Interlaboratory Comparative Tests in Ready-Mixed Concrete Quality Assessment

Abstract

Proper quality assessment of ready-mixed concrete, which is currently the principal material for construction, land engineering and architecture, has an impact on the optimisation and verification of correct functioning of individual stages of the production process. According to the European Standard EN 206 “Concrete–Specification, performance, production and conformity”, obligatory conformity control of concrete is carried out by the producer during its production. In order to verify the quality of concrete, investors generally commission independent laboratory units to perform quality assessment of both concrete mix and hardened concrete, which guarantees a high quality of construction works. One of the essential tools for ensuring the quality of test results is the participation of laboratories in the so-called proficiency testing (PT) or inter-laboratory comparisons (ILC). Participation in PT/ILC programmes is, on the one hand, a tool for demonstrating the laboratory’s performance, on the other hand an aid for maintaining the quality of available concrete tests and validating test methods. Positive evaluation is a confirmation of the laboratory’s capability for performing the tests. The paper presents the results of laboratory proficiency tests carried out by means of inter-laboratory comparisons, as shown in the example of quality assessment of ready-mixed concrete for nine participating laboratories. The tests were performed for concrete of the following parameters: strength class C30/37, consistency S3, frost resistance degree F150, and water resistance degree W8. This involved determining consistencies, air content and density of the concrete mix, and compressive strength of hardened concrete. For the evaluation of laboratory performance results, z-score, ζ-score and En-score were applied. The innovation of the proposed study lies in employing both classical and iterative robust statistical methods. In comparison with classical statistical methods, robust methods ensure a smaller impact of outliers and other anomalies on the measurement results. Following the analyses, clear differences were found between the types of detected discrepancy of test results, which occurred due to the nature of individual parameters. For two laboratories, two scores revealed unsatisfactory results for concrete mix consistency. The main reasons can be pouring into the cone-shaped form a concrete mixture that is too dry, or incorrect use of a measuring tool also creating a possibility that the obtained value can be wrongly recorded. Other possible reasons are discussed in the paper. Participation in inter-laboratory comparison programmes is undoubtedly a way to verify and raise the quality of tests performed for concrete mix and hardened concrete, whereas individual analysis of the results allows the laboratory quality system to be improved.

Construction Products between Testing Laboratory and Market Surveillance: Case study of Cementitious Ceramic Tile Adhesives

“…Measurements of construction products and, thus, carrying out PT/ILC, due to the multi-stage nature of the test procedures, product heterogeneity, and when the methods used are destructive tests, are additionally complex. Thus, the conformity assessment is even more difficult—it often raises the question of to what extent the evaluation of the construction product based on the tests is reliable in the case of construction products [ 20 , 21 , 22 ]. Notably, the opinion of the laboratory often plays a decisive role—this is the case in the assessment of construction products collected from the market by market surveillance authorities and checking whether the product meets the parameters declared by the manufacturer [ 19 , 23 , 24 ].…”

Assessment of the possibility of using the measurement of open time to assess and verify the constancy of performance of cementitious ceramic tile adhesives

“…W literaturze naukowej dotyczącej PT/ILC dominują badania dotyczące biochemii, chemii, medycyny i farmacji (15). Wyroby budowlane nie są często przedmiotem programów PT/ILC (15)(16)(17)21,(23)(24). Często pomiary wyrobów budowlanych, a tym samym PT/ILC, nastręczają wiele trudności, przede wszystkim, ze względu na wieloetapowy charakter procedur badawczych, niejednorodność wyrobu oraz gdy stosuje się niszczące metody badań (25).…”

“…The scientifi c literature on PT/ILC is dominated by research in biochemistry, chemistry, medicine, and pharmacy (15). Construction products are not often the subject of PT/ILC programs (15)(16)(17)21,(23)(24). Usually, measurements of construction products, and thus PT/ILC, pose many diffi culties, mainly due to the multi-stage nature of test procedures, product heterogeneity, and when the methods used are destructive (25).…”

Interlaboratory Comparison as a Source of Information for the Product Evaluation Process. Case Study of Ceramic Tiles Adhesives

“…Thus, it is not possible to repeat the test with the same sample. In the future, the situation will change due to the standardization regulations creating new requirements for selected construction products related to the possibility of ILC/PT performance [ 37 ].…”