When a soil is subject to low temperatures, the freezing of water can lead to an upward forces and the deformation of the soil with the growth of ice. This phenomena, called frost heaving can lead to catastrophic destruction of roads or buildings in cold regions as shown in figure above. The most obvious explanation for this phenomenon comes from the fact that water expands by about 9% when 
it turns into ice. If the water completely fills the porous soil and starts freezing, the ice will subsequently apply pressure on the soil leading to its deformation. This explanation falls short however, as soils are generally not fully saturated and one would then expect the ice to be able to grow where there is room to expand. It is believed that the build-up of ice happens largely because 
water in the unfrozen soil below gets drawn up into the freezing zone and attaches itself to the existing frost crystals to form ever thickening layers of ice. The phenomenon is also known as ice segregation or ice lense formation. The cause of frost heave is therefore somewhat not fully understood, and a lot of questions remain unanswered.

During this master project, you will experimentally investigate the mechanism of phase transition of water to ice in granular materials when partially saturated with water. The objective is to understandwhat the conditions for ice lenses formation are. For that, you will design an experimental set-up similar to a Hele-Shaw cell to study a model soil under freezing conditions. Several parameters will beinvestigated such as: 

- the saturation of the soil,
- its physical properties (hydrophilicity, compaction and poydispersity)
- the freezing temperature

Research conditions:
This master research project is a collaborative project between Weber Beamix and the Soft Matter group at the IoP- UvA. The research will be done in the Soft Matter group at the University of Amsterdam in close collaboration with the R&D department of Weber Beamix. During the project, the student will visit the company to become familiar with their different activities.

Research project:
Gypsum efflorescence is one of the major problems affecting clay brick masonry. Efflorescence consists of the crystallization of various soluble salts at the surface of porous materials (bricks and stones, etc.), appearing as a white-grey stains months or several years after the construction. Gypsum efflorescence adheres very strongly to the rough surface of the bricks and is very difficult to remove because of the low solubility of calcium sulfate crystals. The appearance of gypsum stains can occur on facades after exposure to water and rain followed by evaporation due to environmental fluctuations, i.e. low relative humidity and/or higher temperature.

The objective of this project is to find an ecologically friendly solution for the easy removal of gypsum efflorescence from stones, i.e., rough and porous surfaces. For this purpose, different additives (surfactants and anticaking agents) having the role of nucleation promoters and growth modifiers will be tested with the intention to suppress the adhesive properties of the precipitated gypsum at the surface. Similar to the case of caking the formation of solid bridges between the crystals and the surfaces during the evaporation of thin liquid films can increase the adhesive properties of the salt crystals. The main objective is then to decrease the effective contact area between crystals and the surface and, on the other hand, improves the spreading ability of the water over the crystalline surfaces in order to avoid solid crystalline bridge between crystals and surface.
The student will therefore perform multiscale Experiments: at the microscale precipitated gypsum from evaporating droplets will be exposed to water with different types of additivesand made to evaporate again to induce recrystallization; the kinetics of dissolution/recrystallization will be followed under phase contrast microscopy and confocal Raman microscopy.

At the macroscale, Gypsum-contaminated model stones (limestone and sandstone) will be prepared and exposed to the same water and additives. The drying kinetics and the recrystallization process will be studied using various techniques such as NMR, SEM, and weight measurements. Micro X-ray Tomography analysis on some selected stone samples can also be planned in collaboration with our partner at the University of Pau in France.