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Concrete Analysis for Petrographic Examination in Old Concrete Structures and their Corresponding Photomicrographs

Hamze Y

The old concrete in water structures such as old dams, bridges, piers and other concrete structures exposed to water and freeze thaw were constructed without using the current technologies. To understand their characteristics, we conducted many concrete testing. One of these testing was the petrographic testing of concrete and its corresponding photomicrographs ASTM C856. The examination was carried out by a specialized company that provided 14 core samples: 45, 60 and 100 mm in diameter, from piers 3, 6, 8 and 9 and from the abutment. The samples were subjected to a detailed visual examination completed by thin section examinations of the concrete and aggregate. A Leitz Laborlux II Pol polarizing microscope was used. Also, two samples were prepared to determine the parameters of the air void system under the microscope, in accordance with ASTM C-457. This article discusses the alkali-aggregate reactions in the abutment samples and the percentage and hardness of the cement paste in the mix that will determine the parameters of the air void system, in accordance to ASTM C-457 as well as the petrographic examination results (ASTM C856) and corresponding photomicrographs.