CEMENT FOR THE FARM AND FARM HOME. 



(By Curtis Hill, State Highway Engineer of Missouri.) 



DEFINITION OP TERMS USED. 



Concrete. — An artificial stone made of cement, sand and some 

 third material. 



Mortar. — A mixture of sand and cement. 



Aggregate. — The crushed rock, gravel or other stone used as thi 

 third material of a concrete mixture. 



Mixture. — The mixing together of the mortar and aggregate for 

 concrete. 



Voids. — The open spaces, pores, or interstices between the dif- 

 ferent particles of concrete materials. 



Tamping and ramming. — The pounding of concrete to form a 

 compact mass by forcing the particles closer together and reducing 

 the voids. 



Setting. — The crystallization or the chemical action of cement 

 when in contact with moisture Cement should develop the initial 

 set in not less than 30 minutes and a hard set in not more than 10 

 hours. 



Crazing. — The checking or cracking, as the fine hair cracks, on 

 the surface of stone, concrete, etc. 



Wearing surface. — The outer surface of the concrete where sub- 

 ject to wear or to atmospheric actions, usually covered with a thin 

 coating or wash. 



Molds or forms. — The framework and falsework erected to keep 

 the concrete in place till it sets. 



Green concrete. — Concrete which has not hardened or set. 



Rich Mixture. — Concrete with a large proportion of cement, as a 

 proportion of 1 cement, 2 sand, 4 aggregate. 



Medium Mixture. — Concrete with a less proportion of cement, as 

 a 1-3-6. 



Lean Mixture. — Concrete with still less proportion of cement, as 

 a proportion of 1-4-8 or 1-5-10. 



Reinforcement — The use of steel or iron in concrete to increase 

 the tensile strength. 



(406) 



