Influence of Cooling Methods on the Residual Mechanical Behavior of Fire-Exposed Concrete: An Experimental Study

This work reports the main conclusions of a study on the mechanical behavior of concrete under ISO 834 fire with different cooling methods. The aim of this research was to provide reliable data for the analysis of structures damaged by fire. The experimental program used cylindrical concrete test specimens subjected to ISO 834 heating in a furnace up to maximum gas temperatures of 400, 500, 600, 700, and 800 °C. The compressive strength was measured in three situations: (a) at the different temperature levels reached in the furnace; (b) after a natural cooling process; and (c) after aspersion with water at ambient temperature. The results indicate that the concrete residual compressive strength is fairly dependent on the maximum temperature reached in the furnace and revealed that concrete of a lower strength preserved relatively higher levels of strength. The cooling method significantly influenced the strength, albeit at a lower intensity. In all cases, the residual strength remained in the range of 38% to 67% of the strength at ambient temperature. The statistical analysis showed that the data obtained by the experimental program are significant and confirmed the influence of the conditions imposed on the residual strength.

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Reduction of Postfire Properties of High-Strength Concrete

Advances in Materials Science and Engineering ◽

10.1155/2013/712953 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 6

Author(s):

Neno Torić ◽

Ivica Boko ◽

Bernardin Peroš

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

High Temperature ◽

Ambient Temperature ◽

Modulus Of Elasticity ◽

High Strength Concrete ◽

High Strength ◽

Maximum Temperature ◽

Secant Modulus ◽

Strength Concrete

This paper presents an experimental study of behaviour of high-strength concrete at high temperature. Reduction of the mechanical properties of concrete was determined starting from the period when the concrete specimens were heated to the maximum temperature and cooled down to ambient temperature and the additional 96 hours after the initial cooling of the specimens. The study includes determination of compressive strength, dynamic and secant modulus of elasticity, and stress-strain curves of concrete specimens when exposed to temperature level up to 600°C. The study results were compared with those obtained from other studies, EN 1994-1-2 and EN 1992-1-2. Tests point to the fact that compressive strength of concrete continues to reduce rapidly 96 hours after cooling of the specimens to ambient temperature; therefore indicating that the mechanical properties of concrete have substantial reduction after being exposed to high temperature. The study of the dynamic and secant modulus of elasticity shows that both of the properties are reduced but remain constant during the period of 96 hours after cooling. The level of postfire reduction of compressive strength of the analyzed concrete is substantial and could significantly affect the postfire load bearing capacity of a structure.

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Microstructure and Mechanical Behavior of Hot Pressed Cu-Sn Powder Alloys

Advances in Materials Science and Engineering ◽

10.1155/2016/9796169 ◽

2016 ◽

Vol 2016 ◽

pp. 1-10 ◽

Cited By ~ 8

Author(s):

Ahmed Nassef ◽

Medhat El-Hadek

Keyword(s):

Wear Resistance ◽

Compressive Strength ◽

Mechanical Behavior ◽

Compression Fracture ◽

Intermetallic Phases ◽

Limited Area ◽

Lower Strength ◽

Powder Alloys ◽

Significant Difference ◽

Release Of Load

Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing technique. The influence of densifying on the properties of the hot pressed materials was investigated. The properties, such as the hardness, compressive strength, and wear resistance of these materials, were determined. The hot pressed Cu-Sn specimens included intermetallic/phases, which were homogeneously distributed. The presence of graphite improved the wear resistance of Cu-Sn alloys three times. Similarly, the presence of lead improved the densification parameter of Cu-Sn alloys three times. There was no significant difference in the mechanical behavior associated with the addition of Pb to the Cu-Sn alloys, although Cu-Pb alloys showed considerably higher ultimate strength and higher elongation. The Cu-Sn-C alloys had lower strength compared with those of Cu-Sn alloys. Evidence of severe melting spots was noticed in the higher magnifications of the compression fracture surface of 85% Cu-10% Sn-5% C and 80% Cu-10% Sn-10% Pb alloys. This was explained by the release of load at the final event of the fracture limited area.

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Correlation Analysis of Heat Curing and Compressive Strength of Carbon Nanotube–Cement Mortar Composites at Sub-Zero Temperatures

Crystals ◽

10.3390/cryst11101182 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1182

Author(s):

Heeyoung Lee ◽

Jongkyeong Seong ◽

Wonseok Chung

Keyword(s):

Compressive Strength ◽

Carbon Nanotube ◽

Ambient Temperature ◽

Temperature Change ◽

Maximum Temperature ◽

Cementitious Composite ◽

Mwcnt Content ◽

Heat Curing ◽

Multi Walled Carbon Nanotube ◽

Experimental Parameters

Concrete curing under sub-zero temperatures causes various problems, such as initial cracking and a decrease in mechanical strength. This study investigated the effect of sub-zero ambient temperature and multi-walled carbon nanotube (MWCNT) content on the heat and strength characteristics of heat-cured MWCNT cementitious composites. The experimental parameters were the application of heat curing, MWCNT content, use of an insulation box to achieve a closed system, and ambient temperature. The results showed that the internal temperature change of the MWCNT cementitious composite increased with the ambient temperature and MWCNT content. When an insulation box was installed, the maximum temperature change of the MWCNT cementitious composite during curing increased. Furthermore, heat curing increased the compressive strength of the cementitious composite. Moreover, a microstructure analysis using field-emission scanning electron microscopy verified the formation of a MWCNT network among the cement hydrates.

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Effects of Basalt Fibres on Mechanical Properties of Concrete

MATEC Web of Conferences ◽

10.1051/matecconf/201814901028 ◽

2018 ◽

Vol 149 ◽

pp. 01028 ◽

Cited By ~ 2

Author(s):

A. M. El-Gelani ◽

C.M. High ◽

S. H. Rizkalla ◽

E. A. Abdalla

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Residual Strength ◽

Rupture Strength ◽

Modulus Of Rupture ◽

Experimental Program ◽

Clear Correlation ◽

Basalt Fibre ◽

Aspect Ratios ◽

Average Residual

This paper presents the results of an experimental program carried out to investigate the effects of Basalt Fibre Reinforced Polymers (BFRP) on some fundamental mechanical properties of concrete. Basalt fibres are formed by heating crushed basalt rocks and funnelling the molten basalt through a spinneret to form basalt filaments. This type of fibres have not been widely used till recently. Two commercially available chopped basalt fibres products with different aspect ratios were investigated, which are dry basalt (GeoTech Fibre) and basalt pre-soaked in an epoxy resin (GeoTech Matrix) .The experimental work included compression tests on 96 cylinders made of multiple batches of concrete with varying amounts of basalt fibre additives of the two mentioned types, along with control batches containing no fibres. Furthermore, flexural tests on 24 prisms were carries out to measure the modulus of rupture, in addition to 30 prisms for average residual strength test. Results of the research indicated that use of basalt fibres has insignificant effects on compressive strength of plain concrete, where the increase in strength did not exceed about 5%. On the other hand, results suggest that the use of basalt fibres may increase the compressive strength of concrete containing fly as up top 40%. The rupture strength was increased also by 8% to 28% depending on mix and fibre types and contents. Finally, there was no clear correlation between the average residual strength and ratios of basalt fibres mixed with the different concrete batches.

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Experiment on the Mechanical Behavior of Ceramsite Concrete under Temperature-Load Coupling Field

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.357-360.817 ◽

2013 ◽

Vol 357-360 ◽

pp. 817-820

Author(s):

Pan Wang ◽

Dong Li ◽

Chao Wei Shen ◽

Wen Ting Jiang ◽

Jian Min Wang

Keyword(s):

Compressive Strength ◽

Mechanical Behavior ◽

Elevated Temperatures ◽

Lightweight Aggregate ◽

Deformation Curve ◽

Lightweight Aggregate Concrete ◽

Normal Density ◽

Loading Test ◽

Temperature Load ◽

Temperature Levels

Experiment on the mechanical behavior of ceramsite lightweight aggregate concrete (LWAC) after elevated temperatures was conducted in this paper. The ceramsite LWAC test blocks were first heated at five temperature levels, 200°C, 350°C, 500°C, 650°C and 800°C. The corresponding loading test was carried on after they were naturally cooled down. Changes of compressive strength, elastic modulus and load-deformation curve after different levels of high temperature were analyzed. The results indicate that, the reduction of ceramsite LWAC prism compressive strength is faster than that of cubic compressive strength. Compared with normal-density concrete (NC), whether for cubic or prism blocks, the residual compressive strength ratio of ceramsite LWAC is obviously larger than that of NC. The load-deformation curve of ceramsite LWAC with the elevated temperature is gradually flatter.

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Mass Concrete Placement of the Offshore Wind Turbine Foundation: A Statistical Approach to Optimize the Use of Fly Ash and Silica Fume

International Journal of Concrete Structures and Materials ◽

10.1186/s40069-021-00491-8 ◽

2021 ◽

Vol 15 (1) ◽

Author(s):

Mien Van Tran ◽

Vinh Ngoc Chau

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Wind Turbine ◽

Silica Fume ◽

Temperature Rise ◽

Strength Test ◽

Heat Of Hydration ◽

Maximum Temperature ◽

Experimental Program ◽

Compressive Strength Test

AbstractThe experimental program investigated concrete with a large amount of fly ash (FA) with silica fume (SF) to replace Portland cement on the results of semi-adiabatic test, compressive strength test, and the rapid chloride permeability test (RCPT). The replacement ratios of cement by a combination of FA and SF were 30%, 35%, and 40% by mass. The percentages of SF to replace cement were 0%, 4%, and 8% by mass. Three different water-to-binder ratios (W/B) of 0.34, 0.36, and 0.38 were also investigated. Multiple linear regression was applied to construct the predicted equations (models) for the semi-adiabatic temperature rise test and the compressive strength test. Models were assessed statistically and were used to solve the concrete mixture design optimization problems. The mixture with W/B of 0.36, 31% FA, and 5% SF was found to optimally satisfy the multi-objective problem: 28-day compressive strength of 50 MPa, low heat of hydration, and very low chloride penetrability classification. Field test on the actual wind turbine foundation of the optimal mixture revealed the maximum temperature rise was 74.8 °C and the maximum temperature differential was 21.9 °C.

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The influence of the addition of ground olive stone on the thermo-mechanical behavior of compressed earth blocks

Matériaux & Techniques ◽

10.1051/mattech/2020023 ◽

2020 ◽

Vol 108 (2) ◽

pp. 203

Author(s):

Samia Djadouf ◽

Nasser Chelouah ◽

Abdelkader Tahakourt

Keyword(s):

Thermal Conductivity ◽

Compressive Strength ◽

Mechanical Behavior ◽

Agricultural Waste ◽

Hydraulic Press ◽

Dry Density ◽

Olive Stone ◽

Compressed Earth Blocks ◽

Clay Matrix ◽

Earth Blocks

Sustainable development and environmental challenges incite to valorize local materials such as agricultural waste. In this context, a new ecological compressed earth blocks (CEBS) with addition of ground olive stone (GOS) was proposed. The GOS is added as partial clay replacement in different proportions. The main objective of this paper is to study the effect of GOS levels on the thermal properties and mechanical behavior of CEB. We proceeded to determining the optimal water content and equivalent wet density by compaction using a hydraulic press, at a pressure of 10 MPa. The maximum compressive strength is reached at 15% of the GOS. This percentage increases the mechanical properties by 19.66%, and decreases the thermal conductivity by 37.63%. These results are due to the optimal water responsible for the consolidation and compactness of the clay matrix. The substitution up to 30% of GOS shows a decrease of compressive strength and thermal conductivity by about 38.38% and 50.64% respectively. The decrease in dry density and thermal conductivity is related to the content of GOS, which is composed of organic and porous fibers. The GOS seems promising for improving the thermo-mechanical characteristics of CEB and which can also be used as reinforcement in CEBS.

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Effect of reduced graphene oxide on mechanical behavior of an epoxy adhesive in glassy and rubbery states

Journal of Composite Materials ◽

10.1177/00219983211031659 ◽

2021 ◽

pp. 002199832110316

Author(s):

Ata Khabaz-Aghdam ◽

Bashir Behjat ◽

EAS Marques ◽

RJC Carbas ◽

Lucas FM da Silva ◽

...

Keyword(s):

Graphene Oxide ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Ambient Temperature ◽

Mechanical Behavior ◽

Reduced Graphene Oxide ◽

Epoxy Adhesive ◽

Ultimate Strain ◽

Reduced Graphene

The mechanical behavior of an adhesive, in neat state and reinforced with up to 0.5 wt% of reduced graphene oxide (RGO) was investigated here. Tests were done at temperatures between the ambient temperature and the glass transition temperature ( Tg[Formula: see text] of the adhesive. Using a metal mold, cured plates of the neat and RGO reinforced epoxy adhesive were prepared. The adhesive powder and the bulk dumbbell-shaped specimens, obtained from cured adhesive plates, were subjected to differential scanning calorimetry (DSC) and tensile tests, respectively, to obtain the Tg as well as mechanical properties of the adhesives. The results indicated that adding RGO up to 0.5 wt% increased the glass transition temperature, the modulus of elasticity, and the strength of the adhesive. It was found that the presence of RGO reduced the adhesive’s strain at the break at the ambient temperature. However, at high temperatures, near the Tg, the ultimate strain of RGO-reinforced adhesives decreased slightly when compared to the ultimate strain of the neat specimens. This explains the reduction in toughness at ambient temperature obtained by adding RGO and the increase at high temperatures. Finally, the failure morphology of the neat and RGO-reinforced adhesive specimens was investigated using microscopic imaging of the specimens’ failure cross-sections, which supported and justified the experimental observations.

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Thermo-mechanical behavior of titanium beryllide pebble beds at ambient temperature

Fusion Engineering and Design ◽

10.1016/j.fusengdes.2021.112249 ◽

2021 ◽

Vol 165 ◽

pp. 112249

Author(s):

Joerg Reimann ◽

Benjamin Fretz ◽

Ramil Gaisin ◽

Aniceto Goraieb ◽

Jae-Hwan Kim ◽

...

Keyword(s):

Ambient Temperature ◽

Mechanical Behavior

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Ultrasonic Test on Recycled Concrete: Relationship among Ultrasonic Waves Velocity, Compressive Strength and Elastic Modulus

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.894.45 ◽

2014 ◽

Vol 894 ◽

pp. 45-49 ◽

Cited By ~ 1

Author(s):

Luisa Pani ◽

Lorena Francesconi

Keyword(s):

Compressive Strength ◽

Elastic Modulus ◽

Ultrasonic Wave ◽

Ultrasonic Test ◽

Ultrasonic Waves ◽

Recycled Concrete ◽

Recycled Aggregates ◽

Experimental Program ◽

Static Modulus ◽

Cylindrical Samples

In this paper an experimental program has been carried out in order to compare compressive strength fcand elastic static modulus Ecof recycled concrete with ultrasonic waves velocity Vp, to establish the possibility of employing nondestructive ultrasonic tests to qualify recycled concrete. 9 mix of concrete with different substitution percentage of recycled aggregates instead of natural ones and 27 cylindrical samples have been made. At first ultrasonic tests have been carried out on cylindrical samples, later elastic static modulus Ecand compressive strength fchave been experimentally evaluated. The dynamic elastic modulus Edhas been determined in function of ultrasonic wave velocity Vp; furthermore the correlations among Ed, Ec, fce Vphave been determined. It has been demonstrated that ultrasonic tests are suitable for evaluating different deformative and resisting concrete performances even when variations are small.

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