Abstract
Concrete is widely used in the structures of bridges, flyovers, sidewalks and carriageways that are exposed to freeze-thaw cycles in wet conditions and are treated with de-icing salts. Tests were made to examine the effect of sodium silicate solution on the resistance of hardened cement paste to frost and de-icing salts. 5% sodium chloride, calcium chloride and manganese chloride solutions were used as de-icing salts. The deterioration of hardened cement paste was assessed by the changes in compressive strength, ultrasonic pulse velocity, specimen deformations and amount of scaled matter during cyclic freezing and thawing. Test results have revealed that hardened cement paste modified with sodium silicate solution is less subject to destruction when the surface of cement paste is treated with de-icing salt solutions under cyclic freeze-thaw conditions. The research has proved that sodium silicate solution increases the durability of concrete used in road structures.
Highlights
When de-icing salts are applied on bridges and carriageways in winter, part of the salt usually gets onto road and bridge structures
The biggest drop in compressive strength occurs in specimens without NST additive exposed to 5% CaCl2 solution and the least drop in compressive strength occurs in specimens with 0.5% NST additive exposed to 5% MgCl2 solution
Compressive strength in specimens with NST additive changes insignificantly after 56 freeze-thaw cycles irrespective of the type of de-icing salt solution used as freezing medium
Summary
When de-icing salts are applied on bridges and carriageways in winter, part of the salt usually gets onto road and bridge structures. For this reason particles of all types, irrespective of their initial charge (before adding super plasticizer particles C2S and C3S are negative and particles C3A, C4AF are positive) become negatively charged, i.e. all particles have the same charge and particle sticking and coagulation is disturbed (Yoshioka et al 2002), the workability of cement paste improves, less amount of water is required to produce the paste To this end, the binding phase consisting of colloidal sodium silicate solution (Na2O·nSiO2) and suspension super plasticizer based on modified polycarboxylic ether may be used. It is necessary to explore the possibilities of halting the formation of large crystallized hydration products in the initial stage of structure formation by inducing the formation of amorphous nano-sized hydration structures where more energy is accumulated To this end, the binding phase consisting of colloidal sodium silicate solution and suspension super plasticizer based on modified polycarboxylic ether may be used. The research revealed the effect of sodium silicate solution on the durability of hardened cement paste exposed to de-icing salts under cyclic freeze-thaw conditions
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