Evaluation of nano glass as a partial cement replacement on the fresh mechanical durability thermal and microstructural properties of cement paste

Using nano materials in the construction sector is one of the new directions as the most effective method for improving the quality of produced materials, especially in concrete and mortar that used as a partial replacement of available material or admixture that is considered. These materials, which are produced in nano size, have been investigated in previous research with micro size may also be with higher size. This study investigates the effects of nano glass powder as a partial replacement for cement on the fresh, mechanical, and durability properties of cement paste. Nano glass was incorporated at varying replacement levels (0-50%) and evaluated through a series of experimental tests, including flowability, compressive and flexural strength, acid resistance, thermal conductivity, fire resistance, water absorption, density, permeable voids, drying shrinkage, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results reveal that increasing nano glass content reduces flow values, indicating decreased workability due to higher water demand. Compressive strength (C.S) improved at early (28-day) and later (56-day) ages, peaking at 10% replacement, while flexural strength peaked at 15%, showing an optimal range for mechanical enhancement. Durability tests showed improved acid resistance and reduced thermal conductivity at moderate replacement levels, confirming enhanced long-term performance. Fire resistance analysis indicated improved strength retention and reduced weight loss with higher nano glass contents, particularly between 20% and 30%. Water absorption and permeable voids decreased significantly at higher replacement levels, indicating denser and more durable microstructures, although density dropped at 40% replacement. Drying shrinkage was minimized at 10%, while XRD and SEM analyses confirmed compositional and microstructural improvements due to pozzolanic reactions and densification. Overall, the study demonstrates that nano glass can be effectively used up to 15-20% replacement to enhance strength, durability, and thermal resistance, though excessive amounts may negatively affect workability and structural integrity.