Robust flowable concrete with viscosity agents

The Journal of Engineering and Exact Sciences, 2024

Self-compacting concrete (SCC) represents a recent advancement in the field of concrete technology due to its ease of handling and placement. In order to regulate the internal integrity of the concrete, a supplementary mixture component is employed. The term used to refer to this particular component is a viscosity-modifying agent (VMA). Different quantities of VMA were incorporated into the concrete mixture in order to evaluate its performance in both the fresh and hardened states. This study focused on the impact of VMA (Viscosity Modifying Agent) on various characteristics of concrete mixes. Specifically, the features under examination included flowing time, slump flow, flow time into a 500-mm diameter, and resistance to vertical segregation. In contrast, a measurement was conducted on the compressive strength of the cured concrete. The utilization of the column of segregation test allows for the identification and assessment of static segregation in SCC mixtures. This test offers a direct quantitative determination of the stability of segregation in fresh concrete. The purpose of this experiment is to determine the precise quantity of coarse aggregate with a diameter above 8 mm present within a specimen of 300 mm in height. This can be achieved by conducting sedimentation tests at a specific time interval of 30 minutes after the pouring of concrete. The research results indicate that the addition of VMA had a substantial impact on the rheological characteristics of the concrete mixture. It effectively stabilized the mixture, minimized static segregation, and improved the compressive strength when compared to the reference mixture without VMA. Furthermore, a comprehensive illustration of the segregation phenomenon is provided by the column of static segregation tests.

2013

This paper focusses on the flow behavior of quaternary blended HPC using modified slump cone test. 49 HPC mixes including control mix were developed incorporating mineral admixture combinations of metkaolin, slag and fly ash up to 92.5% replacement levels. Semi-empirical models were proposed for yield stress and plastic viscosity as the function of the slump and slump time. It was found that the fluidity of concrete increased moderately and the plastic viscosity and yield stress decreased noticeably, when mineral admixture combinations were substituted partially for cement. Out of 49 HPC mixes, the quaternary HPC mix developed with 57.5% cement, 7.5% metakaolin, 25% slag, and 10% fly ash, gives a minimum yield stress of 878 Pa and plastic viscosity of 179 Pa.s. © 2013 Elixir All rights reserved ARTICLE INF O Articl e h istory: Received: 6 June 2013; Received in revised form: 24 July 2013; Accepted: 31 July 2013;

Buildings

The development of non-proprietary Ultra-High Performance Concrete (UHPC) is one way to reduce the initial cost of construction. However, workability is a major issue for which such mixtures are not practical in field conditions. Ultra-high performance cannot be achieved in field conditions if the concrete is not placed, finished, and compacted properly during placement. In this research, six UHPC mixtures were developed (three with steel fibers and three without fibers) using materials which are readily available on the local marketplace with water-to-cementitious materials ratios ranging between 0.17 to 0.30. The workability was determined using standard ASTM flow table apparatus, and specimens were prepared to determine compressive strength, splitting tensile strength, and permeable porosity. Flow table test exhibited flow values greater than 250 mm. Such high workability of the mixtures was achieved by optimizing the silica fume content and water reducing admixture dosage. These...

Construction and Building Materials, 2015

The effect of binder type and content on the benefits of SCM in SCC was investigated. Metakaolin was able to increase the plastic viscosity of SCC by 90%. Silica fume and blast furnace slag reduced the plastic viscosity of SCC. Yield stress of the mixtures with SCM was higher than that of the control mixtures.

Periodica Polytechnica Civil Engineering, 2016

Although self consolidating concrete (SCC) has been developed for more than two decades, its practical use is still limited. This is partly because its properties are not fully known and partly because its performance is highly sensitive. In the current study, an experimental program was undertaken to evaluate the robustness of eight selected SCCs. According to the obtained results, the variations of SCC robustness that determined by using innovative method (multi attribute decision making) are studied based on the variations of rheology parameters. The results indicate that there is a direct relationship between robustness and segregation resistance of SCC. Also the greatest reduction in robustness occurs in increase in yield stress together with plastic viscosity. Moreover, the scattering of compressive strength results show that there is a level of robustness in fresh state that after that the scattering of results in hardened state may be affected.

ACI Materials Journal, 2011

The aforementioned three methods have formed the basis for a number of studies designed to optimize mixtures so that SCC mixtures can be designed to meet specific performance requirements in the fresh and hardened states. Sedran and de Larrard (1996), Gomes (2002), BIBM et al. (2005), Alencar and Helene (2008), and Shen et al. (2009) have published work on this aspect. There is still room, however, for a more efficient calibration of the parameters that will give a target compressive strength and self-compactibility by optimizing the quantities of the mixture components. With these needs in mind, some research has been carried out in Portugal by Ferreira (2001) and Nepomuceno (2005). The two mixture design methods are based on the Okamura et al. (Domone 2000; Okamura et al. 2000) and JSCE (Domone 2000; Nawa et al. 1999) methods. The first method also used the Faury method (Faury 1958) with respect to using a reference curve for SCC and the adaptation of the parameters currently used in the reference curves method. This was based on the principle that the optimal particle-size distribution of aggregate of a certain concrete as a function of parameters, such as the target workability and the type of aggregate, is given by a reference curve established experimentally by researchers. The second method introduces new parameters in relation to the methods proposed by Okamura et al. (Domone 2000; Okamura et al. 2000) and JSCE (Domone 2000; Nawa et al. 1999), which are better suited to controlling the SCC's compressive strength. The experimental mixtures used in this study were prepared according to both the Okamura et al. and JSCE methods. This study focused on the production of concrete with target compressive strengths of 40, 55, and 70 MPa (5.80, 7.98, and 10.15 ksi) and the evaluation of consistency and mechanical behavior. The results were then compared. RESEARCH SIGNIFICANCE This study analyzes the viability of two innovative SCC mixture design methods. These methods seek to establish a procedure to obtain satisfactory mixtures-that is, appropriate compositions for each situation so as to achieve different performance levels in terms of target compressive strength and self-compactibility. They do so by introducing new parameters into the calculation and considering some parameters as variables that have until now been taken as constants. This paper presents the results from an experimental study of the technical viability of two mixture designs for self-consolidating concrete (SCC) proposed by two Portuguese researchers in a previous work. The objective was to find the best method to provide the required characteristics of SCC in fresh and hardened states without having to experiment with a large number of mixtures. Five SCC mixtures, each with a volume of 25 L (6.61 gal.) were prepared using a forced mixer with a vertical axis for each of three compressive strength targets: 40, 55, and 70 MPa (5.80, 7.98, and 10.15 ksi). The mixtures' fresh state properties of fluidity, segregation resistance ability, and bleeding and blockage tendency, and their hardened state property of compressive strength were compared. For this study, the following tests were performed: slump-flow, V-funnel, L-box, box, and compressive strength. The results of this study made it possible to identify the most influential factors in the design of the SCC mixtures.

International Journal of Research in Engineering and Technology , 2018

Flow characterization and controlling fresh property of SCC is most critical. Even slight variations in ingredients can have adverse effect on fresh properties; strength and durability of hardened concrete. The material science approach to study rheological properties is essential in order to overcome the paucity posed while characterizing mixes by empirical methods such as the slump flow test. In the present work, the Bingham parameters of SCC were assessed by using the new concrete shear box. The mixes were designed considering volume of paste based on absolute volume concept. Three different volumes of pastes (0.38, 0.40 and 0.42) with water contents of 170 and 190 lt/m 3 and cement contents of 300 and 450 kg/m 3 along with slag as filler was used. A unique test procedure was followed, by applying low normal stresses of 0.10, 0.20 and 0.30 MPa with three different displacement rates of 1, 5 and 15mm/min under static condition. The results indicate that the new concrete shear box shall effectively put to use, as an additional tool for evaluating the rheological properties of SCC viz., yield stress and plastic viscosity.

Construction and Building Materials, 2012

The three key characteristics of self-consolidating concrete are flowability, segregation resistance and passing ability. Quality control of flowability is typically predicted by the final diameter (D F) of the slump-flow test. In this study, the time required to reach the final diameter (T F) of the slump-flow test is correlated to dynamic segregation for mixes with a constant D F and aggregate-to-binder ratio. Segregation was determined by measuring the radial aggregate distribution from the slump-flow test. It was demonstrated that increasing the T F improved dynamic segregation resistance. It was also found that the T F was more indicative of viscosity than the time to reach a diameter of 50 cm (T 50).

ACI Materials Journal, 2013

The hazard rate function for concrete structures often is portrayed as a "bathtub"-shaped 18 curve, with a finite ever-decreasing probability of early-age failures being followed by a life with 19 a relative low, constant probability of failure that ultimately increases dramatically as the end of 20 service is reached. Ideally, new concrete technologies should reduce the failures occurring at 21 both ends of this service life spectrum. VERDiCT (Viscosity Enhancers Reducing Diffusion in 22

Applied Mathematics and Computation, 2005

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.