No abstract

In this study, the possibility of using mixing water containing O2 and O3 micro-nano bubbles (M-NBs) in concrete technology was investigated. In particular, the effect of micro-nano bubbles on the durability and frost resistance of concrete was analyzed. Concretes with two types of micro-nano bubbles were studied. The physical properties of both the modified concretes and the reference concrete were determined, i.e., specific and apparent density, porosity, weight absorption and coefficient of water absorption. Mechanical parameters based on compressive and flexural strength were tested after 14 and 28 days of curing. Concrete durability was determined on the basis of frost resistance and resistance to salt crystallization. The pore distribution in the cement matrix was determined based on porosimetry studies. The use of water with micro-nano bubbles of O2 and O3, among others, contributed to a reduction in the water absorption coefficient from 42.7% to 52.3%, in comparison to the reference concrete. The strength characterizing the concrete with O3 increased by 61% after 28 days, and the frost resistance after 150 F-T cycles increased by 2.4 times. Resistance to salt crystallization improved by 11% when water with O3 was used.

The paper shows the opportunity of application of an organosilicon compound such as triethoxyoctylsilane (OTES) containing long, hydrophobic alkyl sidechains (octyl groups – C8H17) attached to the silicon atoms, as the admixtures for internal hydrophobization of cementitious building materials characterized by a porous internal structure. The study included the cement paste, mortar and concrete with three different hydrophobic admixtures based on triethoxyoctylsilane, but with miscellaneous concentration of the triethoxyoctylsilane in the admixture and different dosage in the fresh mix. The impact of organosilicon hydrophobic admixtures on the mechanical properties such as compressive strength, capillary water absorption of the cement mortar and concrete and the microstructure of cement paste was investigated. The hydrophobic, silicon-based admixtures decrease the capillary water absorption coefficient significantly. Even by 81.1% in case of cement mortar. The mechanical strength of cement mortar is also decreased, by 23.6%. The noticeable changes in the internal structure of pores of cement paste only for one admixture is observed.