Investigating the use of ultra-light weight nano-concrete for construction of evaporation suppression modular floating bodies Atefeh Sadat Hosseini Dolat Abadi as.hosseini@cv.iut.ac.ir Date of Submission: 2020/ / Department of Civil Engineering Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc Language: Farsi Supervisors: Mohammadreza Eftekhar, eft@iut.ac.ir Milad Aminzadeh, m.aminzadeh@iut.ac.ir The growing population and successive droughts have increased the pressure on freshwater resources especially in hot and arid regions of the world. Water storage in rainy seasons has long been a common way to overcome the problem of water scarcity in dry spells; however, evaporation accounts for a significant fraction of losses. Covering the surface of open water reservoirs using floating plastic bodies or polymer coatings is a practical measure to suppress evaporative losses. Nevertheless, degradation of these synthetic materials under severe environmental conditions may affect water quality. Present study aimed at construction of evaporation suppression floating bodies using ultra-lightweight concrete. For this purpose, different fractions of perlite aggregates and cement with nanosilica, microsilica and nano-crystal moisture insulation admixtures in the concrete mixing design were tested to produce floating specimens with low thermal conductivity, permeability and water absorption while maintaining the required compressive strength. Preliminary results showed that lightweight specimens have dry densities about 400 to 620 kg/m 3 . The compressive strength of the reference specimen was obtained 0.665 MPa, while adding 15% microsilica and 2% nanosilica to the mixing design increased the 28-day compressive strength by 68%. Also, adding only 2% nanosilica to the mixture with nano-crystal moisture insulation resulted in 58% reduction in permeability compared to the reference specimen. The results of the thermal conductivity test showed that specimens have heat insulation properties preventing heat transfer to the water body. In general, heat conduction coefficient of dry specimens was obtained between 0.048 to 0.09 W/mK with compressive strength of 0.58 to 1.12 MPa. The minimum 48-hour water absorption was also obtained 35%. Finally, due to the effect of capillary rise within the porous structure of ultra-lightweight concrete that might increase the losses due to evaporation, nano-crystal moisture insulation and glaze coating were used on the surface of the specimens. Key Words Ultra-lightweight concrete; Floating elements; Evaporation suppression; Nanosilica; Microsilica; Perlite
