bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of phenol upon concrete
Authors: Smith M. A. 
Published: October 2009

Synopsis Phenols are common contaminants of sites used for coal carbonization (e.g. for town gas manufacture, coking plants and tar works). Phenol itself (C6H5OH is reported to be detrimental to concrete, but no quantitative data are available. The paper describes the results up to two years of a series of tests carried out on 100 mm cubes immersed in phenol solutions of varying concentrations. It is concluded that concentrations of phenol as low as 0·2% by volume have an adverse efect upon the developmen of the compressive strength of concrete and that concentrations as low as 0·1 % may be detrimental. Concentrations of phenols of this order may sometimes be encountered onsites used for coal carbonization.
Strength gain and calcium hydroxide depletion in hardened cement pastes containing fly ash
Authors: Marsh B. K. , Day R. L. , Bonnery D. G. 
Published: October 2009

Synopsis Hardened cement paste specimens, with and without partial replacement of the cement by fly ash, were cured f o r various ages up to one year at temperatures 20-80°C. Compressive strength, calcium hydroxide content and porosity, by mercury intrusion porosimetry, were measured as curing proceeded. Results indicate that elevated curing temperature accelerates the pozzolanic reaction to a greater extent than the normal hydration reactions of Portland cement. When elevated temperatures are used, the strength of fly ash pastes may surpass that of plain pastes at early ages. Strength degradation was observed in pastes cured at the higher temperatures; this degradation was more pronounced in the plain pastes. Consumption of calcium hydroxide with no corresponding gain in strength, or with a reduction in strength, was observed for ash-pastes cured at 50°C and above. Changes in mercury porosity, on the other hand, correlate well with changes in strength during the early strength-gain periods and also during the later strength-degradation periods.
Strain of concrete during first cooling from 600°C under load
Authors: Khoury Gabriel A. , Grainger Brian N. , Sullivan Patrick J. E. 
Published: October 2009

Synopsis This is the third of three papers presenting the results of an investigation into the transient thermal strain behaviour of concrete during the first heat cycle to 600°C under load. The strains measured during the first cooling of concrete from 600°C are presented here, together with the results of residual compressive strength and elastic modulus tests. These are analysed with reference to the complete thermal cycle and constituent materials property data already given in the two previous papers. Strains during first cooling were primarily influenced by the thermal strain of the coarse aggregate and were unaffected by initial moisture content (as-cast, air-dry or pre-dried at 105°C), heating rate (0·2 or 1°C/min) or concrete age (1 year or 9 years). The applied load level did not affect the cooling strains of concretes with the more thermally stable aggregates of basalt or sintered pulverized-fuel ash, or the siliceous gravel concrete despite the extensive cracking it suffered during heating. This indicated the absence of transient creep during cooling and also the insignificance of any thermal stress effects for the specimen size and cooling rates used, The thermal expansion of limestone aggregate during heating contained an irreversible component which created sufficient differential cooling strain between cement paste and aggregate to cause cracking on cooling. The degree of cracking reduced with increasing levels of applied compressive load (0–30% of the initial unheated strength). The residual strain results represent the sum of all irrecoverable contractions and expansions, during the thermal cycle. These include shrinkage and load-induced thermal strain (LITS) during first heating and the effects of any cracking on cooling. From this work, the residual contractions of the loaded specimens can be successfully predicted by a simple superposition of all irrecoverable strains developed during the thermal cycle. The effect of temperature upon elasticity was dependent upon whether or not the concrete was loaded during the thermal treatment. For loaded concretes tested hot after a heating-cooling-heating cycle, the elastic strain response changed little between 100°C and 600°C compared with the free thermal strain (FTS) and LITS. For concretes tested cold after heating under load but cooling unloaded, the elastic strains increased with temperature level. Residual compressive strength of all the concretes was a function of the load level during the thermal cycle. The residual strength of specimens initially heated at 0.2°C/min was less than that of specimens heated at 1.0°C/min. This indicated that longer time at temperature was more influential than possible structural' effects due to spatial temperature variations in the specimens during heating.
Anchorage of welded wire fabric used as shear reinforcement in beams
Authors: Mansur M. A. , Lee C. K. , Lee S. L. 
Published: October 2009

Synopsis In this paper, welded wire fabric bent into a U shape is considered as web reinforcement in beams, the necessary anchorage at its open ends being furnished by welded cross wires. About 70 pull-out tests were made to investigate the influence of various parameters that affect the anchorage. Four simply supported over-hanging beams were also tested to evaluate the upper anchorage located in the tension and compression zones of the beam and to study their cracking behaviour and ultimate strength. Test results indicate that welded cross wires can provide adequate anchorage if certain restrictions on the relative size and spacing of these wires are followed, and the beams can attain the desired shear capacity. The use of deformed welded wire fabric signlficantly improves the cracking characteristics of a beam by comparison with an equivalent amount of smooth welded wire fabric.
Anchorage zones in prestressed concrete members
Authors: Fenwick R. C. , Lee S. C. 
Published: October 2009

Synopsis In an anchorage zone of a post-tensioned concrete member tensile stresses are induced in different localities. The way in which these arise is briefly discussed. A series of simple anchorage zone tests is reported, in which the forces resisted by reinforcement placed to resist bursting tensile forces were monitored. The test results together with a series of finite analyses show that once a bursting crack forms the resultant loss of transverse stlflness in the member leads to a decrease in the magnitude of the bursting force and a change in its location. A method of assessing the magnitude of this force once a crack has formed is presented.
Indirect and non-destructive methods for assessing abrasion resistance of concrete
Authors: Sadezadeh Massud , Kettle Roger 
Published: October 2009

Synopsis Three non-destructive test methods have been investigated to determine their suitability as indirect methods for assessing the abrasion resistance of concrete slabs. The ultrasonic pulse velocity technique was not found to be sufficiently sensitive to variation in the concrete mix design. The surface hardness method, using the Schmidt rebound hammer, was found to be partially sensitive to factors which are known to influence the abrasion resistance of concrete. The initial surface absorption method was found to be very sensitive to these factors and was closely related to abrasion resistance of concrete as determined by an accelerated abrasion test.
Deleterious expansion of concrete due to alkali-silica reaction: influence of pfa and slag
Authors: Hobbs D. W. 
Published: October 2009

Synopsis The literature dealing with the effectiveness of partial replacement of a high-alkali cement by pulverized-fuel ash (pfa) and ground granulated blast furnace slag (slag) in preventing deleterious expansion due to the alkali–silica reaction (ASR) when a reactive aggregate is used is reviewed, and results are reported of recent tests carried out on concrete at C&CA. It is shown that the effectiveness of pfa's and slags in preventing deleterious expansion due to ASR varies widely and that the use of some pfa's and slags may not reduce the risk of deleterious expansion.
Hollow concrete blocks with enhanced structural efficiency and a compatible grout
Authors: Shrive N. G. , Jessop E. L. 
Published: October 2009

Synopsis Concrete blocks with two hollow cores are commonly used in load-bearing walls. Many variations on this basic type of unit are produced. However, the typical geometry and mortaring practices employed tend to cause such units to fail at much lower stresses than the strength of the concrete from which they are made. When the causes of failure in both hollow and grouted concrete masonry are examined, three criteria can be established which should improve the loadbearing capabilities of concrete blocks. Blocks and grout were manufactured to conform with these criteria and expected strength improvements were observed. A new concrete block ‘system’ has been devised with a more efficient load-bearing capability and a number of additional attributes. The system is 19% lighter and 19% stronger than ‘standard’ masonry, is also more versatile and requires fewer site materials than conventional masonry.
An activation energy approach for the temperature dependence of basic creep of hardened cement paste
Authors: Dias W. P. S. , Khoury G. A. , Sullivan P. J. E. 
Published: October 2009

Synopsis Arrhenius rate theory is used to describe the temperature dependence of basic creep of hardened cement paste, within certain temperature limits. The time shift principle is coupled with this Arrhenius temperature dependence to obtain an overall power law relationship between creep strain and equivalent time (which accounts for both temperature and time dependence). This enables the formulation of an extrapolation technique for basic creep strains in situations where there are time or temperature constraints on experimentation. Two distinct values of activation energy corresponding to two different temperature ranges, are used to arrive at possible creep mechanisms that would operate in each of these ranges.
Shear and moment capacity of reinforced steel-fibre-concrete beams
Authors: Lim T. Y. , Paramasivam P. , Lee S. L. 
Published: October 2009

Synopsis An analytical approach for predicting the shear and moment capacity of reinforced steel-fibre-concrete (RSFC) beams is proposed. Recent plasticity analyses for shear capacity of reinforced concrete beams are extended to RSFC beams by including the contribution of the fibres. Moment capacity is derived using the usual sectional analysis and fully plasticized stress blocks and forces. By establishing relevant capacities for a given beam loaded over a range of span/depth ratios, the capacity and governing mode of failure can be predicted. The observed failure loads and modes of failure for 22 test beams agree well with the predictions. Data presented in the literature are also analysed and compared. The present approach allows for direct comparison between the efectiveness of stirrups and fibres as shear reinforcement. The results suggest that fibres can replace stirrups partially or wholly as long as parity in the shear reinforcement factor is maintained.
Oil-pressure measurement in the two-point workability apparatus
Authors: Wimpenny D. E. , Ellis C. 
Published: October 2009

Synopsis Large fluctuations in the oil pressure within the twopoint apparatus during concrete testing make any reading of the pressure gauge open to operator bias. This paper details the fitting and use of a pressure transducer system capable of measuring, recording and analysing the oil pressure. Results obtained using the pressure gauge and the pressure transducer indicate that operator experience in Combination with mix workability has some influence upon the accuracy of the gauge readings, and this underlines the substantial benefits of the proposed system.
Recycled concrete as fine and coarse aggregates in concrete
Authors: Sri Ravindrarajah R. , Loo Y. H. , Tam C. T. 
Published: October 2009

Synopsis The effects of using crushed concrete as coarse and fine aggregates upon strength and deformation of concrete are reported. The properties of recycled aggregates differ from those of natural aggregates due to the presence of a considerable proportion of mortar attached natural aggregate and loose mortar. For a medium strength concrete, the results show that strength and modulus of elasticity are reduced by about 10% and 35%, respectively, whereas drying shrinkage is nearly doubled when recycled aggregates are used instead of natural aggregates in comparable mixes. The efect of recycledfine aggregate on the deformational properties is less than that of coarse aggregate. Fresh concrete properties are only marginally affected by the use of recycled aggregates.
The resistance of stainless steel partly embedded in concrete to corrosion by seawater
Authors: Flint G. N. , Cox R. N. 
Published: October 2009

Synopsis The corrosion resistance of Type 316 stainless steel, partly embedded in concrete, partly exposed to stagnant seawater and partly exposed to flowing seawater, has been determined over various periods up to about 12; years duration. The exposure tests were carried out in full immersion and tidal conditions, on specially designed concrete blocks. Mild steel specimens were also tested for comparison. Corrosion of exposed stainless steel was localized, not extensive, and affected neither the strength nor ductility of the specimens. Contrary to expectation, crevice corrosion occurred on only one of the 42 test specimens, and only after 12½ years total immersion. It is considered that the alkalinity of the concrete was responsible for minimizing corrosion on both embedded and external areas of stainless steel. Ordinary Portland cement concrete gave more protection to the stainless steel than did sulphate-resisting Portland cement concrete due, it is thought, to the higher cement content of the former and consequent greater reserve of alkalinity. The higher proportion of tricalcium aluminate in the OPC concrete and its known effect in complexing chloride ions and delaying their ingress into concrete was also considered to be of great significance.
Settlement of fresh concrete—an effective stress model
Authors: Clear C. A. , Bonner D. G. 
Published: October 2009

Synopsis The settlement of fresh concrete under load is examined both theoretically and experimentally. It is shown that settlement depends on the effective stress to which the intergranular structure is subjected, and that the settlement has two major components. One of these is immediate settlement due to compression of the pore fluid and the intergranular structure in response to applied load. The other is consolidation settlement created by the dissipation of pore water with time which gradually transfers load from the pore water onto the intergranular structure. A reduction in consolidation settlement will reduce the risk of settlement cracking and void formation around reinforcing bars. For discrete cycles of loading, such as placing of concrete in layers, a direct measure of consolidation settlement as a proportion of total settlement is given by a pore water pressure coefficient.
Grouted and dowelled jointed precast concrete columns: behaviour in combined bending and compression
Authors: Kuttab A. , Dougill J. W. 
Published: October 2009

Synopsis Tests are described on the behaviour of grouted and dowelled jointed precast columns under combined bending and axial load. Only part of the longitudinal steel is used for dowel action so that the axial load capacity needs to be enhanced in the region of the joint. This is done by the use of additional links in each of the units comprising the jointed column. The jointed column had load capacities similar to those expected for monolithic columns but the failure zone was localized. As a consequence, when overall behaviour is determined by failure at the joint, it can be expected that a jointed column will be more brittle than a monolithic column.
Effect of sodium chloride and sodium hydroxide from the surrounding solution on alkali-silica reaction in mortars containing fly ash
Authors: Kawamura Mitsunori , Takemoto Kunio , Terashima Nagamasa 
Published: October 2009

Synopsis It is known that sodium chloride from the surrounding solution promotes the expansive alkali-silica reaction in cementitious materials, and that the incorporation of pozzolanic materials suppresses the expansion caused by the intrusion of alkali salts. However, the mechanisms responsible for these phenomena are not fully understood. In this paper, substantial differences in expansion behaviour between mortars(made with a high-alkali OPC, nine fly ashes at replacement levels of 0, 10, 20 and 30%, and Beltane opal fine aggregate) immersed in I N NaOH and I N NaCl solutions are discussed, taking account of the composition of the pore solutions extracted from the mortars. Mechanisms for the initiation and acceleration of the alkali-silica expansion in mortars exposed to the NaCl solution are also discussed.
Delayed analysis of fresh concrete for cement and water content by freezing
Authors: Clear C. A. 
Published: October 2009

Synopsis Using a domestic chest,freezer, samples of fresh concrete can befrozen and stored, for at least 28 days and then tested for cement and water content by standard, fresh analysis methods. This technique, for delaying, fresh analysis is useful us it provides the option of checking the mix proportions of concrete supplied to construction sites which do not have suitable test equipment immediately available. Frozen 8 kg samples of fresh concrete for cement content analysis must be thawed before they can be tested using the Rapid Analysis Machine. Thawing i s readily achieved by mixing each frozen sample with 2·5 li of hand hot water, for about 10min. Samples for water content analysis do not require any extra preparation before testing, as they can be dried to constant weight from their,frozen state using a suitable microwave oven.
Shear strength of reinforced lightweight concrete beams of normal and high strength concrete
Authors: Ahamad Shuaib H. , Xie Yuliang , Yu Tiejun 
Published: October 2009

An experimental investigation was conducted to study the ultimate shear strength and the load-deformation characteristics of shear critical reinforced lightweight concrete beams of normal as well as high strength concrete. A total of 15 shear critical reinforced concrete beams without and with shear (web) reinforcement were tested in a ‘stiff’ testing facility and complete load–midspan deflection curves including the post-peak portion were obtained. The experimental variables were the concrete compressive strength, shear span to depth ratio (a/d) and the amount of shear reinforcement. Concrete cylinder strength (f'c) was varied between 30·5 MPa (4430 psi) and 89·3 MPa (12950 psi). The shear span to depth ratio was varied between 1 and 4 and the shear reinforcement ratio (γw) was varied between 0 and 0·784 percent. For the range of variables tested, the results indicate that the predicted ultimate shear capacities in accordance with the ACI Code and the BS 8110 Code provide an adequate margin of safety when compared with the observed values for normal as well as high strength lightweight concrete beams using dlflerent types of lightweight aggregates such as stalite, lytag, pellite and pumice. Furthermore, the results indicate that the restriction imposed by the BS 81 10 Code on the strength of concrete not to exceed 40 MPa for shear strength computations may be overly restrictive. The presence of shear (web) reinforcement improves the post-peak deformation characteristics of reinforced lightweight concrete beams of normal as well as high strength concrete.
Non-ferrous reinforcement
Authors: Clarke J. L. , Halcrow William 
Published: October 2009

Traditionally, concrete structures have been reinforced with steel bars or prestressed with steel wires or strands. Generally, embedded steel is very durable, the concrete providing a suitable alkaline environment. However, for structures in highly aggressive environments, the protection afforded by the concrete is often insufficient to ensure the necessary service life for the structure. In addition to attempts to improve the quality of the concrete itself, there are a number of approaches for protecting the steel directly, such as by means of epoxy coating or the use of cathodic protection. A further alternative is to replace the steel completely by a material that will, hopefully, be more durable. One such option, which has great potential, is the use of fibre-reinforced plastics (FRPs), which consist of continuous fibres, generally of glass, carbon or aramid, set in a suitable resin to form a rod or grid. These materials are well accepted by the aerospace and automotive industries and are starting to find applications in the construction industry. The mechanical properties of FRPs are chiefly determined by the amount and type of fibre, while the durability will be a function of both the resin and the fibre. The strength of FRP reinforcement will tend to be between that of high-yield reinforcing steel and prestressing stand (say 1000 N/mm2 for glass fibres and 1500 N/mm2 for carbon fibres) but the stiffness will generally be significantly lower (say 45 kN/mm2 for glass fibres and 150 kN/mm2 for carbon fibres). All FRP materials have a straight line response to failure with no plasticity. The most common method for manufacturing FRP rods is pultrusion, in which the fibres are drawn off storage containers in a controlled pattern, are impregnated with resin and then drawn through a heated die which sets and cures the resin. One limitation at present is that thermoset resins are generally used and, hence, once fully cured, rods cannot be bent into the range of shapes currently used with steel. Thus ‘specials’ are required. Spiral reinforcement, either circular or rectangular in form, is produced by some Japanese manufacturers along with two- or three-dimensional grid. Other manufacturing techniques are being developed in which resin-impregnated fibres are wound on to suitable mandrels to producing closed shapes, such as shear links. As an alternative, thermoplastic resins are being developed, which would allow the fully cured material to be bent.