Concrete paving blocks, commonly known as Cabro in Kenya are used on road carriage way surfaces, car parks, within landscaped compounds and in tented shelters.
The Strength of the block is determined by its thickness, with most common thicknesses ranging from 50mm, 50mm, 80mm and 100mm.
For heavy duty roads, 80mm and 100mm thick blocks are used. For light duty roads such as driveways to private residences, tented shelters and car parks, 50mm thick is appropriate.
The soil underneath, especially if its black cotton soil, needs to be removed until stable ground is reached. Murram is then backfilled and a roller compactor used to compact the soil. The last 300mm depth is filled with hand packed hardcore which is also roller compacted. Fine aggregate is laid on top then finally the paving blocks arranged and held together on the edges by the concrete kerbs.
The construction of the blocks should involve pressure compression and vibrating to ensure no air space and honey combs develop because these make the paving block weaker.
Quick drying cement such as Savannah and chemical additives are added to make the curing process faster.
Currently, we can supply 50mm at a cost of kes 900 Per square meter . We an supply 80mm at a cost of kes 1200 per square meter for the Nairobi anre and its environs.
Architect Francis Gichuhi Kamau.