Improving the Properties and Structure of Magnesium Materials of Sol of Iron Hydroxide

Currently, magnesia materials are widespread in construction. However, the main problems of their mass use have remained unsolved due to a large number of factors, which result in the rise in their already high prime cost due to introduction of such process operations as crushing and milling of the introduced additives to increase their specific surface and hydraulic activity. Therefore, it is rather promising to search for such additives, which would contain active cations of metals and at the same time build in the structure of magnesium silicate hydrates and form insoluble minerals of the magnesia rock. The search for the additives led us to different sols, introduction of which is restricted to 1% of the weight of the binder, and which are able in such a small amount to increase the basic properties of the cement rock. The approbation of such additives and the evaluation of their influence on the properties, phase composition and structure of the magnesia binder are rather important. The article contains the results of evaluating the influence of the added iron hydroxide sol on hardening and curing of the magnesia paste, formation of the structure and properties of the magnesia rock. At carrying these researches out it has been determined that the iron hydroxide sol introduced into the composition of the magnesia-chloride binder in the amount of up to 1% of the weight of the binder is an efficient additive allowing to activate the development of the rock strength at an early age and to obtain the magnesia rock with the strength of 80 MPa and more, the water-resistance of no less than 0,8, and the hygroscopic property of no more than 2%.

Hygroscopic properties of newly formed ultrafine particles at an urban site surrounded by a deciduous forest in northern Japan during the summer of 2011

To investigate the hygroscopic property of ultrafine particles during the new particle formation event, hygroscopic growth factors (g(RH)) of size-segregated atmospheric particles were measured at an urban site in Sapporo, northern Japan, during the summer of 2011. Hygroscopic growth factors at 85% RH (g(85%)) of freshly formed nucleation mode particles were measured at a dry particle diameter (Dp) centered at 20 nm to be 1.11 to 1.28 (average 1.16 ± 0.06), which are equivalent to 1.17 to 1.35 (1.23 ± 0.06) for a dry Dp centered at 100 nm after considering the Kelvin effect. These values are comparable with those of secondary organic aerosols, suggesting that low-volatility organic vapors are important to the burst of nucleation mode particles at the measurement site surrounded by a deciduous forest. Gradual increases in mode diameter after the burst of nucleation mode particles were obtained under southerly wind condition with a dominant contribution of intermediately-hygroscopic particles. However, sharp increases in mode diameter were obtained when wind direction shifted to northwesterly or northeasterly with a sharp increase in highly-hygroscopic particle faction in the Aitken mode particles, indicating that local wind direction is an important factor controlling the growth of newly formed particles and their hygroscopic properties. Higher g(85%) values (1.27 ± 0.05) were obtained at a dry Dp of 120 nm when the air masses originated from the Asian Continent, whereas lower g(85%) values (1.19 ± 0.06) were obtained when clean marine air masses arrived at the urban site. These results indicate that the hygroscopic property of large Aitken and small accumulation mode particles (80–165 nm) is highly influenced by the long-range atmospheric transport of particles and their precursors.