IS© 



ENGINEERING ON THE FARM 



Waterproofing. Tanks, watering troughs, and cisterns need 

 to be water-tight. It is very difficult to obtain absolutely 

 water-tight concrete, but with proper care it is possible to 

 obtain a nearly impervious mixture. This requires a rich 

 mixture such as 1:2:3 or 1:2:4, mixed with sufficient 

 water but not an excess, placed carefully, and well puddled 

 and spaded in the forms. The next consideration is the 

 avoidance of cracks. Cracks come from shrinkage or from 

 settlement; therefore exercise care in proper curing and in 

 providing ample foundations. With adequate attention to 

 these things, practically water-tight work will result without 

 any further provision. Many waterproofing compounds are 

 on the market which are mixed with concrete and are of 

 some benefit, but are unnecessary. Cracks, if they develop, 

 may be filled with a rich mortar. 



Bonding old and new concrete. When work cannot be 

 completed at one placing, the concrete placed the first 

 day will be set and hard when the work is continued. To 

 obtain a good bond and make a water-tight joint between 

 old and new work, special precautions are necessary. The 

 face of the old work should be thoroughly cleaned by scrub- 

 bing with a wire brush or stiff broom. Then it should be 



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Fig. 145. Wall section showing the use of 2" X 4" insert 



wet and a coat of neat cement applied and the new work 

 poured on this before it has a chance to set. It is possible 

 to obtain a good joint by inserting a 2"X4" in the old work 

 when finishing the day 's run and removing it when the work 



