<p>The present study investigates the mechanical and durability properties of high-performance concrete containing rice husk ash (RHA) and nanocellulose fibrils (NCF). The cellulose nanofibrils were added to the concrete mixtures in the percentages of 0 0.2 0.4 0.6 and 0.8 of the binder composition. The mixture proportioning involved w/b ratios of 0.3 0.4 and 0.5. The laboratory experimental program involved compressive strength flexural strength water absorption rapid chloride penetration XRD andSEM analysis. Results from the experimental program indicate that the addition of cellulose nanofibrils showed marginal improvement on the early age compressive strength, whereas the 28 -day strength improved significantly. At 28 days, the mix containing RHA and the mix containing RHA, 0.4% NCF exhibited the highest compressive strength, approximately 39, 53, and 75&#xa0;MPa for w/ ratios of 0.5, 0.4, and 0.3, respectively, compared to the other mixes. Adding 0.4% cellulose nanofibrils increased the flexural strength up to 40.6% compared to the control mix due to the crack-bridging mechanism of NCF. Results from water absorption showed that the values remained within 1.5-5%, whereas chloride penetration reduced up to 55.8% and 66.6% for 28 and 90 days, respectively. Durability results were consistent with the mechanical performance, which is in correlation with the formation of hydration products. Morphology analysis reveals a dense matrix aggregate interface due to the formation of hydration crystals. Also, response surface prediction models developed, using Stat Ease, showed the highest accuracy with R² observed to be 0.991, 0.883, 0.955, and 0.978 for compressive strength, flexural strength, water absorption, and rapid chloride penetration, respectively.</p>