Document Type : Original Article
EGYPTIAN Russian university, faculty of Engineering, construction department, Badr city, Cairo
Kalashnikov Izhevsk State Technical University , Russia
Gypsum is naturally a soft mineral with low strength and with high porous. Without adding additives, it may not possess the desired level of strength for certain applications and have alow moisture resistance, low fire resistance, and low overall durability. Nano-silica and active mineral additives can significantly increase the mechanical properties and structure formation of gypsum binder, making them more durable and resistant to cracking or breaking. To improve the properties of the additive, the nanosilica has been subjected to sonication. It was confirmed that the effect of sonication allowed nanosilica to be used as a key component in additives and that there was no relationship between the initial particle size and this effect. Activated Portland cement and nano-silica have a positive effect on the mechanical properties of the material, and this effect is observed from the hydration process to hardening. The optimal range of nano-silica content was established, equal to 0.05 - 0.1%, while the increase in compressive strength reaches 30-40% compared to the control composition, water resistance increases to 0.47.The modified matrix is characterized by greater density and compressive strength. This result is due to the formation of new growths based on hydrated calcium silicate capable of binding to gypsum crystals and filling the pores at the same time. new growths based on hydrated calcium silicate were identified by IR spectra and physicochemical analyzes including differential thermal analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy.