Phase Transformations in Cement Matrix at Low Temperatures

The paper presents the results of the phase composition and structure of cement, hardened under alternating freezing/thawing. The fluctuation in the density of the cement through the number of freezing/thawing cycles was determined by the method of helium pycnometry. It is shown that the average size of micropores changes in the presence of plasticizing additives. It is determined that the type and size of pores in the cement effect on frost resistance. The positive effect of mineral slag on the frost resistance of the binder is demonstrated. The positive effect of mineral and polymer additives on the frost resistance of the binder has been discovered and presented in this work.

The wood used for carpentry elements in canarian traditional buildings. An example of the practical application for the identification of this wood type

<p>Traditional Canarian Buildings are part of the rural landscape and urban space of the Canary Islands and constitute a relevant element of its architectural heritage, which must be preserved. </p><p>Probability, the Pitch wood is the building material that best represents traditional Canarian architecture. The identification of this wood is essential for establishing strategies for the purpose of the preventive conservation and to ensure the preservation of the original materials of the Canarian architectural model.</p><p>This work presents an example of practical application for the identification of pitch wood used for carpentry elements in a traditional Canarian building. A methodology proposed by the literature based on thermogravimetric analysis and helium pycnometry is used for this purpose.</p>

Cell wall microstructure, pore size distribution and absolute density of hemp shiv

This paper, for the first time, fully characterizes the intrinsic physical parameters of hemp shiv including cell wall microstructure, pore size distribution and absolute density. Scanning electron microscopy revealed microstructural features similar to hardwoods. Confocal microscopy revealed three major layers in the cell wall: middle lamella, primary cell wall and secondary cell wall. Computed tomography improved the visualization of pore shape and pore connectivity in three dimensions. Mercury intrusion porosimetry (MIP) showed that the average accessible porosity was 76.67 ± 2.03% and pore size classes could be distinguished into micropores (3–10 nm) and macropores (0.1–1 µm and 20–80 µm). The absolute density was evaluated by helium pycnometry, MIP and Archimedes' methods. The results show that these methods can lead to misinterpretation of absolute density. The MIP method showed a realistic absolute density (1.45 g cm −3 ) consistent with the density of the known constituents, including lignin, cellulose and hemi-cellulose. However, helium pycnometry and Archimedes’ methods gave falsely low values owing to 10% of the volume being inaccessible pores, which require sample pretreatment in order to be filled by liquid or gas. This indicates that the determination of the cell wall density is strongly dependent on sample geometry and preparation.