THE CUBA REVIEW. 



15 



MAKING CONCRETE BLOCKS IN CUBA. 



A Good and Profitable Business. 



BY GEORGE RICE. 



In Cuba they make concrete blocks 

 on somewhat different plans from those 

 employed in the United States. The 

 Cuban concrete block maker uses wood 

 molds to considerable extent (see Fig. 

 1). Manufacturers of concrete block 

 making machinery have been shipping 

 modern machines into the country, and 

 some block makers are in possession of 

 these machines. Cruder types of de- 

 vices prevail. The business is a good 

 and profitable one in Cuba, for there are 

 many new structures in process of erec- 

 tion, and the tendency toward concrete 

 blocks is very pronounced. Cuban archi- 

 tects utilize considerable stone and ce- 

 ment work in all of their buildings and 

 floors, and floors, walls and ceilings are 

 all of the stony or cement material. 

 Much of the surfacing is polished and 

 looks well. 



In the manufacture of concrete blocks 

 the proportion is four parts of sand to 



Ey'£n(^-Conlr 



one of cement. Water is added, mak- 

 ing the stuff pliable without causing it 

 to stick to the molds, because of exces- 

 sive wetness. Too much water likewise 

 makes the work liable to settle and be- 

 come soggy when removed from the 

 molds. On the other hand, if too dry, 

 the stuff- cannot adhere well and may 

 harden prematurely and crack. In fact, 

 the manufacture of blocks with the some- 

 what defective apparatus used in the 

 average Cuban plant is somewhat dif- 

 ficult. 



The wooden mold is set up in the 

 fashion exhibited by Fig. 1 and filled. 

 The tamping in Cuba is done with a de- 

 vice constructed of hard wood, shaped 

 as shown in Fig. 4. 



All the particles should be tamped un- 

 til the block is compact from bottom to 

 top. The smallest voids should not ex- 

 ist, for air spaces will ruin the block. 

 Blocks are also made under heavy pres- 

 sure by mechanical apparatus, but most 

 of the blocks are tamped by hand. Some 

 of the mechanical tamping devices I saw 

 in use were constructed to compress the 

 blocks from all sides at one time, result- 



ing in the development of thin layers, 

 preventing the air from escaping from 

 the interior and airholes resulted. 



The mold is now ready to turn so as 

 to get the core out. The core (see Fig. 

 1) is quite easily loosened by pounding 

 on the wood with a hammer, and lifted 

 directly upwards without marring the 



^ 



edges of the form. Fig. 2 shows the 

 form of the mold when locked up and 

 a finished block is shown in Fig. 3. Fig. 

 4 shows some of the devices employed 

 in the shaping of blocks to some special 

 design. A gutter tool is exhibited and 

 a combination mallet and one of the 

 trowel devices shaped for doing cor- 

 nering work. An edger of the Cuban 

 pattern is also shown, and a jointer. 



Curing is by no means a simple op- 

 eration. I have seen good blocks ruined 

 at the curing. On the other hand, defec- 

 tively moulded blocks are often improved 

 in the curing operation. One should- 

 pile the blocks as closely as possible to- 

 gether and keep them under cover, free 

 from the effects of high winds and 

 storms. The Cuban does not always re- 

 alize this. He takes chances on the 

 weather and places the blocks outside, 

 where they are oftentimes rained upon 

 before they are cured. After the mate- 

 rial in the blocks is set a spray can be 

 discharged upon them with good effect, 

 and this is done in some of the works. 

 More often, water is deluged over the 

 blocks at interA^als and chances upon reg- 

 ularity of curing are taken. After sev- 

 eral days the blocks will absorb no more 

 moisture, as a rule, and then the middle 

 curing of two weeks' duration occurs. 

 Of course, rush orders come along, and, 

 rather than lose the opportunity of busi- 

 ness, the manufacturer of blocks in this 

 country, like the manufacturer of blocks 

 in the United States, takes the chances 

 on letting the goods go before the blocks 

 are completely cured. He makes a mis- 

 take by doing this. Sometimes the error 

 is a serious one and his business is handi- 

 capped for a long time afterwards. It 

 is best to get a good stock ahead and 

 draw upon the thoroughly cured stock 



