Issue 59

M. A. R. Elmahdy et alii, Frattura ed Integrità Strutturale, 59 (2022) 486-513; DOI: 10.3221/IGF-ESIS.59.32

C REATION OF CRACKS

T

he cubic specimens with dimensions of 70×70×70 mm were removed from the curing water after 7 days from casting to measure the ultimate load in all mixes, and three specimens of each mix were loaded until failure. Also, according to EC203-2016, specific specimens for cracking were loaded until 30–40% of the ultimate load was reached, resulting in micro-cracks of various widths in three 7 cm cubic specimens for each mix, using a hydraulic testing machine with a capacity of 2000 KN and a loading rate in the range of 900–1800 N/S [39]. A visual check of the loaded specimens before and after loading revealed that cracking had occurred. These loaded cracked specimens were returned to curing to allow bacteria to begin precipitating calcite and healing the cracks. Cracked loaded specimens and specimens without pre-cracking from each mix were loaded until failure after 28, 56, 90 days to measure the compressive strength after precipitation calcite.

C OMPRESSIVE STRENGTH TEST

A

ll the specimens were removed from the curing tank before testing and left for about 2 hours to dry in the laboratory. Fresh-water was used for curing. The compressive strength after 7, 28, 56, and 90 days from casting were measured. Three specimen cubes (7×7×7 cm) from each mixture were tested at each testing age. The compressive test was performed according to EC203-2016 by using a hydraulic testing machine with a capacity of 2000 KN and an accuracy of 5 KN in the concrete laboratory, faculty of engineering, Zagazig University as shown in Fig.1 [39]. Three specimens were averaged for each mix.

Figure 1: Compression strength test.

Figure 2: Flexural strength test.

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