Life Cycle Assessment of a Wall Made of Prefabricated Hempcrete Blocks

Hempcrete is a natural building material obtained mixing hemp shives (i.e., the woody core of the hemp plant) with a lime-based binder and water. Hempcrete as construction material is gaining increasing interest as the EU aims to achieve net zero emissions by 2050. This material has, in fact, the ability to uptake carbon dioxide from air (i.e., via carbonation) and to store carbon for long time. The goal of the present work is to deeper analyze the environmental profile of hempcrete, in order to assess its potentials in reducing emissions of construction sector. Specifically, Life Cycle Assessment (LCA) of a non-load-bearing wall made of hempcrete blocks is carried on. The analysis encompasses the whole life cycle from the extraction of raw materials to the end of the service life. The analyzed blocks are produced by an Italian company. Only aerial lime is used as binder, microorganisms are added to the blocks to accelerate carbonation. The impact on climate change is assessed through the GWP 100 method proposed by IPCC. Preliminary results reveal a nearly neutral carbon budget

Microstructural Characterization of Prefabricated Hempcrete Blocks

Sustainable building materials have been developed to reduce the polluting emissions and the exploitation of natural resources of the building sector. Among these materials, an outstanding category is that of nature-based solutions which are produced recovering waste or by-products of agricultural cultivations and using them as vegetal aggregates to replace the traditional ones. This paper focusses on hempcrete which is produced mixing the by-product of industrial hemp cultivation (i.e., shives) and lime to obtain a sustainable, breathable and insulating material. The strength of hempcrete develops through carbonation of the binder that, leading to the formation of calcium or magnesium carbonates and mineralization of shives, determines the microstructure and hence most of the characteristic properties of the material. The aim of this research is to investigate how carbonation influences the microstructure of hempcrete when different recipes are used for blocks production. This study consists in the characterization of the material through techniques such as XRD (X-ray Diffractometry), SEM (Scanning Electron Microscopy) and TG-DTG (thermogravimetric analyses). Moreover, the evolution of carbonation is studied analyzing samples at different maturation times. The investigation of the carbonation reaction degree is also crucial to evaluate the environmental performances of the material because it allows the quantification of the carbon dioxide uptake. Also, periodic characterization allows to assess the durability of hempcrete and to select the best formulation according to the designed application and the corresponding service conditions

Numerical modeling of a hemp-lime blocks wall subject to horizontal in-plane loads

Hemp-lime is one of the nature-based solutions developed since the early 2000s to reduce the huge environmental impact of the building sector; it is produced mixing lime with hemp shives produced by the scutching of industrial hemp plants. The production of such material determines the recovery and enhancement of by-products of agricultural cultivation in accordance with the principles of circular economy. Hemp-lime is a carbon negative material mainly due to the utilization of vegetal aggregates and to the carbonation reaction, characteristic of lime, through which carbon dioxide sequestration takes place. In this research, the behavior of a wall built in prefabricated hemp-lime blocks has been investigated focusing on the mortar joints and on the determination of their eventual seismic and wind bracing contribution in a building. Starting from the determination of mechanical properties of the blocks, a finite element numerical analysis of the hemp-lime wall system has been developed. The results show that mortar joints exert a stiffening action in a hemp-lime system as opposite to other building techniques where joints are generally weak parts. Although the mechanical properties of the hemp-lime wall are generally less performing than those offered by a traditional wall (brick, stone) the bracing effect is appreciable for residential buildings in moderate seismicity areas due to the reduction of stress states in the load-bearing elements as frame or pillars

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

Mechanical and Microstructural Characterization of Rammed Earth Stabilized with Five Biopolymers

International audienceThis study aims to check the compatibility of a selection of waste and recycled biopolymers for rammed earth applications in order to replace the more common cement-based stabilization. Five formulations of stabilized rammed earth were prepared with different biopolymers: lignin sulfonate, tannin, sheep wool fibers, citrus pomace and grape-seed flour. The microstructure of the different formulations was characterized by investigating the interactions between earth and stabilizers through mercury intrusion porosimetry (MIP), nitrogen soprtion isotherm, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The unconfined compressive strength (UCS) was also evaluated for all stabilized specimens. Three out of five biopolymers were considered suitable as rammed earth stabilizers. The use of wool increased the UCS by 6%, probably thanks to the combined effect of the length of the fibers and the roughness of their surfaces, which gives a contribution in binding clay particles higher than citrus and grape-seed flour. Lignin sulfonate and tannin increased the UCS by 38% and 13%, respectively, suggesting the additives’ ability to fill pores, coat soil grains and form aggregates; this capability is confirmed by the reduction in the specific surface area and the pore volume in the nano- and micropore zones