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Split tensile and % Residual split tensile strengths of cylinders after exposing to elevated temperature
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The present study investigated the effect of elevated temperatures ranging from 50 to 250 0 C on the compressive and splitting tensile strengths of Ultra strength concrete of M100 grade. Tests were conducted on 150 mm cubes, 150 mm diameter and 300 mm height cylindrical specimens. The specimens were heated to different temperatures of 50, 100, 150,...
Context in source publication
Context 1
... splitting tensile strength of all heated specimens at any exposure time was expressed as the percentage of 28 days split tensile strength of unheated concrete specimens. The test results are presented in Table 2. The variation of % Residual Split tensile strength with temperature for different exposure durations is shown in Fig.6. ...
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... Sreenivasulu and Srinivasa [32] examined the effect of elevated temperatures ranging from 50 to 250 0 C on the compressive and splitting tensile strengths of ultra high strength concrete UHSC of M100 grade. ...
ABSTRACT
One of the latest advancements in concrete
technology is Ultra-High Strength Concrete (UHSC). UHSC is
defined as concretes attaining compressive strength exceeding
(100MPa). This concrete is a fiber-reinforced, densely packed
concrete material which exhibits increased mechanical
performance and superior durability as compared to normal and
high strength concretes.
In the present study, an experimental work was
performed to investigate the behavior of Ultra High Strength
Reinforced Concrete beams in shear and flexure. Total of
twelve simply supported rectangular beams were casted with
cross section dimension (150 × 250)mm and span of (2150
mm). Three direct shear specimens were also prepared and
tested to study the shear force transfer behavior of ultra high
strength concrete.
The mechanical properties such as compressive
strength, compressive stress strain curve, modulus of elasticity,
and tensile splitting strength of concrete were investigated. The
average values of compressive and tensile strengths of UHSC
were 124 N/mm2 and 7 MPa respectively.
The main considered variables have been the
reinforcement ratios of 0.0129, 0.0204, and 0.0323, and the
method of testing (monotonic and repeated), for beams that
designed to fail in flexure. For beam that designed to fail in
shear the main variables were the main reinforcement ratio and
the shear span to depth ratio. The experimental results were
checked numerically using finite elements method, adopting
ANSYS package.
The behavioral characteristics of UHSC dominantly
depend upon its load history, for this purpose, experimental
investigation for the behavior of UHSC beams under load
history of random cycles is performed as well as it is compared
with its behavior under monotonic load.
Load deflection curves, first cracks and collapse loads, crack
patterns, rotation of the beam, and concrete strain distribution
over the depth of the beams are presented.
Experimental results indicate also that the ability of
UHSC beam resistance under repeated load is greater than
iv
that of other specimens under monotonic load. The percentages
of increasing the beam resistance with reinforcement ratio of
0.0129, 0.0204, and 0.0323 are 2.08%, 6%, and 4.4%
respectively.
For beams designed to fail in shear, the failure types
are shear failure except the member with lowest steel ratio
0.00129 where the failure type was flexural failure that is
because of the shear strength of concrete was greater than the
flexural strength of the beams. The failure load increased with
decreasing the a/d ratio where the increase in the shear spandepth
(a/d) ratio leads to a decrease in the post cracking
stiffness response and decreasing the cracking load and
ultimate load capacity of the beam. At the same loading level
great crack widths are observed in beams having higher (a/d),
this is because the cracks form in the shear span regions at
places of high moments, are towards the applied concentrated
loads.
A finite element model using ANSYS program
(11.0), was used in this study to predict the overall behavior of
the reinforced concrete beams. The load-deflection curves were
showed a good agreement with the test data especially at the
early stage of loading. However, the finite elements model has
shown slightly stiffer results compared with the test data in
nonlinear stage.
The average value of the experimental moment to the
analytical moment ratio of (1.04) for beams with flexural
failure the values of the predicted shear strength of the beams
with shear failure were less than the experimental shear
strength.
... Under elevated-temperature exposure, Portland cement paste experiences physical and chemical changes that contribute to development of shrinkage, transient creep, and changes in strength. Key material features of hydrated Portland cement paste affecting the properties of concrete at elevated temperature are its moisture state (i.e., sealed or unsealed), chemical structure (i.e., loss of chemically bound water from the C-S-H in the unsealed condition, CaO/SiO 2 ratio of the hydrate in the sealed condition, amount of Ca(OH) 2 crystals in sealed or unsealed conditions), and physical structure (i.e., total pore volume including cracks, average pore size, and amorphous/crystalline structure of solid) [50]. ...
... The property variations result largely because of changes in the moisture condition of the concrete constituents and the progressive deterioration of the cement paste-aggregate bond, which is especially critical where thermal expansion values for the cement paste and aggregate differ significantly. The bond region is affected by the surface roughness of the aggregate and its chemical and physical interactions [50]. Chemical interaction relates to the chemical reactions between the aggregate and cement paste that can be either beneficial or detrimental. ...
... The cement component as a constituent of concrete is the main binder in translating the liquid paste into a rigid strong concrete. Studies have shown that pozzolanas can produce concrete that can be relatively compared with normal concrete in its characteristics [2] [3] [4]. Therefore, the replacement of ordinary Portland cement (OPC) by a percentage of pozzolanic material improves the strength and durability of concrete. ...
This study aimed at investigating the effect of subjecting concrete, produced with cement being partially replaced with saw dust ash (SDA) to elevated temperatures. The performance of the test concrete cubes was done by exposing them to elevated temperatures of 200oC, 400oC, 600oC and 800oC, and allowed to cool down to room temperature before testing for their properties. Both the physical and thermal properties of the concrete cubes were determined. The concrete produced by blending cement with 10% SDA with an average percentage loss of 23.04% retained more of its compressive strength when exposed to the different temperatures, than concrete produced using only OPC, which has an average percentage loss of 29.11%. It is also found that, at an elevated temperature of 800oC, concrete fail totally in flexure due to the effect of high heat on binding elements. The flexural strength of both the control concrete (at 0% OPC replacement) and OPC/SDA blended concrete (at 10% OPC replacement) decreased as the temperature is increased. The replacement of OPC by 10% SDA increased the thermal shock resistance of the concrete by 11 cycles than the 0% OPC concrete at the same temperature. The concrete produced with OPC has better thermal conductivity than the concrete produced by blending OPC with SDA, as a result, the dislodgement of the concrete edges is relatively lower in the SDA blended cement concrete than in the OPC concrete. The result shows that, blending OPC with SDA in concrete performed better at elevated temperatures than concrete produced with only OPC. Therefore, the replacement of OPC with 10% SDA can be applied as a fire resisting bonding material in concrete.
... The cement component as a constituent of concrete is the main binder in translating the liquid paste into a rigid strong concrete. In recent times, researches have shown that pozzolanas can produce concrete that can be relatively compared with normal concrete in its characteristics ( Khoury, 1996;Sumaila and Job, 1999;Dashan and Kamang, 1999;Abdulahi, 2006). The replacement of ordinary Portland cement (OPC) by a percentage of pozzolanic material improves the strength and durability of concrete. ...
... The general trend for a strength loss with increasing temperature reflects the influence of the cement paste and the increasing role of the aggregate materials at higher temperatures. Factors have been identified that may contribute to the general trend for loss of compressive strength with increasing temperature: aggregate damage; weakening of the cement paste-aggregate bond; and weakening of the cement paste due to an increase in porosity on dehydration, partial breakdown of the C-S-H, chemical transformation on hydrothermal reactions, and development of cracking ( Khoury, 1996). A number of material and environmental-related factors affect the response of concrete materials to elevatedtemperature conditions. ...
This study is aim at investigating the thermal stability of concrete paste blended with ordinary Portland cement and saw dust ash (OPC/SDA). The SDA is thermally activated at 800oC for 2 hours and the concrete pastes prepared with constant consistency. The pastes were kept in moulds at room temperature and 100% relative humidity for 24 hours and then hydrated for 28 days under water. The hydrated concrete pastes were exposed for 2 hours to temperatures of 200, 400, 600, and 800oC. The hydrated concrete specimens were tested for compressive strength and thermal shock stability after heat treatment. It was found that, the compressive strength of the control cement paste concrete increase up to 400oC and suffers a more loss of compressive strength as the treatment temperatures were increased. However, the blended cement paste concrete experience an increase in compressive strength with temperature up to 600oC and then, the strength decrease as the treatment temperature was increased up to 800oC. The replacement of OPC with 10% SDA in the blended cement paste concrete increases the thermal shock resistance by about 4 times that of the control cement paste concrete. Blending of OPC with about 10% of SDA in concrete can improve on its thermal stability and durability.
... The cement component as a constituent of concrete is the main binder in translating the liquid paste into a rigid strong concrete. In recent times, researches have shown that pozzolanas can produce concrete that can be relatively compared with normal concrete in its characteristics (Khoury, 1996; Sumaila and Job, 1999; Dashan and Kamang, 1999; Abdulahi, 2006). The replacement of ordinary Portland cement (OPC) by a percentage of pozzolanic material improves the strength and durability of concrete. ...
... The general trend for a strength loss with increasing temperature reflects the influence of the cement paste and the increasing role of the aggregate materials at higher temperatures. Factors have been identified that may contribute to the general trend for loss of compressive strength with increasing temperature: aggregate damage; weakening of the cement paste-aggregate bond; and weakening of the cement paste due to an increase in porosity on dehydration, partial breakdown of the C-S-H, chemical transformation on hydrothermal reactions, and development of cracking (Khoury, 1996). A number of material and environmental-related factors affect the response of concrete materials to elevatedtemperature conditions. ...
This study is aim at investigating the thermal stability of concrete paste blended with ordinary Portland cement and saw dust ash (OPC/SDA). The SDA is thermally activated at 800oC for 2 hours and the concrete pastes prepared with constant consistency. The pastes were kept in moulds at room temperature and 100% relative humidity for 24 hours and then hydrated for 28 days under water. The hydrated concrete pastes were exposed for 2 hours to temperatures of 200, 400, 600, and 800oC. The hydrated concrete specimens were tested for compressive strength and thermal shock stability after heat treatment. It was found that, the compressive strength of the control cement paste concrete increase up to 400oC and suffers a more loss of compressive strength as the treatment temperatures were increased. However, the blended cement paste concrete experience an increase in compressive strength with temperature up to 600oC and then, the strength decrease as the treatment temperature was increased up to 800oC. The replacement of OPC with 10% SDA in the blended cement paste concrete increases the thermal shock resistance by about 4 times that of the control cement paste concrete. Blending of OPC with about 10% of SDA in concrete can improve on its thermal stability and durability.
Fire is an extreme event, the occurrence of which affects the behavior of the structures significantly in terms of both serviceability and strength criteria; hence, provision of appropriate fire safety measures for structural members is an important aspect of structural design. However, the impact of fire on steel reinforcement at elevated temperature is analyzed by exposing the concrete beam to fire at an interval of time, the reduced in strength of the steel reinforcement for the 10mm and 12mm in diameter was found.
The changes in the chemical composition of hydration products and pore structure of concrete exposed to high temperature result in the degradation of its mechanical properties and durability characteristics. The effect of high temperature on the properties of concrete depends mainly on various factors related to its quality and the level of temperature exposure. This paper reports the results of a study conducted to study the effect of key concrete factors on its performance on exposure to high temperature. The effect of elevated temperature on the concrete specimens prepared with varying mixture proportions was evaluated by measuring the residual compressive and split-tensile strength. The results indicated an increase in the tensile and compressive strength up to a temperature of 100 °C. However, a significant loss was noted in these values for an exposure temperature of more than 100 °C. The mix design parameters had a significant effect on the performance of concrete exposed to elevated temperature. A concrete mixture with water/cement ratio of 0.30 and fine/total aggregate ratio of 0.375 exhibited maximum resistance to temperature.
