Civil Engineering September 2021 | Vol 29 No 8

Civil Engineering September 2021 19 when it comes to design, construction, maintenance and demolition. The following are some of the advan- tages and benefits of concrete for roads and pavements: Q Q Safety: Surface texturing of concrete pavements can improve water run-off so that traffic on wet roads does not cause splash, spray and skidding. The light colour of concrete pavements deflects light from vehicles and street- lights, improving night-time visibility while effecting energy and materials savings by requiring fewer streetlights per kilometre of road. Q Q Heat retention: Concrete roads reflect sunlight which helps to mitigate the ‘heat island’ effect. Research has shown that black surfaces exposed to sunlight can become 21°C hotter than reflective white surfaces. This heats up the air around roads, contributing to increased temperatures in sur- rounding buildings, necessitating greater use of air conditioning, energy consumption and electricity demand. Q Q Labour-intensive construction: In countries, such as South Africa, where unemployment is a major burden to the economy, the manual aspects of the construction of concrete roads can be carried out by members of the local community after on-site training. Their newly acquired skills can thereafter be utilised in other sectors of civil engineering. Other advantages of concrete roads include: Q Q Better performance in areas with heavy loads and stop-start traffic Q Q Existing subgrade and alignment can be used Q Q Ideal for upgrading existing deterio- rated roads by overlaying or inlaying Q Q Can be built with integral kerb and channel Q Q Can reduce stormwater reticulation if needed Q Q Only simple inexpensive equipment required for construction Q Q Local materials can be used Q Q Requires less lighting energy where streetlights are provided Q Q Built-in skid resistance can be provided Q Q Can be tined to improve drainage. As for allegations that concrete roads are noisy, a five-year Canadian study showed that concrete roads were only 2 to 4 deci- bels louder than asphalt. A conversation registers 60 to 70 decibels and a whisper, 20 decibels, so this is a minor and ir- relevant factor. CONTINUOUSLY REINFORCED CONCRETE PAVEMENTS When it comes to urban public transport, Continuously Reinforced Concrete Pavements (CRCP) have proved extremely popular for heavily trafficked routes such as bus lanes – as is the case in Cape Town and Gauteng – and have also been used for major sections of the Gauteng Freeway Improvement Project. CRCP is constructed with steel rein- forcing bars placed within the concrete along the entire length of the pavement. CRCP naturally forms uniformly spaced, tight transverse cracks to evenly transfer loads. The reinforcing bars control the width of the transverse cracks that form and hold them tightly closed. The narrow, closely spaced transverse cracks do not impair the structural integrity of the pavement and CRCP roads provide continuous, smooth-riding surfaces ca- pable of withstanding heavy traffic loads in adverse environmental conditions. Because of its greater durability, longer life expectancy, and minimal maintenance requirements, CRCP can provide the best long-term value of any pavement type and can easily be overlaid. STRIP ROADS Finally, on a smaller scale, South Africa has yet to properly acknowledge the benefits of concrete strip roads which can be laid as wheel tracks and are economic, durable and particularly suitable for rural areas. Concrete strip roads have proved successful in many countries, but the South African governmental road building sector, as well as private landowners, have yet to fully exploit the advantages of such slim surfaces which can make steep rural roads passable in all weathers. Strip roads can be built without expensive or sophisticated equipment and by comparatively unskilled labour after just basic instruction. No reinforcement of the concrete is necessary and the laying of strip roads can be done in short lengths, so construction can be slotted in when labour and time are available.  Widely recognised as one of the world’s leading authorities on concrete pavements, Bryan Perrie has authored several internationally-acclaimed books on the subject and presented papers at conferences throughout the world. He holds membership and has served on executive committees of major global bodies representing the concrete pavement industry. A concrete strip road on steep terrain A CRCP concrete overlay under construction in KwaZulu-Natal