Volume II: Investigation on Thixotropy of Vibration-Free Concrete Mixtures Intended for Rapid Pavement Construction

Project Details









Dimitri Feys, Piyush Rajendra Lunkad




Admixtures, Concrete pavements, Paving, Thixotropy

Project description

This report discusses the advances and setbacks encountered when attempting to develop a vibration-free, self- consolidating concrete for slipform applications. Such concrete would have significant advantages compared to conventional slipforming, as vibration would not be necessary. All negative aspects of incorrect vibration, such as inadequate air content (too much entrapped air or insufficient entrained air), and segregation, which on its turn could lead to inferior freeze-thaw and scaling resistance or cracking, would be avoided [1] [2] [3] [4]. Based on previous work [5] [6], further referenced in the literature review, the research team wanted to attain a higher slump flow (> 550 mm) to ensure full self-consolidation, while also showing substantial thixotropy to develop the necessary shape stability. Current techniques in the development of 3D printing, which require similar properties of the construction material, use different chemical admixtures added at specific times when necessary. As an example, some mixtures are heavily retarded, and a large amount of accelerator is added just before the material passes through the nozzle [7] [8]. Although this technique would be certainly applicable for slipforming, it is questionable whether this can be executed on a large scale such as slipforming. Any mistakes in timing or dosage of the admixtures, or inadequate incorporation or distribution of the admixtures in the concrete would result in disastrous increases in cost as the concrete would remain too fluid or harden too soon, dependent on the error. As such, the team has chosen to pursue an approach in which intervening on the jobsite would be kept to a minimum in order to avoid those errors. In this report, a literature review is made on previous work on this topic, as well as a revision of how constituent materials influence thixotropy. Some basic concepts from physics and chemistry are also highlighted as they are applicable to this work. The material properties, mix designs and testing protocols are described in section 3, while the results for cement paste and concrete are discussed in sections 4 and 5, respectively. Section 6 concludes this report.