AN EXPERIMENTAL INVESTIGATION INTO MOISTURE-INDUCED EXPANSION OF PLASTERS

This paper presents an experimental study on moisture-induced expansion of selected plasters. Contactless measurement is introduced and a coefficient of moisture expansion for different building plasters is established. It is found that stresses which might develop in building materials due to moisture variations are equal to or higher than stresses which might be caused by temperature variations

ULTRA-HIGH-PERFORMANCE FIBRE-REINFORCED CONCRETE UNDER HIGH-VELOCITY PROJECTILE IMPACT. PART I. EXPERIMENTS

A series of cratering experiments were performed where the response of the Ultra-High-Performance Fibre-Reinforced Concretes with various fibre volume fractions to the high- velocity projectile impact loading was investigated. It was found that the increment of the fibre volumetric fraction did not have a significant influence on the depth of the penetration, but it was very effective in reducing the crater area and volume

AN EXPERIMENTAL INVESTIGATION INTO MOISTURE-INDUCED EXPANSION OF PLASTERS

This paper presents an experimental study on moisture-induced expansion of selected plasters. Contactless measurement is introduced and a coefficient of moisture expansion for different building plasters is established. It is found that stresses which might develop in building materials due to moisture variations are equal to or higher than stresses which might be caused by temperature variations.</p

TRIAXIAL COMPRESSIVE STRENGTH OF ULTRA HIGH PERFORMANCE CONCRETE

The aim of this work is to describe the strength of Ultra High Performance Concrete (UHPC) under triaxial compression. The main goal is to find a trend in the triaxial compressive strength development under various values of confinement pressure. The importance of triaxial tests lies in the spatial loading of the sample, which simulates the real loading of the material in the structure better than conventional uniaxial strength tests. In addition, the authors describe a formulation process for UHPC that has been developed without using heat treatment, pressure or a special mixer. Only ordinary materials available commercially in the Czech Republic were utilized throughout the material design process

Compression behaviour and failure mechanisms of a safety culvert made of hollow high-performance concrete blocks

The safety culvert composed of hollow high-performance concrete blocks is designed to reduce the risk of injury in the event of a collision. This work presents a new design with an opening for water flow, tests it, identifies its weaknesses, and discusses possible improvements. The numerical model is constructed, validated by experiment, and used to study the effect of design parameters on the load capacity, compression behaviour, and failure mechanisms. The response varies most markedly with the opening diameter. The failure mode changes from bending failure to concrete crushing as the diameter decreases. The effect is most pronounced for diameters less than 400 mm, where the load capacity increases by 6 kN per millimetre reduction. If a crack develops in the culvert during its service life, the first such crack will form in the top layer of blocks, followed by a crack in the opening. These areas should be monitored more closely during follow-up tests with passing vehicles

USING TEXTILE ARAMID FABRICS TO INCREASE THE BALLISTIC RESISTANCE OF ULTRA-HIGH-PERFORMANCE STEEL-FIBRE REINFORCED CONCRETE

Thin plates made of Ultra-High-Performance Steel-Fibre-Reinforced Concrete (UHPSFRC) with textile Aramid fabrics were subjected to a projectile impact and its post-test damage was discussed. The damage degrees were the type of the response and crater surface, which was determined by using a 3D scanner. The most common type of ammunition, which is a 7.62 × 39mm calibre with a full-metal jacket and a mild-steel core, was used for all specimens. It was verified experimentally that the UHP-SFRC with textile Aramid fabrics has a better ballistic performance in comparison with its counterpart made of the UHP-SFRC without any textile reinforcement. Also, it was verified that specimens with the point or segment interconnection threads between the front side textile fabrics and rear side textile fabrics have a higher resistance due to the better integrity of the monolithic UHP-SFRC mixture

ULTRA-HIGH-PERFORMANCE FIBRE-REINFORCED CONCRETE UNDER HIGH-VELOCITY PROJECTILE IMPACT - PART 2. APPLICABILITY OF PREDICTION MODELS

Semi-infinite targets of Ultra-High-Performance Fibre-Reinforced Concrete with various fibre volume fractions were subjected to the high-velocity projectile impact using in-service bullets. In this study, a variety of empirical and semi-analytical models for prediction of the depth of penetration and mass ejection were evaluated with respect to the experimental results. Models for the depth of penetration and spalling mass ejection were revisited and applied both with deformable and nondeformable projectiles parameters. The applicability of the prediction models was assessed through a statistical comparison of values from models with experimental results. The evaluation of the applicability was made through the newly proposed measure of a relative prediction accuracy for model selection and model estimation, which was verified with established statistical accuracy evaluations, such as accuracy ratio, logarithmic standard deviation and correlation coefficient. The best fit to the experimental readings was provided by newer semi-analytical models, which are incorporating additional concrete parameters beside compressive strength while the majority of older models failed to provide sufficient accuracy

EFFECT OF FIBRE ASPECT RATIO AND FIBRE VOLUME FRACTION ON THE EFFECTIVE FRACTURE ENERGY OF ULTRA-HIGH-PERFORMANCE FIBRE-REINFORCED CONCRETE

This paper investigates the effective fracture energy of UHPFRC with various fibre volume fractions and various fibre aspect ratios. We have concluded that the effective fracture energy is dependent on both the fibre volume fraction and the fibre aspect ratio. In addition, we have found that both dependencies follow a linear trend

EFFECTIVE FRACTURE ENERGY OF ULTRA-HIGH-PERFORMANCE FIBRE-REINFORCED CONCRETE UNDER INCREASED STRAIN RATES

The main objective of this paper is to contribute to the development of ultra-high performance fibre reinforced concrete (UHPFRC) with respect to its effective fracture energy. Effective fracture energy was investigated in this paper considering different fibre volume fractions and different strain rates. It was concluded that the effective fracture energy is dependent on the strain rate. In addition, it was found that higher fibre volume fractions tend to decrease the sensitivity of the UHPFRC to increased strain rates

Compression behaviour and failure mechanisms of a safety culvert made of hollow high-performance concrete blocks

The safety culvert composed of hollow high-performance concrete blocks is designed to reduce the risk of injury in the event of a collision. This work presents a new design with an opening for water flow, tests it, identifies its weaknesses, and discusses possible improvements. The numerical model is constructed, validated by experiment, and used to study the effect of design parameters on the load capacity, compression behaviour, and failure mechanisms. The response varies most markedly with the opening diameter. The failure mode changes from bending failure to concrete crushing as the diameter decreases. The effect is most pronounced for diameters less than 400 mm, where the load capacity increases by 6 kN per millimetre reduction. If a crack develops in the culvert during its service life, the first such crack will form in the top layer of blocks, followed by a crack in the opening. These areas should be monitored more closely during follow-up tests with passing vehicles