A comparative investigation on the effects of nanocellulose from bacteria and plant-based sources for cementitious composites

Interest in cellulosic nanomaterials has recently gained momentum due to their high tensile strength and hygroscopic properties. This study compared the effects of two different types of cellulose nanomaterials, including cellulose nanofibrils (CNF) produced from wood and bacterial cellulose (BC), on the macro, micro, and nano scale performances of Ordinary Portland Cement (OPC) paste. Effects of CNF and BC on cement paste hydration, microstructure, compressive strength, and flexural strength were monitored. Four dosages of nanocellulose (0%, 0.05%, 0.1% and 0.3%, by weight) were used to prepare cement paste samples. Both CNF and BC were found to increase compressive strengths and flexural strengths by 10% and 55%, respectively, after 90 days of curing. However, only CNF was able to suppress the expansion of mortar samples due to the alkali-silica reaction by 33%. At the microscale, CNF was found to accelerate the early age cement hydration, whereas BC delayed cement hydration. Both nanocellulose types resulted in lower calcium hydroxide (CH) and higher CSH contents compared to the control batch after long-term curing. Statistical nanoindentations showed that the additions of nanocellulose increase the relative amounts of high-density CSH in the hydrated cement paste. The mercury intrusion porosimeter (MIP) and dynamic vapor sorption (DVS) analyses indicated that both types of nanocellulose increase the nanoporosity and reduced the microporosity. However, such advantages were more prominent in the case of CNF compared to the BC.