Kalina Materak

The presented study investigates the impact of internal hydrophobization by using an organosilicon admixture based on triethoxyoctylsilane on the properties and durability of cement-based materials. Internal hydrophobization is an effective method for enhancing water resistance by incorporating hydrophobic agents directly into the cement matrix. The research evaluates the effects of this technique on cement hydration and microstructure of cement paste, as well as, capillary water absorption, compressive strength, resistance to freeze-thaw cycles and water penetration under pressure in concrete. The results indicate that the hydrophobic admixture influences cement hydration by reducing heat release and modifying pore structure. Compared to surface hydrophobization, internal hydrophobization in concrete provides long- lasting protection against water penetration, maintaining effectiveness even after 150 freeze-thaw cycles. However, excessive admixture dosage negatively affects mechanical properties, leading to excessive decrease in compressive strength. The study demonstrates that a carefully controlled dosage of hydrophobic admixture can significantly enhance the durability of concrete while minimizing negative impacts on the other properties of hardened material. These findings highlight the advantages of internal hydrophobization over traditional surface treatments, making it a promising approach for improving the longevity and performance of cementitious materials in aggressive environmental conditions.

The presented research investigates the application of the organosilicon admixtures based on triethoxyoctylsilane (OTES) on the hydration of the cement-based material with addition of supplementary cementitious materials (SCM) such as blast furnace slag and microsilica. The influence of silane-based admixtures on the kinetics of hydration was investigated by isothermal calorimetry. The calorimetric results disclosed that applied admixtures affect the hydration process of cement paste with SCM. The DTA/TG analysis provided the information about impact of triethoxyoctylsilane on the composition and formation of the mineral phases. The DTA/TG measurements showed noticeable changes in the thermal decomposition of the tested materials and amount of bounded water. The impact of OTES on the microstructure and pore size distribution of pastes was examined by mercury intrusion porosimetry. The result showed significant changes in the range of pore diameters. The influence of organosilicon admixtures on the compressive strength of mortars after 2, 7, 28, 56 and 90 days was also investigated. The effect depended on the mineral additive used. In case of blast furnace slag, the development of compressive strength was only delayed, however, in the case of microsilica, it was stopped.

The critical step for any subsequent instrumental analysis of cementitious binders is to stop their hydration reactions, i.e., to remove free water. One of the most available techniques is a solvent exchange method. However, the solvents are known to be strongly bound in ordinary Portland cement (OPC) paste and alter the results of thermogravimetric analysis (TGA) and sensitive hydrates, while their effect on TGA response of alkali-activated slag (AAS) has not been comprehensively investigated. Therefore, the objective of this paper is to track the effects of fundamental aspects of the solvent exchange on the TGA response of AAS with different sodium activators (hydroxide, carbonate, waterglass) and to support these results by X-ray diffraction and effluent gas analysis. All solvents used (acetone, diethyl ether, isopropyl alcohol, ethanol, and methanol) affected the TGA response of all tested pastes, and their effect was enhanced by prolonged immersion time. All solvents induced an additional mass loss at around 800 °C and, especially for OPC paste, increased in situ carbonation, even in an inert atmosphere. Methanol and ethanol had a detrimental effect on ettringite and decreased the basal distance of the C–(A)–S–H gel, while they only marginally affected gaylussite. For AAS, hydration stoppage by washing out the alkali-rich pore solution with water was also investigated and can usually be recommended (except for its detrimental effect on gaylussite), as it is more efficient than organic solvents, which lack solubility for activators. Methanol and ethanol are the most suitable alternatives, particularly for NaOH.

The presented study examined the effectiveness of internal hydrophobization and its impact on the basic properties of cement-based materials such as paste, mortar, and concrete. The obtained results clearly indicate that, in addition to a significant reduction of the capillary water absorption, internal hydrophobization also improves the durability of the material and provides protection against water also in case of cyclic freezing and thawing. Internal hydrophobization using an organosilicon admixture based on triethoxyoctylsilane also ensured an increase in the contact angle for water to over 90 and limited moisture sorption in the material. Moreover, the presented results indicate the interactions of the organosilicon compound with cement, which can be observed as changes in the amount of heat released during cement hydration, impact on the microstructure of the mortar, and a decrease in the compressive strength of the mortar and concrete. Nevertheless, internal hydrophobization by organosilicon compounds such as triethoxyoctylsilane is an effective and efficient method of protecting porous cementitious materials against water and moisture, even during cyclical exposure to negative temperatures

The main purpose of the study was to analyze the influence of internal hydrophobization, conducted using an admixture based on triethoxyoctylsilane, on the properties and durability of concrete. Experimental studies concerned the measurement of compressive strength, capillary water absorption, depth of water penetration under pressure and carbonation resistance of samples subjected to 100 and 150 freeze-thaw cycles. The obtained results indicate that internal hydrophobization is an effective method of protecting cement-based building materials against water, even if the material was subjected to cyclic freezing. For comparison, the tests were also carried out for surface hydrophobized concrete.

In this study, the possibility of using mixing water containing O₂ and O₃ micro-nano bubbles (M-NBs) in concrete technology was investigated. In particular, the effect of micro-nano bubbles on the durability and frost resistance of concrete was analyzed. Concretes with two types of micro-nano bubbles were studied. The physical properties of both the modified concretes and the reference concrete were determined, i.e., specific and apparent density, porosity, weight absorption and coefficient of water absorption. Mechanical parameters based on compressive and flexural strength were tested after 14 and 28 days of curing. Concrete durability was determined on the basis of frost resistance and resistance to salt crystallization. The pore distribution in the cement matrix was determined based on porosimetry studies. The use of water with micro-nano bubbles of O₂ and O₃, among others, contributed to a reduction in the water absorption coefficient from 42.7% to 52.3%, in comparison to the reference concrete. The strength characterizing the concrete with O₃ increased by 61% after 28 days, and the frost resistance after 150 F-T cycles increased by 2.4 times. Resistance to salt crystallization improved by 11% when water with O₃ was used.

The low resistance to harmful acting of water confined in porous, cement-based materials is a negative feature. As the consequence of porous structure these materials have not sufficient resistance as some physical and chemical detrimental factors. The objective of this paper was to evaluate the impact of organosilicon admixture based on silane and siloxane on physical properties of cement mortar. Internal hydrophobization can significantly improve the durability of a cement materials. At this paper the results of mechanical strength, absorbability and capillary water absorption of internally hydrophobized cement mortar are presented. In addition, a contact angle test was used to assess the changes in wetting angle of cement paste.