Paving the way – Construction (Part 5)

Driveways, paths and patios are among the key finishing touches that complete a home. This fifth article in CCANZ’s series on residential concrete focuses on placement.

The basic function of residential pavements, such as driveways, paths and patios, is to provide safe and easy access onto or around a property.

Concrete is typically used to not only provide a durable paving surface (sloped, to provide surface water run-off) but one which can also incorporate a wide range of decorative finishes to complement the design and landscaping of the residence.

While creating a concrete pavement is relatively straightforward, there are a number of design and construction aspects that need to be considered, in order to produce a finished product that satisfies the functional and aesthetic requirements of the homeowners.

Joint sealants

Many types of joint sealants are available. For pavements, high-performance sealants such as polyurethane or silicone should be used. They are supplied in cartridges for easy use with a caulking gun, come in a range of colours to suit various decorative finishes and are UV-resistant. While the life of the sealant depends on a number of factors, the following basic rules concerning their use should be observed to achieve adequate performance:

” For pavements, high-performance sealants such as polyuethanse or silicone should be used

Joint preparation. The surfaces should be clean, dry and primed if necessary. Applying sealants to ‘green’ concrete can result in bubbling and loss of adhesion. The surface temperature should be above 5°C.

Joint geometry. For typical joints, the cross-sectional depth of the seal should be at least half the width, and never greater than the width.

Backing systems. To perform adequately when the pavement moves, sealants should adhere only to the sides of the joint. While the joint filler will normally ensure this, a backing rod may sometimes be necessary to achieve the required joint geometry.

Setting time. The setting time of the sealant determines when it can be brought into service, or when the pavement can be used. Polyurethane sealants will cure at a rate of about 2-3 mm of depth per day in temperatures over 5°C. Fast-curing and two-part products will be marginally faster. Silicones skin quickly but have a slower cure-through-depth time.

” Penetrating sealers, or those with slip-resistant properties, are recommended for steeper grades

Surface sealers

Sealers are used to prevent staining and to facilitate cleaning of the concrete surface. They should be applied after the curing period and when the concrete has dried out sufficiently to allow the sealer to penetrate into the concrete surface.

Note that some sealers may also function as a chemical curing compound and should be applied after finishing. Some sealers may also be tinted and thus provide both a seal and a coloured finish.

As the penetration of sealers into the concrete surface varies, their suitability for a particular application should be discussed with the manufacturer.

Steep driveways warrant special consideration; non-penetrating sealers that form a film on the surface can reduce slip and skid resistance. This means they are generally not suitable for this application, unless the surface texture applied to the concrete is coarse enough to provide adequate slip and skid resistance.

About CCANZ

This article contains information from CCANZ’s Information Bulletin 80 Residential Concrete Driveways and Paths, which provides guidance on the planning, design, construction, maintenance and specification aspects that need to be considered to ensure a successful concrete paving project. Content from Standards New Zealand in this bulletin has been reproduced by CCANZ with permission from Standards New Zealand under licence 000997. Any New Zealand Standard referred to in this bulletin can be purchased from Standards New Zealand by telephoning 0800 782 632 or visiting www.standards.co.nz

CCANZ would also like to thank Cement Concrete Aggregates Australia (CCAA) for their assistance in producing the bulletin. To download the full Bulletin visit the CCANZ website – www.ccanz.org.nz