PSI - Issue 42

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Martina Drdlová et al. / Procedia Structural Integrity 42 (2022) 1382–1390 Drdlova et al/ Structural Integrity Procedia 00 (2022) 000 – 000

1384

2. Materials and methods Nine batches of specimens (with dimensions of 500x250x50 mm) were prepared with different inner and outer reinforcement and varying cement matrix compositions. The compositions of the panels are shown in Table 1. The specimens designated as HPFRC are fibre-reinforced high-performance concrete-based elements prepared from Portland cement 52.5 R (Mokrá, Českomor avský cement), fine sand (grain size 0-2 mm, Bzenec), granodiorite (grain size 2-4 mm and 4-8 mm, Krizanov Quarry), silica fume Elkem 940 BASF, plasticizer MasterGlenium ACE 446 and water. The fibres with hooked ends, length of 30 mm and diameter of 0.6 mm from producer Krampe-Harex were used as reinforcement. The variant HPFRC 3 also contained 3 steel rebars (8 mm diameter). The bulk density, compressive strength and flexural strength of the HPFRC material (without rebar) were 2480 kg/m 3 , 130 MPa and 14.1 MPa, respectively. The specimens designated as UHPFRC are based on fine grain ultra-high-performance concrete with fibre reinforcement same as in the HPFRC specimens. The ingredients (but not mix proportions) are identical with HPFRC specimens except for missing coarse aggregates. The bulk density, compressive strength and flexural strength of the UHPFRC material (without rebar) are 2580 kg/m 3 , 170 MPa and 36.5 MPa, respectively. 8mm steel rebar was incorporated in specimens UHPFRC 3 (3 pieces). PC specimens were prepared from common concrete with coarse aggregate with a bulk density of 2353 kg/m 3 and compressive and flexural strength of 50 MPa and 5.1 MPa, respectively. The ingredients used were as follows: Portland cement 42.5 (Mokrá, Českomoravský ce ment), sand 0- 4 (Bratčice) granodiorite with grain size 4 -8 mm and 8-16 mm (Krizanov Quarry), plasticizer Stachement 2180 and water. A total of 6 groups of test specimens were prepared. The PC variant did not include any internal or external reinforcement. The PC PU variant was reinforced with an additional 4 mm thick outer layer of polyurea. Polyurea was developed at the Research Institute of Building Materials. Specimen PC3 contained 3 pieces of 8 mm diameter steel bars. The PC 3 PU samples were covered by a polyurea layer (4 mm) and contained 3 pieces of 8 mm rebar reinforcement. The PC DR specimen was reinforced with dispersed fibres identical to the fibers added to the HPFRC and UHPFRC specimens. The last group of test samples (PC MESH) was reinforced with steel mesh with 100 mm wire distance and 8 mm wire diameter. The wire mesh and rebar were placed 20 mm from the impact rear side. The presented set of test samples allows for a comparison of the effectiveness of various reinforcement options as well as the effect of matrix character on impact toughness and durability.

Table 1 Description of the test specimens composition (kg/m 3 ) and reinforcement type

Designation/ Ingredients Cement 52.5 R Cement 42.5

HPFRC 3

PC MESH UHPFRC

UHPFRC 3

HPFRC

PC PU

PC 3

PC 3 PU

PC DR

700

951

392

624

1026

Sand 0/2 Sand 0/4

753

- - - -

298 446

Granodiorit 2/4 Granodiorit 4/8 Granodiorit 8/16 Silica fume Elkem 940 Plasticising agent MasterGlenium Plasticising agent Stachement 2180

173 831

150

134

25.1

132 0.19

114 0.29

215 0.24

Water

Water/cement ratio

160

215

Steel fibres

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