58 



was poured. Keep also a record in your field book, or 

 marked plainly on the blue prints. 



FREEZING WEATHER. 



The end to be attained is to keep the temperature of 

 the wet concrete above the freezing point until the 

 "set" will have advanced to the point where there is no 

 "free" water in the concrete. This is done either by 

 heating the aggregates to such a point as to retain in 

 them enough heat to keep the mass above freezing point 

 until after sufficient set has taken place, or by pro- 

 tecting the concrete in the forms from frost, or by 

 using salt in the mix. The best method is a combi- 

 nation of the most practical features of those men- 

 tioned. 



The best method is a combination of the most prac- 

 tical features of the other two. 



Heat your sand and gravel by steam pipes by placing 

 in hoppers with double bottoms or long kilns, roughly 

 made out of cylinders of steel are also used. 



Run a live steam line down into the water barrel to 

 heat the water. 



Use salt (sodium chloride) or calcium chloride to 

 lower the freezing point of the water about a pound 

 or so of calcium chloride to a sack of cement. 



Usirg these' precautions so far mentioned, concrete 

 should come to the barrows about as warm as milk, or 

 warmer. After it is in the forms, use every precaution 

 to keep the frost away from it. 



On floor work, close all window openings on the 

 floor below with boards or muslin and place salaman- 

 ders or build wood fires. In using salamanders, be 

 careful not to expose the men to the gases liberated. 

 As the floor is run spread a thin building paner and 

 cover up with straw, shavings or manure. On wall 

 work, hang canvas outside of the centering and run 

 steam pipes or build fires between the canvas and the 

 centering. 



