Influence of formwork material on transport properties of self-consolidating concrete near formed surfaces B.M. Aïssoun a,b , J.-L. Gallias b , K.H. Khayat a,c,⇑ a Université de Sherbrooke, Département de Génie civil, 2500 boul. de l’université, J1K 2R1 Sherbrooke, Canada b Université de Cergy Pontoise, 5 Mail Gay-Lussac, 95011 Neuville-sur-Oise cedex, France c Missouri University of Science and Technology, 224 ERL, 500 W. 16tyh St., Rolla, MO 65409, USA highlights  New experimental method using image analysis to quantify wall effect is proposed.  The use of Plywood (PW) formwork reduced sorptivity of concrete cover.  The rough and absorbent PW modified significantly local w/c and wall effect of SCC cover.  The decrease of w/c and the wall effect in the case of PW guaranteed higher durability. article info Article history: Received 7 September 2016 Received in revised form 10 April 2017 Accepted 12 April 2017 Keywords: Aggregate packing Capillary absorption Concrete cover Formwork Rheology Self-consolidating concrete Sorptivity Wall effect abstract This study aims at determining the influence of the formwork material on transport properties of con- crete cover when using self-consolidating concrete (SCC). Two types of formwork were used. The ply- wood (PW) formwork material which is relatively rough and absorbent compared to the PVC material that has a very smooth and non-absorbent surface. A total of 17 SCC and highly flowable concrete mix- tures with wide range of slump flow and T 50 values were investigated. The concrete was used to fill 400  500  200 mm 3 moulds made with either PVC or PW. Sorptivity tests were performed on core sam- ples (100 mm in diameter and 50 mm in length) taken from the sides and center of the prepared moulds after 28 days of moist curing. This paper presents new experimental method using image analysis to quantify the relative surface area of coarse aggregate along different sections near formed surfaces. Sorptivity of concrete near the surface cast against the PW formwork was found to be significantly lower than that of PVC one due to the decrease of local w/c and wall effect. The examination of packing density of coarse aggregate near PVC and PW surfaces showed limited wall effect near the PVC formwork and sig- nificant wall effect within a thickness comparable to the maximum size of coarse aggregate near the PW formwork. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction The ingress of water and aggressive agents in concrete affect concrete durability. Ensuring low permeability of the so called con- crete cover is of prime importance since it constitutes the first bar- rier to reducing the attack by aggressive agents. Transport properties and permeability of concrete depend on the mix design and curing conditions [1–4]. The durability of concrete, and in par- ticular self-consolidating concrete (SCC), can vary with the rheo- logical properties of the concrete that affect the consolidation, bleeding, surface settlement, segregation, as well as stability of entrained air [5,6]. Due to the presence of a formed surface, the change in packing of aggregate at the boundary layer against that surfaces (also known as the wall effect) can affect the in-situ transport properties [7]. Kreijger [8] showed that in the case of conventional vibrated concrete, the material found in the first 5 mm near the formwork is essentially composed of mortar with a water-to-cement ratio (w/c) greater than that found in the bulk concrete. This is the result of the wall effect induced by coarse aggregate packing against formed surfaces where a lower concentration of coarse aggregate was noted [8]. The study by Kreijger did not provide discussion regarding to the distribution of coarse aggregate in the first cen- timeter of formed concrete surfaces. Numerical studies dealing http://dx.doi.org/10.1016/j.conbuildmat.2017.04.104 0950-0618/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Missouri University of Science and Technology, 224 ERL, 500 W. 16tyh St., Rolla, MO 65409, USA. E-mail address: khayatk@mst.edu (K.H. Khayat). Construction and Building Materials 146 (2017) 329–337 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat