Concrete Strength: Cores vs. cylinders

Abstract

The present work arises from the necessity to verify the different results found in national and international literature on the relationship among the resistance of concrete cylinders cured in laboratory (standardized cylinders), the resistance of cylinders cured in work (witness cylinders) and the resistance of extracted nuclei of structural elements made in laboratory but cured with the same conditions of work. In the Spanish speaking countries, little has been
written on this subject during the last decade, which calls for more research. In general, the bibliography shows that bo th the witness cylinders and the nuclei offer less resistance than the cylinder made following the norms. Nevertheless, there is no uniformity in the
results when factors like root diameter, relation length-diameter, height of extraction, direction of extraction (according to the direction of drainage and curing conditions before and during rehearsal) become involved.

He authors measure the properties of resistance of concrete in the standardized cylinders, the witness cylinders and the nuclei. They also evaluate the resistance by the ultrasound method in order to verify and complement the results. The studied variables were the root diameter, the height of extraction, the direction of extraction and the curing conditions of the cylinders. A total of 48 cylinders
and 36 extracted nuclei of beams and columns were tested, finding that the resistance of the nucleus is affected insignificantly by the variables mentioned above.