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The motivation behind this research is to enhance concrete using a coating fabricated from waste materials. Polyethylene terephthalate (PET) was added to asphalt (AP) cement of 60/70 penetration grade at different percentages. Scanning electron microscope (SEM) images show that 6% PET is the optimum mix proportion, and then ternary blends were done by mixing the prepared AP/PET with nano silica (nS) at different ratios (0.5, 1, 1.5, 2, and 2.5) wt./wt. The prepared coatings were evaluated by determining drying time, dry film thickness (DFT), adhesion strength, impact resistance, and flexibility. The formulated coatings were applied to concrete substrates, and the performance of coated concrete cubes was examined by determining water absorption, contact angle, and chloride diffusion. The durability of coated concrete was evaluated by measuring the changes in compressive strength after immersion in both sulfuric acid and sodium chloride solutions separately. The study proved the eco-efficient use of PET waste bottles in protective coating preparation, and the experimental results detected that nS has a significant mechanism for improving coating performance as follows; drying time of AP/PET-2 reduced with 61% as compared to AP/PET, the increment of DFT of AP/PET-2 was 25%, and adhesion strength was improved by 90%. On the same time, silica nano particles are mainly contributes for enhancing coated concretes. Where water absorption reduced with 75%, contact angle increased by 55%, and chloride permeability resistance enhanced to 40%. Finally, improvement durability of coated concrete was 25% and 20% after immersion for 28 d in both sulfuric (3%) acid and sodium chloride (5%) solutions, respectively. [ABSTRACT FROM AUTHOR]

Recently, asphaltic polyurethane coatings were prepared by mixing asphalt with limited ratios of polymers, but this method has many disadvantages. So the novel contribution of this work is using the in situ polymerization method to prepare asphaltic polyurethane nano-silica (As/PUR-NS) coatings. The novelty of this work is using asphalt as one of the polyurethane raw materials by mixing it with castor oil, and the obtained mixture acts as a mixed polyol (80% asphalt and 20% castor oil). As/PUR-NS coatings were prepared with a 1.3 NCO/OH molar ratio by reacting 4,4′-diphenylmethane diisocyanate (MDI) with the prepared mixed polyol, and then NS was added with different ratios of 0.5, 1, 1.5, 2, and 2.5%. The prepared coatings were characterized by determining both curing time and physico-mechanical characteristics and then applied to concrete cubes as a protective coating. The uncoated and coated concrete cubes were tested with regard to water absorption, contact angle, and chloride diffusion, as well as their durability against both sulphate and chloride attacks. The study revealed the high efficiency of concrete coated with a low-cost, eco-efficient, novel protective coating. • Asphaltic polyurethane nanosilica coatings were prepared. • Asphaltic polyurethane nanosilica was applied as protective coating for concrete. • The coated concrete showed high performance in aggressive media. [ABSTRACT FROM AUTHOR]

• Asphaltic polyurethane coatings with different NCO/OH ratio were prepared. • Asphaltic polyurethane was applied as protective coating for concrete. • The coated concrete showed high performance in aggressive media. This work aims at enhancing the concrete performance using a new protective coating named as asphaltic polyurethane (As/PU) coating, which prepared at different NCO/OH molar ratios (1, 1.1, 1.2, 1.3 and 1.4). As/PU coating was prepared by the reaction of a fixed amount of methylene diphenyl diisocyanate (MDI) with the equivalent weight of mixed polyol (80% asphalt and 20% polyester). The performance of the prepared coatings was examined by the determination of curing time, dry film thickness (DFT), adhesion strength, and flexibility. The formulated coatings were applied on 28-days-cured concrete. The coated and uncoated concrete samples were evaluated regarding contact angle, water absorption, and chloride permeability. The resistivity of coated and uncoated concrete against sulfuric acid and sodium chloride solutions was evaluated. The preliminary results proved that the increase of NCO/OH molar ratio results in a remarkable increase in DFT, adhesion strength accompanied by decrease in curing time and flexibility of the prepared coatings. The concrete sample coated by As/PU with NCO/OH molar ratio of 1.4 demonstrates the highest contact angle associating with the lowest water absorption and chloride permeability. In addition the increase in NCO/OH molar ratio of the applied coating has a positive impact on the mechanical properties of concrete. The coated concrete samples recorded higher resistivity against acid and salt attack compared to uncoated one. This proves the eco-efficient use of the prepared As/PU as an innovative protective coating for concrete. [ABSTRACT FROM AUTHOR]