Effect of Nanostructured Additive Based on Graphene Oxide and Lignosulphonate on Water Absorption and Thermal Conductivity of Non-Autoclaved Aerated Concrete

Abstract
The assessment of the effect of various modifiers introduced into the composition of non-autoclaved aerated concrete (NAC) was made. The modifiers were graphene oxide (GO) in the form of an aqueous suspension, lignosulfonate (LS) and a complex GO/LS additive. The samples of gas blocks containing GO – 0.0001, 0.0002, 0.003 wt. %; LS – 0.032, 0.16, 0.32 wt. % by weight of cement and their various combinations were molded. Thermal conductivity and water absorption tests were carried out on the samples of standard and modified NAC aged for 28 days. The research results confirmed the positive effect of reducing thermal conductivity and water absorption, which varied depending on the amount and type of additive. After the addition of LS, GO and GO/LS (0.0002/0.16 wt. %) modifiers, there was a corresponding reduction in water absorption by 12–34 %, 30–50 % and 63 %, respectively, and a decrease in the thermal conductivity coefficient by 6–12 %, 14–18 %, and 29 %, respectively. It is assumed that the introduction of the complex nanomodifier GO/LS increases the degree of crystallinity and homogeneity, as well as changes the composition and size of mineral neoformations of cement stone. Consequently, by changing the structure of silicate matrix through the addition of a modifyer developed by the authors, an improvement in the performance properties of thermal insulating cellular concrete was achieved.

Keywords: non-autoclaved aerated concrete, Portland cement, graphene oxide, lignosulfonate, crystal formation in solution, crystalline phases, thermal conductivity, water absorption