*Article* **Investigation of the Mechanical, Microstructure and 3D Fractal Analysis of Nanocalcite-Modified Environmentally Friendly and Sustainable Cementitious Composites**

**Mahmoud Ziada 1, Yosra Tammam 2, Sava¸s Erdem 1,\* and Roberto Alonso González Lezcano 3,\***


**Abstract:** Unlike conventional concrete materials, Engineered Cementitious Composites (ECC) use a micromechanics-based design theory in the material design process. Recently, the use of nanoparticles in various concretes and mortars has increased. This study used nanocalcite to investigate the mechanical, microstructural fractal analysis of environmentally friendly nanocalcite-doped ECC (NCa-ECC). This paper investigated the effects of nanocalcite (NCa) with different contents (0.5, 1, and 1.5% by mass of binder) on the mechanical properties of engineered cementitious composites (ECC). For this purpose, compressive strength, ultrasonic pulse velocity (UPV), and flexural strength tests were conducted to investigate the mechanical properties of the ECC series. In addition, SEM analyses were carried out to investigate the microstructural properties of the ECC series. The content of nanocalcite improved the mechanical and microstructural properties of the nanocalcite-modified ECC series. In addition, the 1 NCa series (1% nanocalcite modified to the mass of the binder) had the best performance among the series used in this study.

**Keywords:** nanocalcite; environmentally friendly cementitious composite; mechanical properties; microstructure analysis; 3D fractal analysis; sustainability; fly ash
