Effect of nano-modified additives on properties of concrete mixtures during winter season

The construction of cast-in-situ reinforced concrete structures in the cold season imposes special requirements for the concrete mixes and the technology of work. In the cold season at negative outdoor temperatures, the flowability of the concrete mix decreases, the chemical processes of hardening and curing are slowed down or stopped. Construction works without special additives become very difficult, and in some cases impossible. The aim of the study is to develop a nanomodified high-tech plasticizing additive applied to the conditions concreting and curing at an outdoor temperature of −5 °C. The originality of this additive lies in a complex of four components: sulfo-naphthalene-formaldehyde based superplasticizer (SNF), amorphous nano-silica (nano-SiO2), saponified wood resin (WSR), antifreeze inhibitor (NaNO3). The selected ratio of plasticizing, stabilizing, air-entraining and antifreeze components ensures a stable physical and mechanical properties in terms of strength and workability without segregation. Some regression equations have been developed for better determination of the optimal proportion of superplasticizer dosages. Mathematical models relating the parameters of slump and slump flow with the dosage of a nano-modified additive allow to design the concrete mixes with the required flowability. It is shown that the use of a nano-modified additive prevents the risk of segregation of the concrete mix and ensures the hydration of cement during winter concreting. Nano-modified additive was tested under production conditions. © 2019 Elsevier Ltd