Leaching of Concrete Admixtures Containing Thiocyanate and Resin Acids

Abstract

There is an increasing concern about the emission of pollutants during the construction and lifetime of buildings. The leaching of concrete admixtures containing thiocyanate and resin acids was studied using standard leaching tests and chemical analysis. Ecotoxicological risk was assessed for each admixture. Thiocyanate leaching from concrete, with a chlorine-free accelerating admixture, was determined by ion chromatography. Of the total amount of thiocyanate added, 6-8% was emitted within 30 d. The thiocyanate diffusion curve indicates a fast dissolution process from the surface layer, followed by a slower continuous diffusion process. Thiocyanate exhibits both acute and chronic toxicity, which makes it of immediate environmental concern. Resin acid leaching from concrete test specimens containing an admixture of air-entraining agents with tall oil was determined by solid-phase extraction, methylation, and GC/MS. Of added resin acids, 10% was emitted over 143 d. The leaching curves for the resin acids indicate a continuous diffusion that is proportional to the square root of time and follows Fick's first law of diffusion. The chemical composition of the resin acids in the leachate demonstrates degradation and rearrangement of the resin acids during diffusion. Resin acids emitted from concrete are of environmental concern because they are persistent and have the ability to bioaccumulate in aquatic organisms.

Ionic Thiocyanate (SCN−) Production, Fate, and Phytotoxicity in Soil Amended with Brassicaceae Seed Meals

“…The environmental fate of SCN − released from Brassicaceae meal soil amendments is of interest because of its known toxicity to aquatic organisms and mammals , . Toxicity to fish has been observed in water containing 90 mg of SCN − L −1 , with sudden death syndrome in freshwater trout, and fish embryo deformities resulting from SCN − concentrations at or below 85 mg L −1 – .…”

Recombinant expression of Thermosynechococcus elongatus BP-1 glutathione S-transferase in Arabidopsis thaliana: an efficient tool for phytoremediation of thiocyanate

“…Several previous studies have shown that thiocyanates can be produced naturally in plants, and that organisms capable of degrading thiocyanates are widely distributed [6,7]. SCNis characterized by a high degree of toxicity as it has a strong binding tendency to protein and causes inhibition of halide transport [8][9][10]. It also acts as a non-competitive inhibitor to block a variety of enzymatic reactions [11][12][13].…”

Development of a New Type of Green Switch Air Entraining Agent for Wet-Mix Shotcrete and Its Engineering Application

“…Americans firstly developed the rosin type AEA In 1937, and then other types of AEA such as anionic, cationic, and nonionic surfactant AEA appeared one by one [10,11]. AEA that is used more in commercial concrete construction has some anionic surfactant varieties and its price is relatively higher; in particular, more chemosynthetic AEA may influence the environment because of being degradationresistant [12]. However, as early as the Ming dynasty in China, outstanding medical scientist Shizhen Li once recorded a kind of pollution-free and biodegradable surfactant "Sapindus mukorossi" in Compendium of Materia Medica that can produce abundant microbubbles and shampoo [13].…”