Investigation on Physical and Chemical Protecting Mechanism of SME-PS as a Concrete Surface Protectant

Abstract

Soy methyl ester-polystyrene (SME-PS) is a biodegradable and nontoxic blend of soybean oil and waste polystyrene that can be used as a surface treatment to improve concrete deterioration and rebar corrosion caused by freeze–thaw cycles and chloride salt exposures. Although SME-PS has shown promising results for concrete protection, the mechanism by which it protects concrete is relatively unknown. The current study utilizes thermal analysis techniques to explore the physical and chemical protecting mechanism of SME-PS. The potential chemical reaction, reaction rate, and reaction products among SME-PS, hydrated cement paste, and cement hydration products are investigated using isothermal calorimetry and thermogravimetric analysis. Dynamic vapor sorption analysis is conducted to physically evaluate the effect of SME-PS on the pore structure of concrete. The results indicated that the SME-PS can occupy the pores with sizes smaller than 50 nm, physically preventing the ingress of detrimental ions and water into the concrete porous structure. It was also found that SME-PS can chemically interact with cement paste products rapidly occurring at the first 12 min of blending of cement paste powder with SME-PS. The thermogravimetric results indicated the SME-PS reaction mainly occurs among calcium hydroxide, pore solution, and gypsum. Additionally, the hydrophobic nature of SME-PS is beneficial in terms of protecting the cementitious material surface from aggressive chemicals.