Preparation of nano-carbon black and silica fume modified foam concrete: Compressive strength, pore structure and electromagnetic property

In this paper, absorbent nano-carbon black and silica fume are added into foam concrete. Considering hydration products and pore size distribution, the foam concrete compressive strength is analyzed, and its conductivity and electromagnetic parameters are tested. The effects of adding silica fume on the electromagnetic wave loss characteristics of carbon black foam concrete are studied. The results demonstrate that the incorporation of carbon black greatly promotes the formation of calcium hydroxide, ettringite and amorphous calcium silicate hydrate (CSH) during cement hydration, making the foam concrete average pore size larger. Meanwhile, mixed silica fume can offset the adverse effects of carbon black on pore size distribution and improve the compressive strength of carbon black foam concrete. The conductivity of the specimen rises with the increase of carbon black, and conductive percolation occurs at the same time. When the added carbon black is 2 wt%, the foam concrete has adequate ability of electromagnetic wave loss. After being mixed with silica fume, the conductivity of the specimen increases, and the electromagnetic wave loss capacity decreases slightly over the frequency range of 4.0 GHz to 5.0 GHz.