Mortier (matériau) | EPFL Graph Search

thumb|Trois briques maintenues ensemble par un mortier. Le mortier est le mélange à consistance de pâte ou de boue, d'un liant et d'agrégats avec de l'eau. Il est utilisé en maçonnerie comme élément de liaison, de scellement ou comme enduit. Techniquement parlant, c'est une colle. Les professionnels du bâtiment qui utilisent le mortier sont le maçon, le couvreur, le carreleur et le tailleur de pierre. Jadis, la fonction était dévolue au gâcheur de mortier, qui le gâchait, c'est-à-dire le mélangeait. Étymologie Le latin mortarium, désigne d'abord l'auge du maçon, puis son contenu. Cette distinction nous est restée puisque le terme mortier désigne le récipient (Voir Mortier et pilon) et son contenu. Le mortellier est le fabricant d'auges de pierre qu'on appelle mortiers et ensuite celui qui brise certaines pierres dures pour en faire du ciment. Les morteliers ont constitué une des premières organisations de métier, entérinée par le Livre des métiers d'Étienne Boileau, ré

Resistance of cementitious materials to sulfate attack: quantifying performance with a reliable unidirectional approach

Qiao Wang

Depending on the environmental conditions, concrete materials can come into contact with sulfate ions which are widely present in rivers, underground water, sewers, seawater and soil. Sulfates can react with the cement paste in concrete and cause damage which impacts the service life of concrete structures. Cement chemistry, transport of sulfate ions, and physical properties of the host material all interact in the complex process of sulfate degradation. Given different conditions of concrete exposure, sulfate attack is commonly divided into "chemical" and "physical" sulfate attack. However, the processes are not fully understood and there is still a need for in-depth investigations of the whole deterioration process. The current standard testing method is adapted for Portland cement systems affected by the "chemical sulfate attack" in submerged conditions. However, only expansion is monitored, which is not suitable for characterizing the increasingly common usage of supplementary cementitious materials in the cement. Moreover, several key factors (e.g., RH & temperature) are usually overlooked so lab tests do not well represent the field conditions. Particularly, the understanding of the damaging mechanism of "physical sulfate attack" is very limited even if different testing approaches have been established. The division into "chemical" and "physical" attack is in itself misleading. In this context, this research project was launched to establish a unidirectional penetration approach for the in-depth comprehensive investigation of joint sulfate attack mechanisms. First, the feasibility of this newly established approach was studied for Portland cement mortars and pastes. A high concentration of sulfate solution and a high water-to-cement ratio was chosen to accelerate the degradation and to obtain results in a reasonable period. Results showed that this new concept of combining chemical and physical sulfate attack mechanisms into a single experiment was viable. Moreover, results showed that using cement paste samples can accelerate the degradation, compared to mortar samples. The sulfate degradation process was more rapid with the capillary rise and water evaporation. A comparison of the macroscopic manifestation of damage (visual appearance and expansion) with the underlying microscopic changes was made considering different key parameters, i.e., water-to-cement ratio, exposure solution concentration, cement type, temperature and humidity conditions (constant or cyclic). Regarding the different cement types, Ordinary Portland cement pastes and sulfate-resisting cement pastes showed higher expansion and cracking, whereas, spalling damage was more pronounced in blended-cement pastes/mortars (slag Portland cement and limestone calcined clay cement). Damage from the chemical attack was more extensive and rapid when high concentrations and cyclic exposure conditions were applied. However, lower water-to-cement ratios leading to lower porosity and/or higher mechanical strength could usually reduce the extent of the damage. Thermodynamic modelling was also conducted with GEMS to better explain the pore solution environment and the link between supersaturation and expansion. The interacting factors of porosity and strength were decoupled. The effect of the curing temperature on the expansion mechanism was also investigated in sulfate-resisting cement mortars under submerged sulfate exposure.

EPFL2022

Properties of mortars produced with reactivated cementitious materials

Ricardo Javier Serpell Carriquiry

The production of reactivated cementitious materials is an option for the recycling of hydrated-cement-rich fines discarded during recycled aggregate production. Reactivation is based on a thermal process where calcium silicate hydrates present in the fines decompose forming new hydraulic compounds. In the reported study, materials reactivated at temperatures between 660 °C and 940 °C were characterized using X-Ray diffraction and particle size analysis, and evaluated as binders using a central composite experiment to model the effects of reactivation temperature and reactivated material substitution level on the flowability, compressive strength and expansion of mortar mixtures. Reactivation temperature effects correlated with the relative concentration of reactive phases, particularly a stabilized form of alpha'-C2S identified in the materials. Substitution effects depended on the supplementary material tested, and lacked significant interaction with reactivation temperature. In the region explored, mortars based on materials produced at 800 °C, 40% substituted by silica fume, achieved highest strength but lowest flowability.

2015

A mesoscale fracture model for concrete

Jean-François Molinari, Okan Yilmaz

We analyze the dynamic failure of concrete using two and three-dimensional finite-element models. In particular, the current results extend, using a unique parallel computing approach, previously published two-dimensional results. Concrete is treated at the mesoscale with an explicit representation of coarse aggregates and mortar paste. The propagation and coalescence of cracks are modeled with dynamically inserted cohesive elements. Stress-strain response, dissipated fracture energy and crack evolution are compared under tensile loading at several strain rates. The artifacts of the two-dimensional approach regarding microcrack coalescence are discussed in detail. Nonetheless, the dynamic increase factors for the peak strength and dissipated fracture energy show that in both two and three dimensions, micro-inertial effects are not enough to simulate the rate dependency in concrete with a simple rate-independent cohesive law. Rate-dependent damage parameters can be introduced to obtain a more accurate dynamic response.

Elsevier2017

Resistance of cementitious materials to sulfate attack: quantifying performance with a reliable unidirectional approach

Qiao Wang

EPFL2022