Concrete Trouble Shooting in Socorro

The implementation of the concrete biosand filters is going great. We are working with a group of concrete workers from Socorro who already have a lot of experience is their profession. However our presence, specifically that of our old (just celebrated his 49th birthday) U of I graduate and concrete expert Thomas Van, have lead to the slight modification of some construction practices that are going to make a big difference in the long run.

First, the issue of curing. Concrete material gets its strength from the water while it is curing. The cement and water react to generate the matrix that holds that concrete together. When we first arrived, the workers were filling the set concrete filters with water, however the outside of the filter was exposed to the elements. Simply soaking a large cloth in water, laying it over the filter, covering it with a black plastic garbage bag, and letting it cure for 15 days will ensure that the concrete filter is stronger and less likely to crack in the future.

Second, we noticed a trend that at the edges of the square concrete filter and at the edges of the top the concrete was cracking. We at first had multiple hypotheses. First, that the vegetal oil that they used was flowing to the cracks and edges thereby preventing the concrete from fully setting. However, they use very thick vegetal oil and thus that flow would not happen. Then we that that rodding, in addition to the vibrating generated by a rubber hammer, would help the concrete consolidate at the edges. However, the day after we thoroughly rodded a filter the problem remained. Finally, we realized that the edges of the mold were not completely sealed and thus the smaller concrete materials were leaking out of the mold leaving larger aggregates at the edges. The larger aggregates led to the cracking edges that appeared on all of the filters. Therefore we will be buying C clamps to close the opening and improve the structure of the filters.

While the problem solving is confined to a finite system, our engineering knowledge will lead to a better filter and prolonged progress for the people of Socorro.