Viscosity Of Concrete Research Articles

EFFECT OF VARIATION OF AGGREGATE GRADING ON PROPERTIES OF FRESH CONCRETE

In this study, the effect of variation of the grading of fine and coarse aggregate within the range specified in JIS on the fluidity, viscosity and segregation resistance of fresh concrete was investigated. Additionally, the effect was considered based on the excess paste theory. The following findings were obtained as the results. (1) The variation of grading of fine aggregate has a great effect on the fluidity and the segregation resistance of concrete. On the other hand, that of coarse aggregate has a relatively small effect on these properties. (2) The effects mentioned above can be theoretically controlled based on the distance between each aggregate in dispersion. (3) The fluidity of concrete is dominantly affected by the properties of aggregate such as grading. On the other hand, the viscosity of concrete is greatly affected by the properties of cement paste.

INFLUENCE OF MAIN CHAIN LENGTH OF POLYCARBOXYLATE-BASED SUPERPLASTICIZER ON ULTRA-HIGH-STRENGTH CONCRETE

Recently, design concrete strength of 150MPa has been used, and polycarboxylate-based superplasticizer has become an essential ingredient to produce ultra-high-strength concrete. In this study, the main chain length of polycarboxylate-based superplasticizer was focused on to optimize performance of dispersing ability at low water cement ratio on ultra-high-strength concrete. Short main chain length exhibited high dispersing ability and low concrete viscosity at low water cement ratio. It was estimated that the thickness of water film on cement particle demanded three times of the main chain length. The main chain length was found to have influence on dispersing ability.

A numerical approach to determine viscosity-dependent segregation in fresh concrete

In this study, the mechanism of segregation during the filling of fresh concrete into formwork is numerically investigated. A mathematical model, which considers fresh concrete as a non-Newtonian fluid, is developed. The aggregates are considered as Lagrangian particles whose trajectories determine segregation. Aggregate segregation is partially affected due to concrete viscosity. The study presented here will show the relationship between viscosity and segregation during fill of fresh concrete in formwork. The relationship in between aggregate segregation and viscosity during the fill of fresh concrete for both MC concrete mixture and MCS concrete mixture is investigated. MCS concrete mixture includes superplasticizers for the same composition of MC. Cylindrical formwork (30 cm by 150 cm) is employed. It is found that MC concrete mixture has an aggregate segregation level of 50%, while it reduces to a level of 20% for MCS concrete mixture. The use of superplasticizer reduces aggregate segregation.

The segregation tendency in the vibration of high fluidity concrete

The introduction of superplasticizer (Sp) has produced concrete that could flow easily under its own weight. In balancing the concrete's ability to flow at the same time maintaining the coarse aggregate distribution, the viscosity of concrete must be enhanced. This study aimed to investigate the effect of vibration on such flowable yet viscous concrete. Concrete flowability and viscosity are quantified by the standard slump cone and V-funnel test, respectively. Despite being flowable, the study concluded that concrete viscosity is an important parameter in determining the tendency for coarse aggregates to segregate. Large-sized coarse aggregates are affected more by the vibration process than the small-sized ones.

Relating Fresh Concrete Viscosity Measurements from Different Rheometers.

Concrete rheological properties need to be properly measured and predicted in order to characterize the workability of fresh concrete, including special concretes such as self-consolidating concrete (SCC). It was shown by a round-robin test held in 2000 [1,2] that different rheometer designs gave different values of viscosity for the same concrete. While empirical correlation between different rheometers was possible, for a procedure that is supposed to “scientifically” improve on the empirical slump tests, this situation is unsatisfactory. To remedy this situation, a new interpretation of the data was developed. In this paper, it is shown that all instruments tested could be directly and quantitatively compared in terms of relative plastic viscosity instead of the plastic viscosity alone. This should eventually allow the measurements from various rheometer designs to be directly calibrated against known standards of plastic viscosity, putting concrete rheometry and concrete workability on a sounder materials science basis.

Influence of concrete viscosity on the behaviour of continuous foundations (in Italian) : Gatti, G F; Iori, I Riv Ital Geotech, V15, N1, Jan–March 1981, P27–36

Influence of concrete viscosity on the behaviour of continuous foundations (in Italian) : Gatti, G F; Iori, I Riv Ital Geotech, V15, N1, Jan–March 1981, P27–36

Two devices for measuring concrete viscosity

DETAILS ARE GIVEN OF TWO ROTATING VISCOMETERS WHICH CAN BE USED IN THE LABORATORY OR ON CONSTRUCTION SITES FOR CEMENT PASTE, MORTAR AND CONCRETE. /LCPC/RRL/