This study is a preliminary attempt to present the preparation and the first time a κ-carrageenan/PVA/eggshell nanostructure is used as a novel biodegradable and homogeneous nanostructure in cement composition. In order to clearly understand the effects these additives have on the mechanical properties of cementitious composites, they were synthesized in double and triple combinations and added into mortar mixtures. Three different cement mortar specimens were prepared by integrating the additives in ratios of 0, 0.1, 0.5 and 1% by cement weight and flexural and compressive strengths of the specimens were determined at the ages of 7 and 28 days. The flowability of the presented nanostructures was also discussed. The results revealed a 10–11% increase in both compressive and flexural strengths for the specimens prepared with the triple combination of the proposed additives. Moreover, strain capacity was enhanced as a result of the efficient dispersion of additives in the cement matrix.

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This research discusses the chloride diffusivity of concrete as well as corrosion performance of rebars in cracked and uncracked states. Prismatic concrete specimens with two water-tocement ratios, two concrete cover thicknesses with and without steel fibers were used. Threepoint flexural loading was applied to form cracks and cracks were sustained by a bolt system. Half-cell potential and corrosion rate measurements were carried out following wettingdrying cycles in chloride environment which were continued for 80 weeks. The positive effects of lower water-to-cement ratio and greater cover depth were found to be surpassed by existence of cracks in concrete.

This study presents novel nano-mixtures containing ZnO nanoparticles (NPs) to enhance the mechanical properties of cement mortars. Different morphological ZnO NPs were synthesized, through the green sonochemical method, using tragacanth gum/Kappa carrageenan (TG/κ-C) and tragacanth gum/chitosan (TG/CS) as biopolymer matrices. The ZnO NPs were characterized using SEM, FTIR, XRD, Zetasizer, and BET techniques. The intrinsic viscosities of TG/κ-C-ZnO and TG/CS NPs were investigated to determine the miscibility of the polymeric blends in aqueous solution as affected by sonication time and composition ratios. The average diameters for the spherical and prism-like ZnO NPs were around 266 nm and 355 nm, respectively. Seven different cement mortar specimens containing TG/κ-C-ZnO and TG/CS-ZnO NPs were prepared in ratios of 0, 0.1, 0.5, and 1% by weight and flexural and compressive strengths of the specimens were determined at the ages of 7 and 28. The results indicate that there is a significant improvement in the mechanical performance of different morphological ZnO NPs based cement mortar composites. In comparison, it is observed that specimens containing TG/κ-C-ZnO NPs had much better results than TG/CS-ZnO NPs. Moreover, the workability problem encountered by using only ZnO NPs has been overcome with the presented biopolymers used in this study.

Magnesium phosphate cements are implemented for several purposes demonstrating significant mechanical properties in limited durations. However, brittle behavior of this material needs utmost concern and tensile performance may be enhanced with the proper application of fibers increasing both ductility and energy absorption capacity. This research studies the effect of basalt fibers (BF) and silica fume (SF) on the fracture parameters of magnesium phosphate cement (MPC). MPC mortar mixtures were prepared with different SF (0, 5, 10%) and BF amounts (0, 0.5, 0.75, 1 % by wt.). Also fly ash was adopted with a constant ratio for all mixes. Compressive strength and splitting tensile strength results indicated that addition of SF into mixtures extensively developed the matrix structure and improvements were noted with the increasing SF content. The inclusion of BF enhanced the flexural behavior although there were significant improvements in the fracture energy as well as the double-K parameters. Improvements in the tensile capacity of specimens with high BF were prone to the amount of SF percentage such that inclusion of 1 % BF performed best with 10 % SF added mixtures. Load-CMOD (crack mouth opening displacement) curves obtained from notched three-point tests were given for all specimen series and parameters were calculated according to the double-K criterion. Addition of BF resulted in higher toughness values however presence of SF was very significant in establishing appreciable development in toughness values. Brittleness index was implemented to establish clear conclusions on the findings and best performance was seen for specimens with 10% SF and 1% BF.