Waterproofing membranes

WATER - WATERPROOFING AND WATER/OIL REPELLENCY] (Vol 25) Waterproofing membrane... 

A composite concrete slab or a stressed-skin system can also provide a roof diaphragm, but the latter may severely restrict the provision of subsequent roof penetrations. Concrete roof slabs are unusual, due to the greatly increased mass over the more normal metal decking/in-sulation/waterproof membrane or insulated metal decking options. 

Pitched roofs. Pitched roofs are typically sloped at a minimum of 6° to ensure the weather resistance of lapped sheeting without sophisticated seals or a waterproof membrane. Portal frames are also more liable to snap through buckling at very shallow pitches. A pitched roof means a greater dead volume to heat, although there is additional space for high-level service distribution. 

Figure 6.15 A typical external waterproof membrane detail...

The roof must be able to shed water that falls on it, although it need not be waterproof in the sense of being a waterproof membrane structure. The roof surface is exposed to sun, wind and driven debris and must be resistant to erosion by the action of sunlight and the abrasive action of wind driven debris. In most cases the roof is insulated thermally to... 

Asphalt—mbber is mixed and applied to roadways by several techniques. In one method, mbber and asphalt are mixed at ca 175—220°C for one to two hours. The hot mixture is applied to the roadway and covered with a layer of stone chips to form a chip seal. The mbber cmmb consists of scrap tires ground into particles less than 2 mm in diameter. Rubber-modified asphalt is also used for waterproofing membranes, crack-and-joint sealers, hot-mix binders, and roofing materials. The mbber improves asphalt ductility and increases its softening point. The aggregate adhesive bond is stronger, and the asphalt lasts longer. Production of rubber-modified asphalt has increased from 405 t in 1970 to 27,000 t in 1980 (41). Typically, about 2 t of mbber is used for 1 km of roadway. If it is assumed that asphalt—mbber contains ca 25% mbber and 75% asphalt, the potential demand for scrap mbber would be ca 40,500 t/yr, or ca 2% of the amount available. 

Exemplary materials for the waterproofing of masonry surfaces are waterproof membranes such as poly(vinyl chloride), PE, butyl rubber, and sealants such as tar, asphalt, paints, poly(urethane), epoxy or mastics. While these waterproofing agents can offer excellent resistance to water penetration and other contaminants, they can alter the appearance of the masonry surface, e.g., they may change the color of the surface or leave it with a shine. Waterproofing treatments can also trap moisture within the masonry surface and promote spalling. 

A large apphcation of latex is in blends with asphalt to produce a waterproof membrane on cinder block and concrete walls. Here, as well as when incorpevated into concrete mortars, the rubber fraction produces better adhesion, durability, and temperature expansion tolerance than the asphalt or mortar base alone. 

Liquid-applied polyurethane waterproofing membranes have several advantages, as follows ... 

Figure 4.7 Elastomeric polyurethane waterproofing membrane on a roof terrace. Reproduced with permission from Fosroc...

C-836-89 Standard specification for high-solids-content, cold-applied elastomeric waterproofing membrane for use with separate wearing course. C-898 Guide for use of high-solids-content, cold-liquid-applied elastomeric waterproofing membrane with separate wearing course. 

Characterisation Protective layer Waterproofing membrane Bedding... 

Samples to be tested were kept more than 61 hours in the temperature condition of 23°C and relative humidity of 50% this corresponded to the requirements of SN-ISO 291. Sample stripes were taken from the system composed of protective mat, waterproofing membrane, and the underlying polymeric geotextile polymer bedding the length of the strips amounted to 250 mm. The strips were bonded at discrete end points according to the actual conditions of waterproofing systems. 

Falling object Protective mat Thickness [mm] Thickness of Waterproofing membrane [mm] Fall height [mm]... 

Figure 1. The falling object with the spherical nuzzle mounted on the testing device and the specimen which is constituted of protective mat, the waterproofing membrane, and the geotextile polymeric sheet.

The perforated protection mats depicted a one-sided lapping as shown in the photograph (3). Because of this lapping, during placement of fresh concrete—and due to loading—the waterproofing membrane may be damaged. 

Architectural Institute of Japan (AIJ) Recommendation and Guideline (Japan) PMC, PC and PIC Recommendation for practice of concrete-polymer composites Recommendation for practice of survey, diagnosis and repair for deterioration of reinforce concrete structures Guideline for polymer-modified cement waterproofing membrane work... 

Architectural Institute of Japan (AU) Guideline for Polymer-Modified Cement Waterproofing Membrane Work (in Japanese), AU, Tokyo (2006). 

This type of corrosion (known as black or green rust due to the colour of the liquid when first exposed to air after breakout) is found under damaged waterproof membranes and in some underwater or other water saturated conditions. It is potentially dangerous as there is no indication of corrosion by cracking and spalling of the concrete and the reinforcing steel may be severely weakened before corrosion is detected. Rebars may be hollowed out in such deoxygenated conditions particularly under membranes or when water is permanently ponded on the surface. 

Examples of rebars attacked in this way are shown in Figure 2.3. These bars were taken from underneath damaged waterproof membranes. 

Figure 2.3 Reinforcing bars taken from under the end of a waterproofing membrane. They have been subjected to low oxygen conditions and therefore one of them shows severe local wasting. There was no expansive oxide growth.

The hammer survey (or chain drag used on decks) is usually quicker, cheaper and more accurate than the other more sophisticated alternatives such as radar, ultrasonics or infrared thermography. However, these techniques do have their uses for instance in large scale surveys of bridge decks (radar and infrared) of waterproof membranes or other concrete defects (ultrasonics and radar). A vehicle mounted radar system is show in Figure 4.4a. The more sophisticated techniques may be needed for deep delaminations and are discussed later in this chapter. 

Figure 6.8 Waterproofing membranes can fail to bond, dissolve into the concrete under application of the hot mix wearing course or be punctured by the aggregates.The photograph shows a failed membrane after testing at the UK Transport Research Laboratory.

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