Concrete Conduit.

Progress, Volume V, Issue 6, 1 April 1910, Page 195

Concrete Conduit.

This Mexican concrete conduit is nearly a mile long, draining nearly 17,000 acres. It has a grade of four feet per thousand, and has a thickness of 10 inches of concrete, reinforced by double rings or round corrugated bars. These bars are placed one foot apart longitudinally, in two circles, the inner and outer bars alternately. The bars each measure half on inch in diameter. The total concrete in the structure measures 13.000 cubic yards the steel used for reinforcing weighing 300,000 pounds. In the construction of this conduit 40 per cent of river sand was utilised and 60 per cent of sand made from crushed rock. Three parts of this sand was used with three of crushed rock and one of cement, the latter being of the Hidalgo brand made at Monterev. one of the very few factories producing Portland Cement in Mexico. One of the illustrations shows a portion of the completed conduit and the moving of the high exterior forms by means of travelling gallows frames. This system of moulds and the apparatus for shifting them is simple and very efficient There was a test made of the strength of the conduit about 25 f^et in length when f) week old. by passing a roller weighing 32 000 pounds over it, and also bv allowing the roller to stand over the top of the conduit for 120 minutes. After this severe test it was found that no crack developed, the earth filling over the top of the conduit in the test being about three feet in depth.