Residual properties of recycled concrete after exposure to high temperatures

2019 ◽  
Vol 71 (15) ◽  
pp. 781-793 ◽  
Author(s):  
Zongping Chen ◽  
Jianjia Chen ◽  
Fan Ning ◽  
Yi Li
Keyword(s):  
High Temperatures ◽  
Recycled Concrete ◽  
Residual Properties

scholarly journals Properties of Ambient-Cured Normal and Heavyweight Geopolymer Concrete Exposed to High Temperatures

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 740 ◽  
Author(s):  
Farhad Aslani ◽  
Zohaib Asif
Keyword(s):  
Mass Loss ◽  
High Temperatures ◽  
Offshore Structures ◽  
Normal Weight ◽  
Geopolymer Concrete ◽  
Coarse Aggregates ◽  
Residual Properties ◽  
New Type ◽  
Heavyweight Concrete ◽  
Underwater Structures

Ambient-cured heavyweight geopolymer concrete (HWGC) is a new type of concrete that combines the benefits of both heavyweight concrete (HWC) and geopolymer concrete (GC). HWGC provides proper protection from the sources that emit harmful radiations in medical and nuclear industries. Furthermore, HWGC may also be used in offshore structures for pipeline ballasting and similar underwater structures. In this study, heavyweight aggregates (magnetite) have been used and replaced by normal-weight coarse aggregates in GC at volume ratios of 50, 75, and 100% to attain heavyweight classification according to British standards. This study investigates the impacts of high temperatures on standard ambient-cured geopolymer concrete and ambient-cured HWGC through its residual properties regarding compressive and tensile strengths, mass loss, spalling intensity, and flexural strength. The residual properties were examined by heating 100 × 200 mm cylinder specimens to 100, 300, 600, and 900 °C. The results indicated that the maximum compressive strengths of 40.1 and 39.0 MPa were achieved by HWGC at 300 and 100 °C, respectively. The overall result shows that the strength of HWGC increases by increasing magnetite aggregate proportion, while the mass loss, intensity of spalling, and loss of strengths is proportional to temperature after a certain point. Minor spalling with holes and cracking was observed only at 900 °C in HWGC.

Recycled concrete exposed to high temperatures

2006 ◽  
Vol 58 (10) ◽  
pp. 675-682 ◽  
Author(s):  
C. J. Zega ◽  
A. A. Di Maio
Keyword(s):  
High Temperatures ◽  
Recycled Concrete

Understanding the effect of recycled concrete aggregate and cementitious materials on concrete's fire resistance

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammed Ahmed Abed ◽  
Eva Lubloy
Keyword(s):  
Fly Ash ◽  
High Temperatures ◽  
Fire Resistance ◽  
Blended Cement ◽  
Cementitious Materials ◽  
Recycled Concrete ◽  
Supplementary Cementitious Materials ◽  
Concrete Aggregate ◽  
Recycled Concrete Aggregate ◽  
Content Type

PurposeFire can severely affect concrete structures and with knowledge of the properties of materials, the damage can be assessed. Aggregate, cement matrix and their interaction are the most important components that affect concrete behaviour at high temperatures. The effect of incorporating recycled concrete aggregate or cementitious materials, namely, cement type and pulverized fly ash, are reviewed to provide a better understanding of their involvement in fire resistance.Design/methodology/approachMore investigation research is needed to understand the fire resistance of such sustainable concrete that was already constructed. The present study illustrates the effect of using recycled concrete aggregate and cementitious materials on the fire resistance of concrete. To do so, a literature review was conducted and relevant data were collected and presented in a simple form. The author's selected research findings, which are related to the presents study, are also presented and discussed.FindingsRecycled concrete aggregate enhances the concrete behaviour at high temperatures when it substitutes the natural aggregate by reasonable substitution (more than 25–30%). It also almost eliminates the possibility of spalling. Moreover, utilizing both supplementary cementitious materials with recycled concrete aggregate can improve the fire resistance of concrete. The incorporation of pulverized fly ash and slag in Portland cement or blended cement can generally keep the mechanical properties of concrete at a higher level after heating to a high temperature.Originality/valueRecycled concrete aggregate enhances the concrete behaviour at high temperatures when it substitutes the natural aggregate by reasonable substitution (more than 25–30%). It also almost eliminates the possibility of spalling. Moreover, utilizing both supplementary cementitious materials with recycled concrete aggregate can improve the fire resistance of concrete. The incorporation of pulverized fly ash and slag in Portland cement or blended cement can generally keep the mechanical properties of concrete at a higher level after heating to a high temperature.

Influence of lightweight aggregates on the physical and mechanical residual properties of concrete subjected to high temperatures

2021 ◽  
Vol 268 ◽  
pp. 121221
Author(s):  
Georges Roufael ◽  
Anne-Lise Beaucour ◽  
Javad Eslami ◽  
Dashnor Hoxha ◽  
Albert Noumowé
Keyword(s):  
High Temperatures ◽  
Lightweight Aggregates ◽  
Residual Properties

Steel and PVA Fibres Reinforced UHPC Exposed to High Temperatures - Analysis of Residual Properties

2017 ◽  
Vol 902 ◽  
pp. 26-32
Author(s):  
Jan Fořt ◽  
David Čítek ◽  
Milena Pavlíková ◽  
Jaroslav Pokorný ◽  
Martina Záleská ◽  
...  
Keyword(s):  
Pore Size ◽  
High Temperatures ◽  
High Performance ◽  
Structural Changes ◽  
High Performance Concrete ◽  
Colour Change ◽  
Fibre Reinforcement ◽  
Transport Parameters ◽  
Steel Fibres ◽  
Residual Properties

Residual parameters of Ultra High Performance Concrete (UHPC) exposed to high temperatures were experimentally accessed. The UHPC was provided by hybrid fibre reinforcement based on polyvinyl alcohol (PVA) and steel fibres. Among the studied material properties, bulk density, matrix density, total open porosity, pore size distribution, water vapour transmission and liquid water transport properties were examined. The UHPC samples were exposed to the temperatures 400 °C, 600 °C, 800 °C, and 1000 °C respectively. For comparative purposes, the reference UHPC samples cured at laboratory temperature were tested as well. Based on the obtained results, correlation between concrete structural changes and tested parameters was found out. The applied temperature load highly affected the concrete porosity, pore size, and thus both liquid and gaseous moisture transport parameters. Disintegration of concrete structure, colour change, cracking, damage of steel fibres (melting), and failure of their cohesion was apparent from optical microscopy analysis.

Effects of high temperature on the mechanical behavior of calcium silicate hydrate under uniaxial tension and compression

2021 ◽  
pp. 105678952199187
Author(s):  
Yao Zhang ◽  
Qing Chen ◽  
J Woody Ju ◽  
Mathieu Bauchy
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
High Temperature ◽  
High Temperatures ◽  
Calcium Silicate ◽  
Calcium Silicate Hydrate ◽  
Atomic Scale ◽  
Stress Strain ◽  
Residual Compressive Strength ◽  
Residual Properties

When subjected to high temperatures, cement-based materials can dehydrate, which, in turn, affects the mechanical property of the main binding phase (calcium silicate hydrate) at the atomic scale. However, the effects of high temperature on the tensile and compressive behavior of calcium silicate hydrate (C−S−H) grains under uniaxial loading remains poorly understood. In this work, based on reactive molecular simulations, the tensile strength, compressive strength, and stress-strain relations of C−S−H grains with four calcium/silicon (C/S) ratios (1.10, 1.33, 164, and 1.80) both under and after (residual properties) high temperatures are investigated. It is shown that C−S−H grains can shrink due to the water loss induced by high temperature, and a low C/S ratio can lead to a thermo-stable molecular structure. Meanwhile, the residual tensile strength can be enhanced, particularly the tensile strength in the z-direction. Upon the residual compressive strength, in the x and y directions, high temperature can decrease the residual compressive strength for C/S = 1.10 or 1.33 but has no apparent effect for C/S = 1.64 or 1.80. While in the z-direction, the residual compressive strength can be enhanced due to the reduction in the interlayer space. In addition, high temperature can improve the residual tensile ductility but has no obvious effect on the residual compressive stress-strain relations. As for the mechanical properties under high temperature, both the tensile and compressive strengths can be weakened except that the tensile strength in the z-direction can undergo an increasing trend when the temperature is below 800 K due to significant shrinkage in the z-direction. Moreover, high temperature can make stress-strain curves exhibit good plasticity. Discussion indicates that the strength degradation of C−S−H gels or cement paste exposure to high temperatures is likely caused by the increasing porosity and coarsening of the void or defect size.

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