scholarly journals Compressive Behaviour of Coconut Fibre (Cocos nucifera) Reinforced Concrete at Elevated Temperatures

Fibers ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 5 ◽  
Author(s):  
Gideon Bamigboye ◽  
Ben Ngene ◽  
Omotolani Aladesuru ◽  
Oluwaseun Mark ◽  
Dunmininu Adegoke ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Elevated Temperature ◽  
Fire Resistance ◽  
Elevated Temperatures ◽  
Cocos Nucifera ◽  
Fibre Content ◽  
Cement Concrete ◽  
The World ◽  
Coconut Fibre

Fire outbreaks in buildings have been a major concern in the world today. The integrity of concrete is usually questioned due to the fact that after these fire outbreaks the strength of the concrete is reduced considerably. Various methods have been adopted to improve the fire resistance property of concrete. This study focused on the use of coconut fibre to achieve this feat. In this study, varying percentages of treated and untreated coconut fibres were incorporated into concrete and the compressive strength was tested for both before heating and after heating. The percentages of replacement were 0.25, 0.5, 0.75 and 1% fibre content by weight of cement. Concrete cubes that had 0% fibre served as control specimens. After subjecting these concrete cubes to 250 °C and 150 °C for a period of 2 h, the compressive strength increased when compared to the control. The compressive strength increased up to 0.5% replacement by 3.88%. Beyond 0.5% fibre, the compressive strength reduced. Concrete having coconut fibre that had been treated with water also exhibited the highest compressive strength of 28.71 N/mm². It is concluded that coconut fibres are a great material in improving the strength of concrete, even after it was exposed to a certain degree of elevated temperature.

Properties of Fly Ash Based Geopolymer Concrete Exposed to Sustained Elevated Temperatures

2011 ◽  
Vol 250-253 ◽  
pp. 962-968 ◽  
Author(s):  
M.S. Sudarshan ◽  
R.V. Ranganath
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Elevated Temperatures ◽  
Research Work ◽  
Acid Resistance ◽  
Geopolymer Concrete ◽  
Cement Concrete ◽  
Beneficial Effects

Fly ash based geopolymer concrete is gaining importance in the context of developing alternatives to cement concrete. The research work available in the literature shows many beneficial effects of the material in terms of its high early compressive strength, tensile strength, reduced shrinkage, good acid resistance etc., However, there are very few studies carried out on the influence of sustained elevated temperature on the properties of geopolymer concrete. This paper presents the results of some of the properties of fly ash based geopolymer concrete activated using sodium silicate and sodium hydroxide and subjected to elevated temperature at 150°C, 200°C, 300°C, 400ºc under sustained durations of 1 hour, 2 hours and 4 hours. The results show that residual compressive strength is about 20% less than the normal at about 200°C itself possibly due to the development of vapour pressure formed by the non-reactive water present in the system. Beyond 2 hours of sustenance, there is not much of a difference in the properties of concrete.

scholarly journals Study the Fire Resistance of Desert Sand Concrete (DSC) with Interface Phase through Uniaxial Compression Tests and Analyses

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Qian Zhang ◽  
Haifeng Liu ◽  
Qiang Liu ◽  
Jialing Che ◽  
Weiwu Yang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Fire Resistance ◽  
Elevated Temperatures ◽  
Fine Aggregate ◽  
Compression Tests ◽  
Desert Sand ◽  
Simulation Results

The shortage of sand resources and high-rise building fires are becoming increasingly prominent. Desert sand (DS) with smaller particles can effectively fill the concrete voids and further improve its working performance; it is used as a fine aggregate to produce concrete. This article studied the performance of desert sand concrete (DSC) against fire resistance by using mathematical modeling for simulation. The stress-strain curves of desert sand mortar (DSM) after elevated temperatures were tested, and the constitutive model was established. By comparing the experiment and simulation results, it was verified that the model is suitable to be adopted in this study. Data from experiment and past literature can serve as parameters for the subsequent simulation. The destruction process of DSC under uniaxial compression after elevated temperature was simulated by using ANSYS. The simulation results indicated that, after elevated temperature, compressive strength reduced with increase of interface thickness. The compressive strength of DSC had a substantially linear increase as the interface compressive strength increased. For two-grade coarse aggregate, the optimum volume content was 45%, and particle size of it showed a significant effect on the compressive strength of DSC. The DSM constitutive model and simulation results can provide a sound theoretical basis and technical support for DSC engineering applications.

Effects of Elevated Temperatures on the Compressive Strength of HFCC

2011 ◽  
Vol 261-263 ◽  
pp. 416-420 ◽  
Author(s):  
Fu Ping Jia ◽  
Heng Lin Lv ◽  
Yi Bing Sun ◽  
Bu Yu Cao ◽  
Shi Ning Ding
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Relative Strength ◽  
Ordinary Concrete ◽  
Residual Compressive Strength ◽  
Fly Ash Concrete ◽  
The Relationship

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

Isothermal Fatigue Behavior and Damage Modeling of a High Temperature Woven PMC

1999 ◽  
Vol 122 (1) ◽  
pp. 62-68 ◽  
Author(s):  
A. L. Gyekenyesi
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Stiffness Degradation ◽  
Fatigue Properties ◽  
Residual Compressive Strength ◽  
Stiffness Reduction ◽  
Fatigue Damage Accumulation ◽  
Strength Tests

This study focuses on the fully reversed fatigue behavior exhibited by a carbon fiber/polyimide resin woven laminate at room and elevated temperatures. Nondestructive video edge view microscopy and destructive sectioning techniques were used to study the microscopic damage mechanisms that evolved. The elastic stiffness was monitored and recorded throughout the fatigue life of the coupon. In addition, residual compressive strength tests were conducted on fatigue coupons with various degrees of damage as quantified by stiffness reduction. Experimental results indicated that the monotonic tensile properties were only minimally influenced by temperature, while the monotonic compressive and fully reversed fatigue properties displayed greater reductions due to the elevated temperature. The stiffness degradation, as a function of cycles, consisted of three stages; a short-lived high degradation period, a constant degradation rate segment covering the majority of the life, and a final stage demonstrating an increasing rate of degradation up to failure. Concerning the residual compressive strength tests at room and elevated temperatures, the elevated temperature coupons appeared much more sensitive to damage. At elevated temperatures, coupons experienced a much larger loss in compressive strength when compared to room temperature coupons with equivalent damage. The fatigue damage accumulation law proposed for the model incorporates a scalar representation for damage, but admits a multiaxial, anisotropic evolutionary law. The model predicts the current damage (as quantified by residual stiffness) and remnant life of a composite that has undergone a known load at temperature. The damage/life model is dependent on the applied multiaxial stress state as well as temperature. Comparisons between the model and data showed good predictive capabilities concerning stiffness degradation and cycles to failure. [S0742-4795(00)01001-2]

New Composite Materials that Reduce the Effect of Reinforcement Corrosion

2013 ◽  
Vol 837 ◽  
pp. 265-270 ◽  
Author(s):  
Vasile Constantinescu ◽  
Gheorghe Veniamin Bogus ◽  
Rares George Taran ◽  
Ioan Carcea
Keyword(s):  
Carbon Dioxide ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Service Life ◽  
Concrete Structures ◽  
Reinforcing Steel ◽  
Reinforcement Corrosion ◽  
Corrosion Initiation ◽  
Deicing Salts ◽  
The World

Concrete is a complex material of construction that enables the high compressive strength of natural stone to be sed in any configuration. In tension, however, concrete can be no stronger than the bond between the cured cement and the surfaces of the aggregate. This is generally much lower than the compressive strength of the concrete. Concrete is therefore frequently reinforced, usually with steel. When a system of steel bars or a steel mesh is incorporated in the concrete structure in such a way that the steel can support most of the tensile stresses and leave the immediately surrounding concrete comparatively free of tensile stress, then the complex is known as reinforced concrete. Corrosion of reinforcing steel in concrete leads to the premature failure of many structures exposed to harsh environments. Rust products form on the bar, expanding its volume and creating stress in the surrounding concrete. This leads to cracking and spalling, both of which can severely reduce the service life and strength of a member. Corrosion of reinforcing steel in concrete structures is one of the most expensive problems facing civil engineers in the world. The structural integrity of many bridges, overpasses, parking garages, and other concrete structures has been impaired by corrosion, and repairs are urgently required to ensure public safety. Corrosion-induced deterioration of reinforced concrete can be modelled in terms of three component steps: (1) time for corrosion initiation; (2) time, subsequent to corrosion initiation, for appearance of a crack on the external concrete surface (crack propagation); and (3) time for surface cracks to progress into further damage and develop into spalls, to the point where the functional service life, is reached. The two most common causes of reinforcement corrosion are: (i) localized breakdown of the passive film on the steel by chloride ions and (ii) general breakdown of passivity by neutralization of the concrete, predominantly by reaction with atmospheric carbon dioxide. Sound concrete is an ideal environment for steel but the increased use of deicing salts and the increased concentration of carbon dioxide in modern environments principally due to industrial pollution, has resulted in corrosion of the rebar becoming the primary cause of failure of this material. The scale of this problem has reached alarming proportions in various parts of the world. Corrosion in reinforced concrete structures is causing deterioration of our infrastructure. Structures in or near marine environments and transportation structures on which deicing salts are used are especially vulnerable. A widely promoted method for repairing damaged structures or for protecting structures in corrosive environments is the application of fiber-reinforced composite wraps over the surface of the structures elements.

An Engineering Mechanics Based Approach to Predict Safety of RC Columns under High Temperatures

2013 ◽  
Vol 351-352 ◽  
pp. 42-45
Author(s):  
Yao Yao
Keyword(s):  
Reinforced Concrete ◽  
Elevated Temperature ◽  
Fire Resistance ◽  
Design Code ◽  
Rc Columns ◽  
Scientific Approach ◽  
Engineering Mechanics ◽  
Structural Engineers ◽  
In Fire

Up till now, the design code for the determination of fire resistance of reinforced concrete (RC) columns is essentially based on tabulated data. Clearly, a more scientific approach based on an understanding of the fundamental behavior of columns in fire is timely andwill be useful to structural engineers. This paper develops a straightforward and rational method to predict the fire resistance of RC columns，which is based on the traditional Rankine approach. The effect of shear bond, if included in the Rankine approach, will yield moreaccurate predictions. Material deterioration at elevated temperature with regard to the strength and stability of columns is also quantified.

Strength Recovery of Lightweight Concrete under Elevated Temperature

2014 ◽  
Vol 905 ◽  
pp. 300-305
Author(s):  
Salim Barbhuiya ◽  
Tommy Lo ◽  
Shazim Memon ◽  
Hamid Nikraz
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Relative Humidity ◽  
Elevated Temperatures ◽  
Lightweight Concrete ◽  
Curing Conditions ◽  
Strength Recovery ◽  
Curing Methods ◽  
Limited Application ◽  
Water Curing

This research is aimed at investigating the effect of elevated temperature, curing duration and curing methods on the strength recovery of lightweight concrete. Concrete specimens were subjected to elevated temperatures ranging from 300 to 600°C in a controlled heating environment. The specimens were subjected to three types of curing conditions: continuous water curing at 27°C, curing in a relative humidity of 95% at 27°C and curing in water at 60°C for three days and then curing in water at 27°C. The curing duration ranged from 7 to 56 days. The results indicated that the re-curing of concrete for the recovery of compressive strength is most effective in the temperature range from 300 to 500°C. For temperatures outside the range of 300 to 500°C, re-curing was either not effective or had limited application.

scholarly journals Strength and Durability of Kenaf Fiber Reinforced Concrete for Marine Structures

2019 ◽  
Vol 1 (1) ◽  
pp. 113-118
Author(s):  
Nur Fikriah Hashim ◽  
Nuraqilah Mohd Zainal ◽  
Nurain Jamil ◽  
Nurul Nasuha Mohd Nor ◽  
Suriani Mat Jusoh
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Fiber Reinforced Concrete ◽  
Cement Matrix ◽  
Control Specimen ◽  
Fiber Reinforced ◽  
Cement Concrete ◽  
Marine Structures ◽  
Kenaf Fiber ◽  
Manufacturing Defects

Nowadays, Kenaf fiber is sustainably useful in marine structures and has become one of the materials that may be high in demand as it is light, biodegradable and environmental friendly. This study investigates the effect of fiber percentage on compressive strength of fiber reinforced concrete (FRC) and the relationship between compressive strength and time of FRC immersion in seawater. FRC concrete cubes were prepared using four different percentage of fiber (0%, 1.5%, 3.0% and 4.5%). These FRC were immersed in seawater for 7, 14 and 21 days for three consecutive weeks. Based on the experiment, it was found that there was improvement in compressive strength of FRC when compared to plain cement concrete. The results showed that 3.0% of KF to cement matrix concrete determined the highest compressive strength of 205.43 Pa while 0% of KF fiber to cement concrete matrix (control specimen) showed the lowest compressive strength of 158.28 Pa. Also the addition of Kenaf fiber to cement concrete decreased the seawater absorption more than concrete with absolutely 0% of KF fiber to cement concrete (control specimen). In conclusion, the results did show significant improvement and a consistent trend on strength with the addition of FRC. This study also revealed that the percentage of water absorption was on the increase for 0, 7 and 14 days and become constant after day 21. This is due to manufacturing defects that occurred which block the water from entering the material and making the material absorb less water.

scholarly journals The effect of elevated temperature on the lightweight concrete containing waste PET aggregate

2018 ◽  
Vol 6 (3) ◽  
pp. 1-14
Author(s):  
Semiha Akçaözoğlu
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Structural Integrity ◽  
Elevated Temperatures ◽  
Lightweight Concrete ◽  
Physical And Mechanical Properties ◽  
Lightweight Aggregate ◽  
Unit Weight ◽  
Residual Compressive Strength ◽  
Flexural Tensile Strength

In this study, the effect of waste PET as lightweight aggregate (WPLA) replacement with conventional aggregate on the some physical and mechanical properties and residual compressive strength of concrete was investigated. For this purpose, five different mixtures were prepared (the reference mixture and four WPLA mixtures including 30%, 40%, 50% and 60% waste PET aggregate by volume). The fresh and dry unit weights, compressive strengths, flexural-tensile strengths, water absorption and porosity ratios of the mixtures were measured. In addition the specimens exposed to elevated temperatures at 150, 300 and 450 °C and the residual compressive strengths were measured. Test results indicated that the unit weight, compressive strength and flexural-tensile strength of the specimens decreased as the amount of WPLA increased in concrete. After exposing to elevated temperature, WPLA mixtures retained their structural integrity and compressive strengths at 150 °C and 300 °C. However there was a significant decrease in the residual compressive strength values of WPLA mixtures at 450 °C.

scholarly journals Performance of ultra-high performance fibre reinforced concrete plates under impact loads

2021 ◽  
Author(s):  
Hesham Othman
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Fracture Energy ◽  
High Performance ◽  
Steel Reinforcement ◽  
Fibre Content ◽  
Fibre Reinforced Concrete ◽  
Concrete Plates ◽  
High Performance Fibre

The next generation of concrete, Ultra-High Performance Fibre Reinforced Concrete (UHP-FRC), exhibits exceptional mechanical characteristics. UHP-FRC has a compressive strength exceeding 150 MPa, tensile strength in the range of 8-12 MPa, and fracture energy of several orders of magnitudes of traditional concrete. The focus of this research is to investigate and analyze the advantage of using UHP - FRC in impact resistance structures. To achieve these goals, two experimental testing programs and major numerical investigations have been conducted. The material experimental investigation has been conducted to determine the effects of strain rate on UHP - FRC. Two parameters are investigated, namely: compressive strength (80, 110, 130, and 150 MPa); and steel fibre content (0, 1, 2, and 3%). Experimental results showed that the rate sensitivity decreases with the increase in the compressive strength ; and the dynamic enhancement of tensile strength is inversely proportional to the fibre content. The structural impact testing program focuses on the dynamic response of full - scale reinforced concrete plates as well as generating precise impact measurements. Twelve reinforced plates with identical dimensions are tested under high-mass low-velocity multi-impacts. The investigated parameters include: concrete type (NSC, HSC, and UHP - FRC), fibre volume content, and steel reinforcement ratio. The results showed that the use of UHP -FRC instead of NSC or HSC is able to change the failure mode from punching to pure flexural; and UHP -FRC containing 3% fibre has superior dynamic properties. For plates with identical steel reinforcement, the total impact energy of UHP-FRC plate containing 3% fibres is double the capacity of UHP - FRC plate containing 2% fibres , and 18 times the capacity of NSC plate. A three-dimensional finite element analysis has been performed using ABAQUS/Explicit to model multi-impacts on RC plates and the applicability is verified using existing experimental data. Concrete damage plasticity (CDP) model is adapted to define UHP - FRC. The CDP constitutive model parameters for the new material are calibrated through a series of parametric studies. Computed responses are sensitive to CDP parameters related to the tension, fracture energy, and expansion properties. The analytical results showed that the existing CDP model can predict the response and crack pattern of UHP - FRC reasonably well.

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