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Silanes, as "integral water repellents", are often used on concrete to prolong the service life of structures.However, their performance is significantly affected by chemical compound and form.In this paper, three silanes (ethylene-triethoxy silane, methyl-triethoxy silane, octyl-triethoxy silane) with different forms (monomer,polymer, emulsion) were assessed with water capillary absorption test, chloride diffusion coefficient and chloride ion profiles in concrete.The results showed that sliane polymer (polyethylene-triethoxy silane) displayed the best resistance toward capillary water absorption and chloride ion corrosion.The chloride ion diffusion coefficient was only 1.1-10-12 m2·s-1, and water absorption coefficient was reduced by more than 87%.But its penetration depth in concrete was very low (< 2 mm).The results revealed that silane monomers,with simple structure, low molecular weight, and low viscosity exhibited greater penetration depth (> 7 mm) in concrete.Although silane emulsions had relatively poor protective effect compare to silane polymer and silane monomer, its good penetration ability, significant stability and low evaporation rate make them become the best candidates in construction.