Przemysław Brzyski

Properties of Hemp–Flax Composites for Use in the Building Industry

ABSTRACT This article presents the results of research concerning lightweight composites produced on the basis of lime, cement, and clay binders, with the addition of perlite, hemp shives, and flax straw. Tests of physical and mechanical properties of composites were performed and their basic characteristics were determined, i.e. absorptivity, density, thermal conductivity coefficient, and compressive and flexural strength. The study was conducted to determine the use of hemp and flax composites to fill the frames of a wooden house. The results prove that the composites have low thermal conductivity, apparent density, and low strength properties compared with conventional building materials.

Composite Materials Based on Hemp and Flax for Low-Energy Buildings

The article presents the results obtained in the course of a study on prospective application of flax/hemp wastes as a filling material of lime-based composites in the construction of low-energy buildings. The utilized filler comprised the hydrated lime with clay and Portland cement used as additives. The analysis involved evaluation of such properties as porosity, density, thermal conductivity, absorptivity, permeability, as well as compressive and flexural strength. Depending on the quantity of the filler, the properties of the composite changed. This, in turn, enabled to evaluate whether the utilized composite met the thermal requirements established for low-energy buildings. Afterwards, the obtained data were cross-referenced with the results gathered in the case of a room built of autoclaved aerated concrete. In order to prevent reaching the critical surface humidity, the internal surface temperature had to be calculated. Moreover, the chances of interstitial condensation occurring in the wall made of the analyzed lime–flax–hemp composite were determined as well. The study showed that the composite exhibits low strength, low density, low thermal conductivity, and high absorptivity. The external walls made of the lime–flax–hemp composite receive a limited exposure to condensation, but not significant enough to constitute any threat. The requirements established for low-energy buildings can be met by using the analyzed composite.

Hydrophobization of Lime Composites with Lignocellulosic Raw Materials from Flax

ABSTRACT The aim of the study was to evaluate the possibility of applying lime binder together with flax fibers and straw to the production of wall materials. Properties of the composites were modified by additives and admixtures. The following laboratory tests were performed: the analysis of the physical characteristics, compressive strength, a water droplet absorption test, water absorption of hydrophobized and standard samples, drying time, and analysis of the structure using scanning electron microscope (SEM). In the paper, there was examined the effectiveness of two formulations differing in the degree of hydrolytic polycondensation, viscosity, and concentration, as these are the factors that determine the final impregnation effect.

Thermal Properties of Raw Hemp Fiber as a Loose-Fill Insulation Material

ABSTRACT The article presents the possibilities of using hemp fiber as a loose-fill insulation material. The article presents the results of research concerning raw hemp fiber obtained from the Polish crop of industrial hemp of Białobrzeskie variety. The analysis involved evaluation of thermal conductivity in function of bulk density and air permeability, the properties important for insulation materials. The results of laboratory investigation were used to create the numerical simulation models of heat transfer in the frame wall partitions filled with hemp fibers. The study showed that with the increase of bulk density, the thermal conductivity and air permeability of material decrease. The obtained lambda values are comparable with the characteristic values for conventional thermal insulation materials. The results of heat transfer and temperature distribution reveal that hemp fibers characterize with strongly air permeance, what affects on the need for additional barriers against air filtration.

Estimation of water absorption coefficient using the TDR method

Moisture accumulation and transport in the building barriers is an important feature that influences building performance, causing serious exploitation problems as increased energy use, mold and bacteria growth, decrease of indoor air parameters that may lead to sick building syndrome (SBS). One of the parameters that is used to describe moisture characteristic of the material is water absorption coefficient being the measure of capillary behavior of the material as a function of time and the surface area of the specimen. As usual it is determined using gravimetric methods according to EN 1925:1999 standard. In this article we demonstrate the possibility of determination of water absorption coefficient of autoclaved aerated concrete (AAC) using the Time Domain Reflectometry (TDR) method. TDR is an electric technique that had been adopted from soil science and can be successfully used for real-time monitoring of moisture transport in building materials and envelopes. Data achieved using TDR readouts show h...

Moisture and wetting properties of thermal insulation materials based on hemp fiber, cellulose and mineral wool in a loose state

ABSTRACT The paper presents the results of research concerning three fiber materials – hemp fiber, cellulose fiber and mineral wool as a loose-fill thermal insulation materials. It focused on the study of moisture properties and wettability of these materials. The analysis involved evaluation of moisture sorption in different relative humidity conditions and evaluation of wettability of fibers by contact angle measurement. The study showed that the sorption equilibrium has been achieved at different times, which proves the various nature and properties of the materials. Hemp fibers were less wet than cellulose fiber, but the time needed to stabilize was shorter. The largest contact angles, indicating the strongly hydrophobic properties, were shown by mineral wool. Some samples of hemp and cellulose fibers were characterized by similar contact angles providing high wetting properties.