Quality of the surface finish of self-compacting concrete

Abstract

In this work, surface damage due to the presence of pores in self-compacting concrete specimens is studied and cataloged with the QSI method which simplifies the inspection of concrete samples with optimal results, even in curved areas. 48 test tubes distributed in a total of 12 mixtures were analyzed. The rheology of the concretes was analyzed and controlled. In concretes that obtain viscosities higher than 42 Pa s, a large number of large pores are detected on its surface, compared to concretes with lower viscosity and/or shear stress. The specimen with the worst surface finish that was manufactured (mixture nº. 11) had a viscosity of 58 Pa s and a shear stress of 26 Pa (QSI = 5.9%), compared to 14 Pa s and 15 Pa, respectively, of the concrete element that less surface area affected (QSI = 0.6%). The mixes H-2, H-3 and H-12 have the combination of lower values of viscosity and shear stress. This allows obtaining the best surface finishes, with average QSI values, respectively of 1.3% 1.6% and 1.6%. By increasing the flowability of the SCC, the number of pores and their size decrease. The values of viscosity and shear stress must be balanced to ensure an adequate flowability of the SCC.