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Influence of Starch Admixtures and Silver Colloids Stabilised with Starch Hydrolysates on the Course of Electrochemical Potential Difference of Reinforcing Steel in High-chloride Environment
The purpose of the conducted study was to verify whether the use of concrete admixtures with modified starches and starches modified with stabilised silver colloids affects the course of electrochemical potential difference, and hence corrosion, of reinforcing steel in a chloride environment. In the tests, cross-linked starches and products of acid hydrolysis of starch (dextrins) were used as admixtures. The 1-molar aqueous solution of sodium chloride was used as an aggressive environment. The tests consisted of measuring the potential difference generated in the reinforcement corrosion cell on the surface for a period of 60 days and then assessing the risk of corrosion. The effect of the addition of starch derivatives on the properties of cement paste was investigated through a one-way ANOVA analysis of variance followed by post hoc tests. The test results showed that the use of concrete admixtures with cross-linked starches positively affects the passivation of the steel. The likelihood of reinforcing steel corrosion when using distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate admixtures is less than 5%. The results obtained showed an improved effect on the passivation of reinforcing steel in cement composites. Additionally, concrete samples may have microbicidal properties.
Destructive Effects of Slag from Municipal Waste Incineration Plants on Cement Composites
The increasing production of solid waste and the scarcity of natural aggregates as a matter of fact have made waste recycling a necessity. One such waste, which is generated in large quantities, is slag. However, slag from incineration plants may contain harmful elements that adversely affect the physical, chemical and mechanical properties of cement composites. This study presents laboratory research results on the effect of slag from the Poznan Municipal Waste Thermal Conversion Plant (Poland) on the physicochemical properties of cement composites. The samples were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown that the slag analyzed contained significant amounts of aluminum, which had a direct effect on the structure of the concrete. An example of this influence is the release of hydrogen during reactions, which causes swelling and cracking of the concrete and reduces its mechanical strength. The authors emphasize that waste aggregate (slag) can be effectively used in the production of concrete after appropriate processing that reduces the risk of adverse effects.
Surface Activity of Hydrophobized Modified Starch Hydrolysates in Mixed Systems
The manuscript presents research focusing on the adsorption and emulsion properties of starch hydrolysates modified through acetylation, oxidation, and cross-linking. The techniques used in this study included measurements of equilibrium surface tension (du Noüy ring) dynamic surface tension (drop shape analysis), and the preparation and evaluation of emulsion stability (TURBISCAN). The surface activity of the acetylated starch hydrolysates is affected by the degree of acetylation. The acetylated starch 0.02Ac-H exhibited higher surface activity than the more highly substituted derivative 0.1Ac-H. Furthermore, it was shown that the surface activity of the components increased as the acetylated oxidized starch underwent hydrolysis. The fractions collected after 180 min using a membrane with a low separation capability (8 kDa) revealed the highest capacity for reducing surface tension. In binary systems consisting of starch derivatives and surfactants, synergistic effects in reducing surface tension were particularly noticeable in systems containing ionic surfactants. The addition of a cationic surfactant to the modified starch hydrolysate solution (1:6 mol/mol) resulted in a significantly more efficient saturation of the air/water interface. This study demonstrated that emulsions stabilized with modified starch hydrolysates remained stable over time, even when these hydrolysates constituted up to 60% of the emulsifier mixture.