Influence of the disparities between lab and in-situ application on the penetration depth of a hydrophobic agent

Over the last few years, the application of a hydrophobic agent on a masonry wall has become popular due to its ability to reduce the amount of rain water absorption without changing the facade’s appearance. While the hygric properties of such hydrophobised materials are often investigated, research towards its penetration depth into materials is limited. Additionally, most existing research involves small samples made in a lab rather than masonry walls. This paper therefore focuses on two key differences between lab application and application on an actual masonry wall and their influence on the penetration depth of a hydrophobic agent. As the hydrophobic agent is applied differently on an in-situ masonry wall than on laboratory samples, the method of hydrophobisation is investigated first. It is shown that the penetration depth varies significantly for different methods of hydrophobisation as well as within single samples. Secondly, the existing research often targets separate brick or mortar samples rather than full-scale masonry walls. Therefore, several experimental methods are used to quantify the penetration depth in a masonry wall. From these experiments, it is shown that the penetration depth is not only variable throughout this wall, but within separate bricks or mortar joints as well.

Grain Density-Based Approaches to Predict the Mechanical, Thermal and Hygric Properties of Carbon-Negative Aggregate Concretes

The suitability of replacing mineral aggregate with carbon-negative ones mainly depends on the properties of the aggregates produced from waste recycling, reducing CO2 emissions. This study aimed to investigate the predictive approaches adapted to concrete mixtures where mineral aggregates are replaced by carbonated aggregates (at different substitution rates from 25 to 100% with aggregates of various origins). A large experimental campaign of aggregates and carbonated aggregate concretes highlighted their physical, mechanical, thermal and hygric properties and the influence of density and porosity of aggregates on these properties. Thanks to these results, predictive approaches were formulated to establish the main engineering properties: mechanical compressive strength, elasticity modulus, thermal conductivity, thermal mass capacity and hygric diffusivity. These empirical and analytical models were based on the density of aggregates. Maximum deviations of around 15% were obtained with the experimental data, highlighting the influence of grain density on carbonated aggregate concretes. These models could then be used to optimize the formulation of concrete mixtures with carbonated aggregates, replacing international standards adapted to mineral aggregates.

Combined Effect of Superabsorbent Polymers and Cellulose Fibers on Functional Performance of Plasters

Plaster has, from ancient times, been used as a decorative material. However, the advances in materials engineering such as thermal and moisture control provide new opportunities. Superabsorbent polymers (SAPs) have been found to possess passive moisture control that may find utilization in modern buildings. However, the main drawback is associated with a limited number of applicable SAPs due to mechanical strength loss. In this regard, concurrent utilization of cellulose fibers may provide additional benefits linked with the reinforcing of plaster structure and preservation of superior hygric properties. In this regard, this study investigates the combined effect of SAP and cellulose fibers on the material properties of cement-lime plaster in terms of its mechanic, thermal, and hygric properties. To access the capability of such modified plasters to control the interior moisture fluctuations, the moisture buffering value is determined. Obtained results show the effect of both applied admixtures on material performance, whilst the synergic effect was most obvious for humidity control accessed through the moisture buffer coefficient.

LIGHTWEIGHT COATING MORTARS FOR BUILDINGS RESTORATION

In this paper, crushed lava-based aggregate was used in mortar mix composition as a full silica sand substitution to improve thermal properties of mortar fulfilling also other physical, mechanical and technical requirements. As a binder, natural hydraulic lime was used. Workability of fresh mortar mixes was characterized by spread diameter. The casted samples were matured for 28 days in a high relative humidity to avoid cracking. For the hardened samples, structural, mechanical, and hygric properties were tested. Thermo-physical properties of the developed mortars were measured as function of moisture content, from the dry to fully water saturated state. The application of lava-based aggregate led to the mortar’s increased porosity, improved mechanical strength, lower water absorption, and significantly better thermal performance compared to the control materials with silica aggregate. The newly developed lightweight mortar met the technical, compatibility and functional criteria on rendering mortar and was found well usable for conservation and restoration of historical and heritage masonry and buildings.

Stochastic generation of multiscale 3D pore network models of building materials

The current experimental determination of hygric properties of porous building materials are demanding in time and effort, merge ad- and desorption techniques, fuses static and dynamic methods, and finally do not yield complete nor robust results. Therefore, numerical pore-scale-based prediction of the hygric properties of building materials is on the rise as an alternative. For building materials, this is mostly based on pore network modelling (PNM), given that these are more efficient compared to lattice Boltzmann or particle hydrodynamic methods. Pore network modelling however requires data of the complete pore network for the building material. With the currently available characterization and visualization techniques, this cannot be readily obtained, as the pore sizes in building materials often span several spatial scales. The aim of this paper is to present a scale invariant stochastic generation. To realize this objective, distributions of direct parameters (pores’ sizes, shapes, positions, connections, ...) as well as indirect parameters (overall pore size distribution and open porosity value) are derived from the input data obtained by micro-CT and FIB-SEM and subsequently applied to generate a complete pore network of the porous building material. The quality of the generated PNMs is assessed by comparing them to the original PNMs.