PSI - Issue 13

René Čechmánek et al. / Procedia Structural Integrity 13 (2018) 1780 – 1785 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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In order to measure highly heterogeneous suspensions, such as cement paste and mortar, a helical rotor was designed and manufactured. The advantage of its use is that during measurements the material is carried by the rotor and heavier particles do not settle which avoids slippage like when coaxial cylinders or bladed rotors are used.

3. Glass fibre reinforced concrete (GFRC)

The thin-walled elements with a matrix based on the high-value Portland cement with dispersed reinforcement in the form of alkali-resistant glass fibres are used in a range of applications. Within a preparation of these fibre-cement composites an exact amount of alkali-resistant glass fibres with length of 12 mm is added into fine-grained matrix consisting of cement, aggregate and admixtures in the last stage of a mixing process and in this way properly dispersed in the whole volume of the mixture. This technology requires the use of highly flowable mixtures free from bleeding and sedimentation of heavier mixture components, as mentioned by Čechmánek et al. (2014). SIFCON was first developed in 1979 by Lankard Materials Laboratory, Columbus, Ohio, USA, by incorporating large amounts of steel fibres in steel fibre reinforced cement-based composites, as described by Lankard (1984). It possesses excellent mechanical properties coupled with very good energy-absorption characteristics. SIFCON specimens can be produced with fibre volume V f = 5% up to 30%, as specified by Lankard (1984); Homrich and Naaman (1987). SIFCON is prepared by infiltrating pre-placed fibres with fine grain aggregate mortar. It has been reported that SIFCON slab elements exhibit excellent behaviour in flexure and punching shear when compared to HPFRC, reinforced cement concrete (RCC) and plain cement concrete (PCC) slabs, by Sudarsana and Ramana (2005); Sudarsana et al. (2008). Due to extraordinary ductility of SIFCON, it seems to be very promising material for applications in structures subjected to impact load, but the literature review reveals only a few studies dealing with the SIFCON under dynamic loading. The results of our own investigation carried out on SIFCON slab panels under impact loading can bring significant contribution to the current knowledge in the field, as reported by Drdlová et al. (2015). 4. Slurry infiltrated fibre concrete (SIFCON) Four formulas representing different types of fibre reinforcement used in fine-grained cement composites were selected: glass fibre reinforced concrete (GFRC), composite reinforced with PVA fibres (PVA), composite reinforced with steel fibres (SFRC) and composite with a high content of steel fibres infiltrated in a slurry (SIFCON). In the first stage, all formulas were prepared according to the standard procedures recommended for the respective composite and fibre reinforcement using a standard agitator, always three test boards for each formula. 5.2. Test specimens Each 500 × 500 × 40 mm test board was divided by cutting into a total of 22 specimens with dimensions 250 × 40 × 40 mm according to the proposed scheme in order to allow identification of the position of each test specimen of the test board. The end of the test specimen directed towards the edge of the board was labelled A and the end of the test specimen directed towards the centre of the board was labelled B. 5. Preparation of fibre reinforced concrete specimens 5.1. Fibre reinforced concrete boards

6. Tests performed 6.1. Ultrasound measurements

The so-called ultrasonic impulse method is used for non-destructive testing of concrete. Our goal is to use this method for testing of a cement composite material. The principle of concrete testing using the aforementioned method is described in the ČSN 73 1371 standard – Ultrasonic impulse concrete testing method. Ultrasonic impulses are repeatedly transmitted into the test material and subsequently registered while measuring the transmission time of these impulses.