Hallow Blocks From Farm Wastes
Rural folks can beat the high prices of housing materials. Out of farm waste and ordinary soil, one can make durable hallow blocks comparable in strength to commercial ones. The hallow blocks can be made right on the building site fashioned similar to commercial hallow blocks. Although considered strictly non-load bearing, it is very satisfactory for low-cost housing. Its compressive strength ranges from i97 to 386 pounds per square inch (psi).
This simple technology, developed by the Forest Product Research and Industries Development Commission, makes use of a minimum amount of cement to make a stronger hallow block. One bag is enough to make 20 four-inch blocks or 12 six-inch blocks.
The first step is to gather agri-wood wastes such as sawdust, coconut trunk particles, sugar cane bagasse or ordinary soil. The latter has to be pulverized and sifted using a 1/4 inch wire mesh. Abaca waste, left after extracting fiber from the stalk, as well as coconut coir dust, the residue from processing coconut husk in coirflex plants, can also be used. Rice hull works too, but additional soil is needed when mixing this with cement.
Improvise a hand mold (see illustration) to shape the hallow block. This can be made out of steel or wood of relatively high density such as apitong, guijo or yakal. The mold should have three movable core blocks, and the sides should easily be opened and secured. Place hinges and lockpins as illustrated.
Using a cubic foot measuring box, mix together one box of cement and three boxes of agri-waste, or the equivalent proportion. With the materials, form a hill with a crater on top. Pour water slowly, then thoroughly mix them with a shovel until a paste is formed. The mixture must be neither too dry-nor too wet such that they would stay packed when molded and would not spread out when removed from the mold.
Place a flatboard at the bottom of the hand mold, and then fill it with the mixture. Tamp and level off extra paste, then place another flatboard on top. Turn the mold upside down, and tamp and level off as before.
After a while, remove the three core’ blocks and then lock the pin to let the sides open. Gently push the molded hallow blocks from the mold, leaving it in place in the flatboard.
Place the hallow blocks in a shade for a few hours to dry. After one side has dried, turn the block upside down to dry the other side. Store these blocks standing on their narrow edges.
For about 10 days, cure them by occasionally sprinkling water over the blocks. Afterwards, they are ready for use.
• Wire mesh
• Measuring container/box (preferably the 12′ x 12′ type commonly used in construction work to facilitate proportioning since a bag of cement is about 1 cubic foot volume) Wooden hand mold (If manufacture is to be undertaken on a self-help basis, the use of an easily devised hand mold is recommended. This tool can be made out of steel or wood of medium to high densities preferably apitong, guijo, yakal).