Abstract
Durability improvement is always important for steel–concrete structures exposed to chloride salt environment. The present research investigated the influence of a novel nano-precursor inhibiting material (NPI), organic carboxylic acid ammonium salt, on the mechanical and transport properties of concrete. The NPI caused a slight reduction in the strength of concrete at later ages. NPI significantly decreased water absorption and slowed down the speed of water absorption of concrete. In addition, the NPI decreased the charge passed and the chloride migration coefficient, and the results of the natural chloride diffusion showed that the NPI decreased the chloride concentration and the chloride diffusion coefficient. The NPI effectively improved the resistance of chloride penetration into testing concrete. The improvement in the impermeability of concrete was ascribed to the incorporation with the NPI, which resulted in increasing the contact angle of cement pastes. The contact angle went up from 17.8° to 85.8° for 0% and 1.2% NPI, respectively, and cement pastes became less hydrophilic. Some small pore throats were unconnected. Besides, the NPI also optimized the pore size distribution of hardened cement paste.
Highlights
Chloride salt-induced corrosion of reinforcement steel, in concrete structures exposed to chloride environments, has caused huge losses and casualties
The results indicated that incorporation of the nano-precursor inhibiting material (NPI) significantly decreased the water absorption
A novel nano-precursor inhibiting material (NPI), organic carboxylic acid ammonium salt, was used to modify the properties of concrete. It was a promising material for increasing the hydrophobicity of cement paste to improve the resistance of water and chloride ion penetration into concrete, minimizing the negative effect of the hydrophobic hydrocarbon chain on the compressive strength of concrete
Summary
Chloride salt-induced corrosion of reinforcement steel, in concrete structures exposed to chloride environments, has caused huge losses and casualties. Chloride diffusion coefficient is a key parameter of concrete that closely relates with rebar depassivation. Many approaches have been applied to decrease the chloride diffusivity of cement-based materials or increase the time of rebar depassivation, including lowering the water–cement ratio of the concrete, replacing cement with mineral admixtures [2], expanding the thickness of cover, and using some nanomaterials [3,4,5,6] and polymers [7,8,9,10,11]. Lowering the water–cement ratio and adding mineral admixtures can increase the viscosity and autogenous shrinkage of concrete in practical engineering applications. The application of nanomaterials should solve the effective dispersion problem in concrete, and polymers could cause huge loss of strength
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