Mechanical Behavior and Recovery of FRC after High Temperature Exposure

2016 ◽  
Vol 711 ◽  
pp. 457-464 ◽  
Author(s):  
Abdullah Huzeyfe Akca ◽  
Nilüfer Özyurt
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Melting Point ◽  
Modulus Of Elasticity ◽  
Morphological Changes ◽  
Heated Surface ◽  
Fiber Reinforced Concrete ◽  
Partial Recovery ◽  
High Temperature Exposure ◽  
Temperature Exposure

During fire, one or two faces of structural members experience higher temperatures than other faces and the deterioration on these faces may continue after fire. High temperature exposure above 400 °C causes deterioration in strength, modulus of elasticity and durability of concrete. Inclusion of fibers and air entraining agents in concrete mixes may reduce the destructive effects of high temperatures on concrete. Therefore, 8 groups of 0.45 w/c ratio of concrete were designed by using polypropylene fibers as low melting point fibers and hooked end steel fibers as high melting point fibers and air entraining admixture as a chemical additive. 15 cm cubic concrete specimens were produced and the five sides of the cubes were insulated with gypsum boards to maintain one face heating. An electrical furnace was used to heat concrete to 1000 °C and K-type thermocouples were placed in specimens to monitor temperature distribution in concrete. Moreover, two different re-curing methods, air and water, were applied after heating to see the change in mechanical properties and crack occurrences on the heated surface of concrete specimens. SEM and XRD investigations were conducted on the samples taken from the heated surfaces and the inner parts of the concrete in order to understand the morphological changes due to heating and re-curing. Results showed that deterioration on the surfaces due to high temperature exposure continued during air re-curing process and compressive strength and modulus of elasticity values of these specimens also diminished. On the other hand, compressive strength of water re-cured concrete stayed constant after heating and partial recovery of modulus of elasticity were obtained and the positive effect of water re-curing were observed on polypropylene fiber reinforced concrete prominently.

scholarly journals Mechanical Properties of Concrete with Various Water-Cement Ratio After High Temperature Exposure

2019 ◽  
Vol 2 (2) ◽  
pp. 126-136
Author(s):  
M.I Retno Susilorini ◽  
Budi Eko Afrianto ◽  
Ary Suryo Wibowo
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Temperature ◽  
Modulus Of Elasticity ◽  
Building Materials ◽  
Heating Process ◽  
High Temperature Exposure ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Temperature Exposure

Concrete building safety of fire is better than other building materials such as wood, plastic, and steel,because it is incombustible and emitting no toxic fumes during high temperature exposure. However,the deterioration of concrete because of high temperature exposure will reduce the concrete strength.Mechanical properties such as compressive strength and modulus of elasticity are absolutely corruptedduring and after the heating process. This paper aims to investigate mechanical properties of concrete(especially compressive strength and modulus of elasticity) with various water-cement ratio afterconcrete suffered by high temperature exposure of 500oC.This research conducted experimental method and analytical method. The experimental methodproduced concrete specimens with specifications: (1) specimen’s dimension is 150 mm x 300 mmconcrete cylinder; (2) compressive strength design, f’c = 22.5 MPa; (3) water-cement ratio variation =0.4, 0.5, and 0.6. All specimens are cured in water for 28 days. Some specimens were heated for 1hour with high temperature of 500oC in huge furnace, and the others that become specimen-controlwere unheated. All specimens, heated and unheated, were evaluated by compressive test.Experimental data was analyzed to get compressive strength and modulus of elasticity values. Theanalytical method aims to calculate modulus of elasticity of concrete from some codes and to verifythe experimental results. The modulus elasticity of concrete is calculated by 3 expressions: (1) SNI03-2847-1992 (which is the same as ACI 318-99 section 8.5.1), (2) ACI 318-95 section 8.5.1, and (3)CEB-FIP Model Code 1990 Section 2.1.4.2.The experimental and analytical results found that: (1) The unheated specimens with water-cementratio of 0.4 have the greatest value of compressive strength, while the unheated specimens with watercementratio of 0.5 gets the greatest value of modulus of elasticity. The greatest value of compressivestrength of heated specimens provided by specimens with water-cement ratio of 0.5, while the heatedspecimens with water-cement ratio of 0.4 gets the greatest value of modulus of elasticity, (2) Allheated specimens lose their strength at high temperature of 500oC, (3) The analytical result shows thatmodulus of elasticity calculated by expression III has greater values compares to expression I and II,but there is only little difference value among those expressions, and (4)The variation of water-cementratio of 0.5 becomes the optimum value.

scholarly journals Influence of concrete admixture on the bond strength of reinforced concrete submitted to high temperature

2020 ◽  
Vol 13 (2) ◽  
pp. 212-221
Author(s):  
V. A. JERÔNIMO ◽  
A. C. PICCININI ◽  
B. V. SILVA ◽  
D. S. S. GODINHO ◽  
A. M. BERNARDIN ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
High Temperature ◽  
Bond Strength ◽  
Modulus Of Elasticity ◽  
Significant Loss ◽  
Group I ◽  
Influence Of Temperature On ◽  
Strength Curve ◽  
Temperature Exposure

Abstract High temperatures can affect the macro and micro structural properties of reinforced concrete. This work aimed to analyze the bond strength behavior after high temperature exposure of two classes of concrete, the conventional 30 MPa and the high compressive strength 65 MPa concrete. The pullout test proposed by RILEM CEB / FIP RC6 (1983) was used for the evaluation of the compressive strength and modulus of elasticity. The influence of temperature on the physical-mechanical properties of concrete samples under a simulated fire situation was also studied for the evaluation of the resistant capacity in a post-fire situation. In addition to the analysis at 28 days, samples of the 30 MPa (group I) and 65 MPa (group II) classes were also investigated at 90 days exposed to room (23 °C), 400 °C and 800 °C temperatures. The bond strength curve was similar to that of compressive strength, where, at 400 °C, there was no statistical difference regarding room temperature and, at 800 °C, there was significant loss of strength in all cases. At 90 days age there was a loss of bond strength of 51 and 40 % for groups I and II, respectively. At 800°C the reductions were above 50 % in compressive strength and above 80 % in the modulus of elasticity, for both groups. These results show the structural impairment under high temperature. Comparing the test 28 and 90 days ages, there was no significant influence of age on the bond and compressive strength of the concretes.

scholarly journals Effect of Cement Type on the Mechanical Behavior and Permeability of Concrete Subjected to High Temperatures

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3021 ◽  
Author(s):  
Izabela Hager ◽  
Tomasz Tracz ◽  
Marta Choińska ◽  
Katarzyna Mróz
Keyword(s):  
High Temperature ◽  
Modulus Of Elasticity ◽  
Experimental Investigations ◽  
Test Results ◽  
Cement Type ◽  
High Temperature Exposure ◽  
Static Modulus ◽  
Granulated Blast Furnace Slag ◽  
Temperature Exposure ◽  
Static Modulus Of Elasticity

The paper presents experimental investigations concerning the influence of the cement type (CEMI 42.5 R Portland cement and CEMIII/A 42.5 N slag cement—with 53% granulated blast furnace slag) on the mechanical and transport properties of heated concretes. The evolution of properties due to high temperature exposure occurring during a fire was investigated. High temperature exposure produces changes in the transport and mechanical properties of concrete, but the effect of cement type has not been widely studied in the literature. In this paper, concretes were made with two cement types: CEMI and CEMIII, using basalt (B) and riverbed aggregates (RB). The compressive and tensile strength, as well as the static modulus of elasticity and Cembureau permeability, were tested after high temperature exposure to 200, 400, 600, 800, and 1000 °C. The evaluation of damage to the concrete and crack development due to high temperature effects was performed on the basis of the change in the static modulus of elasticity. The test results clearly demonstrated that permeability increases with damage, and it follows an exponential type formula for both types of cement.

scholarly journals Effect of the Curing Condition and High-Temperature Exposure on Ground-Granulated Blast-Furnace Slag Cement Concrete

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Eskinder Desta Shumuye ◽  
Jun Zhao ◽  
Zike Wang
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Curing Temperature ◽  
Stable Phase ◽  
Cement Concrete ◽  
Slag Cement ◽  
High Temperature Exposure ◽  
Curing Condition ◽  
Temperature Exposure

AbstractIn this study, the effect of curing temperature on the properties of slag cement concrete after high-temperature exposure was studied, and elevated curing temperature (45 ± 2 °C and 95% relative humidity (RH)) was selected to compare with the standard curing temperature (20 ± 2 °C and 95%RH). Four different concrete mixes with the same mix proportion, except for different slag replacement ratios, were used: 0% (reference), 30% (slag), 50% (slag), and 70% (slag). After high-temperature exposure at 200, 400, 600, and 800 °C, the effect of slag replacement, high temperature, and curing temperature on the compressive strength and mineralogical and microstructural properties of slag cement concrete were studied. Test results indicated that the compressive strength of concrete cured for 7 d at elevated temperatures increased by 28.2, 20.7, 28.8, and 14.7% compared with that cured at the standard curing condition at slag percentages of 0, 70, 50, and 30%, respectively. X-ray diffraction (XRD) and Scanning electron microscope (SEM) results revealed that concrete cured at elevated temperatures exhibited a more condensed phase and contained a higher percentage of hydrates than that cured for 7 d in the standard curing condition. However, after 56 d of curing, concrete in the standard curing condition exhibited a more stable phase and a higher concentration of hydrates.

scholarly journals Prediction of the Tensile Strength of Normal and Steel Fiber Reinforced Concrete Exposed to High Temperatures

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Mehrdad Abdi Moghadam ◽  
Ramezan Ali Izadifard
Keyword(s):  
Tensile Strength ◽  
Reinforced Concrete ◽  
High Temperature ◽  
High Temperatures ◽  
Steel Fiber ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Steel Fiber Reinforced Concrete ◽  
High Temperature Exposure ◽  
Temperature Exposure

AbstractThe tensile strength of concrete has a great impact on the performance of concrete structures, especially for members exposed to high temperatures. The inclusion of steel fibers in concrete is one of the measures to retrieve the loss of tensile strength. The previous equations for the prediction of the tensile strength, are valid for conventional concrete and can predict the tensile strength after high-temperature exposure. Therefore, they are unsatisfactory for forecasting the tensile strength of plain and steel fiber reinforced concrete under high-temperature exposure. To establish a model that can effectively simulate the tensile strength of plain concrete, specimens with compressive strengths of 20–80 MPa are tested. Then by performing tensile strength tests on the specimens containing various content of steel fiber, an equation for prediction of the tensile strength at the ambient temperature is proposed. Meanwhile, the tensile strength tests are conducted at temperatures of 100–800 °C to develop a model for high-temperature exposure. The results indicate that an increase of compressive strength from 20 to 84 improves the tensile strength by 169.4%, and the incorporation of 0.25 and 0.5% of steel fibers can improve the tensile strength of normal concrete by 58.48 and 80.29% on average at the tested temperatures, respectively. Moreover, the proposed model is able to predict the tensile strength of normal and steel fiber reinforced concrete exposed to high temperatures accurately. This equation would help a wider application of the steel fibers in the construction industry with the risk of a fire accident.

scholarly journals Image analysis on disintegrated concrete at the post-heating stage

2020 ◽  
Vol 10 (2) ◽  
pp. 219-229
Author(s):  
A. H. Akca ◽  
N. Özyurt
Keyword(s):  
Compressive Strength ◽  
Image Analysis ◽  
High Temperature ◽  
Crack Growth ◽  
High Temperature Exposure ◽  
Single Lens ◽  
Temperature Exposure ◽  
Extent Of Damage ◽  
Damage In Concrete ◽  
Non Destructive

The relation between crack growth and reduction in the compressive strength after high temperature exposure and after air re-curing was investigated in this study. Concrete specimens were heated to 1000 ºC and they were subjected to air re-curing for 28 days. During re-curing period, their heated surfaces were monitored by using a digital single-lens reflex camera and the images were analyzed by using image analysis software. After cooling, the maximum reduction in the compressive strength of concrete was 49.5% and that of air re-cured concrete was 66.8%. Image analyses showed high correlations between crack growth and reduction in the compressive strength. This non-destructive method has the potential to represent the extent of damage in concrete after high temperature exposure.

The Effect of High Temperature Exposure on Properties of Hybrid Fiber Reinforced UHPC

2017 ◽  
Vol 909 ◽  
pp. 275-279
Author(s):  
Jan Fořt ◽  
David Čítek ◽  
Milena Pavlíková ◽  
Zbyšek Pavlík
Keyword(s):  
High Temperature ◽  
High Performance ◽  
Structural Changes ◽  
Physical And Mechanical Properties ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
High Temperature Exposure ◽  
High Performance Fiber ◽  
Concrete Damage ◽  
Temperature Exposure

High Performance Fiber Reinforced Concrete (HPFRC) became very popular material for its high mechanical strength, elastic modulus and corrosion resistance. However, also its high-temperature resistance is of a particular importance because of the fire safety. Therefore, the effect of high-temperature exposure on UHPC reinforced by combination of steel and PVA fibers was studied in the paper. PVA fibers were used to moderate concrete damage induced by water vapor evaporation from dense UHPC matrix. The UHPFRC samples were exposed to the temperatures of 200 °C, 400 °C, 600 °C, 800 °C, and 1 000 °C respectively. Concrete structural changes induced by high temperature action were described by the measurement of basic physical and mechanical properties. The realized experiments provide information on the changes of concrete porosity and loss of mechanical resistivity.

Performance of Concrete at Sustained High Temperature in Material Applications

2012 ◽  
Vol 578 ◽  
pp. 150-153
Author(s):  
Hong Zhu Quan
Keyword(s):  
Weight Loss ◽  
Compressive Strength ◽  
High Temperature ◽  
Portland Cement ◽  
Test Results ◽  
Test Procedures ◽  
High Temperature Exposure ◽  
Concrete Properties ◽  
Early Strength ◽  
Temperature Exposure

The effects of sustained high temperature on concrete properties are discussed in this paper. In this experiment, concrete with 6 types of cement were tested after high temperature exposure. Although, test procedures were the same as past literature, test results showed different tendency. The temperature of 50°C at which compressive strength was minimal were found for concrete with high-early strength and medium-heat portland cement, which concrete with other cements showed no change up to 110°C. Relationship between weight loss and compressive strength differed from past literature.

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