This paper describes the use of cement-based waterproofing screed and waterproofing coating, in which 10% of the original amount of cement was replaced by fly ash and 2% of the crystallization admixture was added by weight of cement, as a mean of protection of concrete against aggressive environments. The modified materials were applied to the underlying concrete and subjected to testing of physical and mechanical properties after exposure to effects of aggressive environments for up to 18 months. The results of the analysis have shown that after the application of waterproofing materials, there is a sufficient development of the crystals in the underlying concrete to enhance its durability. Thus, it is possible to use fly ash functionally and efficiently in polymer cement systems as a substitute for the cement together with the crystallization admixture.

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The paper focuses on the study of the durability of cement mortars made with secondary crystallization additives. It investigates the influence of the crystalline additives on the degradation process of cement mortars exposed to gaseous CO2and freezing cycles. The specimens with were tested for compressive and flexural strength at the following ages and after being treated by the following curing techniques: 28 days, 180 days and 25 freezing cycles, 28 days and 180 days in gaseous CO2. In order to explain the obtained results and to gain new information about the microstructure of the cement mortars being studied, the SEM sampling and RDA analysis were performed. The research results confirm an improvement in the resistance of cement based mortars using crystalline additives against cyclic freezing as well as gaseous CO2. An important parameter that influences the effectiveness of the crystalline additive is the curing conditions during the first 28 days of ageing.

Crystalline admixtures and industrial by-products can be used in cement-based materials in order to improve their mechanical properties. The research examined long-term curing and the exposure to environmental actions of polymer–cement mortars with crystalline admixture (CA) and different by-products, including Bengħisa fly ash and Globigerina limestone waste filler. The by-products were introduced as a percentage replacement of the cement. A crystallization additive was also added to the mixtures in order to monitor the improvement in durability properties. The mechanical properties of the mortar were assessed, with 20% replacement of cement with fly ash resulting in the highest compressive strength after 540 days. The performance was analyzed with respect to various properties including permeable porosity, capillary suction, rapid chloride ion penetration and chloride migration coefficient. It was noted that the addition of fly ash and crystalline admixture significantly reduced the chloride ion penetration into the structure of the polymer cement mortar, resulting in improved durability. A microstructure investigation was conducted on the samples through Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS). Crystals forming through the crystalline admixture in the porous structure of the material were clearly observed, contributing to the improved properties of the cement-based polymer mortar.

The paper focuses on examining the properties of mortars in which secondary crystallization (crystalline additive) was used. Laboratory tests have found that the effect of secondary crystallization is influenced by conditions in which specimens have been stored during the first 28 days. The investigation focused on the physical-mechanical properties and microstructure of mortar specimens containing a crystalline additive and polypropylene fibres stored at different levels of humidity for 28 days. The influence of crystalline additive on strength was studied as well and the results show that crystalline additives improves the 28-day strength of the mortars.