Assessment of the Concrete Compressive Strength in Existing Structures Based on Core Test Results

Tur, Viktar; Derechennik, Stanislav S.

doi:10.4028/www.scientific.net/ssp.272.238

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…2b), there is an obvious overstatement of confidence level γ , which corresponds to a significant underestimation of in-situ characteristic strength. How it was shown in [5] the estimates The confidence level of estimates γ obtained by method C varies in a relatively narrow range 0.70 0.80 γ =  (see Fig. 2), which corresponds to the declared fixed value of the confidence level 0.75 γ = for this method.…”

Section: Comparison With Known Methodsmentioning

confidence: 85%

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Adaptive Estimation of the <i>In Situ</i> Characteristic Concrete Strength

Derechennik

Tur

2019

SSP

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For calculation of existing concrete structures on the basis of the partial factor format, the main representative value is the actual in-situ characteristic value of the concrete strength. When samples are tested, the concrete in-situ strength of the structure shall be determined, statistically if possible, from the test results. In accordance with EN 1990 the 5% percentile value is calculated on the basis of a unilaterally limited constant confidence level. It was found the in some case, estimation of the in-situ characteristic concrete strength taking a constant confidence level does not allow to adequately assess the reliability of the existing structures. A new estimator based on non-parametric statistical method was proposed for estimating of the in-situ characteristic concrete strength with a given arbitrary confidence level. The procedure that was proposed allows one to re-establish of the estimator pdf even with a very limited sample size. It is established, that the choice of the confidence level of the estimator should be based on the average reliability of the structure.

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Section: Comparison With Known Methodsmentioning

confidence: 85%

“…established with usage of proposed a new method[5] based on the generated samples of test results (with a sample size 3 n = ) by varying of the confidence level with the step 0.05 ∆γ = (see Fig.2). As can been seen from the histograms for in-situ characteristic concrete strength estimator ,…”

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confidence: 99%

Adaptive Estimation of the <i>In Situ</i> Characteristic Concrete Strength

Derechennik

Tur

2019

SSP

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“…The relationship between the core and the cylindrical/cubic strength of concrete, i.e. in situ vs standard laboratory strength of concrete, has long been discussed by the academic community [9-13 among the others] and are still nowadays research issues [14][15][16][17][18][19]. Even though several parameters affecting the core strength have been studied, modern codes honestly admit that: "There is no unique relationship between the compressive strength of a core and the corresponding compressive strength of standard-cured moulded cylinders.…”

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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