تقویت کامپوزیت های الیاف - سیمان به کمک افزایش چسبندگی الیاف با استفاده از نانوسلولز باکتریایی

مواد پایه سیمانی به دلایلی همچون ارزانی و مقاومت بالا به‌ عنوان یکی از پرمصرف‌ترین مواد در ساخت‌وسازهای عمرانی و به شکل‌های مختلفی همچون ملات، بتن و شاتکریت به ‌کار برده می‌شوند. مقاومت خمشی پایین مواد پایه سیمانی به‌ عنوان یک ضعف ذاتی در این مواد محسوب می‌گردد. با توجه به کاربرد گسترده این ماده، در این پژوهش توانایی استفاده از نانوسلولز حاصل از باکتری به ‌منظور بهبود خصوصیات مکانیکی و فیزیکی ملات سیمانی تحت ارزیابی قرار گرفت. بدین منظور از نانوسلولز باکتریایی در حالت پودر، ژل و پوشش‌دهنده الیاف پلی‌پروپیلن به ‌عنوان تقویت‌کننده در ملات سیمانی استفاده شد. نتایج مقاومت خمشی نشان داد که استفاده از 0.5 درصد وزنی پودر نانوالیاف سلولزی، مقاومت خمشی ملات سیمان را تا 103 درصد نسبت به نمونه شاهد افزایش می‌دهد. همچنین نمونه‌های حاوی الیاف پلی‌پروپیلن تقویت‌شده با نانوسلولز باکتریایی نسبت به نمونه‌های حاوی پلی‌پروپیلن ساده، مقاومت فشاری و خمشی را بهبود داد.

Strengthening FiberCement Composites by Increasing Fiber Adhesion Using Bacterial Nanocellulose

SummaryThe cementbased material is a strong and relatively cheap construction material and is therefore presently the most used construction material worldwide. This material is used as a mortar, concrete or shotcrete. Low tensile strength is an unavoidable and inherent weakness of most cementbased construction materials. Considering the wideranging applications of these materials, in this study, the potential of bacterial nanocellulose on mechanical and physical properties of cement pastes was evaluated. For this purpose, the potential of bacterial nanocellulose (BNC) as powder, gel, and coated onto Polypropylene fiber as a reinforcement in cement materials was investigated. The results of the flexural strength test showed, up to 103% increase in flexural strength of specimens containing 0.5 wt.% BNC powder compared to control specimens. In addition, specimens containing BNCcoated fibers showed improvement in compressive and flexural strength in comparison with normal fiber mortal specimens. IntroductionCementbased materials, such as concrete, are the most consumable substance after water and make up most of the construction environments such as bridges, dams, skyscrapers, roads, and apartments. In addition, the concrete is a heavyweight and brittle composite with a lower flexural and tensile strength compared to its compressive strength. To prevent crack expansion, the use of synthetic fibers, such as polypropylene has attracted the attention of researchers due to their high performance in concrete. Methodology and ApproachesThe aim of the present study is to peruse the effect of the bacterial nanocellulose (BNC), produced by Gluconacetobacter xylinus microorganism, directly and indirectly (as a polypropylene fiber coating) in the preparation of cement mortar samples with different ages. In the direct procedure, bacterial nanocellulose was added to mixing water in different percentages and in the indirect method the cement mortar samples made with plain polypropylene fibers and polypropylene fibers treatment with BNCs. The effect of both approaches on flexural strength, compressive strength, and water absorption of the resulting mortar was investigated. Results and ConclusionsResults indicated that samples containing BNC gel and powder enhanced mechanical properties. However, BNCgel indicated inferior properties compared to powder. Also, BNCgel and powder decrease the water absorption of cement mortar. It was found that coating the polypropylene fibers with BNC improves the performance of these fibers in the cement composite due to the increase of the interfacial adhesion between the cement matrix and fibers. The results give clear evidence supporting the utility of BNC for enhancing the durability of cement paste.