502 STANDARD RECEIPTS. 



HOW TO USE CEMENT. 



Quality of Sand. The sand should be clean, sharp and coarse. 

 When the sand is mixed with loam the mortar will set comparatively 

 slow, and the work will be comparatively weak. Fine sand, and espe- 

 cially water- worn sand, delays the setting of cement, and deteriorates 

 strength. Damp sand should not be mixed with dry cement, but the 

 cement and sand should be mixed thoroughly and uniformly together, 

 when both are dry, and no water should be applied until immediately 

 before the mortar is wanted for use. 



Proportion of Sand. The larger the proportion of cement the 

 stronger the work. One part of good cement to two parts of sand is 

 allowable for ordinary work; but for cisterns, cellars, and work requir- 

 ing special care, half and half is the better proportion. For floors, the 

 cement should be increased toward the surface. 



Water in Concrete. Use no more water in cement than abso- 

 lutely necessary. Cement requires but a very small quantity of water 

 in crystalizing. Merely dampening the material gives the best results. 

 Any water in excess necessarily evaporates and leaves the hardened ce- 

 ment comparatively weak and porous. 



Concrete in Water. Whenever concrete is used under water, care 

 must be taken that the water is still. So say all Fnglish and American 

 authorities. In laying cellar floors, or constructing cisterns or similar 

 work, care must always be taken to avoid pressure of exterior water. 

 Cement will not crystalize when disturbed by the force of currents, or 

 pressure of water, but will resist currents and pressure after hardening 

 only. In still water good cement will harden quicker than in air; and 

 when kept in water will be stronger than when kept in air. Cements 

 which harden especially quick in air are usually slow or worthless in 

 water. 



Delay in Use. Do not permit the mortar to exhaust its setting 

 properties by delaying its use when ready. Inferior cements only will 

 remain standing in the mortar beds any length of time without serious 

 injury. 



How to Put Down Concrete. When strong work is wanted, 

 for cellar floors and all similar work, the concrete should be dampened 

 and tamped down to place, with the back of a spade, or better, with the 

 end of a plank or rammer, then finished up with a trowel, thus leveling 

 and compacting the work. Only persons ignorant of the business wiU 



