a masonry substrate. We show that the water retentivity may be characterised by a well-defined and reproducible parameter, the desorptivity. Two methods of measurement are investigated: a capillary suction technique and a pressure cell technique. The pressure cell technique proved to be the better method, capable of measuring the water desorption behaviour of mortars over the full range of pressures which represent the suctions of typical masonry materials. Values of desorptivities of cement/sand, lime/sand and cement/lime/sand mortars are presented. The empirical test to assess the water retentivity of cement mortars included in BS 4551 is evaluated.
Effects of a washing pre-treatment of municipal solid waste incineration fly ash on the hydration behaviour and properties of ash—Portland cement mixtures
Authors: Mangialardi T.
Published: October 2009

The effects of a washing pre-treatment of municipal solid waste incineration (MSWI) fly ash with deionised water on both the physico-chemical characteristics of this material and the hydration behaviour and physical properties of ash—Portland cement mixtures rich in MSWI fly ash (55 wt% of total solids) were investigated in view of a possible reuse of such solidified products as concrete aggregates in the building industry. A four-stage washing pre-treatment was found to be able to convert the raw MSWI fly ash into a material with improved chemical characteristics for its incorporation into cementitious matrices (reduced concentrations of alkali chlorides and sulphates, transformation of metallic species in less reactive forms). As a result, the cementitious mixtures incorporating washed fly ash in place of raw fly ash were found to exhibit better performance characteristics in terms of setting, dimensional stability, compressive strength and environmental quality.
Sodium-silicate-activated slag for acid-resistant geothermal well cements
Authors: Sugama T. , Brothers L. E.
Published: October 2009

This paper evaluates the usefulness of sodium-silicate-activated slag (SSAS) cement for completing geothermal wells containing highly concentrated H2SO4 and some CO2· Using a 20wt% sodium silicate solution (SiO2/Na2O mol ratio of 3·22) as the alkali activator, the SSAS cements autoclaved at temperatures up to 200°C displayed an outstanding compressive strength of more than 80 MPa, and a minimum water permeability of less than 3·0 × 10−5 darcy. The combination of calcium–silicate–hydrate (C–S–H) and tobermorite phases was responsible for strengthening and densifying the autoclaved cement. At 300°C, an excessive growth of wellformed tobermorite and xonotlite crystals generated an undesirable porous microstructure, causing the retrogression of strength and enhancing water permeability. Although all the phases formed in the autoclaved cements were vulnerable to reactions with H2SO4, so depositing bassanite scales as corrosion product over the cement's surfaces, the C–S–H phase played an important role in retarding the rate of acid erosion. Thus, after the uptake of Ca by the H2SO4, Ca-destitute C–S–H preferentially reacted with the Mg from the slag to form the lizardite phase that not only retarded the rate of acid erosion, but also retained the integrity of the cementitious structure. Therefore, SSAS cement has good potential as an acid-resistant geothermal well cement at temperatures up to 200°C.
Tensile behaviour of hybrid fibre-reinforced concrete
Authors: Sukontasukkul P.
Published: October 2009

In this work, the tensile behaviour of hybrid fibre-reinforced concrete (FRC) was studied. Two different fibres, steel and polypropylene, were used to form single and hybrid FRC systems at five different volume fractions (1% to 5%). It was found that the tensile properties of FRC depended mostly on the type, content and selected FRC system. Single type steel fibre-reinforced concrete (SS-FRC) was found to behave in a typical manner, with peak load occurring at a very small deformation followed by a drop of the load to zero with no sign of load recovery. In the case of single type polypropylene fibre-reinforced concrete (SP-FRC) the behaviour was more ductile and presented mostly a double-peak response: a first peak at small deformation and a second peak large deformation. Steel fibres are believed to contribute more to strength whereas polypropylene fibres are believed to contribute to the ductility (i.e. toughness). For hybrid systems (Hy-FRC), it was found that the behaviour was in fact the combined behaviour of steel and polypropylene. The response of Hy-FRC was more balanced in terms of strength (first peak) and post-peak ductility.
On the formation of thaumasite CaSiO3·CaSO4·CaCO3·15H2O: Part II
Authors: Bellmann F.
Published: October 2009

The thermodynamics of the formation of thaumasite in concrete subjected to sulphate attack were investigated in this paper. This second part is intended to perform calculations based on the value of Gibbs free energy that wasestablished in the first part. The impact of phases that can be present in the hardened cement paste on the formation of thaumasite was evaluated by modelling the relevant reactions. It was determined that thaumasite can be formed from a mixture of gypsum, calcite, portlandite, quartz and water. C—S—H phases can also react with gypsum and calcite to form thaumasite. Pure carbon and cement pastes seem to be immune. It is indicated by the calculations that thaumasite can not be formed from a reaction of C—S—H phases with ettringite and calcite. A precipitation of thaumasite is estimated to be possible at very low sulphate concentrations from an aggressive environment, even below those that are specified as moderate sulphate attack.
Alkali-activated fly ash matrices for lead immobilisation: a comparison of different leaching tests
Authors: Palacios M. , Palomo A.
Published: October 2009

The present paper reports on the lead stabilisation capacity of certain new containment systems, in which fly ash from steam power plants is activated (made to set and harden) with high-alkalinity solutions. Lead is immobilised in such systems because it is precipitated as a highly insoluble silicate. Results are reported from various leaching trials conducted to determine the amount of lead fixed by activated fly ash systems. Finally, the nature of the initial fly ash is another factor found to have a significant impact on the effectiveness of lead fixation in these systems.
Electrically conductive cement-based materials
Authors: Chung D. D. L.
Published: October 2009

Electrically conductive cement-based materials are useful for electrical grounding, lightning protection, resistance heating, static charge dissipation, electromagnetic interference (EMI) shielding, cathodic protection, and thermoelectric energy generation. The science and applications of electrically conductive cement-based materials are reviewed. In addition, a comparative study of the effectiveness of various electrically conductive admixtures (discontinuous forms of steel and carbon) for lowering the electrical resistivity of cement shows that the effectiveness decreases in the order: steel fibre of diameter 8 μm, steel fibre of diameter 60 μm, carbon fibre of diameter 15 μm, carbon nanofibre of diameter 0·1 μm, coke powder (< 75 μm) and graphite powder (< 1 μm). For EMI shielding, the effectiveness decreases in the order: steel fibre of diameter 8 μm, coke powder (< 75 μm), carbon nanofibre of diameter 0·1 μm, graphite powder (< 1 μm), steel fibre of diameter 60 μm, carbon fibre of diameter 15 μm, and steel dust of size 0·55 mm. By using steel fibre (8 μm diameter) at 0·72 vol.%, a resistivity of 16 Ω cm and an EMI shielding effectiveness of 59 dB (1 GHz) were attained. The carbon admixtures cause the absolute thermoelectric power to be more positive, whereas the steel admixtures can cause the absolute thermoelectric power to be more positive or more negative. In particular, steel fibre of diameter 60 μm at 0·2 vol.% causes the absolute thermoelectric power to be strongly negative (−63 μV/°C). Moisture loss has no effect on the absolute thermoelectric power, but increases the resistivity.
Correlations between porosity, chloride diffusivity and electrical resistivity in volcanic pumice-based blended cement pastes
Authors: Hossain K. M. A.
Published: October 2009

This paper reports the results of an investigation on the chloride diffusivity of volcanic pumice (VP)-blended hardened cement pastes with varying curing age of up to 1 year. The pastes had 0, 20 and 40% VP as cement replacement and water to binder ratios (W/B) of 0·40, 0·50 and 0·60. The accelerated chloride ion diffusion test was used to calculate the chloride ion diffusion coefficient (Di) of pastes using the Nernst–Plank equation for steady-state condition. In addition, electrical resistivity, mercury intrusion porosimetry, and differential scanning calorimetry (DSC) tests were also conducted. Good correlations were found between Di, total pore volume and electrical resistivity of the pastes. The Di values of VP-blended pastes were within the range of 10−7–10−9 cm2/s. It was also found that blending cement with VP significantly reduced the long-term chloride ion diffusion coefficient and hence increased the long-term corrosion resistance of pastes. This fact was also supported by the presence of lower quantity of Ca(OH)2 and higher quantity of Friedel's salt in the VP-blended pastes as observed from the DSC tests. Pastes with 40% VP showed better performance in terms of chloride ion diffusivity. The water to binder ratio was also found to affect the Di at the early ages of curing, but became less important at the later ages of curing.
Solubility reactions of cement components with NaCl solutions: I. Ca(OH)2 and C-S-H
Authors: Glasser F. P. , Pedersen J , Goldthorpe K. , Atkins M.
Published: October 2009

Synthetic calcium silicate hydrogels, of Ca/Si mole ratios 0·85, 1·10, 1·40 and 1·80, were prepared and homogenised at 25°C. Solubilities of Ca(OH)2 and of C-S-H were measured in initially pure water at 25, 55 and 85°C. Equilibration times ranged from a few days up to 9 months: data are presented for the longer reaction times, 4·5 to 9 months. These solids were also equilibrated with NaCl solutions, approximately 0·5, 1·0 and 1·5 mol/l, at 25, 55 and 85°C. The expected solubility trends emerge in initially pure water: C-S-H dissolved incongruently and Ca solubilities decreased with either rising temperature or at lower Ca : Si molar ratios. The presence of NaCl enhanced Ca solubilities, especially in the range 0–0·5mol/l NaCl. However pH remained almost unaffected, ± 0·1 unit, as a function of NaCl concentration, other factors remaining constant. The C-S-H gel partially crystallised in the course of solubility determinations made at 85°C. Sorption of NaCl on C-S-H was negligible. Comments on the experimental procedures and quality of data are made. The long-term durability of cement exposed to dissolution in NaCl solutions is discussed.
Acid-resistant cements for geothermal wells: sodium silicate activated slag/fly ash blends
Authors: Sugama T. , Brothers L. E. , Van de Putte T. R.
Published: October 2009

Sodium silicate activated slag/class F fly ash (SSASF) blend cements were prepared by varying two parameters, the SiO2/Na2O mol. ratio in the sodium silicate activator, and the slag/fly ash weight ratio, and then autoclaving them at 100, 200 and 300°C. The usefulness of the autoclaved SSASF cements as acid-resistant geothermal well cements was evaluated by exposing them for 15 days to 90°C CO2-laden H2SO4 (pH 1·1). Among the combination of these two parameters, the most effective one in inhibiting acid erosion consisted of 50/50 slag/fly ash ratio cement and 2·50 SiO2/Na2O ratio activator. The weight loss by acid erosion of this cement was less than 7%. The major contributor to such minimum acid erosion was the zeolite phase formed by interactions between the mullite in fly ash and the Na ion liberated from the activator. Further characteristics of this cement included a long setting time for its slurry of approximately 1770 min at room temperature, and a water permeability ranging from 2·4 × 10−4 to 1·9 × 10−5 Darcy, and a compressive strength from 4·0 to 53·4 MPa after autoclaving at 100–300°C for 24 h.
Reservoirs Act 1975—Environment Agency proposals for change
Authors: Hamilton-King Liana J , Hope Ian M
Published: October 2009

In October 2004 the Environment Agency became the enforcement authority for the Reservoirs Act 1975 (the Act) in England and Wales. Since the Environment Agency took on this role, the authors have been considering the changes to the Act they would like to see incorporated. The Environment Agency's initial proposals were published in the last biennial report to the Department for the Environment Food and Rural Affairs (Defra) and the Welsh Assembly Government (WAG). Latest recommendations for changes to the Act follow the publication of the Pitt Review of the 2007 summer floods. Recommendation 58 of Sir Michael Pitt's review stated that ‘The Government should implement the legislative changes proposed in the Environment Agency's biennial report on dam and reservoir safety through the forthcoming flooding legislation.’ The key change proposed by the authors is to introduce a risk-based approach that would determine which reservoirs should come under the Act, instead of the current 25 000 m3 threshold. This paper describes the various proposals in more detail and outlines the potential programme for including these changes in the forthcoming Floods and Water Bill.
Queen Mary reservoir, Surrey, UK
Authors: Philpott Bryn
Published: October 2009

Around 20 members attended the British Dam Society visit to Thames Water's Queen Mary reservoir, Littleton, in Surrey on the fine sunny afternoon of 19 November 2008. The aim of the visit was principally to view a demonstration of the newly installed draw down siphons, but the attendees were also given a viewing of some of the other activities undertaken at the site.
Scottish canal reservoirs – a historical perspective. Part 1: Lowlands
Authors: Brown David H.
Published: October 2009

This paper is based on a presentation made to the Institution of Civil Engineers' Panel for Historic Engineering Works and the British Dam Society in Glasgow on 11 March 2009. This first part of the paper and covers the canals in the Lowlands. The Highland canal reservoirs will be discussed in later issues of Dams and Reservoirs.
Report on the European working group on internal erosion, St. Petersburg
Authors: Brown Alan , Bridle Rodney
Published: October 2009

This article reports on the seventh meeting of the working group, which was held on 27–29 April 2009 in St. Petersburg, hosted by VNIIG institute. There were 28 attendees from the UK, Canada, France, Sweden, Austria, Netherlands, Czech Republic and Poland and 12 attendees from Russia comprising, as in previous meetings, a mixture of researchers, practising engineers and dam safety managers. The workshop included 27 presentations and a visit to the hydraulic and soils laboratory of VNIIG. The participants included the authors of the current paper, which summarises the main points of relevance to dam engineers in the UK. The slide presentations are available on the VNIIG website http://www.vniig.ru/en/news/news25.htm . Selected summaries of work that had progressed since the intermediate report published at the European conference in Freising in September 2007 and presented in 2008 at Obergurgl in Austria and in 2009 at St. Petersburg are noted in the paper. VNIIG is a Russian research and development institute which carries out analysis and model testing in the fields of hydraulics, soil mechanics, concrete materials and safety of existing structures. One of its main clients is RusHydro, which was founded in 1921 and is the second largest generator in the world in terms of installed capacity, with 49 plants and 24 GW installed capacity.
ICE Reservoirs Committee's advice on applications for appointment and reappointment as a panel engineer
Authors: Taylor Paul J.
Published: October 2009

In 2003, and again in 2006, retiring chairmen of the Reservoirs Committee's two sub-committees published articles in Dams and Reservoirs to give advice to existing and aspiring panel engineers about how to become appointed and, when the term of appointment is due to expire, become reappointed. This article is intended to reinforce the advice given in those two articles and includes some observations about applications now being received.
High Level Bridge: engineering successful heritage solutions
Authors: Abbott T , Ayling L
Published: October 2009

In May 2008 the High Level Bridge, which spans the River Tyne between Gateshead and Newcastle-upon-Tyne, reopened following a seven-year, £42 million programme of repair and strengthening that also encompassed its conservation as an important piece of UK national heritage. The bridge has a statutory designation as a grade I listed building, the highest designation, and is a strategic part of the rail and road systems in the north east of England. A decision was taken that the bridge required more than its regular maintenance; it required ‘renewal’—a term used by English Heritage not for replacement but for a process that occurs at a longer cycle than maintenance and is more drastic in terms of interventions and the loss of heritage values. The varied nature of necessary repairs and interventions to historic buildings (bridges are buildings under the protective legislation) means that there are no easily defined rules; judgement and the application of principles of conservation are how protection and change are managed. This paper seeks to explain the methods and processes used to give this bridge a sustainable future while managing the changes to protect and respect its historic value.
Seismic displacements of geosynthetic-reinforced soil modular block walls
Authors: Huang C. C. , Chou L. H. , Tatsuoka F.
Published: October 2009

Four geosynthetic-reinforced soil modular block (GRS-MB) retaining walls that behaved differently during the 1999 Taiwan Chi-Chi earthquake were investigated by field surveying and soil testing. Pseudo-static analyses based on the two-wedge failure mechanism were performed to investigate the seismic stability of such GRS-MB walls. The analyses considered the structural function of the stacked block facing and the contribution of reinforcement-facing connection strength to the seismic stability of GRS-MB retaining walls. It was found that the facing-reinforcement connection strength and the block–block shear resistance strongly affect the seismic stability and seismic displacement of GRS-MB retaining walls. Newmark's sliding block theory together with a ‘displacement diagram’ were used to evaluate the seismic displacements of the investigated walls. The displacement analyses give the values of horizontal seismic displacement of the discrete modular block facing and the vertical settlement of the backfill soil. It was found that the calculated values of wall displacements were comparable with the measured ones when the structural effects of the facing were properly accounted for. The effect of buckling mode deformation of the stacked blocks on the horizontal displacement of the GRS-MB walls is also evaluated quantitatively.
Simplified method for estimating geosynthetic loads in landfill liner side slopes during filling
Authors: Liu C.-N. , Gilbert R. B.
Published: October 2009

Tensile loads can develop in geosynthetic layers in landfills on steep base-liner side slopes during filling. These loads develop due to interim geometries during the filling sequence where the soils and/or waste materials placed on the side slope are supported partially by the geosynthetics. In this paper, a simplified method for estimating these geosynthetic loads is proposed. This method provides a solution that maintains strain compatibility and that can be implemented easily with a spreadsheet. The validity of this approach is supported with one case study where field measurements of geosynthetic tension during cover soil placement are available. In addition, a design example is presented to demonstrate how the proposed approach can be used in practice.
Evaluation of four equivalent diameter formulations for prefabricated vertical drains using flow rates
Authors: Welker A. L. , Herdin K. M.
Published: October 2009

The rectangular cross-section of a prefabricated vertical drain (PVD) is typically converted to a circular cross-section to aid in design. This conversion is performed regardless of whether the PVD will be used for soil improvement or for remediation. An experimental programme to evaluate four of the most commonly used equivalent diameter formulations based on flow rates is described, and the results from those experiments are presented. The results indicate that the formulation recommended by Hansbo in 1979 adequately simulates a PVD under both injection and extraction conditions. Furthermore, there was no dramatic difference observed for the flow rates from, or into, a PVD with and without smear. It should be noted, however, that the tested material was a silty sand, and hence the effect of smear should not be significant.
Effect of straining on gas advective flow of a needle-punched GCL
Authors: Bouazza A. , Vangpaisal T.
Published: October 2009

Although geosynthetic clay liners (GCLs) have gained advantage over compacted clay liners regarding the ability to withstand large differential settlement in cover systems, the ability of strained GCLs to mitigate gas flow is still not known. A series of gas permeability tests on partially hydrated GCLs subjected to straining is presented in this paper. Tests were performed on partially hydrated needle-punched GCLs subjected to straining (up to 30% of area strain). The GCL samples were strained either before hydration or after hydration. It was found that the gas flow rate through the strained GCL depended on GCL moisture content and straining conditions. The tensile strain seemed to have no adverse effect on dry GCL (straining before hydration) as long as the geotextile components were able to maintain their functions, and the mass of bentonite per area was preserved. However, in the case of straining (up to 15% area strain) after hydration, tensile strains possibly induced tension cracks in the bentonite component, providing preferential gas flow paths and higher gas flow rate than that of an unstrained GCL. At higher degree of area strain (15% < ε ≤ 30%), the gas flow rate was found to be similar to the flow through an unstrained GCL, particularly at high moisture content (MC > 90%). Poiseuille's equation for laminar flow of fluid through space between parallel solid planes can be used to describe the flow of gas through cracks in the hydrated bentonite component.
Determining the design parameters for geosynthetic reinforcements subject to single-stage actions using the isochronous strain energy approach
Authors: McGown A. , Khan A. J. , Kupec J.
Published: October 2009

Geosynthetic-reinforced soil systems are required to resist a variety of actions during their design lifetime. These actions may act over different periods of time, and they may be sustained or transient in nature. Furthermore, these actions may be applied to the structure either singularly or in combination. This paper describes the implications of single actions, applied over a substantial period of the design lifetime, termed ‘single-stage actions’. The current practice for the determination of design parameters for geosynthetic-reinforced soil structures (GRSSs) subject to single-stage actions is described in detail, with special consideration given to the determination of reference strengths, factors of safety or partial factors, and design strengths. It is shown that the recently developed isochronous strain energy (ISE) approach may be used to overcome the problems associated with material characterisation within the current design methods/codes. The determination of reference strengths, factors of safety or partial factors and design strengths based on the ISE approach is shown, and compared with the current practice. Finally, it is shown that the design strength determined using the ISE approach takes account of both time and strain level dependence where this occurs.
Numerical analysis of stress–deformation response in reinforced unpaved road sections
Authors: Leng J. , Gabr M. A.
Published: October 2009

Aggregate base course (ABC) layers of unpaved structures show significant plastic behavior under traffic load, including stress-dependent modulus and structural degradation. Geosynthetic reinforcement is commonly placed between the ABC and the subgrade to improve the performance of unpaved structures. Numerical analyses using the finite element program ABAQUS were conducted to investigate the performance of geogrid-reinforced aggregate over soft subgrade. Elasto-plastic constitutive models were used to model aggregate, subgrade and geogrid layer. Interaction between geogrid and aggregate was simulated as a shear-resistance interface. The reinforcement effects were seen in reducing surface deformation and improving vertical stress distribution on the subgrade layer. A parametric study indicated that ABC thickness and ABC/ subgrade modulus ratio greatly affect the contribution of the reinforcement. As the ABC thickness decreases, or as the ABC/subgrade modulus ratio decreases owing to deterioration or degradation of the ABC layer, the modeled sections show larger deformation, and the benefit due to geogrid inclusion becomes more apparent. Reinforcement with higher tensile modulus and better interface friction coefficient yielded better section performance in terms of less stress on the subgrade and surface deformation.
Methane gas migration through geomembranes
Authors: Stark T. D. , Choi H.
Published: October 2009

The objectives of this technical note are to review the gas transport mechanisms through flexible geomembranes, and to measure the methane gas transmission rate, permeance, and permeability coefficient of PVC, LLDPE, and HDPE geomembranes by performing the standard gas transport test ( ASTM D 1434 ). The measured methane gas permeability coefficient through a PVC geomembrane is 7.55×104 ml(STP).mil/m2.day.atm, which is slightly less than the gas permeability coefficient of 8.61×104 ml(STP).mil/m2.day.atm through an LLDPE geomembrane, but slightly higher than the gas permeability coefficient of 3.91×104 ml(STP).mil/m2.day.atm through an HDPE geomembrane. Thus HDPE exhibits a lower gas permeability coefficient than LLDPE. A field design chart for estimating the methane gas transmission rate for different geomembrane thicknesses is proposed using the measured permeability coefficients for PVC, LLDPE, and HDPE geomembranes and Fick's law. This chart can be used by landfill designers to evaluate the methane gas transmission rate for a selected geomembrane type and thickness and expected methane gas pressure in the landfill.
Large-scale tests for leachate flow through composite liner due to geomembrane defects
Authors: Chai J.-C. , Miura N. , Hayashi S.
Published: October 2009

Large-scale and relatively long-term model tests of leachate flow through a composite liner due to geomembrane defects were conducted. The model composite liner consisted of a 0.363 m thick soil layer and one layer of geomembrane. The diameter of the model device is about 1.2 m. The equipment used is capable of applying up to 200 kPa effective overburden pressure, p, to the model composite liner. Test and analysis results indicate that increasing the p value on the geomembrane reduces the leachate flow rate significantly. It is considered that this reduction is due mainly to the reduction of geomembrane/soil interface transmissivity, θ. After a leachate flow test, by measuring the concentration of target source ions, it was confirmed that there was flow at the geomembrane/soil interface. Comparing the measured data with predicted values using existing equations shows that assuming a perfect contact condition at the geomembrane/soil interface is not applicable for the conditions tested. Empirical equations by Giroud and Touze-Foltz for the good contact condition can provide a reasonable prediction of the flow rate through a defect in a geomembrane of composite liner under lower p values (close to zero). Based on the test results of this study, equations by Giroud and Touze-Foltz are modified to consider the effect of the p value. Using analytical solutions by Rowe and Touze-Foltz et al., the θ values are back-evaluated from the test results.
Settlement Studies in Egypt
Authors: Hanna W. S.
Published: October 2009

Synopsis

Settlement studies have formed an important part of the research carried out at Fouad I University, Cairo. Comparisons between observed and theoretical settlements, based on the results of the consolidation tests, showed that, relatively, the results were quite close; but numerically the theoretical settlements were, in many buildings, 3–4 times the observed values. Studies made seemed to indicate that the disturbance of swelling clays on removal from samplers accounted for an important part of the difference. This led to the development by the Author of a sampler that permitted the testing of the sample without removal from the sampler. Under the clay conditions existing in Egypt the “ring” sampler seems to justify itself: comparisons are made in proof of this point.

A few examples are given of buildings on rafts and footings, which raise many foundation problems, including that of a lock resting on swelling clays, and also the subject of subgrade reaction. One case of piled foundations is mentioned, bringing to light the special problem of piled foundations under soil conditions such as exist in Egypt.

Les études de tassement du sol ont formé une partie importante des travaux de recherches entrepris à l'Université Fouad Ier au Caire. Les comparaisons entre les tassements observés et ceux théoriques, barées sur les résultats des essais de consolidations, ont montré que les résultats étaient relativement proches; mais en chiffres, les tassements théoriques ont été, dans de nombreuses constructions, de 3 à 4 fois les valeurs observées. Des études faites sur ce point ont semblé indiquer que le dérangement de l'argile foisonnante provoqué par l'éloignement de dedans les échantilloneuses était la cause d'une partie importante de la différence dans les réultats. Ceci a conduit l'Auteur à la mise au point d'une échantilloneuse permettante les essais des échantillons saris avoir à les retirer de 1'échantilloneuse. Si l'on considère les argiles en présence desquelles on se trouve en Egypte, l'échantilloneuse “annulaire” se justifie de luimême: des essais de comparaison sont faits pour venir à l'appui de ce point.

Quelques exemples sont donnés constructions sur radiers et sur empattements qui soulèvent de nombreux problèmes de fondation, y compris la construction d'une écluse reposant sur de l'argile foisonnante, et aussi le sujet de réactions de la plate-forme. On mentionne un cas de fondations sur pieux, faisant ressortir le problème particulier des fondations sur pieux dans les conditions de sol existantes en Egypte.