Statistical analysis of concrete quality testing results

Abstract

This paper statistically investigates the testing results of compressive strength and density of control concrete specimens tested in the Laboratory for materials, Faculty of Civil Engineering, University of Belgrade, during 2012. The total number of 4420 concrete specimens were tested, which were sampled on different locations - either on concrete production site (concrete plant), or concrete placement location (construction site). To be exact, these samples were made of concrete which was produced on 15 concrete plants, i.e. placed in at 50 different reinforced concrete structures, built during 2012 by 22 different contractors. It is a known fact that the achieved values of concrete compressive strength are very important, both for quality and durability assessment of concrete inside the structural elements, as well as for calculation of their load-bearing capacity limit. Together with the compressive strength testing results, the data concerning requested (designed) concrete class, matching between the designed and the achieved concrete quality, concrete density values and frequency of execution of concrete works during 2012 were analyzed.

U radu je prikazana statistička analiza rezultata ispitivanja čvrstoće pri pritisku i zapreminske mase kontrolnih betonskih uzoraka dobijenih u Laboratoriji za materijale Građevinskog fakulteta Univerziteta u Beogradu, u toku 2012. godine. Ispitivanja su obavljena na ukupno 4.420 betonskih uzoraka, uzorkovanih na više lokacija - na mestu proizvodnje (u fabrikama betona) i na mestu ugradnje (na različitim gradilištima). Naime, reč je o uzorcima proizvedenim na petnaest betonskih baza, odnosno o uzorcima betona ugrađenih u 50 armirano- betonskih konstrukcija različite namene, koje je tokom 2012. godine izvodilo dvadeset dva različita izvođača. Poznata je činjenica da su ostvarene vrednosti čvrstoće pri pritisku betona veoma važne, kako za procenu kvaliteta i trajnosti betona u konstruktivnim elementima, tako i za proračun njihove granične nosivosti. Osim rezultata ispitivanja čvrstoće pri pritisku, analizirani su i podaci o zahtevanim (projektovanim) markama betona, o tome koliko se ostvarene marke poklapaju s projektovanim markama betona, zatim o dobijenim vrednostima zapreminskih masa, kao i o učestalosti izvođenja betonskih radova u toku predmetne - 2012. godine. .