World Journal of Engineering The use of nanocomposites to develop the microstructure and impermeability of high performance concrete Saaid. I. Zakia1, Khaled. S. Ragabb and Alaa. M. Rashada a : Building Materials Research and Quality Control Institute, Housing & Building National Re search Center, HBRC, Cairo, Egypt b : Rienforced Concrete Research Institute, Housing & Building National Research Center, HBRC, Cairo, Egypt. modified fresh and hardened state properties when compared with conventional mineral additions. Qing et. al. [10] reported that nano-silica accelerated cement hydration process this led to decrease the setting time of mortar when compared with silica fume. Table 2 Properties of nano-SiO2 Description Results Diameter (nm) 8-18 Purity (%) 98 Surface area (m2/g) 240 Density (g/cm3) 0.5 Molecular SiO2 Molecular weight 60.08 1.Introduction In this new century, the technology of nano has attracted considerable scientific interest due to the new potential uses of particles in nanometer (10-9 m) scale. The nano scale-size of particles can result in significantly improved properties from conventional grain-size materials of the same chemical composition. Thus, industries may be able to re-engineer many existing products and to design new and novel products that function at unprecedented levels. The use of nano-particles can improve the function and properties of many types of materials, reinforced plastics, fire-retardant materials, protective films or cloths [1] . Nano-SiO2 has been added to polymer to increase strength, flexibility and aging resistance [2]. Application of nano-materials into the production of cement and concrete can lead to improvements in civil infrastructure because the mechanical strength and life of concrete structures are determined by micro-structure and by the mass transfer in nano-scale [3]. In Portland cement, when ultra-fine particles are incorporated into paste, mortar or concrete materials with different characteristics from conventional materials were obtained [4-6]. Previous research [7-9] indicated that the inclusions of nano-particles 1 Counts/s 40 SF 30 20 10 0 N-Si 40 20 0 10 20 30 40 50 Position [°2Theta] Fig 1 XRD analysis of SF and NS Corresponding author: saaid_zaki@yahoo.com 1297 World Journal of Engineering Fig 3 TEM photographs of NS Table 3 Details of mix proportions Mix Cement (kg) SF (kg) NS (kg) Dolomite (kg) Sand (kg) Water (liter) HRWR (liter) Slump (mm) M0 M0.5 M0.7 M1 450 447.25 446.5 444.5 100 100 100 100 0 2.75 3.5 5.5 1070 1070 1070 1070 575 575 575 575 192.5 192.5 192.5 192.5 9 11 12 13 20 20 20 20 (cm/sec) k:coefficient of permeability in (cm/sec). Q: quantity of accumulated water in (cm3).coefficient of permeability in (cm/sec). t: tested duration time in (sec). s: surface area that exposed to water pressure in (cm2). ϒ: unit weight of water in (g/cm3). h: maximum penetration depth in (cm). p: hydrostatic pressure in (kg/cm2). hydroxide which results additional formation of calcium silicate hydrate (C-S-H) gel and more improvement of interface structure. The application of nano-SiO2 particles with newly developed superplasticizer (polycarboxylic either polymer based PCE sky) improved the workability and water tightness of high performance concrete scince nano-SiO2 interpentrates polymer network and causes the above Slump improvements. Flow (mm) The efficiency of nano-particles such as 57 nan-SiO2 depends on their morphology 55 54 as well as the application of effective 53 superplasticizer which help to disperse formation of agglomerates and decrease concrete permeability. Nano-silica concrete requires additional amount of superplasticizer. 5.References 1. Ke Y. C. and Stroeve P., “Polymer-layered silicate and silica nanocomposites”, Amsterdam, Elsevier B. V., 2005p. 52-55, 330-341. 2. Zhand Q., Wang J. and Cheng S., “Study on the CPE/nano SiO2 blends”, J. Funct. Polym., 15 (3),2002, 271-275. 3. Hanehara S. and Ichikawa M., “Nanotechnology of cement and concrete”, Journal of the Taiheiyo Cement Corporation, 2001, 141, 47-58. 4. Björnström J., Martinelli A., Matic A., Börjesson L. and Panas I., “Accelerating effects of colloidal nano-silica for beneficialcalcium-silicate-hydrate formation in cement”, Chem. Phys. Lett., 2004, 392(1-3), 242-8. Fig 6 Microstructure of nano-SiO2 concrete (M1) 4.Conclusions and recommendations The properties of concrete are improved by using Nano-SiO2 where nano particles fill the voids between cement grains and consume the part of calcium 1298