Effect of Carbon Nanotube Size on Compressive Strengths of Nanotube Reinforced Cementitious Composites

Application of nanoscale science to construction material has already begun. In recent times, various nanofibers have raised the interest of researchers due to their exceptional mechanical properties and high potential to be used as reinforcement within cement matrix. Carbon nanotube (CNT) is one of the most important areas of research in the field of nanotechnology. The size and exceptional mechanical properties of CNT show their high potential to be used to produce high performance next generation cementitious composites. In this study, an attempt has been made to investigate the effect of size of CNTs on compressive strengths of CNT reinforced cement composites. Seven different sizes of multiwalled nanotubes (MWNTs) were used to produce MWNT-cement composites. A trend was observed regarding the effect of nanotube size on compressive strength of composites in most cases. MWNT with outside diameter (OD) of 20 nm or less exhibited relatively better performance. Smaller MWNT can be distributed at much finer scale and consequently filling the nanopore space within the cement matrix more efficiently. This in turn resulted in stronger composites

Suitability of locally manufactured galvanized iron (GI) wire fiber as reinforcing fiber in brick chip concrete

A case study has been conducted in order to improve concrete quality in Bangladesh, using fiber reinforcing techniques with locally available low-cost Galvanized Iron (GI) wire fibers. GI wire is in fact mild steel wire with a thin coating of zinc. In order to assess the suitability of GI wire fibers as an alternative to steel fibers, various properties of GI wire fibers i.e. tensile strength, bending capacity etc. have been investigated and compared with the properties of steel fibers in light of relevant ACI and ASTM guidelines. Various tests were conducted on GI wire fibers as well as plain concrete reinforced with GI wire fibers. The experimental results show that GI wire fiber has compatible properties with steel fibers. Moreover, compressive strength, flexural strength, toughness indices and residual strength factors of GI wire fiber reinforced concrete (GFRC) have shown significant improvement compared to normal concrete. A comparison with Steel Fiber Reinforced Concrete (SFRC) revealed that performance of GFRC is quite similar to that of SFRC. It was observed that fiber content of 2.5-3.5% by weight produces relatively better results for the particular mix design used in the study. Furthermore, a cost analysis reveals that SFRC is about 19% more expensive than GFRC in Bangladesh; for 1 cubic meter of concrete work when fiber dosage is 2.5% by weight. Therefore, the study finds that GFRC has shown some promising results to be a low-cost alternative to steel fiber reinforced concrete from Bangladesh’s perspective

Mechanosensitive changes in the expression of genes in colorectal cancer-associated fibroblasts

Abstract Most solid tumors become stiff with progression of cancer. Cancer Associated Fibroblasts (CAFs), most abundant stromal cells in the tumor microenvironment (TME), are known to mediate such stiffening. While the biochemical crosstalk between CAFs and cancer cells have been widely investigated, it is not clear if and how CAFs in stiffer TME promote metastatic progression. To gather insights into the process, we controlled the mechanical stiffness of the substrates and collected gene expression data with human colorectal CAFs. We cultured human primary CAFs on 2D polyacrylamide hydrogels with increasing elastic modulus (E) of 1, 10 and 40 kPa, and performed genome-wide transcriptome analyses in these cells to identify expression levels of ~16000 genes. The high-quality RNAseq results can be an excellent data-source for bioinformatic analysis for identifying novel pathways and biomarkers in cancer development and metastatic progression. With thorough analysis and accurate interpretation, this data may help researchers understand the role of mechanical stiffness of the TME in CAF-cancer cell crosstalk