Damp-proofing admixtures

Damp-proofing admixtures include soaps and fatty acids which react with the cement hydrates to modify workability, bleeding and settlement, air content, compressive strength and durability characteristics. Mix proportions, mix consistency, admixture dosage and poor mixing influence the effects produced by the admixture. In cement-rich mixes void content is often increased, resulting in increased permeability. Since the admixture... 

DAMP-PROOF CONCRETE (COMPATIBILITY PROBLEMS WITH WRA/DAMP-PROOFING ADMIXTURE COMBINATIONS)... 

Superplasticizers 12 Damp-proofing admixtures and integral waterproofers... 

Damp-proofing admixtures are chemicals which reduce the rate of moisture adsorption into unsaturated concrete. They do not reduce the permeability of saturated concrete and are not suitable for resisting hydrostatic pressure. 

The principal chemicals used for damp-proofing admixtures are ... 

Damp-proofing admixtures reduce the rate of adsorption of moisture into the pores of the concrete and retard the rate of transmission of water through unsaturated concrete. When combined with a water reducer such as a lignosulphonate they enable these damp-proofing properties to be combined with the benefits of denser and less permeable concrete achieved by water reduction. 

Damp-proofing admixtures and integral water-proofers are a valuable aid to the achievement of watertight concrete but they are not a substitute for good workmanship. 

Damp-proofing admixtures or water repellents can also be added to concrete. However, several researchers indicate that they offer little benefit to corrosion protection in good quality concrete [52,53]. Succinate type admixtures have been tested at the Universities of Connecticut and Massachusetts [54,55]. Good dampproofing and corrosion resistance properties were shown however, due to the extreme drying conditions and artificial cracks, it is not known if these materials raise the chloride threshold level at the reinforcing steel for corrosion initiation. 

These admixtures decrease water penetration across a hardened porous cement matrix, bnt cannot be used to eliminate water migration and the term damp-proofing is not correctly applied. They are used on concrete surfaces against rain and gronnd water penetration. The water repellents are produced on the basis of silicones, acrylic resins or petroleum products. 

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