Rebuilding Foundations

An exploration of international development work in Africa

Pavement

Unlike other disciplines, civil engineering has arguably not changed significantly for the past couple hundred years.  Granted, we’ve had a few advancements such as computer-aided design or composite materials, but the basic principles have largely remained the same.  Furthermore, civil engineering tends to be conservative: we build infrastructure to be safe, not cutting-edge.  If a certain approach works, why change it?

This sort of thinking means that industry advancements tend to be slow.  Even though labs all over the world keep proving that fibre-reinforced concrete display better strength under tension, most engineers and construction companies still use regular concrete and rebar.

However, a “good” engineer, in my opinion, questions the status quo.  It’s easy to design according to code – it’s safe and established – but that doesn’t advance the industry.  Moreover, your designs may work fine but they could probably be better (safer, cheaper, more user-friendly, etc.).

For example, we use the same criteria to judge roads all over the world – paved – for which there is one established method of construction: you place a base layer of gravel, run over it a few times with a compactor, and then lay your asphalt on top

That works fine in certain environments, but not all.  More and more we’re discovering that the conventional paving method has more negative side effects than we initially realized, such as pollution run-off and massive stormwater surges.  As a result, people have experimented with alternative methods such as permeable pavement or white-topping.

In Canada, for instance, engineers have found that daily freeze-thaw periods experienced in some cities during the winter cause rapid pavement degradation.  As a result, Canadian engineers have developed alternative methods to conventional techniques –such as using different subgrade materials that aren’t frost-susceptible or providing capillary breaks so that less water sits in the soil directly below the pavement.

In South Africa, on the other hand, the environment is completely different.  Instead of dealing with rapid freeze-thaw cycles, we have thunderstorms and flashfloods during the summer months.  If you’re from Vancouver, you’re probably thinking something along the lines of, “A little rain?  Big deal.  Our roads handle rain just fine.”

But this isn’t just “a little rain.”  I was caught in a hail storm a couple months ago and I was completely soaked (right through my bra and underwear) within 2 minutes.  I was halfway through my 10 minute walk from the minibus taxi route to my house and I had to take cover with a security man in his tiny roadside security hut until the rain diminished 10 minutes later.  By then, the roads were mini rivers.

Think of the most rain you’ve ever seen pouring down the road because a ditch gets blocked during a storm in Vancouver.  That happens once a week in Jozi from November to April.

As a result, the subgrade gravel beneath the pavement quickly gets washed out and there are huge potholes all over the city.  There’s nothing better than driving home at night – especially through a sketchy area and the streetlights aren’t working – and hitting a deep pothole!

The city can’t keep up with road maintenance, so often locals put traffic cones or tires over the larger holes.  Sometimes they get filled up with gravel, but that quickly washes away in the next rainstorm.  My favourite are the “Caution Potholes” signs that look like they’ve been there for years.

As a transportation engineer, driving through this city makes me crazy for a variety of reasons.  Mostly I want to coordinate the traffic lights.  Seriously, give me a team of 10 people to preform traffic counts during peak hours and in 2 years I’ll transform this city!

Maybe even more critical, however, is this problem with road washout.  There must be a better method!  I’ve been thinking about this issue ever since summer started in November.  At first I considered permeable pavement, but that won’t solve the gravel washout.  Green geogrid?  That works on driveways, but is it an option for city roads?

I’m not an expert on road materials, but I’d be willing to do the research and the testing.  Seriously.  Because, right now, the system is terribly inefficient.  But I’d rather someone else solve this problem.

C’mon, engineers!  You know you want to.

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