134 CEMENT AND CONCRETE 



which are subjected to bending, the forms should be left two 

 weeks or longer. 



Care of Forms: 



Forms for concrete posts, etc., should be oiled with a heavy 

 oil before they are used. As soon as they are removed, they 

 should be thoroly cleaned with a stiff wire brush. Oiling 

 metal forms or molds after using is better practice than to 

 wait, as a coat of oil prevents rust. In removing wooden 

 forms, care must be observed to avoid splitting boards. All 

 boards should be cleaned, the nails pulled, and boards 

 stacked to prevent warping. 



Curing Concrete: 



Proper curing of concrete is very essential to success. It 

 must not be allowed to dry out too rapidly. If freshly made 

 and exposed to the intense heat of the summer's sun, it must 

 be protected. The drying out not on ] y produces check 

 cracks, but hinders the setting action of the concrete, making 

 it weak. Floors and walks that are protected and kept moist 

 for some days will harden into a very dense and almost dust- 

 less material, while those not adequately protected will wear 

 rapidly and be dusty. 



