Mechanical properties and interface improvement of bamboo cellulose nanofibers reinforced autoclaved aerated concrete

Autoclaved aerated concrete (AAC) has low density, suitable compressive strength, and excellent thermal and sound insulation capacity for building non-bearing walls. However, porous AAC blocks usually have low flexural strength and thus are prone to cracking during service life. Herein, bamboo cellulose nanofibers (BCNF) were incorporated into AAC matrix to enhance mechanical strengths. The BCNF was further modified by 3-mercaptopropyl-trimethoxysilane (KH590) to improve the interfacial bonding between BCNF and AAC matrix. Results showed that the AAC with the addition of 0.3 wt% KH590-modified BCNF had 49.2% and 20.7% higher flexural strength and compressive strength than those without BCNF, respectively. AAC slurry belongs to a pseudoplastic fluid with a yield value, which can be described by Bingham rheological model. With the increase of shear rate, the stress of AAC slurry increased and the viscosity decreased exponentially. The interfacial bonding of BCNF/AAC-matrix was characterized by FTIR, XPS, NMR, and SEM analyses. It was confirmed that the siloxane groups of KH590 react with the hydroxyl groups of BCNF, thus grafting the BCNF with hydrophobic moieties and improving their interfacial adhesion with AAC matrix. In addition, granite powders collected from stone processing mill were utilized as a main component of AAC matrix. This study provides a feasible way of utilizing renewable materials and solid waste in preparing high-performance AAC as green building materials.