Effect of Highly Dispersed Hybrid Carbon Nanomaterials on the Durability of High-Volume Fly Ash Based Cementitious Mortar

This research focused on increasing the durability of high-volume fly ash (HVFA) cementitious mortar with the incorporation of dispersed graphene oxide (GO), functionalized carbon nanotubes (FCNTs), and their hybrids (HCNMs) at different dosages. The dispersion levels of GO, FCNTs, and HCNMs, both with and without superplasticizer (SP), were assessed via UV–vis spectroscopy in an aqueous medium. The effects of these nanomaterials were evaluated by electrical resistivity, water absorption, and resistance to acid and sulfate attacks on HVFA cementitious mortar. The hybrid GO/FCNTs mixture, incorporated at a dosage of 0.04% by weight of binder (cement + fly ash), exhibited the highest electrical resistivity (69.23 kΩ·cm) compared to individual GO and FCNTs. Moreover, incorporating 0.04% HCNM in HVFA cementitious mortar significantly reduced water absorption, achieving values of 3.9047 mm at 28 days and 2.44172 mm at 90 days of curing. After an acid attack, HVFA cementitious mortar with 0.04% HCNMs (by the weight of binder) presented the minimum decrease in compressive strength, with losses of 10.33% at 28 days and 38.89% at 90 days. Similarly, after the sulfate attack, the exact dosage of HCNMs led to the most remarkable improvement in compressive strength, increasing by 30.85% at 28 days and 11.84% at 90 days compared to simple water-cured samples. The results of this investigation show that HCNMs considerably enhance the durability performance of HVFA cementitious mortar.