Investigation of the properties of single-walled carbon nanotube reinforced ultra high performance concretes.

With the development of nanotechnology, the use of nanomaterials with different properties in the construction industry, especially in the field of building materials, attracts the attention of researchers. It is seen from the studies that carbon nanotubes (CNT), which is believed to be one of the greatest inventions of today among nanomaterials, have a high potential to produce high-strength new generation cementitious composites thanks to their size and extraordinary mechanical properties. The need for structures to be higher, longer, more durable and lighter also affects the emergence of new composite materials. In order to meet these expectations, as a result of the latest research on concrete, ultra-high performance concrete (UYPB), which has superior properties compared to conventional concrete, has been developed. In this study, the effects on the fresh and hardened properties of the concrete designed with SWCNT reinforcement in the production of UYPB required by the construction industry were investigated. Within the scope of the study, the mechanical, physical, electrical and microstructural properties of ultra-high performance concrete (UYPB) produced by using SWCNT at the ratio of 0,01; 0,02 and 0.03% by cement weight and micro steel fiber at the rate of 4% by total weight were investigated. Only micro steel fiber was added in 1 of the 4 different UYPB mixtures prepared, and SWCNT+Micro steel fiber was added in 3 of them. The consistency, fresh concrete density, air content, shrinkage and hydration temperatures were measured to determine the fresh concrete properties of the prepared UYPB mixtures. Density, ultrasound transmission rate, surface hardness, and physical properties of hardened UYPBs at 2, 7, 28, 56 and 90 days, with color change experiments at 90 days, compressive strength, flexural strength at 2, 7, 28, 56 and 90 days and on the 90th day, mechanical properties with impact strength tests, durability properties with böhme abrasion test, electrical properties with resistivity measurements were determined. In addition, SEM, FT-IR, XRD, TGA-DTA analyzes were carried out within the scope of microstructural analysis. As a result, it has been determined that the fresh concrete and durability properties of UYPBs can be improved with the use of SWCNT, and acceptable reductions occur in the hardened concrete properties. It has been observed that the electrical resistivity decreases with the addition of SWCNT and its ratio increases, and conductive UYPB can be produced with the use of SWCNT. Keywords: Ultra high performance concrete, Carbon nanotube, Nano technology, Shrinkage, Electrical property.