In the last decades, nano-silica (NS), nano-alumina (NA), and nano-calcium oxide (NC) particles have been incorporated into cementitious materials, and it seems that each one of them contributes uniquely to the materials’ properties. This research explores the influence of each nanomaterial on the fresh properties of cement pastes and their compressive strength evolution over one year. Low proportions (1.5% by weight) of nanomaterials were added to cement pastes, and their fresh properties, such as heat of hydration and X-ray diffraction patterns in the first hours, were analyzed. The compressive strength and open porosity were also measured long-term. The acceleration of hydration heat in NA-cement pastes is linked to enhanced hydration product formation at early ages. Among the tested nanomaterials, NA increased compressive strength by 10% at later ages. Although the fresh properties of NC-cement pastes remained unaffected, their open porosity decreased by 54% at 28 days. In contrast, the increase in heat of hydration in NS-cement pastes did not result in significant strength improvement. Based on these findings, NA was selected for ultra-high-performance cement (UHPC)-based material use. Its incorporation not only preserved the ultra-high-performance (UHP) properties but also provided additional benefits such as an increase in compressive strength under a CO₂ atmosphere. Through detailed analysis, this research establishes that nano-alumina incorporation optimizes the microstructural development and compressive strength of ultra-high-performance cement-based systems, presenting a novel advancement in enhancing the mechanical properties and durability of these materials under various environmental conditions.

The purpose of the present work was to study the corrosion protection that relatively low-cost magnesium hydroxide coatings offer to concrete by stabilizing the surface pH. To facilitate the material’s adhesive ability, methyl-cellulose and carboxymethyl-cellulose were used as environmentally friendly additives in three different concentrations, 1, 0.4 and 0.1 wt.% of solids, respectively. The coatings were applied on the surface of concrete blocks, in two different coating thicknesses. A sulfuric acid solution was used to simulate the biologically produced acid in sewer pipes. Sulfuric acid was sprayed on the specimens, while the total amount of acid sprayed was calculated, in order to correspond to a specific reaction’s stoichiometry daily. The surface pH of coated specimens was monitored daily with a surface pH meter. The gypsum production was studied with X-ray diffraction, to evaluate the coatings’ protection. The experimental time period that coatings were consumed was compared with the theoretically consumption time.

The self‐healing mechanism of cementitious materials has been investigated by many researchers in the last two decades. In the journey of this quest, more and more advanced methods of analyzing the efficiency of healing have been employed. These methods are intended to clarify and quantify the healing mechanism. This paper presents five techniques, which are either common in the microstructure and nanostructure study or innovative in this field, which was used in order to identify the healing efficacy. Specifically, the application of scanning electron microscope (SEM) analysis, 3‐D ultrasound tomography, nanoindentation, water absorption test (sorptivity), and software development in the Python programming environment for monitoring the crack closure have been used. The main objective of this study was to quantify several parameters, such as the geometry of the cracks, the properties of the healing products, as well as the healing depth. SEM analysis is a well‐known technique that can contribute to identify the elements of the healing products and give the morphology of the surface. The methodology for nondestructive 3‐D ultrasound tomography of healed specimens clarifies the ability of healing in depth. The nanoindentation technique enables localized contact response, which allows accurate estimates of the nanomechanical properties of the tested areas. The absorption method (sorptivity) is a representative method of recording cracks and open porosity. The software developed in a Python programming environment aimed at quantifying the surface crack closure and is an attempt to minimize the parameters that affect the inaccurate results, usually caused by the program's inability to detect only the crack. In addition, the results of each of the above methods are also presented, and their contribution to the study of healing is analyzed.