Issue 50

S. Gavela et alii, Frattura ed Integrità Strutturale, 50 (2019) 383-394; DOI: 10.3221/IGF-ESIS.50.32 387 Additionally, ten specimen of composition I-G were prepared, half of which were tested at 7 days of age, while the rest were tested at the age of 14 days. These additional results where needed in order to apply the experiment II multifactorial model on the results of experiment I tests. Composition Cement [kg/m 3 ] W/C [-] Sand [kg/m 3 ] Coarse aggregates 4-16mm [kg/m 3 ] Coarse aggregates 16-31.5mm [kg/m 3 ] Superplasticizer [kg/m 3 ] Slump [mm] Experiment I I-A 300 0.45 1021.2 623.1 341.3 4.20 10 I-B 300 0.50 1001.4 610.0 334.7 3.60 200 I-C 300 0.55 980.9 598.5 327.8 3.60 250 I-D 330 0.45 988.4 603.1 330.4 4.62 170 I-E 330 0.50 966.7 589.8 323.1 3.96 240 I-F 330 0.55 944.1 576.1 315.6 3.96 250 I-G 360 0.45 956.7 583.7 319.7 4.32 230 I-H 360 0.50 932.0 568.7 311.5 4.32 250 I-I 360 0.55 908.3 554.2 303.6 3.60 260 I-J 360 0.45 956.7 583.7 319.7 4.32 220 Experiment II II-A 280 0.46 1112.9 372.0 679.0 6.16 30 II-B 280 0.48 1104.7 369.2 674.0 6.16 70 II-C 280 0.50 1090.7 364.5 665.5 6.16 100 II-D 280 0.52 1088.2 363.7 664.0 6.16 140 II-E 280 0.54 1081.3 361.4 659.7 5.32 180 Table 1 : Mix compositions. Slump test for each composition was performed according to EN 12350-2 and Slump test results are shown in Table 1. Curing procedure according to EN 12390-2 was followed. After demolding, specimens were immersed in water. The curing temperature was about 20 °C. A number of different metal moulds, labeled with a serial number, were used to prepare the specimens for experiment I. These moulds were used in a randomized manner in order to prepare the specimens for all the various compositions presented in Table 1. The use of different moulds has led to an expected and reasonable dispersion of the geometric char- acteristics of the specimens (e.g. lack of surface flatness and perpendicularity, edge dimensional accuracy). Therefore, the following results are expected to be representative of reasonable dispersion of the geometric characteristics of the specimens been tested by a laboratory that uses any of these moulds and the parameter of the specimen’s geometry is expected to have contributed into the results of this study. Also, the uniaxial compression apparatus used was successfully calibrated with a subsequent correction of its calibration, according to International Standard ISO 7500-1. It can be assumed that the calibration of the apparatus contributes to the final combined uncertainty only when the corresponding systematic errors occur. M ETHOD OF ANALYSIS xperiment II results were used into a multifactorial regression analysis procedure leading to a sigmoidal - by time equation: ሺ ⁄ , ሻ ൌ ௥௘௙ ∙ ቂି൫ ఛ ௧ൗ ൯ ೙ ቃ ൌ ൫ ଴ ൅ ଵ ∙ ሺ / ሻ൯ ∙ ቂି൫ ఛ ௧ൗ ൯ ೙ ቃ (1) E