452 



Missouri Agricultural Report. 



pear upon the surface of concrete, can frequently be prevented by 

 keeping the concrete dampened and shaded from the sun for a week, 

 A very rich mixture of mortar or concrete is more liable to these 

 weather cracks than a lean mixture. If well made concrete blocks 

 are kept moistened for a week after making and are then sub- 

 merged in water for twenty days, crazing is not likely to appear. 



Concrete is not everlasting. A good concrete may last for an 

 age, or for ages, but many of the concrete structures now being 



Figure 42. Residence of Col. Moore, Nevada Mo. Concrete block walls, with 

 asbestos shingles on roof and sides, thus making the entire exterior fireproof and 

 enduring. The asbestos slilngle is manufactured of mineral fibre, asbestos and cement, 

 and cost, on this roof, $13.50 per square, in place. 



built will crumble long before many of their most ardent admirers 

 realize. Too much depends upon the quality of the "ingredients" — ■ 

 cement, sand and stone, and upon the method and manner of build- 

 ing, mixing and placing, as well as upon the climatic and other condi- 

 tions, to say that, ordinarily, concrete has the longevity that some 

 give it. Generally speaking, however, good concrete is as enduring 

 as the most lasting of building materials. 



