Durability and Self-Sealing Examination of Concretes Modified with Crystalline Waterproofing Admixtures

Repairing concrete structures costs billions of dollars every year all around the globe. For overcoming durability concerns and creating enduring economical structures, chemical admixtures, as a unique solution, have recently attracted a lot of interest. As permeability of a concrete structure is considered to play a significant role in its durability, Permeability Reducing Admixtures (PRA) is one of the ideal solutions for protecting structures exposed to water and waterborne chemicals. Different products have been developed to protect concrete structures against water penetration, which, based on their chemistry, performance, and functionality, have been categorized into PRA. As it has previously been tested by authors and proven to be a promising solution, a hydrophilic Crystalline Waterproofing Admixtures (CWA) has been considered for this study. This paper aims to investigate how this product affects concrete’s overall freeze–thaw resistance, self-sealing, and corrosion resistance. Various testing methods have been utilized to examine the performance of CWA mixtures, including the linear polarization resistance, resonance frequency testing, half-cell potential, and self-sealing test. The reinforcement corrosion potential and rate measurements indicated superior performance for CWA-treated samples. After being exposed to 300 freeze–thaw cycles, concrete mixes containing CWA—even non-air-entrained ones—showed a Durability Factor (DF) of more than 80% with no signs of failure, while non-air-entrained control samples indicated the lowest DF (below 60%) but the greatest mass loss. The major causes are a reduction in solution permeability and lack of water availability in the concrete matrix—due to the presence of CWA crystals. Furthermore, evidence from the self-sealing test suggests that CWA-treated specimens can seal wider cracks and at a faster rate.

Opuntia Ficus-Indica (OFI) Mucilage as Corrosion Inhibitor of Steel in CO2-Contaminated Mortar

The present investigation is directed to determine if a natural/botanical addition, from Opuntia ficus-indica (OFI) cactus, increases durability for cement-based materials exposed to CO2-laden environments (urban and industrial). The use of this botanical addition in cement-based material applications has shown good performance when these materials are exposed to chloride-laden environments, but no investigations to date have shown the performance of this addition in urban/industrial environments. Therefore, the aim of this investigation is to complement OFI mucilage performance in the most hazardous environments where most of these construction materials are naturally exposed: marine, urban, and industrial. Steel-reinforced mortar prisms, containing OFI mucilage at different addition levels (0%, 1.5%, 4%, 8%, 42%, and 95%, by water mass replacement concentration), were exposed for 14 years (5110 days) in a natural CO2-laden environment. Linear polarization resistance measurements were performed in a wet–dry cycle (between 5020 and 5110 days of age, after mortar fabrication) to determine the possible corrosion-inhibiting effect of OFI mucilage additions. Little corrosion-induced cracking was observed in carbonated mortars with OFI mucilage additions, compared with the carbonated control mortar that showed high corrosion-induced cracking. The electrochemical results showed corrosion-inhibiting efficiencies for steel in carbonated mortar with OFI mucilage additions of 40–70% for low OFI mucilage concentrations (1.5% and 4%), and 70–90% for medium and high OFI mucilage concentrations (8%, 42%, and 95%). Experimental findings suggest that adding OFI mucilage might be useful as a corrosion inhibitor for steel in carbonated cement-based materials (i.e., mortar) because corrosion rates and cracking initiation/propagation were decreased.

Corrosion Rate of Carbon Steel A106 Gr B in Amine-CO2 Contained Solutions

Carbon dioxide (CO2) is one of the corrosive element which exists in oil and gas industries. To prevent CO2 corrosion on carbon steel pipelines, amine-base solvent and caustic solutions are commonly applied. Accordingly, effectiveness of amine base solvent and caustic solutions to reduce risk of corrosion becomes key parameters in determining service lifetime of pipelines made of carbon steel. In this research, the corrosion rate of carbon steel A106 Gr B in amine solutions combined with saturated CO2 gas and caustic solution was studied. The experiments were carried out in static conditions and the Linear Polarization Resistance (LPR) technique was used to measure the corrosion rate (as per ASTM G 5-94). It was found that the corrosion rate in the amine-based solution had shown remarkable results. Somehow, the corrosion rate in an amine-based solvent containing saturated CO2 gas has increased to 200%. The temperature increment to 50°C from room temperature has also increased the corrosion rate. Meanwhile, the caustic addition in amine solution has reduced the corrosion rate of carbon steel.

Electrochemical Analysis and In Vitro Assay of Mg-0.5Ca-xY Biodegradable Alloys

In recent years, biodegradable Mg-based materials have been increasingly studied to be used in the medical industry and beyond. A way to improve biodegradability rate in sync with the healing process of the natural human bone is to alloy Mg with other biocompatible elements. The aim of this research was to improve biodegradability rate and biocompatibility of Mg-0.5Ca alloy through addition of Y in 0.5/1.0/1.5/2.0/3.0wt.%. To characterize the chemical composition and microstructure of experimental Mg alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM), and X-ray diffraction (XRD) were used. The linear polarization resistance (LPR) method was used to calculate corrosion rate as a measure of biodegradability rate. The cytocompatibility was evaluated by MTT assay (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) and fluorescence microscopy. Depending on chemical composition, the dendritic α-Mg solid solution, as well as lamellar Mg2Ca and Mg24Y5 intermetallic compounds were found. The lower biodegradability rates were found for Mg-0.5Ca-2.0Y and Mg-0.5Ca-3.0Y which have correlated with values of cell viability. The addition of 2–3 wt.%Y in the Mg-0.5Ca alloy improved both the biodegradability rate and cytocompatibility behavior.

Effect of Biological Solution and pH on Corrosion Resistance of 304L SS for Dental Brackets

This study is undertaken to evaluate the accuracy of corrosion resistance of commercially available 304L stainless steel in biological solutions with different composition and pH. Electrochemical methods such as: open circuit potential (OCP), potentiodynamic polarization curves (PD), linear polarization resistance (Rp) and cyclic polarization (CV) were used for corrosion investigations. The results show different behavior during corrosion tests in the solutions with different pH, different content of chlorides and different oxidizing character. Highest instability is revealed for 304L stainless steel in Hank`s solution due to the presence of chloride aggressive ions.

Electrochemical Evaluation of Galvanized Steel and AISI 1018 as Reinforcement in a Soil Type MH

This work presents the electrochemical evaluation of bars of Galvanized Steel and AISI 1018 with 3/8” and ½” of diameter, this bars are commonly used for the construction of elements based on Soils Mechanically Reinforced (SMR), the bars were buried in a fine soil predominant in the region of Xalapa City, Ver., México, soil classified in the USCS (Unified Soil Classification System) as a high plasticity silt (MH). Corrosion evaluation was conducted by monitoring the corrosion potential Ecorr and corrosion rate, Icorr, using techniques half-cell potential according to the standard ASTM C-876-15 and Linear Polarization Resistance (LPR), respectively. The experimental setup simulates the real conditions when the steel is used as reinforcement in structures of SMR, where they remain buried throughout the useful life of the structure. The results of the first 110 days of exposure show that the Galvanized Steel bars have a better corrosion performance compared to the AISI 1018 steel regardless of their diameter.

Raphanus sativus L. Extract as a Scale and Corrosion Inhibitor for Mild Steel in Tap Water

The Raphanus sativus L. ethanol extract was prepared by radish cake maceration in ethanol end tested as a scale and corrosion inhibitor of mild steel in tap water. Antiscalant efficiency was tested with electrochemical and thermal scaling techniques, and changes in hardness content were determined titrimetrically. No deposits were found on the metal surface at the extract concentration of 10 mL/L in chronoamperometry test, and scaling suppression was established 5 times in thermal scaling conditions. The linear polarization resistance technique was used to determine corrosion rate. Inhibition efficiency was found to be 75% in thermal scaling conditions. The formation of the surface film was responsible for both scaling and corrosion suppression on mild steel surface as was established with FT-IR spectroscopy and SEM. The surface film was found to contain polymerization products of isothiocyanates.

Anticorrosion Behaviour of Calcareous Deposits Formed on Steel Heat-Exchange Surfaces

A new electrode to study both scaling and corrosion processes of mild steel in tap water was developed. Two identical steel rings are placed on the outside of a glass tube which is heated from inside with an electric spiral; the rings are connected to a corrometer to form a two-electrode corrosion probe. The corrosion rate variations with scale thickness, scale deposition time, and solution composition are measured using the linear polarization resistance technique. The deposited scale was formed of calcite crystals of 50–100 μm as established with SEM and XRD. The scale layer of 0.2 mm formed in tap water within 90 hours reduces the steel corrosion rate from 0.8 to 0.1 mm/year and serves as a barrier layer to prevent further corrosion.

Silane-Based Hybrid Coatings for the Corrosion Protection of AA 2024-T3 Alloy

In order to contribute to the corrosion protection of aluminum alloys, silane-based hybrid coatings have been widely studied in the aerospace industry for their good adhesion to aluminum substrates, compatibility with organic paintings and to protect the underlying material, in addition to being much less toxic than the commonly used chromatization process. In this work, hybrid and inorganic sol-gel coatings were evaluated as corrosion inhibitor films for AA2024-T3 alloy. The films were characterized by linear polarization resistance (LPR) and scanning electron microscopy (SEM), which indicated that these coatings provide a lower tendency for the substrate corrosion.