Interactions between Superplasticizer and Release Agents at the Concrete/Formwork Interface

Abstract

Improving the knowledge of rheological and tribological characteristics of fresh concrete is important to contribute to the progress of construction sites and the final quality of the work. The objective of this study is to identify the effect of a superplasticizer based on polycarboxylic ether on the tribological behavior of fresh concrete at the concrete/formwork and concrete/oil/formwork interfaces. Friction tests on fresh concrete were carried out using a plan/plan tribometer. In order to study the behavior of the superplasticizer close to the formwork, three concretes with 30% of paste and different dosage of superplasticizer were formulated. The results show that the increase of the dosage of superplasticizer reduces the friction stress. The properties of the superplasticizer generate a deflocculating action of concrete grains and lead to a stabilisation of the soap-oil micellae present in the vicinity of the formwork. Thus, the efficiency of superplasticizer depends on the quantity of fines, on the quantity of soap formed and so, on the release agent formulation.

On functional signatures of bare and coated formwork skin surfaces

“…The friction stress at the concrete-formwork interface was estimated in the 10 to 30 kPa range according to other works [8], [14], [36], [46], [47]. This friction stress is 10 6 orders of magnitude smaller than the calculated critical shear stress for the delamination of the oxide layer from the formwork substrate.…”

“…The adhesion of the concrete on the skin may possibly arise from electrical bonding [4] [5] and chemical bonding through the Ca(OH) 2 formation [4]- [6]. The interfacial bonding depends partly on the water-cement ratio [7], the polymer additives [5] [7] [8] and the filler substitutes [7]. The concrete adhesion is partially avoided by modifying the skin surface through the condensation of a water layer [9], the application of a polymer coating [4], or the spreading of release agents [10]- [13] prior to concrete pouring.…”

Palm Olein Lubricates and Removes Freshly Baked Concrete From Its Formwork

“…In general, acceptable SV of plant oils is ranged 176-244 mg KOH g -1 oil (Gnanasekaran and Chavidi, 2018;Joseph and Saxena, 2017). A higher SV range is undesirable as it mobilises the concrete particles within the oil-formwork interface, thus softening takes place resulted in concrete sticking on formwork and striping is difficult (Bouharoun et al, 2012, Freedman, 1975. The saponification ability of a vegetable esters in forming soap layers at the formwork interface is an added advantage for surface release lubrication, as oil participates in the formation of interstitial mediums creating a stable emulsion in the vicinity of formwork (Bouharoun, 2016).…”

Designing metallic surfaces in contact with hardening fresh concrete: A review

“…In fact, polymeric skins have proven an efficient anti-adherence solution [8][9][10]24,93,94,98,[121][122][123][124] but have weak resistance to fresh concrete-induced abrasion [52,88]. The study of concrete friction on substrates was mainly investigated using the plane/plane tribometer [16,19,21,52,88,[143][144][145][146][147][148][149][150] and few rheological models [52,88,151]. The friction and wear behavior have highlighted the dependence of interfacial friction stresses of fresh concrete on a substrate with the demoulding agents [19,150,152], the aggregate contents [149], the paste volume [16] and the optional addition of superplasticizer [16,19,150].…”