Construction materials and techniques
With the woody parts of the hemp stalk, after mechanical defibering, in a low-polluting process and little energy consumer is reached specific granules to be used as a construction material. Hemp granules have a very low density and with excellent thermal and acoustic properties. Due to their porous structure are used for the confection of mortars and insulating hemp concrete (IHC).
These granules must have specific properties, in relation to size, shape and characteristics, to be used in concrete. Those who do not meet the following criteria should not be used in hemp construction.
IHC is a dry mixture based on air and/or hydraulic binders, hemp granules and some additives that give it specific characteristics. Its insulating and acoustic properties allow it to be applied as insulation material on walls, roofs and floors.
In environmental terms hemp and lime allow a negative CO2 balance allowing construction with “Zero Carbon”. Compared to conventional concrete, the amount of energy incorporated is 30 times lower and the balance in relation to carbon emissions is negative, about -190 kg.CO2eq/m3, 280 kg.CO2eq/m3 for conventional concrete.
In addition to the environmental advantage and multiple applications, IHC has a high vapor permeability (Hygroscopic), passive self-regulation of temperature and humidity, can be used in load applications with an integrated structure of wood, steel or reinforced concrete, presenting low density, fire resistance, comfort and amortization of indoor and outdoor noise.
The IHC with a dry density of about 300 kg/m3 has a compressive strength of more than 200 KPa and a thermal conductivity about 0.07 W/m.k As an example, a wall of 30 cm thickness has a thermal conductivity coefficient of about 0.22 W/m2K.
Thus, it meets the U reference values for climatic zones of Continental Portugal, with a more demanding value of 0.35 W/m2K for I3.
For the durability of constructions with IHC, this product requires a knowledge of the raw materials and their properties, the ideal amount of water, conditions and curing times, type of support substructure, protections, etc.
Traditionally hemp concrete building elements are performed with support for reusable side formwork with the spacing of the wall thickness. Wall preparation and laying of hemp concrete should follow the applicable technical documents.