Microstructure Evolution of a Magnesium Phosphate Protective Layer on Concrete Structures in a Sulfate Environment

Abstract

This study investigates the resistance of an uncoated magnesium phosphate cement (MPC) protective layer to sulfate attacks through changes in its compressive strength and appearance. X-ray Diffraction (XRD) and scanning electron microscopy (SEM) microanalyses are conducted on the MPC layer concrete both before and after etching, where changes in the microstructure of the magnesium phosphate protective layer are analyzed during the corrosion process. In addition, this study also explores the intrinsic mechanisms of the MPC protective layer in terms of the resistance of concrete to sulfate. The results showed that the erosion resistance of the concrete to sulfate can be dramatically improved by the MPC protective layer. The structure and composition of the MPC protective layer are different in the sulfate erosion environment compared with those exposed to other environments: the protective layer is more closely bonded to the concrete and has a more compact structure. Therefore, the MPC protective layer is verified to have a significant protective effect on concrete against sulfate corrosion.

Manufacturing Errors of Concrete Cover as a Reason of Reinforcement Corrosion in a Precast Element—Case Study

“…In the case of manufacturing errors causing the implementation of concrete cover that do not meet the standard requirements for thickness and tightness, it is recommended to use appropriate protective coatings to obtain an element with parameters that meet the durability design assumptions for the given environmental conditions [6,11].…”

“…For this purpose, protective coatings [6] can be used, which improve the desired parameters of the element to be used in accordance with the design objectives. It is important to choose the right type of protective coating depending on both the type of aggressive environmental factor acting on the damaged element and the type of element itself [11][12][13].…”

“…A diffractogram of a sample of concrete taken from loggia wall near point(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Signs: C-Calcite, Q-Quartz, and G-Gypsum.…”

Effect of water content on microstructure and properties of magnesium potassium phosphate cement pastes with different magnesia‐to‐phosphate ratios

“…Magnesium phosphate cement (MPC) is a type of clinker‐free cement, which is also well‐known as a chemically bonded ceramic 1,2 . Because of its numerous unique properties, such as rapid setting, high early‐age strength, excellent adhesive properties, and near‐neutral pH, 3‐8 MPC is attracting increasing attention in several fields of concrete repair, nuclear waste encapsulation, corrosion and fire protection, and biomedical technology 2,3,9‐11 …”

Variations in Mass and Resistance Due to Accelerated Weathering Effects in Concrete Specimens Used in Low-income Housing

“…Due to the above, it is important to carry out studies according to the environment where the material in question is used, in the most aggressive environments such as the marine environment, these effects are accentuated, requiring a set of additives that reduce degradation [13] that can be used in other abrasive environments, as well as taking advantage of the formation of by-products such as phosphates [14] reducing degradation.…”