Concrete Class 101: Steelworker 1st Class Coogan J. Kennedy reports on some training he gave to an Afghan contrator

Today the contractor from the Lower Shamalan School Project came into the Delhi office to go over some techniques on how to identify and mix the material for concrete. He was very pleased that I wanted to take some time with him to talk about concrete.

The class took about one hour and thirty five minutes going over the 1-1.5-3 mix design for concrete. We went over the differences between crushed rock vice smooth river rock and why crushed rock is better to use with concrete.

The contractor is aware of the type of sand that should be added to cement and knows that course sand is much better than very fine sand when mixed with cement to make concrete. Sai Fullah the contractor is aware of the cement in the area that is poor quality, when asked he knew that elephant cement was very poor and he said that he buys the best concrete for the projects he works on.

During our training we also talked about using good quality water and how much water to use and the importance of using a mixer. We went over the way his workers mixed concrete for the cylinders to be tested and he was not pleased, saying that when the grade beam for the latrine was placed there was a mixer in site and the concrete was not mixed that way and that it was screened and mixed in a mixer.

Showing Sai Fullah the difference between river rock and crushed rock

I asked him why the mixer was not there when we went to the site and he replied with “the mixer was getting repaired and it will be on site when we return to do a site visit.”

When the training was over the contractor was tested to see if he could retain the information and passed all tests with flying colors, we went outside and he showed me the differences between good materials and bad materials, he also told me when I asked him if you wanted to mix 2 buckets of concrete, How much of the other materials should be added? He replied with 3 buckets of sand, 6 buckets of rock, and 1 bucket of water.

The contractor has stopped construction on Lower Shamalan due to money issues during the rehiring process, so this should give him ample time to properly train his workers and get the mixer back on site.