Influence of Carding and Pressing on Hygrothermal Properties and Fire Reaction of Hemp Fiber Nonwoven Mats

This article depicts the effect of carding and pressing on hygrothermal properties of hemp fibers nonwoven mats, trying to understand if their implementation can improve their behavior when employed as insulation materials in buildings. Hemp fibers belonging to Cannabis Sativa species and coming from local area (Apulia - Italy) were examined, then samples of carded and pressed hemp fibers nonwoven mats were prepared. According to European standards, the thermal conductivity, the vapor permeability and the fire reaction of hemp fibers samples were measured. Results were compared to each other and with those of a commercial nonwoven mat made with hemp (90 wt. %) and synthetic fibers (10 wt. %), used as reference. We observed that carded and pressed hemp fibers were characterized by a lower thermal conductivity when compared to unprocessed hemp fibers, likely because the removing of wood elements. On the other hand, not processed hemp fibers show higher breathability when compared to carded and pressed ones, as well as with respect to the commercial nonwoven mat. Moreover, it was proved that the absence of synthetic commingled fibers in hemp fibers allows a better behavior in fire reaction. At last, the improvement in terms of insulation properties of a hollow brick when filled with hemp fibers was verified, by comparing the thermal conductivities of an empty and a filled hollow brick; as expected, the filled hollow brick shows a lower thermal conductivity, underlining the effectiveness of hemp fibers as insulation material

Hempcrete Buildings: Environmental Sustainability and Durability of Two Case-Studies in North and South Italy

In the framework of Circular Economy policies aimed at reducing the consumption of raw materials, shives, as an agricultural by-product of hemp cultivation, have gained a renovated life in the construction sector. Its excellent thermal insulating properties permitted the development of new building materials to be used in various executive technologies. When shives are mixed with a mineral binder such as lime or cement, the mixture is usually referred to as hempcrete. In Italy, the use of hempcrete and the development of new production chains and implementation techniques dates back only to about the last decade, while other European countries have more long-lasting experiences (90s). In order to assess the potential benefits of hempcrete in the construction sector, its environmental performances were evaluated using the LCA methodology, by comparing four non-loadbearing representative walls, one made with hempcrete blocks and the others with more “traditional” materials. This research constitutes a solid basis for the development of future guidelines and/or regulations at national and international level in order to guarantee the maximum diffusion of this type of product. Then, a study has been carried out regarding the functionality of hempcrete blocks in masonry, layered with finishing plaster made of fine hemp shives, to evaluate the in-situ hygrothermal building performance. In particular, measurement methods were developed and analysis were carried out on two houses, one in northern Italy and one in southern Italy, and precisely in Sicily, focusing the study on the performances of the walls subjected to warm Mediterranean climates. Indeed, the literature on masonry behavior in hot Mediterranean climates is much scarcer than in cold climates

Combining the bi-objective approach and conditional coring for a reliable estimation of on-site concrete strength variability

In real practice, to assess concrete strength in structures, engineers usually use non-destructive tests (NDT) (e.g. rebound hammer or ultrasonic pulse velocity) in addition to destructive tests (DT) that are carried out on cores extracted from the structure. The results of these tests (NDT and DT) are used to identify a relationship (a conversion model) between the non-destructive measured features and the concrete strength. This model can be then used to assess the strength at any location within the structure under consideration, as well as the mean strength and the strength standard deviation (strength variability). In fact, the assessment of concrete strength variability is as important as the mean strength since the mean strength alone cannot provide a clear picture about the concrete under investigation. However, due to the presence of many uncertainties, the reliability of the values estimated by NDTs need to be improved. In the present study, a wide range of concretes having mean strengths of 10–50 MPa and concrete strength variabilities of 10–30% (defined by the coefficient of variation) is analysed. The main target of this paper is to analyse how would the reliability of assessing the concrete strength variability changes if the bi-objective method is used as a model identification approach and the conditional coring concept is applied for selecting core locations. Results are analysed in terms of the minimum number of cores NC that corresponds to a specific uncertainty level, concrete characteristics, and quality of NDT measurements. The results show an important improvement in the reliability of assessing the strength variability when both the bi-objective method and conditional coring are applied togethe