Comportement thermohydrique d’une paroi en béton : influence du type de béton, influence du type de chargement

2007 ◽  
Vol 34 (10) ◽  
pp. 1364-1370
Author(s):  
M Shekarchi ◽  
G Debicki
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Phase Transfer ◽  
Moisture Distribution ◽  
Transfer Model ◽  
Concrete Wall ◽  
Two Phase ◽  
Ordinary Concrete ◽  
Hygrothermal Behavior ◽  
Hygrothermal Behaviour

Tests simulating “the accidental conditions” and the “test of heating,” without the contribution of humidity, have been carried out on test equipment that we designed and fabricated in the scope of this work. The tests have been carried out on laterally sealed and insulated cylindrical specimens of ordinary or high-performance concrete having a thickness of 1.3 m. Experimental results present temperature, pressure, and moisture distribution throughout the specimens and permit to characterize the hygrothermal behaviour of a concrete wall. The different aspects of the phenomena affecting a two-phase transfer (steam, water) in a porous medium are presented. Test results show that high-performance concrete exposed to an increase in temperature presents a particular hygrothermal behaviour, because of its microstructure, that is put into evidence, notably while looking at the role of the silica fume. The migration of water is not as rapid in high-performance concrete as in ordinary concrete, which is favourable for tightness. Numerical investigation consists of adapting a heat and mass transfer model, initially built for ordinary concrete, to the high-performance concrete used in this work.Key words: hygrothermal behavior, concrete wall, ordinary concrete, high-performance concrete, leak tightness, temperature distribution, pressure distribution, moisture distribution.

Optimized Cost of High Performance Concrete in the Build

2014 ◽  
Vol 911 ◽  
pp. 479-483 ◽  
Author(s):  
Samir Bouhedja ◽  
Boualem El Kechebour ◽  
Ahmed Boukhaled
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Economic Benefits ◽  
Reinforced Concrete Structures ◽  
National Plan ◽  
Conventional Concrete ◽  
Ordinary Concrete ◽  
Morphology And Structure ◽  
The Cost

The objective of this work is an analysis of the use of high performance concrete and it impact on the morphology and structure costs. The use of high performance concrete (HPC) in the construction of buildings and civil engineering works offers advantages in terms of durability, ease of implementation, reduction of deformation and shrinkage, increase the resistance of reinforced concrete structures. The economic benefits of the use of high performance concrete, compared to conventional concrete are illustrated by the reduction of the following costs: the implementation of concrete, the geometric sections of bearing elements of the built space and the maintenance of structures. The cost of high performance concrete, for the resistance inferior to 80 Mpa, gives a significative advantage comparatively to the steel and the ordinary concrete. The generalized use of this type of concrete in many countries has been stimulated by a national plan.

Future Research Trends in High-Performance Concrete: Cost-Effective Considerations

1997 ◽  
Vol 1574 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Chao-Lung Hwang ◽  
Long-Sherng Lee
Keyword(s):  
Cycle Length ◽  
High Performance ◽  
High Performance Concrete ◽  
Construction Material ◽  
Cost Effective ◽  
Research Trends ◽  
Future Research ◽  
Ongoing Research ◽  
Ordinary Concrete ◽  
High Rise

High-performance concrete (HPC) prepared on the basis of eugenic considerations (cost-effectiveness and life-cycle length) is proposed to resolve actual concrete problems. HPC is safe, durable, workable, economical, and ecologically sound. Concrete in Taiwan is always designed with large amounts of water and paste (even though it is generally accepted that the concrete will tend to crack and deteriorate). Therefore, HPC with fewer problems is the target of ongoing research. Eugenic HPC is produced from ordinary concrete, superplasticized concrete, pozzolanic concrete, and high-flowing concrete. Without the drawbacks of past forms of concrete, eugenic HPC is a better construction material on the basis of individual material characteristics. The characteristics of eugenic HPC are presented and illustrated by two high-rise buildings in Taiwan constructed with high-flowing HPC.

Prefabricated Box Girder with Ultra High Performance Concrete

2018 ◽  
Author(s):  
Keli Xiao ◽  
Yanjun Jin ◽  
Lin Li ◽  
Wei He ◽  
Duan Xinlong
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Slab Thickness ◽  
Low Carbon ◽  
Ultra High Performance Concrete ◽  
Dead Weight ◽  
Box Girder ◽  
Ordinary Concrete ◽  
Shear Connectors ◽  
Thin Beams

<p>In order to solve traffic difficulty brought by the bridge construction in the city, and difficult transportation of beams, this paper puts forward the prefabricated-box-girder bicycle viaduct with ultra - high performance concrete (UHPC) through which will achieve light and thin beams, easy transportation and rapid construction. Based on the bicycle viaduct with 5.5m in width, this paper not only designs a prefabricated ribbed thin-walled box girder with 30m in span, including the detailed design of prefabricated segment stiffeners, shear connectors and external prestressing but also compares the UHPC box girder with ordinary concrete box girder and steel box girder. The research shows that with the application of UHPC in prefabricated viaduct in city, the ratio of height to span of beams and the slab thickness decrease to 1/30 and 10cm respectively, the dead weight is 50% lower than that of the ordinary concrete beams and the 3m long lifting weight is only 10 tons. Light and thin beams are suitable for transportation in city because of their low requirements for transportation and hoisting equipment. UHPC beams have no steel bars and own the advantages of dense texture, good durability, low maintenance costs, reflecting the concept of low carbon environmental protection and green bridge.</p>

Modeling of Moisture Distribution Evolution in High-Performance Concrete under Fire Exposure

2014 ◽  
Vol 629-630 ◽  
pp. 279-283
Author(s):  
Jie Zhao ◽  
Gai Fei Peng
Keyword(s):  
Vapor Pressure ◽  
High Performance ◽  
High Performance Concrete ◽  
Water Saturation ◽  
Initial Moisture Content ◽  
Moisture Distribution ◽  
Distribution Analysis ◽  
Vapor Pressure Gradient ◽  
Fire Conditions

High-performance concrete (HPC) will undergo severe damage under fire conditions. It is well known that vapor pressure induced by high temperatures plays an important role in the damaging process. Therefore, the determination of the moisture distribution evolution in concrete is essential to the damage analysis of heated HPC. This paper presents a numerical method for the prediction of the moisture distribution evolution in HPC under fire conditions. In the method, the vapor pressure and the moisture transport induced by the vapor pressure gradient are analyzed. The effect of the thermal decomposition on the moisture distribution and the effects of the slippage flow and the water saturation degree on the permeability are considered. The proposed method is applied to the moisture distribution analysis of a concrete cube with 90% initial moisture content under fire conditions and can be further used for the analysis of the thermal damage of heated HPC.

Investigation of the Bond Behavior of UHPC

2014 ◽  
Vol 617 ◽  
pp. 225-228 ◽  
Author(s):  
David Čítek ◽  
Petr Huňka ◽  
Stanislav Řeháček ◽  
Jiří Kolísko
Keyword(s):  
Experimental Research ◽  
High Performance ◽  
High Performance Concrete ◽  
Anchorage Length ◽  
Bond Behavior ◽  
Ordinary Concrete ◽  
Pull Out ◽  
Prestressed Girders ◽  
Average Shear ◽  
Prestressing Strands

Ultra High Performance Concrete - UHPC has become increasingly used. Its outstanding features are generally known. It is a fact that the bond of the reinfocement in UHPC is better than that in ordinary concrete, but this bond needs to be quantified .The aim of the experimental research was to determine the average bond stress between prestressing strands and different types of UHPC and to show very significant increase in the average shear stress in bond with UHPC compared to ordinary concrete. In order to determine the bond capacity, an experimental research was carried out. Experimental details of the models in real structures – parts of prestressed girders made from UHPC, were tested in the laboratory and the results were compared with specimens prepared according to standard. The influence of different material properties and different anchorage length of prestressing strands to bond behavior of UHPC was examined in pull out tests. Test results of bond test led to the conclusion that the application of UHPC can significantly reduce the anchorage length of reinforcement compared with the ordinary concrete.

Assessment of Bond Behavior of UHPC and Prestressing Strands

2014 ◽  
Vol 1000 ◽  
pp. 247-250 ◽  
Author(s):  
David Čítek ◽  
Jan L. Vítek ◽  
Jiří Kolísko ◽  
Petr Huňka ◽  
Stanislav Řeháček
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Tensile Force ◽  
Bond Stress ◽  
Bond Behavior ◽  
Ordinary Concrete ◽  
Pull Out ◽  
High Durability ◽  
Prestressing Strands ◽  
Average Bond

Ultra High Performance Concrete - UHPC is a relatively new type of composite material with outstanding features (high compressive strength, high tensile strength and high durability). Also the bond strength between steel reinforcement and UHPC is better than that in ordinary concrete. This fact needs to be quantified, because no standard prescribes the bond behavior of UHPC and design of UHPC in general. The main aim of the experimental research was to determine the average bond stress between prestressing strands and different types of UHPC. The second aim was to show very significant increase of the average shear stress in bond of UHPC compared to that of ordinary concrete. In order to determine the bond capacity, two types of experimental specimens – parts of prestressed girders and specimens prepared according to standard, were tested in the laboratory. The specimens were prepared for pull out test, in which the prestressing strand is pulled out from the cube or part of girder made from UHPC. The tensile force in strand and slip of the end of reinforcement were measured and then the average bond stress was examined. The influence of different material properties and different anchorage lengths of prestressing strands to bond behavior of UHPC was examined and results were compared to these phenomena of ordinary concrete. The results of bond test led to the conclusion that the application of UHPC can significantly reduce the anchorage length of reinforcement compared with that in ordinary concrete.

Properties of Cracking Resistance of Cemfiber Reinforced Concrete

2007 ◽  
Vol 280-283 ◽  
pp. 1765-1770 ◽  
Author(s):  
Feng Xing ◽  
Fa Guang Leng ◽  
Wei Wen Li
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Polypropylene Fiber ◽  
Shrinkage Strain ◽  
Early Age ◽  
Polypropylene Fibers ◽  
Cracking Resistance ◽  
Ordinary Concrete ◽  
Concrete Form

Polypropylene fiber is a new measure to prevent plastic cracks of concrete. Effects of the parameters, such as dosage and types of fibers, on the plastic cracks were studied systematically. The properties of cracking resistance of mortar, ordinary concrete and high performance concrete were investigated by using samples of two types in shape. The results show that: (1) polypropylene fibers may increase the cracking resistance of concrete further; (2) as smaller quantity of cement and higher quantity of aggregate as possible should be used to prevent concrete form cracking; (3) the main reason why polypropylene fibers increase cracking resistance of concrete is that they increase strain capacity of concrete at early age, decrease shrinkage strain, improve plastic tensile strength and decrease tensile stress of the capillary.

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