Biochar addition to inorganic binders

Cement based composites have a low conductivity and a reduced capacity to absorb electromagnetic waves. This latter feature becomes a serious problem with the multiplication of wireless telecommunication devices in our modern lives. Therefore, many researches aimed at enhancing the electromagnetic interference shielding effectiveness of cementitious composites through the addition of conductive carbonaceous nano/microparticles. Carbon dioxide emissions in the construction industry are a serious concern and account from 4 to 6% of anthropogenic CO2 emissions yearly [1]. One of the potential solutions to address this issue is to transform building materials in carbon sinks. Depending on the type of feedstock and preparation conditions, biochar has the potential of reducing greenhouse gas emissions by about 870 kg CO2 equivalent per tonne dry feedstock [2]. Thus, biochar can be mixed with cement or other inorganic binders to sequester carbon for a long time. In addition, in the pre-cast industry, biochar incorporation can be associated to carbon mineralization process to increase the CO2 of the obtained products. Recently, internal curing has been proposed, it is based on saturated porous aggregates that constitute reservoirs inside a concrete and provide water for concrete curing internally [3]. The same concept was applied to biochar to partially replace cement powder in Ultra-High Performance Concrete (UHPC), enhancing its hydration due its internal curing ability and favoring nucleation of hydrated cement phases. These effects were also observed on magnesium phosphate cements and in activated slags. Finally, when entrapping bacteria in biochar, self-healing of cracks was possible in mortars because of calcium carbonate precipitation. Therefore, this short review aims at providing a survey of recent researches dealing with carbonaceous materials produced from different sources of biochars used for increasing electromagnetic shielding properties of cementitious materials, as well as to favor cement paste late hydration and to make them act as carbon sinks. At the really end, a short survey on the presented patents on these topic is exposed.