Abstract
Shrinkage-reducing admixture (SRA) and expansive admixture (EXA) were used in high performance selfcompacting concrete (HPSCC) to mitigate autogenous shrinkage. In order to evaluate the fresh properties of concretes, the rheological parameters were determined in a ICAR rheometer at 10, 25, 40, 60 and 90 min. The flow behavior of the mixtures was described by Bingham, Herschel-Bulkley, and modified Bingham models. Slump flow test, V-funnel test and J-Ring test were also carried out at 10 min. Slump flow test was performed also after 90 min of mixing. The test results showed that, at 10 minutes, all mixtures had similar performances, independently of the SRA and EXA contents. However, the slump flow test shows a reduction of up to 24% of its diameter at 90 min for mixtures with EXA. Mixtures with EXA revealed a gradual increase in dynamic yield stress with elapsed time. In contrast, concretes with SRA exhibited less variation in its rheological properties. Statistical analysis (ANOVA) showed that, regardless of the rheological model adopted, the admixture content was not a significant factor for the yield stress, while the type of admixture and the time of testing greatly influenced the concretes rheological response. Keywords: Shrinkage-reducing admixture (SRA), expansive admixture (EXA), rheological behavior, high performance self-compacting concrete.
Highlights
High performance self-compacting concrete (HPSCC) is a type of concrete that has been developed to exhibit high flowability and mix stability and, at the same time, high strength and durability [1,2]
The slump flow test shows a reduction of up to 24% of its diameter at 90 min for mixtures with expansive admixture (EXA), which is higher than the observed in the reference and Shrinkage-reducing admixture (SRA) mixtures
Deference higher than 5 cm are considered as extreme blocking [31], these J-Ring values are reported for high performance selfcompacting concrete (HPSCC) [38,39,40]
Summary
High performance self-compacting concrete (HPSCC) is a type of concrete that has been developed to exhibit high flowability and mix stability and, at the same time, high strength and durability [1,2]. The shrinkage-reducing admixture acts by reducing the surface tension of concrete pores solution and, reducing the capillary stress. This approach is clear when one analyses the Young-Laplace equation ((1), where the surface tension is directly proportional to the capillary stresses. Viscometers and advanced rheometers are usually designed to be operatively insensitive and, retrieve the materials parameters in terms of fundamental physical quantities independent on the details of the apparatus with which they are measured [19] This way, rheology can be used as a tool to accurately describe the workability of selfcompacting concrete by its flow curves. The second part of this study will be an analysis about the hardened properties of these concretes
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