The plate test carried out on fresh cement-based materials: How and why? S. Amziane a , A. Perrot b, ⁎ a Clermont Université, Université Blaise Pascal, UMR 6602, Institut Pascal, Clermont-Ferrand, France b Université de Bretagne Sud, LIMATB, Lorient, France abstract article info Article history: Received 28 August 2016 Received in revised form 2 December 2016 Accepted 21 December 2016 Available online xxxx The plate test consists in measuring the mass variation of a rough tool (plate or cylinder) immersed in a fresh ce- ment-based material with time. It has been used to study the evolution of the rheological behavior of cement- based materials with time. This device was initially developed to enable a simple measurement of the increase of the yield stress. Therefore, it can provide an accurate value of the structuration rate during the so-called dor- mant period and also provide an evaluation of the initial setting time. However, as the immersed tool remains static, the success of the test depends on the movement of the cement- based material at the interface. The relative translation between the freshly made cement-based material and the tool must be sufficient to overcome the critical shear strain of the sample. During the very early age of the ce- ment-based material many phenomena occur (consolidation, shrinkage, thermal expansion, bleeding…) and lead to volume variation of the material. Those volume variations need to be controlled in order to ensure a cor- rect measurement of the yield stress. After providing and explaining the test physical background and procedure, we first aim to warn researchers about possible measuring artefacts that lead to a too low strain at the tool interface. Then, this paper shows all the possibilities and information provided by during the dormant period and setting. In this paper, an attempt to extend the test duration and to get also information on the thermal expansion is pre- sented. This paper shows how to perform a successful and highlights the versatility of the plate tests that is able to provide interesting information about structural build-up, setting and thermal expansion. © 2016 Published by Elsevier Ltd. Keywords: Setting Yield stress Structural build-up Dimensional variations 1. Introduction Despite the long tradition of characterizing cement paste time evolu- tion by the initial and final setting time, these values are not sufficient to answer some of the more practical questions related with constructabil- ity. The answer to these questions is of paramount importance for the civil engineer to plan a concrete delivery for a given construction site. However, to answer the above questions, the flow properties of the ma- terial and their evolution need to be known. In contrast with a mechan- ical method that will be always dependent on the geometry and the applied forces, the proposed investigation was carried out on the idea that it was possible to monitor the setting through the variation of yield stress. Roussel and other authors have shown that during the dor- mant period and at rest, self-compacting concrete (SCC) structure build- up and its yield stress increases [21,22,24,27]. This increase is responsi- ble for lot of practical application such as multilayer casting, 3D printing, formwork pressure decay… [3,4,14,18,19,21,23,26]. The increase rate of yield stress is commonly determined using rheological measurements carried out after different resting time. Portable system has been devel- oped to monitor the yield stress increase on site [3,4,8]. Another strate- gy is to use the plate test measurement [1,3,4,6,25,26]. The plate test device, consisting of a rough plate (or needle) immersed in the fluid sample, was developed to enable a simpler measurement of the increase of the yield stress of non-Newtonian suspensions such as self- compacting concrete. Due to the deformation of the material at rest along the vertical axis, shearing appears at the plate surface inducing the plate apparent mass to vary with time. The plate test device has been first used for concrete in 2008 [1,26]. The problem is the same as the steel rebar immersion in concrete form- work [15]. The elastoplastic properties and deformation of the fresh ce- ment paste are used. Due to local vertical deformation of the cement paste at very early age (shrinkage, dilatation, settlement), stresses are mobilized at the interface between the paste and the rough plate. This induces variation of the apparent mass of the plate or needle, as pro- posed by Sleiman et al. [25]. Moreover, since the plate or needle is static and the material shrinkage is slow, the dynamic effects are, therefore, negligible. The plate tests measurements have also been shown to be able to give accurate values of the setting times [25]. However, as the Cement and Concrete Research 93 (2017) 1–7 ⁎ Corresponding author. E-mail addresses: sofiane.amziane@univ-bpclermont.fr (S. Amziane), arnaud.perrot@univ-ubs.fr (A. Perrot). http://dx.doi.org/10.1016/j.cemconres.2016.12.002 0008-8846/© 2016 Published by Elsevier Ltd. Contents lists available at ScienceDirect Cement and Concrete Research journal homepage: www.elsevier.com/locate/cemconres