Coal ash has long been in effective use as an admixture in cement and concrete. In our research and development, a technique was studied for the manufacture of new concrete products that contain a greater amount of coal ash than in present use.

2. Conclusion

Concrete products containing coal ash as additive are less resistant to corrosion than common concrete. Such products, however, each meet their respective strength requirements and will remain useful unless steel reinforcement is required. Strength, coal ash content, cost, and other general points were investigated. From the investigated products, we selected wall bricks, interlocking blocks, and hollow blocks as products to be put into practical use. Prototype tests were conducted using a block machine that has mass-production ability. As specified in Table 1, we determined the optimum composition that enables a large content of coal ash to retain as high strength as required.

Table 1 Optimum Composition of Concrete Products that Contain Coal Ash

3. Production Process

Prototype concrete products containing coal ash were produced in the following manner:

1) Weigh the calculated amounts of coal ash, aggregate, and other materials to 
   comply with the specifications in the table of mix proportion.
2) Add cement and water, and mix.
3) Use a belt conveyer to transport concrete mixture into the hopper of the block 
   machine.
4) Use the block machine to apply pressure and vibration, and to shape the concrete 
   mixture into blocks.
5) After shaping, leave the blocks in a chamber for curing.