Compressive Strength of Various Types of Concrete Exposed to Elevated Temperature

2020 ◽  
Vol 309 ◽  
pp. 62-67
Author(s):  
Kateřina Horníková ◽  
Marek Foglar
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
High Temperatures ◽  
High Performance ◽  
High Performance Concrete ◽  
Experimental Results ◽  
Experimental Program ◽  
Polypropylene Fibres ◽  
Compressive Strength Of Concrete ◽  
Air Entrained Concrete

This paper presents the results of experimental program focused on change of compressive strength of concrete exposed to elevated temperature. The change of compressive strength was studied for several types of concrete with different properties (common concrete, air-entrained concrete, concrete with polypropylene fibres, high performance concrete with steel fibres and concrete with basalt fibres). The samples were exposed to high temperatures up to 1000 0C at, the compressive strength was measured at the elevated temperature. This paper presents results of this experiment and comparison of experimental results with available data from literature and valid Eurocodes.

scholarly journals Effects of polypropylene fibers on ultra high performance concrete at elevated temperature

2020 ◽  
Vol 21 ◽  
pp. 11-16
Author(s):  
Ahmed Maher Seyam ◽  
Samir Shihada ◽  
Rita Nemes
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elevated Temperature ◽  
Fire Resistance ◽  
Quartz Sand ◽  
High Performance ◽  
High Performance Concrete ◽  
Mineral Admixture ◽  
Ultra High Performance Concrete ◽  
Polypropylene Fibres

This paper presents an experimental study to evaluate the influence of polypropylene on fire resistance of ultra-high performance concrete (UHPC). Concrete mixtures are prepared by using different percentages of polypropylene fibres 0%, 0.75% and 1.5%, by volume. Samples are heated to 250 or 500 °C, for exposures 2.5 or 5 hours, and tested after cooling for compressive strength and flexural tensile strength. The research includes the use of mineral admixture of a recognized, polypropylene fibre, quartz sand, superplasticizers and without using any type of aggregates other than the quartz sand. The effect on subjected samples to elevated temperature up to 250 ºC and 500 ºC for durations 2.5 hours and 5 hours was studied for each mix and comparing the results of compressive strength and tensile strength among the mixes. Results obtained, showed that adding 0.75% of polypropylenes fibres only to a concrete mixture, improved the fire resistance of the concrete by 27% and 72% when the samples exposed to 250 ºC and 500 ºC for 2.5 hours respectively, compared with concrete mixes without fibres. In addition, the residual strength was improved by 39% and 14% when the samples exposed to 250 ºC and 500 ºC for 5 hours, respectively.

Macroscopic and Microscopic Properties of High Performance Concrete with Partial Replacement of Cement by Fly Ash

2019 ◽  
Vol 292 ◽  
pp. 108-113 ◽  
Author(s):  
Josef Fládr ◽  
Petr Bílý ◽  
Roman Chylík ◽  
Zdeněk Prošek
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
High Performance ◽  
High Performance Concrete ◽  
Partial Replacement ◽  
Experimental Program ◽  
Second Phase ◽  
Depth Of Penetration ◽  
Cement Replacement

The paper describes an experimental program focused on the research of high performance concrete with partial replacement of cement by fly ash. Four mixtures were investigated: reference mixture and mixtures with 10 %, 20 % and 30 % cement weight replaced by fly ash. In the first stage, the effect of cement replacement was observed. The second phase aimed at the influence of homogenization process for the selected 30% replacement on concrete properties. The analysis of macroscopic properties followed compressive strength, elastic modulus and depth of penetration of water under pressure. Microscopic analysis concentrated on the study of elastic modulus, porosity and mineralogical composition of cement matrix using scanning electron microscopy, spectral analysis and nanoindentation. The macroscopic results showed that the replacement of cement by fly ash notably improved compressive strength of concrete and significantly decreased the depth of penetration of water under pressure, while the improvement rate increased with increasing cement replacement (strength improved by 18 %, depth of penetration by 95 % at 30% replacement). Static elastic modulus was practically unaffected. Microscopic investigation showed impact of fly ash on both structure and phase mechanical performance of the material.

Usage of Heat Pretreatment for Reduction of Explosive Spalling of High Performance Concrete

2014 ◽  
Vol 1054 ◽  
pp. 37-42
Author(s):  
Iveta Nováková ◽  
Ulrich Diederichs ◽  
Lenka Bodnárová
Keyword(s):  
Compressive Strength ◽  
Water Vapour ◽  
High Performance ◽  
High Performance Concrete ◽  
Mercury Porosimetry ◽  
Concrete Structures ◽  
Explosive Spalling ◽  
Polypropylene Fibres ◽  
Rapid Reduction ◽  
Micro Cracks

Fire resistance of concrete structures could be improved by add of polypropylene fibres in to the concrete mixture in butch from 1 to 2 kg per 1 m3 of fresh concrete. This method is effective, but it is not possible to use it for existing concrete and existing reinforced concrete structures. The new method which has good potential for fire protection of existing structures is based on creation of capillary pore and micro cracks system, which allowed water vapour evaporate from concrete. This study deals with determination of appropriate temperature in which is created adequate network of capillary pores and micro cracks which has no influence on strength and durability of the concrete. The formation of macro cracks and bigger pores could cause rapid reduction of compressive and tensile strength, decrease of resistance to aggressive substances and decrease of the frost resistance. The high performance concrete (HPC) has very low porosity, which can cause explosive spalling while the water vapour tries to evaporate from concrete structure during the fire. The HPC concrete has high compressive strength and high density. The HPC samples were exposed to temperatures 150, 250, 350 a 450°C, and after cooling down to normal ambient were carried out tests to define changes in porosity by mercury porosimetry, mass looses and compressive strength changes. The heated HPC concrete is regaining humidity into its structure from surrounding atmosphere, which can cause rehydratation of some chemical compounds. [1] For verification of these hypotheses the HPC samples were kept in water storage for 4 weeks and then tested.

scholarly journals The Statistical Analysis of Relation between Compressive and Tensile/Flexural Strength of High Performance Concrete

2016 ◽  
Vol 62 (4) ◽  
pp. 95-108 ◽  
Author(s):  
M. Kępniak ◽  
P. Woyciechowski
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Flexural Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Influential Factors ◽  
Experimental Results ◽  
Model Code ◽  
Splitting Test ◽  
Model Code 2010

AbstractThis paper addresses the tensile and flexural strength of HPC (high performance concrete). The aim of the paper is to analyse the efficiency of models proposed in different codes. In particular, three design procedures from: the ACI 318 [1], Eurocode 2 [2] and the Model Code 2010 [3] are considered. The associations between design tensile strength of concrete obtained from these three codes and compressive strength are compared with experimental results of tensile strength and flexural strength by statistical tools. Experimental results of tensile strength were obtained in the splitting test. Based on this comparison, conclusions are drawn according to the fit between the design methods and the test data. The comparison shows that tensile strength and flexural strength of HPC depend on more influential factors and not only compressive strength.

scholarly journals Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures

Buildings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 416
Author(s):  
Yunfeng Qian ◽  
Dingyi Yang ◽  
Yanghao Xia ◽  
Han Gao ◽  
Zhiming Ma
Keyword(s):  
Compressive Strength ◽  
Transport Properties ◽  
High Temperatures ◽  
High Performance ◽  
High Performance Concrete ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Capillary Absorption ◽  
Self Healing

Ultra-high performance concrete (UHPC) has a high self-healing capacity and is prone to bursting after exposure to high temperatures due to its characteristics. This work evaluates the damage and improvement of UHPC with coarse aggregates through mechanical properties (compressive strength and ultrasonic pulse velocity), transport properties (water absorption and a chloride diffusion test), and micro-properties such as X-ray diffraction (XRD), Mercury intrusion porosimetry (MIP), and Scanning electronic microscopy (SEM). The result demonstrates that polypropylene (PP) fibers are more suitable for high temperature tests than polyacrylonitrile (PAN) fibers. The result shows that 400 °C is the critical temperature point. With the increase in temperature, the hydration becomes significant, and the internal material phase changes accordingly. Although the total pore volume increased, the percentage of various types of pores was optimized within 400 °C. The mass loss gradually increased and the ultrasonic pulse velocity gradually decreased. While the compressive strength first increased and then decreased, and the increase occurred within 25–400 °C. As for the transport properties, the chloride migration coefficient and capillary absorption coefficient both increased dramatically due to the higher sensitivity to temperature changes. The results of the property improvement test showed that at temperatures above 800 °C, the compressive strength recovered by more than 65% and the ultrasonic pulse velocity recovered by more than 75%. In terms of transport properties, compared to the results before self-healing, the chloride migration coefficient decreased by up to 59%, compared with 89% for the capillary absorption coefficient, after self-healing at 800 °C. With respect to the enhancement effect after exposure to high temperatures, the environment of a 5% Na2SO4 solution was not as good as the clean water environment. The corresponding changes in microstructure during the high temperatures and the self-healing process can explain the change in the pattern of macroscopic properties more precisely.

scholarly journals Mechanical Properties of Ultra-High Performance Concrete before and after Exposure to High Temperatures

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 770 ◽  
Author(s):  
How-Ji Chen ◽  
Yi-Lin Yu ◽  
Chao-Wei Tang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Temperatures ◽  
High Performance ◽  
High Performance Concrete ◽  
Silicon Powder ◽  
Supplementary Cementitious Materials ◽  
Ultra High Performance Concrete ◽  
Splitting Strength ◽  
Experimental Group

Compared with ordinary concrete, ultra-high performance concrete (UHPC) has excellent toughness and better impact resistance. Under high temperatures, the microstructure and mechanical properties of UHPC may seriously deteriorate. As such, we first explored the properties of UHPC with a designed 28-day compressive strength of 120 MPa or higher in the fresh mix phase, and measured its hardened mechanical properties at seven days. The test variables included: the type of cementing material and the mixing ratio (silica ash, ultra-fine silicon powder), the type of fiber (steel fiber, polypropylene fiber), and the fiber content (volume percentage). In addition to the UHPC of the experimental group, pure concrete was used as the control group in the experiment; no fiber or supplementary cementitious materials (silica ash, ultra-fine silicon powder) were added to enable comparison and discussion and analysis. Then, the UHPC-1 specimens of the experimental group were selected for further compressive, flexural, and splitting strength tests and SEM observations after exposure to different target temperatures in an electric furnace. The test results show that at room temperature, the 56-day compressive strength of the UHPC-1 mix was 155.8 MPa, which is higher than the >150 MPa general compressive strength requirement for ultra-high-performance concrete. The residual compressive strength, flexural strength, and splitting strength of the UHPC-1 specimen after exposure to 300, 400, and 500 °C did not decrease significantly, and even increased due to the drying effect of heating. However, when the temperature was 600 °C, spalling occurred, so the residual mechanical strength rapidly declined. SEM observations confirmed that polypropylene fibers melted at high temperatures, thereby forming other channels that helped to reduce the internal vapor pressure of the UHPC and maintain a certain residual strength.

Influence of Metakaolin on Mechanical Properties of High-Performance Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 1904-1909
Author(s):  
Bao Min Wang ◽  
Wei Liu
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Equal Mass ◽  
Test Results ◽  
Optimum Temperature ◽  
Compressive Strength Of Concrete ◽  
And Performance

Kaolin is a material with broad sources and a low price. Metakaolin is made from kaolin which is calcined, finely ground at an optimum temperature of 750 being kept constant for 4 hours. High strength and performance concrete can be mixed from metakaolin as a substitute for equal mass cement. The influences of 5%, 10% and 15% metakaolin in substitution of equal cement masses were studied on the mechanical properties of high-performance concrete. The test results showed that the addition of metakaolin improved the cubic compressive strength, splitting tensile strength and flexural strength of HPC, among which the improvement in compressive strength was the most siginificant, and simultaneously, there was also an improvement in concrete toughness in a certain degree. The optimum content of metakaolin is 10% resulting in an increase of the cubic compressive strength of concrete by 8.3% correspondingly.

scholarly journals COMPORTAMENTO DO CONCRETO MEDIANTE A ADIÇÃO DE POZOLANA ARTIFICIAL

e-xacta ◽  
2013 ◽  
Vol 6 (1) ◽  
pp. 55
Author(s):  
Nathália Maria Assi Rabelo ◽  
Christianne Rodrigues Garcia
Keyword(s):  
Air Pollution ◽  
Compressive Strength ◽  
High Performance ◽  
Laboratory Tests ◽  
High Performance Concrete ◽  
Cement Ratio ◽  
Compressive Strength Of Concrete ◽  
Reduce Energy Consumption ◽  
Para Determinar ◽  
Mineral Waste

<p align="justify">A utilização de resíduos minerais vem sendo empregada na indústria do concreto, trazendo vantagens em âmbitos técnicos, econômicos e ambientais. Ao substituir o cimento por esses resíduos, há a redução do consumo de energia e poluição do ar, gerados por sua produção e, ainda, contribui na busca por concretos de alto desempenho. Nesse contexto, o presente trabalho teve como objetivo adicionar pozolana artificial ao concreto e determinar a resistência à compressão, assim como a sua trabalhabilidade, além de estabelecer um comparativo entre o concreto adicionado de pozolana artificial e o concreto sem adição, contendo somente o cimento Portland. Através de ensaios laboratoriais, observou-se que a pozolana, devido a características específicas, não apresentou resultados favoráveis. Em sua adição ao concreto, observou-se que a quantidade de água necessária para a realização dos ensaios foi maior, alterando assim a relação água/cimento, sendo consequentemente necessário um aumento da quantidade de cimento. Observou-se, também, que houve uma queda na resistência à compressão do concreto, devido à presença da pozolana. Verificou-se que o material estudado necessita de modificações em suas propriedades para a sua utilização como insumo do concreto, portanto novas pesquisas, com um maior número de ensaios, foram sugeridas para determinar a sua viabilidade.</p><p align="justify">Abstract</p><p align="justify">Mineral waste has been used in the concrete industry, bringing advantages in technical fields, economic and environmental. By replacing the cement by these residues eventually reduce energy consumption and air pollution generated by their production and also help in the search for high performance concrete. In this context, the present study aimed to add artificial pozzolan to concrete and to determine the compressive strength, as well as its workability, and establish a comparison between the concrete and artificial pozzolan added without adding concrete containing only Portland cement. Through laboratory tests, it was observed that the pozzolan, due to specific features, showed no favorable results. In its addition in concrete, it was observed that the amount of water required for the tests was greater, thus altering the water / cement ratio, and is therefore required an increased amount of cement. It was also observed that there was a decrease in the compressive strength of concrete due to the presence of pozzolan. It was found that the studied material requires changes in its properties for use as an input of the concrete, thus further research, with a greater number of tests have been suggested to determine their viability.</p>

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