Influence of basalt-polypropylene fibres on fracture properties of high performance concrete

2019 ◽  
Vol 209 ◽  
pp. 23-33 ◽  
Author(s):  
Piotr Smarzewski
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Polypropylene Fibres ◽  
Fracture Properties

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.

Relaxation of Structural Concrete due to its Shrinkage in Terms of Age-Adjusted Effective Modulus Method

2017 ◽  
Vol 737 ◽  
pp. 471-476
Author(s):  
Lukáš Zvolánek ◽  
Ivailo Terzijski
Keyword(s):  
Residual Stresses ◽  
High Performance ◽  
High Performance Concrete ◽  
Relaxation Mechanism ◽  
Effective Modulus ◽  
Tensile Creep ◽  
Ring Test ◽  
Polypropylene Fibres ◽  
Creep Effect ◽  
Modulus Method

This paper focuses on the calculation of residual stresses due to shrinkage with a tensile creep effect. Whereas the shrinkage of concrete causes stresses in the material, the tensile creep counteracts the shrinkage as a stress relaxation mechanism. The main objective of this paper is to evaluate the ageing coefficient c (referred to as Trost-Bazant Coefficient) reflecting the load history. The coefficient is used for the residual stress analysis by means of a simplified method called Age-adjusted Effective Modulus Method. The tensile creep effect was evaluated according to the rheological model provided by Eurocode 2. Although the Eurocode predicts the creep for the structural members subjected to compressive stresses, this study proves that it can be used for the tensile creep prediction as well. We tested three types of concrete: reference concrete, high-performance concrete with reduced shrinkage magnitude by means of special admixtures, and fibre concrete with the content of polypropylene fibres. From the obtained results, it can be stated, that the ageing coefficient can be considered to be the value of 0.45 for any shrinkage development. It was also proved, that the tensile creep value essentially affects the magnitude of residual stresses, even in the “early age” concrete. The correctness of the calculated residual stresses was verified by means of a Ring-test.

Evolution from High Strength Concrete to High Performance Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 49-54
Author(s):  
Vlastimil Bílek ◽  
Vladimíra Tomalová ◽  
Petr Hájek ◽  
Ctislav Fiala
Keyword(s):  
High Strength Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Maximum Size ◽  
Point Of View ◽  
Fracture Properties ◽  
Strength Concrete ◽  
Time Period ◽  
Long Term Observation

High strength concrete for the production of concrete railway sleepers was designed more than 20 years ago. The compressive strength of the concrete was very high from the start, but flexure strengths showed some irregular development - a decrease in time. Later, also a significant decrease of fracture properties was recorded. Microcracking was found to be the reason for this; therefore some modifications were performed to avoid this happening (especially the reduction of the maximum size of aggregates from 22 mm to 16 mm or 11 mm). Some problems concerning frost resistance of the concrete with a slag addition were reduced by applying ternary binders. All of the results are discussed from the point of view of a long-term observation of the strengths and fracture properties ́ development during the time period of 5 years or even more.

Fracture properties of high-performance concrete containing fly ash

2012 ◽  
Vol 226 (2) ◽  
pp. 170-176 ◽  
Author(s):  
P Zhang ◽  
Q Li ◽  
H Zhang
Keyword(s):  
Fly Ash ◽  
Crack Opening Displacement ◽  
High Performance ◽  
High Performance Concrete ◽  
Crack Opening ◽  
Ash Content ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Fracture Properties ◽  
Fracture Parameters

A parametric experimental study has been conducted to investigate the effect of fly ash on the fracture properties of high-performance concrete (HPC), with four fly ash contents used. By means of three-point bending method, the fracture toughness, fracture energy, effective crack length, critical crack opening displacement, and maximum crack opening displacement of the specimen were measured, respectively. The results indicate that fly ash has great improvement on the fracture parameters, and these fracture parameters gradually increase when the content of fly ash increases from 10 per cent to 20 per cent. However, these fracture parameters begin to decrease after the fly ash content exceeds 20 per cent. Besides, as the fly ash content increases from 10 per cent to 20 per cent, the relational curves between the vertical load and the mid-span deflection ( PV– δ), crack mouth opening displacement ( PV– CMOD), and crack tip opening displacement ( PV– CTOD) become plumper and plumper, which indicates that the capability of HPC containing fly ash to resist crack propagation is becoming stronger and stronger, while the curves become shriveled after the fly ash content exceeds 20 per cent. The contribution of fly ash on the fracture properties of HPC containing fly ash seems to be performed only when the fly ash content does not exceed 20 per cent.

scholarly journals Probabilistic fatigue analysis of ultra-high-performance fibre-reinforced concrete under thermal effects

2018 ◽  
Vol 165 ◽  
pp. 12001
Author(s):  
José D. Ríos ◽  
Héctor Cifuentes
Keyword(s):  
Reinforced Concrete ◽  
Thermal Effects ◽  
High Performance ◽  
High Performance Concrete ◽  
Fatigue Behaviour ◽  
Fibre Reinforcement ◽  
Fibre Reinforced Concrete ◽  
Ultra High Performance Concrete ◽  
Polypropylene Fibres ◽  
High Performance Fibre

This paper describes the influence of the temperature and the fibre reinforcement on the flexural fatigue behaviour of an ultra-high-performance fibre-reinforced concrete. Three-point bending fatigue tests were carried out for an ultra-high-performance concrete subjected to different temperatures ranging from room temperature up to 300 ºC and considering three different types of reinforcement: a) steel fibres, b) hybrid steel and polypropylene fibres and c) non-reinforced (reference matrix). The fatigue behaviour was assessed from the S-N fields obtained through a probabilistic fatigue model developed by Castillo and Fernández-Canteli. The influence of the type of reinforcement on the fatigue behaviour was analysed by SN curves. An analysis of the thermal effects in the fatigue life of the ultra-high-performance concrete has also been carried out. The results showed the most suitable fibre reinforcement among the analysed options to get the best fatigue behaviour in accordance to the exposure temperature.

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