QSI Methods for Determining the Quality of the Surface Finish of Concrete

Francisco Benito Saorin,Carlos Rodriguez Lopez,Carlos Parra Costa,Isabel Miñano Belmonte,Manuel Valcuende Paya

doi:10.3390/su10040931

Francisco Benito Saorin, Carlos Rodriguez Lopez + Show 3 more

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https://doi.org/10.3390/su10040931

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Abstract

The surface finish of a concrete element may become an index of its quality, relating the external and internal porosity with the mechanical and durability properties. Few methods are used to determine the surface quality of concrete elements. Mention must be made the Quality Surface Index (QSI) proposes a simplified method to quantify the surface occupied by the pores in relation with the total surface inspected, analyzing groups of pores by their diameter. The method of the CIB W29 (Commission W29 “Concrete Surface Finishings”) proposes an inspection of the concrete element and its visual comparison with some standard templates. Finally, the digital processing of images allows the zones with surface defects to be delimited and quantified according to premises of quality introduced into the control software. These three methods are employed in this work and are applied in three concrete walls situated three meters from the observer (M-1, M-2 and M-3). Following the conversion of the results of the method with ImageJ and QSI, the results suppose differences that go from 0.1 tenths (2%) for M-3 up to 0.3 tenths (8%) for M-1. All values are within the obtained range with CIB W29 templates. This can validate the QSI and digital processing methods and allows a quick verification of the results. With the digital method, it is obtained that 23.5% of the total pores of M-1 have a diameter of less than 10 mm2 and 44% of less than 100 mm2. For M-2 and M-3 the proportions of pores with a dimension below 10 mm2 is of 43.1% and 27.7%, respectively, and that 77.5% and 60.7% are smaller than 100 mm2. From all the above it can be highlighted that M-1 is the one with the lowest amount of pores, however the proportion of the largest is greater than for M-2 and M-3. In the case of M-3, although it has a lower proportion of larger pores than M-1, its greater amount means it is the worst in terms of surface finish of the three.

Highlights

A good surface finish should be demanded of concrete elements, especially for architectonic concretes that are not to be coated
The following conclusions can be drawn from the results of this experimental work: (1) Following the conversion of the results of the method with ImageJ and Quality Surface Index (QSI), the results suppose that differences that go from 0.1 tenths (2%) for M-3 up to 0.3 tenths (8%) for M-1
(2) With the digital method, it was shown that 23.5% of the total pores of M-1 have a diameter of less than 10 mm2 and 44% of less than 100 mm2

Summary

Introduction

A good surface finish should be demanded of concrete elements, especially for architectonic concretes that are not to be coated. There are several investigations [1,2,3,4,5,6,7,8,9,10], that developed methods of visual inspection and non-destructive tests. Except the QSI method [3], is a simple method to be used in the work by a non-specialist operator. The surface finish of a concrete element may become an index of its quality, relating the external and internal porosity with the mechanical properties and durability. Surface pores are the result of not having liberated some of the air bubbles present in the concrete in contact with the formwork. The amount of occluded air in the concretes is influenced principally by the dosage, the granulometry of the aggregates, the type of mixing, the height of the pouring, and the type of formwork [11]. High viscosity limits the evacuation of the occluded air [12]

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