Performance of Cementitious Composites with Nanofibrillated Cellulose and High-Volume Slag

In this study, the effects of nanofibrillated cellulose (NFC) on the performance of cementitious composites have been explored. The composite mixtures contained cement that was replaced by 40% slag to prepare a high-performance composite, along with fine aggregate and NFC. The air content reduced drastically in the presence of NFC; hence, air entraining admixture (AEA) was added to maintain the criteria of CSA A23.1. In total, eight mixtures were tested with varying dosages of NFC of 0.25%, 0.5%, and 0.75%, where four mixtures contained AEA. Different properties such as fresh (slump flow, air content), mechanical (compressive strength, tensile strength, flexural strength), and durability (rapid chloride penetration, rapid chloride migration, bulk resistivity, resistance against freeze–thaw) have been investigated to evaluate the effectiveness of NFC with high-volume slag after 7 and 28 days. The microstructure of the composites and the distribution of the nanofibers within the paste are also studied by using SEM images. The results revealed that NFC improved the specimen’s splitting strength, flexural strength, and durability. Splitting tensile strength increased by up to 50% at 0.75% NFC, while flexural strength improved by 162% at 0.5% dosage. A negative impact on the compressive, flexural, and durability properties was observed for the 0.75% dosage of NFC due to fiber agglomeration, whereas the 0.5% dosage exhibited the best overall performance. The optimum NFC dosage is found to be 0.25–0.5% which yields a high-strength and durable composite. This research will provide an understanding of the effect of air concentration and NFC on cementitious composites.