Capillary Uptake Monitoring in Lime-Hemp-Perlite Composite Using the Time Domain Reflectometry Sensing Technique for Moisture Detection in Building Composites

Abstract

The use of waste plants in the production of building materials is consistent with the principles of sustainable development. One of the ideas involves using hemp shives as an aggregate for the production of a composite used as a filling of the timber frame construction of the walls. The most important disadvantage of using the building materials based on organic components is their susceptibility to the water influence. The wall material is exposed to rising groundwater. The research part of the paper presented the preparation method and the investigation of the hemp-perlite-lime composites. Flexural and compressive strength, apparent density, total porosity, thermal conductivity, and mass absorptivity were examined. The main research part pertained to the analysis of capillary uptake occurrence in the composites, being the important phenomenon present in the external walls. The study on this phenomenon was carried out using the technique of indirect moisture evaluation—Time Domain Reflectometry (TDR). The indirect readouts were additionally verified with the traditional evaluation using the gravimetric method based on the PN-EN 1925 standard. The study proved that the tested composites were characterized by low apparent density, thermal conductivity, strength parameters, high total porosity, and mass absorptivity. The partial replacement of hemp shives by expanded perlite had a beneficial effect on the tested properties of composites.

Influence of Hemp Shives Size on Hygro-Thermal and Mechanical Properties of a Hemp-Lime Composite

“…The mass water absorption of composites containing fine shives was 126.9% after 1 week of the test, while for composites containing thick shives it was 115.5%. These results are similar to those presented in the literature, e.g., in [12] where composites with a density of 432.6 kg/m 3 were characterized by mass water absorption of the order of 128%. The biggest differences in the results between the two composites are visible in the initial period of the study.…”

“…The greater susceptibility to water rising of a composite containing longer shives may be due to larger pores between the shives than in the case of FHS, where shives fractions are smaller and therefore more closely matched to each other. Similar conclusions were drawn in [12], where an additional filler in the form of expanded perlite was used in the composite containing long shives, which filled the spaces between the shives, thus limiting capillary rise. Walker et al [13], in their research on composites with the same ratio of shives to binder, presented the capillary uptake coefficient after 24 h of the test; it was 2.65 and 3.37 kg/(m 2 h 1/2 ) depending on the type of binder.…”

“…The binding would only take place after removing the plates. This material has been investigated before [3,12]. The hemp shives are a highly absorbent filler.…”

“…Long fractions of hemp shives (>30 mm) can cause difficulties in mixing and arranging the mix. It is then necessary to thicken and mix the mixture more thoroughly to eliminate technological voids created by randomly arranged longer shives limiting the access of smaller fractions which can fill the space between them [12]. The stronger compaction will lead to an increase in the weight of the composite and a reduction in thermal insulation properties [13].…”

Wettability of Asphalt Concrete with Natural and Recycled Aggregates from Sanitary Ceramics

“…The application of recycled products and additives is currently one of the most popular methods of modifying building materials. The waste materials from industry, households, agriculture, and other sectors of the economy are subjected to processing, e.g., grinding, crushing, melting, separation of chemical compounds and substances [ 9 ]. Depending on the properties that characterize them, the obtained products can be used as additives in building materials, mainly in composites.…”