Damp proofing

The third and perhaps most important class of water repellents consists of materials appHed to the surface of concrete for above-grade stmctures or others where water pressure on the concrete is small. This iacludes damp-proofing ia which treatments cannot be subjected to continuous or even intermittent hydrostatic pressure (83). Repellents that may be used are oils, waxes, soaps, resias, and siUcon-based systems (84). 

Slip membrane serves to reduce friction between the slab and sub-base to minimize subsequent slab cracking. This is normally a polyethylene sheet. It may also serve as a damp-proof membrane ... 

Lead is relatively easily corroded where acetic acid fumes are present and under such conditions it either should not be used or should be efficiently protected. Generally, any contact between lead and organic material containing or developing acids will cause corrosion for instance, unseasoned wood may be detrimental. Trouble from this cause may be prevented by using well-seasoned timber, by maintaining dry conditions, or by separating the lead from the timber by bitumen felt or paint. Lead is also subject to attack by lime and particularly by Portland cement, mortar and concrete, but can be protected by a heavy coat of bitumen. A lead damp-proof course laid without protection in the mortar joint of a brick wall may become severely corroded, especially where the brickwork is in an exposed condition and is excessively damp. 

Careful sealing of the floor-to-wall joints and of the ground floor walls was unsuccessful in reducing pressure-driven flow of radon from the subsoil. This merely diverted the flow of radon up through the internal walls of the dwelling and into upstairs rooms. The problem arose in this old dwelling because it has very porous walls and no damp proof course, thus allowing radon to by-pass the sealed floor. Incorporation of a passive radon barrier into the floor of a modern house with less porous walls is likely to be effective. 

Hill, C.A.S. and Jones, D. (1996c). Chemical modification of wood new results and potentials. In British Wood Preserving and Damp-proofing Association Annual Convention, Stratford-upon-Avon, UK, pp. 42 6. 

It was explained earlier that materials of this type are added to concrete products to reduce the ingress of rain and ground water for aesthetic and damp-proofing reasons, rather than to prolong the structural capabilities of the construction. The improvements in aesthetic qualities are not short lived, and results [15] for a stearate-based composition over a 10-year period are given in Table 4.8. 

DAMP-PROOF CONCRETE (COMPATIBILITY PROBLEMS WITH WRA/DAMP-... 

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... 

CA 64, 19311 (1966) (A fire damp-proof Dynamite contg NG 33 5, NC 1.5, AN 20, NaCl 40 Sc guhr 5% has a deton rate of 2350m/sec in free air w/o confinement. When guhr is replaced by an equal amt of finely ground Zr silicate, the firedamp-proof quality is retained, except that the rate of deton, under the same conditions, is 5590m/sec)... 

ACI (1985) A Guide to the use of Waterproofing, Damp Proofing, Protective and Decorative Barriers for Concrete, Committee 515, American Concrete Institute, Detroit, MI. 

The addition of potassium dichromatc to the glue is stated to make the match co.mposition gradually damp[Pg.457]

Bitumen roofing felt, damp proof courses, mastic sealant and adhesive type materials. 

Mitsubishi (refs. 26-29) describes the use of anisole for oxygen-proof and damp-proof materials which have a protecting function. 

Lucobit . [BASF AG] Ethylene copoly-mer/bitumen for pi. of damp-proof courses in construction of buildings, as protection against corrosion for steel tanks, for improving quality of road bitumen, for i od. of inj. molded parts. 

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. 

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