Effects of silicon fume and latex on properties and hydration of modified mortars
Polybutadiene-graft-polystyrene (PB-g-PS) latex with a weight ratio of 50/50 was used to modify cement mortar. This study examines the effects of silicon fume content and the polymer-cement ratios (P/C) on the flow, compressive and flexural strength and water absorption rate of PB-g-PS latex modified cement mortar. The experimental results show that the flow of modified mortar is increased with increasing polymer-cement ratios, and it is decreased with increasing silicon fume content, PB-g-PS latex and suitable silicon fume content can markedly reduce capillary water absorption rate. PB-g-PS latex can marked influences much on the mechanical properties of modified mortars. The compressive of the polymer modified mortar decreased, and the flexural strength of a portion of polymer modified mortar increased. The suitble silicon fume can improve mechanical properties of modified mortats. The effect of PB-g-PS latex and silicon fume content on cement hydration was explored by XRD, the analysis results showed that the cement hydration was influenced by silicon fume content and P/C.
Polymer‐Impregnated portland cement mortars
Cured precast portland cement mortars were impregnated with the monomer-initiator mixture (mmA or styrene or both and AIBN or benzoyl peroxide), polymerized, and cured and the change in compressive strength, and, in some cases, the change in tensile strength were studied. The effect of impregnation on the compressive strength and environmental stress (freezing and thawing, acid resistance, weathering effect, and sea water resistance) were studied. It was found that the incorporation of polymer into the pores of the already-set cement increased the compressive strength even after freezing and thawing, acid resistance, and sea water resistance and weathering. Among the monomers used, mmA was found to give the best properties to the mortar. Fly ash, when added in small amounts, increased the compressive strength.
Ozonation of polycyclic aromatic hydrocarbons in oil/water-emulsions: mass transfer and reaction kinetics.
The ozonation of highly condensed polycyclic aromatic hydrocarbons (PAH) was studied in oil/water-emulsions, which are comparable to poorly water-soluble PAH in industrial wastewaters and at contaminated sites. As there was a lack of knowledge about the ozonation in oil/water-emulsions, first the ozone mass transfer was studied and optimized from the gas to the water phase and from the water to the oil phase. The ratio of mass transfer and oxidation reaction was determined by the Hatta-number and revealed a slow, quasi homogeneous reaction of ozone with PAH inside the oil droplets. Because the ozone gas concentration had no influence under the optimized conditions, the selective PAH-ozonation could be described microkinetically by a direct ozone reaction of pseudo-first order regarding PAH-concentrations. The determined PAH mean reaction rate constants of 1.02 min(-1) in oil/water-emulsions are in the upper range as found for PAH dissolved in water. These results give a new insight into the ozonation in the three-phase systems and into the treatment of highly condensed, hardly biodegradable PAH.