March 2003
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4 Reads
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Publications (24)
March 2003
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105 Reads
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163 Citations
Construction and Building Materials
The effects of highly reactive aggregate, fused silica, and slowly reactive aggregate, Thames Valley sand, on the mechanical properties of concrete were investigated in this paper. The mechanical properties studied over a period of 12 months were the compressive strength, direct tensile strength, tensile splitting strength, flexural tensile strength (modulus of rupture), static modulus of elasticity and water absorption. The effects of both reactive aggregates on the mechanical properties of concrete were compared with that of sound concrete mix. The results presented in this investigation show that the effect of the reactive aggregates on the mechanical properties varies, depending on the type of reactive aggregate. From this study it appears that the direct tensile and static modulus of elasticity were the best indicators of reactivity.
October 2001
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14 Reads
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13 Citations
December 1999
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1 Read
August 1999
The paper deals with the effect of Alkali-Silica Reaction on the bearing capacity of plain and reinforced concrete.
July 1999
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17 Reads
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17 Citations
ACI Structural Journal
This paper summarizes the results of an experimental investigation on the effect of alkali-silica reaction (ASR) on the bearing capacity of both small- and large-scale specimens of both plain and reinforced concrete. Surface expansion and ultrasonic pulse velocity (UPV) were used to monitor the deterioration of the concrete specimens due to ASR. Empirical equations are proposed to predict the bearing capacity of ASR concrete subjected to symmetric and eccentric square, rectangular, or strip loadings. It can be concluded that the bearing capacity is more affected by ASR and change in loading geometry than by changes in any other variable.
July 1999
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54 Reads
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21 Citations
ACI Materials Journal
The effect of alkali-silica reaction (ASR) on bond strength in 26 reinforced concrete beams was studied. The reinforced beams were tested under static and cyclic loading. The test results showed that the reduction in bond strength due to alkali-silica reaction are consistent with the lap length of the tensile reinforcement. Alkali-silica reaction also causes a reduction in the fatigue life of the reinforced concrete beams with the tension reinforcement lapped in the bending zone.
January 1999
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32 Reads
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24 Citations
The fatigue strength of concrete is an important factor in the design of many structures. However, the behaviour of concrete under indirect tensile repeated load has never been clarified to date by researchers. Therefore one of the objectives of this investigation was to study the effect of alkali-silica reaction (ASR) on the fatigue behaviour of concrete tested in flexure as well as under repeated indirect tensile load. The other objective of this investigation was to study the effect of ASR on the fatigue behaviour of plain concrete tested in compression. The latter is of particular importance to the structural engineer. Its importance lies in that it is a quality control test as well as a basic physical property for use in theoretical analysis of concrete structures. The lack of understanding of the basic nature of the fatigue behaviour of unreinforced alkali-silica-reacted concrete has led to this part of the investigation, which aims to relate the effect of the reaction not only to the performance of small specimens which are used to obtain basic design information but also to the lifetime of complete structures. The data obtained in relation to the fatigue performance of ASR-affected concrete could allow engineers to maintain and repair such structures with greater confidence.
January 1999
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235 Reads
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27 Citations
This paper reports the results of experimental research into assessing the fractured state of fire-damaged concrete under rapid cooling in an attempt to establish the effects of fire-fighting operations on the structural integrity of concrete buildings subject to a fire. The investigation was driven by the need to improve the material models used in predicting the fire resistance of concrete members or redesigning such members after a fire incident. The extent of damage was quantified using the stiffness damage test. The stiffness characteristics of 40 fired limestone concrete cores were determined from a series of quasi-static load-unload cycles. The strain energy dissipated in the specimen during such cycles provides a quantitative measure of the damage. The damage index is defined as the area of the hysteresis loop divided by the stress range. Other stiffness parameters, such as the initial and chord moduli of elasticity, were also determined. The extent of damage was also examined using ultrasonic pulse velocity (UPV) and dynamic modulus methods. Visual examination and scanning electron microscopy were also used to provide qualitative assessment. Quenching hot concrete with water was found to result in a reduction in the stiffness of fire-affected concrete over the entire range of temperatures investigated. The damage index for air-cooled concrete after firing to 320°C is at the same level as that for concrete heated to 220°C and cooled by quenching. The inference here is that the traditionally held view that 300°C marks the onset of significant damage in concrete is debatable. UPV measurements confirmed the damaging effect of rapid cooling on the stiffness properties of fire-affected concrete. A further 10% reduction of the UPV of quenched concrete compared to air-cooled concrete was observed. The dynamic modulus measurement also confirmed the adverse effect of quenching on the modulus of elasticity of fired concrete.
August 1998
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1 Read
Citations (17)
... Although the vast majority of existing research on ASR has been performed using laboratory specimens under unrestrained (i.e., free expansion) conditions [10,56,61], a few works have been conducted to understand the effect of confinement on ASR-induced development. Some of these studies [64,65] observed no to negligible ASR-induced expansion in restrained directions; moreover, no transfer of induced expansion and thus deterioration has been noticed to directions with less or no confinement [55,66]. ...
- Citing Article
October 2001
... They found a general reduction of the anchorage strength of 20-30% from a relatively small test series. Ahmed et al. (1999) tested 26 beams with varying lap splice lengths under static and cyclic loading [18]. The beams were unidirectionally reinforced as no stirrups were used. ...
- Citing Article
July 1999
ACI Materials Journal
... The depth of the concrete cover is a very important durability indicator for the deterioration of structures due to steel corrosion. A survey in the U.K. showed that 77 out of 200 bridges have too low cover depths (Wallbank, 1989) that resulted in spalling of the cover and rust. The rate of penetration of aggressive agents (CO 2 , Cl − ) into concrete follows the general equation: ...
- Citing Article
July 1996
... In this investigation, three types of materials were used representing the full range of repair materials available, namely, a basic cementitious, a polymer modified cementitious and an epoxy render. The main properties of the three materials including bond strengths were reported by Abu -Tair et al [4][5][6][7][8], Abu -Tair el al [9] also reported on the effectiveness of resin injection of cracked reinforced concrete beams similar to those in this investigation and using similar loading systems. The cost of the repair materials is a major factor in deciding on a repair system, the cost of typical cementitious: polymer modified: epoxy mortars vary in the ratio 1:6.5:20 respectively [10]. ...
- Citing Article
October 1991
... This means the residual expansion with bigger volume will be higher due to less external amounts of moisture and microcracks' discontinuity to the surface. The previous studies implemented on specimens of different sizes concluded the large specimens would expand less than the small specimens, which reduced the concrete bearing strength by about 3%, and 35% in large and small specimens, respectively [40,41]. The relationship between the expansion of two cylindrical sizes can be plotted by a linear fit with an R 2 nearly at unity (R 2 = 0.999) at all levels of replacement of FS, as shown in Fig. 14. ...
- Citing Article
July 1999
ACI Structural Journal
... Various devices and methods are commonly deployed for the preparation of the substrate surface, in which the superficial concrete layer is removed and any dust or debris will be eliminated from the surface, including shotblasting, scarifying, sandblasting, grinding, bush-hammering, brushing, chipping, water-jetting, hydro-demolition and in-form retarders, each associated with benefits and drawbacks regarding their cost, time consumption, provided level of roughness and challenges [3,9,125,126]. Some of the approaches have already been proven to promote damage in the substrate, like hammering and needlegun [126]. ...
- Citing Article
November 1996
ACI Materials Journal
... In this investigation, three types of materials were used representing 7 the full range of repair materials available, namely, a basic cementitious, a polymer-modified 8 cementitious and an epoxy render. The main properties of the three materials including bond 9 strengths were reported by Abu -Tair et al [2][3][4][5][6], Abu-Tair el al [7] also reported on the 10 effectiveness of resin injection of cracked reinforced concrete beams similar to those in this 11 investigation and using similar loading systems. The cost of the repair materials is a major 12 factor in deciding on a repair system, the cost of typical cementitious: polymer-modified: 13 epoxy mortars vary in the ratio 1:6.5:20 respectively [8]. 14 ...
- Citing Article
March 1997
ACI Materials Journal
... The bearing capacity can be calculated by the steel plate positioned at the touching surface of the concrete cubes. The increase in bearing capacity was related to the increase in the concrete strength, reduction in the height of the concrete blocks and the total to loaded area ratio either for the plain or unreinforced concrete cubes [37]. Ince and Arici [12] found that parameters such as the loaded area, loaded member cross-section, specimen size, specimen height, conditions of loading and concrete compressive strength can hugely affect the bearing resistance of the concrete blocks. ...
- Citing Article
May 1998
ACI Structural Journal
... Additionally, Monette et al. [27] observed that ASR damage can inhibit the development of shear cracks. Ahmed et al. [28] studied both the flexural and shear capacity of ASR-damaged RC beams and discovered a slight increase in both capacities following ASR damage. Similarly, Aryan and Gencturk [29] found through experiments that the shear behavior of beams with ASR damage was comparable to that of undamaged beams. ...
- Citing Article
July 1998
ACI Materials Journal
... Many experimental works have sought to answer these questions. Uni and multiaxial loadings have been studied, under passive or active restraints [1][2][3][4][5], under applied stresses [6][7][8][9][10][11] or under combinations of passive restraint and applied stress [12]. Under uniaxial restraint, 0.1% of stress-free ASR expansion can lead to 1 MPa of compressive stress [2,8]. ...
- Citing Article
January 1999