Enhancement of Performance of Concrete with Nano Materials

Enhancement of Performance of Concrete with Nano Materials

Ch Darshan Subudhi1 and I.Saikrishnamacharyulu2

1,2GIET University, Gunupur, Odisha, India

Abstract

Nano technology is a new emerging area in field of engineering. Development of nanotechnology in the field of material science and evolution of advanced instrumentation have paved way for application of nanotechnology in the construction field. Incorporation of nano sized particles in cement composites makes a significant change in structural and non-structural properties of cement paste, mortar and concrete. The particles converted from micron size to nano size results in more specific surface area. The increase in surface area leads to surface changes in morphology, increase in the chemical reactivity, structural modification of cement hydrates and enhancement in the property of concrete. Nano particles are produced by two approaches. In “top down” approach in which larger particles are reduced to smaller particles without altering the original properties and in “bottom down” approach very small nanoscopic molecules and atoms combine to form bigger structures wherein the particles properties can be altered. The scaled down particles are to be checked for their size and some of the equipment’s available to determine particle size are scanning electron microscope, atomic force microscope and transmission electron microscope. Specific surface area plays a very important role in determining the properties of cement-based materials. The cement in nano scale has more specific surface area and reacts faster with water and results in faster rate of development of strength. The different types of nano particles possess different property. Many techniques like Energy dispersive X-ray analysis, X-ray diffraction, X-ray absorption spectroscopy, Fourier transform infrared spectroscopy, Nuclear magnetic resonance spectroscopy, Thermal gravimetric analysis, Low-energy ion scattering spectroscopy, UV-V’s spectroscopy, v Photoluminescence spectroscopy, Dynamic light scattering are available for the surface chemical analysis and characterization of nano materials. The recent research on nano materials and nanotechnology have highlighted the potential use of nano materials as building materials. However, the research with incorporation of large percentage of nano materials carried out so far is very less. Therefore, finding the mechanical and durability properties of cement mortar and concrete with large amount of nano particles is the need of the hour. In the present investigation, an attempt has been made to study the behaviour of concrete with nano materials. Ball grinder was used to grind micron sized particle to nano size. Nano cement, nano fly ash, nano silica and nano silica fume were the nano materials considered for the study. Cement, fly ash, silica and silica fume when converted into nano size particles, the specific surface area becomes more and hence results in enhanced performance. The size of the particles was determined through surface morphology studies using SEM. The specific surface area was found by Braeuer Emmett Teller theory using BET apparatus and the elemental compositions were found by X-ray spectroscopic method using EDAX. Studies indicated that micron sized particles were converted to nano size without much change in the chemical composition but with an enormous increase in specific surface area. The nano particles produced were used as a partial replacement material for cement. The consistency and setting time of the cement with nano particles were determined by using Vicat’s apparatus and the results were found to be within the prescribed limits given in relevant bureau of Indian standard code. Compressive strength on cement mortar with nano particles was found to give more strength compared to normal cement mortar. Workability vi of fresh concrete was found to increase with the addition of nano particles. The fine particles act as a lubricant thus enhancing the workability. The mechanical and durability properties were found for M20, M30, M40 and M50 grades of concrete in which 10, 20, 30, 40 and 50 percentage of cement was replaced with nano particles. The compressive strength, tensile strength, flexural strength, and modulus of elasticity were found for concrete with different proportions of nano materials and the optimum replacement levels were obtained. The strength characteristics were investigated on 28, 56 and 90 days. The increase in the compressive strength was found to range between 2% and 71% for different replacement percentages of nano materials. It was also found that the gain in the compressive strength of concrete with nano cement was significantly higher than that of the concrete with nano fly ash, nano silica and nano silica fume. The durability studies such as permeability, rapid chloride penetration, porosity, water absorption, corrosion, acid resistance and impact strength were also carried out on concrete with nano materials. Results indicated that nano particles act as a filler material producing denser concrete. They also block the continuity of pores thus resulting in decrease in permeability, chloride ion penetration, porosity, water absorption, acid resistance and corrosion. Ductility factor and the impact strength of concrete with nano materials were found to be significantly better than those of the normal cement concrete. Air pressure resistance test were carried out to determine the internal radial pressure sustaining capacity. The test set up was fabricated to carry out the test and the results indicated that the air pressure resistance of concrete increased with addition of nano particles. From the experimental studies conducted, it is concluded that micron sized particles cement, fly ash, silica and silica fume are converted to nano sized particles on ball grinding. The size of nano particles was found to vii range between 45nm to 173nm.The addition of nano particles have pivotal role in the development of strength and durability aspects of concrete. It is found that the compressive, split tensile and flexural strength increases by 31.5%, 96.8% and 25.3% respectively on incorporation of nano particles. Similarly, there was a reduction in permeability, porosity, chloride penetrability, water absorption and acid resistance up to 96%. The overall performance of concrete with nano particles was found to be much better than that of the normal cement concrete. Hence it can be concluded that this concrete with nano materials has a lot of scope for structural applications.

KEYWORDS: Cement, Fine Aggregate, Coarse Aggregate, Crushed Tiles and Silica Fume,Fly Ash.