Anchorage of reinforcement bars in Hennebique structures

Brencich, Antonio; Nebiacolombo, Matteo

doi:10.1016/j.conbuildmat.2020.120184

Cited by 2 publications

(1 citation statement)

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“…Historical concrete, i.e. the concrete produced before building codes had been issued or before the provisions of the codes entered the professional and building practice, is somehow more troublesome since it is characterized by large and smooth aggregates [22][23][24], high porosity and high inhomogeneity [25][26][27], all parameters that may significantly affect the compressive strength. All these "defects", and mainly the use of large and smooth aggregates, add further uncertainty to the compressive strength and need a verification if the procedures already tested on modern concrete, although affected by some approximation, may be applied, and to which extent, to historical concrete.…”

Section: Introductionmentioning

confidence: 99%

Core-to-Cubic Strength Ratio for Historical-Like Concrete

Brencich¹,

Hasweh²,

Pera³

2021

cea

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Coring is considered to provide the best estimate of concrete compressive strength in existing structures and is commonly used to calibrate Non-Destructive and Moderately Destructive Techniques. Historical concrete, produced in the pre-code period until the '20s, significantly differs from modern concrete due to lack of standardization, improper rules of thumbs and to aggregate shape (round, smooth and often excessively large aggregates) and proportioning. Therefore, the applicability of the procedures calibrated on modern concrete to a historical one, also coring, is an issue that needs to be discussed. In this paper, an experimental campaign on historical-like concrete, i.e. with the same defects as historical concrete, aims at identifying the reliability of drilled cores due to the effect of round aggregates. The results show that standard procedures commonly used on modern concrete cannot be directly applied to historical concrete: drilled cores suffer from scale effects (core diameter) and from cutting damage of the material much more than modern concrete. In detail, the core-to-cubic ratio, that modern codes assume in the range 0.70-0.85, due to the dimension and shape of the aggregates is found inside a larger range, 0.70-1.00, and, as opposed to modern concrete, is found to be decreasing as concrete strength increases. Besides, the diameter of the core is found to have a relevant effect on the estimate of the material compressive strength and on the core-to-cubic strength ratio, pointing out that the dimension of the core affects the results much more than for modern concrete. This latter result, which needs further research, points out that historical concretes may be rather different from modern ones and probably need larger cores to be drilled than modern concrete due to the larger dimension of aggregates that are often found in pre-code concrete.

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