In some mix designs, LWAC containing Leca and silica fume have less water absorption than concrete containing silica fume. Volsifer has shown in his researches that using silica fume in concrete decreases water absorption of concrete. Many researches have been done in the field of using silica fume in concrete. Also in order to solve the problem of water absorption from fresh concrete paste, all of the used aggregates were saturated. ratios on capillary and volumetric water absorption of hardened concrete are compared with each other. The effects of different S.F/C.M ratios and different W/C.M. Since Leca (light weight expanded clay aggregates) has low external porosity, in this research, it is used as a part of fine aggregates in order to solve the problem of high water absorption of LWA from the paste. Capillary water absorption properly indicates the durability of concrete, particularly in structures which are not exposed to the water pressure. Another criterion for determining concrete permeability is the capillary water absorption, and it can be defined as the value of water absorbed by unsaturated concrete due to capillary action and has direct relationship with continues voids of concrete. In this research, because of misleading results of weighted absorption, volumetric water absorption has been used.Ģ. Volumetric water absorption indicates permeability, especially in structures which are exposed to water (i.e piles of retaining walls). Water absorption as an index of durability should also be noticed. One of the effective factors on durability of concrete is the quality of surface layer. High water absorption of LWAC will result in corrosion of reinforcements and consequently make LWAC an inefficient material. Lower density and higher insulating capacity are the characteristics by which LWAC has been distinguished as an appropriate composite material in construction. Nowadays, application of Lightweight Aggregate Concrete (LWAC) has developed throughout the world. Silica fume in Lightweight Aggregate Concrete LWAC: We provide Micro Silica as per American Standard C1240-04, European Standard EN 13263:2005, Canadian Standard CAN/CSA A23.5-98, Japanese Standard JIS A6207 2000, Chinese Standard GB/T18736-2002, Brazilian Standard NBR 13956:1997, Korean Standard KS F2567 2003, Vietnamese Standard TCXDVN 311-2003 and India Standard IS 15388:2003. Silica fume is a super pozzolana or a finely powdered material used for providing strength and durability in concrete mix.
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