Patrick Tintillier

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

In 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.

Multi-technique investigation of calcium hydroxide crystals at the concrete surface

The durability and aesthetic qualities of high-performance concrete, which makes it particularly suitable for architectural applications, are constantly compromised by environmental aggressions. In this study, an innovative solution was developed to protect the concrete from these aggressions, which consists of growing a mineral coating on the concrete surface. The coating is composed of layered calcium hydroxide crystals, whose nucleation and growth are triggered byvarious non-ionic surfactants (the details of the process will not be presented). This paper describes the procedure used to investigate the structure of the formed crystals. Scanning Electron Microscopy and optical microtopography were used to determine the morphology of the crystals. Image analysis allowed the quantification of their amount, size and shape. The contribution and limits of each technique are discussed.