PSI - Issue 17

Piotr Smarzewski / Procedia Structural Integrity 17 (2019) 5–12 Piotr Smarzewski / Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1. Physical and chemical properties of cement and silica fume. Material characteristics Cement Silica fume Specific surface area (m2/kg) 484 17 000 Water demand (%) 30 ― Start of setting (min) 160 ― End of setting (min) 210 ― Volume stability acc. to Le Chateliere (mm) 0 ― Compressive strength at 2 days (N/mm2) 40.3 ― Tensile strength at 2 days (N/mm2) 6.46 ― Composition (%) SiO 2 19.99 94.80 Al 2 O 3 4.19 1.30 Fe 2 O 3 3.76 0.83 CaO 64.82 0.56 MgO 1.14 0.71 SO 3 3.25 ― K 2 O 0.46 1.26 Na 2 O 0.24 0.41 Cl 0.07 ― Loss on ignition 3.01 0.12 Insoluble matter 0.18 ―

2.2. Mixtures details

With the experience gained from the trial mixtures, it was considered feasible, with the aid of superplasticizer, to produce workable HPC with W/(C+SF) = 0.25 and a maximum SF content of 25%. The quantities used in the reference mixture were as follows: cement (C) – 745 kg/m 3 , water (W) – 186 kg/m 3 , coarse aggregate (CA) – 1000 kg/m 3 , fine aggregate (FA) – 500 kg/m 3 , superplasticizer (SP) – 20 kg/m 3 . The SF mixtures were formulated on the basis of the reference HPC with various replacements of cement by SF. Table 2 shows the details of the HPC mixtures employed in the present study.

Table 2. Mixture proportions. Mixture C (kg/m 3 ) SF (kg/m 3 )

SF * (%)

CA (kg/m 3 )

FA (kg/m 3 )

SP (kg/m 3 )

SP ** (%)

W (kg/m 3 )

CSF0 CSF5 CSF10 CSF15 CSF20 CSF25

745 708 670 633 596 559

0

0 5

1000 1000 1000 1000 1000 1000

500 500 500 500 500 500

20 20 20 20 20 20

2.7 2.7 2.7 2.7 2.7 2.7

186 186 186 186 186 186

37 75

10 15 20 25

112 149 186

SF * – percent of silica fume by weight of the cement. SP ** – percent of superplasticizer by weight of the cementitious materials (C+SF).

2.3. Specimens preparation Cube specimens 100 mm × 100 mm × 100 mm were prepared for the compressive and tensile splitting strength tests, 150 mm diameter × 300 mm long cylinders for the static modulus of elasticity tests and 80 mm wide × 150 mm high × 700 mm long beams with a notch for the fracture energy tests. Cubes and cylinders were prepared in plastic moulds as well as notched beams were formed in wooden moulds. All specimens were demoulded after 48 hours. The test specimens were then cured in fresh water at 20 ºC. For each test three specimens were prepared.