Surfactant-induced growth of a calcium hydroxide coating at the concrete surface

Abstract

International audienceIn addition to its remarkable mechanical properties, high-performance concrete (HPC) also exhibits a very smooth surface with low porosity, which makes it particularly suitable for esthetic applications. Unfortunately, the constant environmental aggressions to which the urban buildings are exposed (organic or inorganic particles, algae, micro-organisms, staining from various sources) are a threat to their structural and esthetic durability. This article proposes an innovative method to protect HPC surfaces based on Ca(OH)2 growth at the fresh concrete/formwork interface. With the adequate surfactants used as demolding agents, it is possible to grow a continuous layer of Ca(OH)2 at the concrete surface which closes the porosity, reduces the water uptake, and gives the surface super-hydrophilic properties, facilitating self-cleaning mechanisms

Characterisation of the variations of tint and the adhesion of pigments onto the surface of mortar

“…However, the reference, casted in a steel mould coated by demoulding oil, has a luminance number greater than the luminance of the mortar casted in a PVC mould coated by a demoulding solution containing surfactants. This result may be explained by the fact that the very smooth PVC mould related to the presence of surfactants tends to promote the creation of a smoother mortar surface (with a close porosity), partly composed of portlandite crystals, as detailed in a previous publication [12].…”

“…Indeed, non-ionic surfactants, ethoxylated fatty alcohols with one hand and an ethoxylated fatty amine on the other hand, have been tested [4,12,18]. These products, which are not normally used as release agents, have been selected for their hydrophilic and hydrophobic properties combined, the idea being to keep a fat side to ensure demoulding, adding a hydrophilic side to facilitate the bond between pigments and cement paste.…”

“…Although a few muralist precursors raised the question of mortar aesthetic at the beginning of the 20th century [1][2][3][4], it only became a major concern in the last decades [4][5][6][7][8][9][10]. The development of high-performance and self-compacting concretes [11][12][13][14], which show a significant improvement in terms of aesthetics, contributed to develop their use in architecture.…”

Microstructure and Surface Properties of Frescoes Based on Lime and Cement: The Influence of the Artist's Technique

“…Then, the evaporation of water implies a nucleation of calcium hydroxide, which later becomes a dense layer of calcite, as already proposed by different authors (Colfen and Mann ; Gueit et al . ). The latter showed the occurrence of portlandite crystals overlying parallel to the surface plan and leading to closing of the surface porosity.…”

Study of the Interface and Durability of the Adhesion Between Photovoltaic Cells and Concrete-Based Façade Panels

“…Based-on previous results showing that the surface of concrete can be designed in terms of smoothness and flatness (by choosing the right mix-designs and moulding conditions [9]- [11]), some experiments were conducted to establish if this kind of concrete-based solution could be an alternative to glass-based and metallic-based structures to manufacture aesthetical façade panels with photovoltaic function. Indeed, a technical process that can be described by the direct pouring of fresh concrete on the backside of the photovoltaic cells, previously placed at the bottom of the formwork and coated by specific adhesives, was developed and patented in 2015.…”