Haiti rubble may hide opportunity

This post by Tom Vail was first published on Haiti Rewired.

It has been a year now and for the most part, we can say that little of substance, at least for the long-term, has been done to rebuild Haiti.  The country is still buried under some 20+ Million Cubic meters of rubble.  A million plus people currently live in makeshift “temporary shelters”.

In my humble opinion, we have a few choices and it is time to make decisions and get moving. We must assume that most of the 20 Million cubic meters of rubble will need to be moved or removed.  To give a point of reference to this, imagine a medium-sized bucket loader (tractor) with a 1 cubic meter bucket loading a series of trucks capable of hauling 20 cubic meters of material at a time.  If the tractor bucket loader could fill a 20-meter truck every 10 minutes (and there was never a delay to get the next truck in place to load it) it would take 45 of these tractors working 10 hours a day, 365 days to load all the trucks.  That still does not address the problem of where (how far) the trucks go to dispose of the material.  Realistically it would take more than 100 of the tractors and, pending how far the loads must travel, 500 to 1000 of the trucks to accomplish the job within a year.   That does not account for the workers and equipment required to break apart the rubble so it can be loaded on trucks.

What we can assume is that if there are 20 million cubic meters of rubble, to rebuild Haiti, we will need about 20 million cubic meters of replacement concrete.  That amounts to almost 20 million cubic meters of sand and rock plus about 12 billion pounds of cement powder. All of the cement has to be imported.  The sand and rock must either be imported or newly quarried.

There have been many suggestions:

1. Push all of the rubble into the Caribbean to make levies and sea walls.  This doesn’t sit too well with most folks, environmentalists in particular.  What will all the chemicals in the rubble do to the ecosystem of the Caribbean?

2. Bundle it up in wire frames and use it as building blocks for large structures or walls. There are serious concerns about the stability of wire cage blocks and they can only be used in so many applications,certainly not for walls of small houses. And how much will be the cost of sorting the rubble, buying and forming the wire cages, and filling them with properly sized rubble?  Is the rubble stable enough that it will hold its shape in the wire cages?

3. Crush it and use it in place of new materials to rebuild.  It will make excellent road base and is also useful for base preparation under foundations, etc.  It can even be used in the place of some of the aggregates required to make new concrete for foundations and buildings.   However, tests have shown that crushed rubble, if used in place of all of the normal aggregates in the manufacture of concrete will result in poorer quality concrete.  Isn’t that the problem that allowed a relatively small earthquake to create all this rubble in the first place?

So each of these “solutions” has its problems.

My thought is that we would do best to reuse the material as much as possible.  It could definitely be used in road building and prep for new foundations.  It can also be used as part of the aggregate in the production of new concrete for foundations and building walls.  This would save much of the cost of finding a place to dump all the rubble. It would also save the cost of much of the need for newly quarried or imported material.  In concrete, to compensate for the poorer quality aggregate that would come from crushed rubble, we need to either use more cement powder or use mechanical mixing devices to ensure proper mixing of materials.  The work done by Kimberly Kurtis and Reginald DesRoches shows that mixing concrete with shovels (the traditional Haitian method) produces a very dangerous quality of concrete. We will produce concrete that is 3 to 4 times as strong by using a mechanical mixer with proper material proportioning.  That means that good quality concrete can be made using some crushed rubble with other aggregates mixed in a mechanical mixer with proper material proportioning.

The Concrete MD mixer from Cart-Away Concrete and PermaShelter SA of Haiti resolves both the problem of proper proportioning (a critical flaw in traditional Haitian shovel mixing according to Kurtis and DesRoches) and it does a superior job of properly blending the material to make sound quality concrete.

If we don’t want to create an ecological disaster, we need to find a way to use or properly dispose of all of the existing rubble.  If we don’t want the next storm or earthquake to again destroy thousands of buildings and take tens of thousands of lives, we need to stop making inferior quality concrete.  To me, the approach is simple.  Crush and use most of the rubble  for base rock and to make concrete using mechanical mixers and appropriate proportioning.  To do otherwise is only providing window dressing and setting up the next Haiti disaster.

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About cementtrust

I am a director with Cement Trust and passionate about improving cement-based production in the poorest nations of the world.
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