Wednesday, 8 February 2017

Improving Construction Speed by Mass Block Production - Engr. Osaz’ ENOBAKHARE

In most completed building projects, the items of work either classified as wall or associated with the use of block/bricks normally constitutes at least 20 percent of the total volume of work done. Now that’s substantial. Block/Brick wall often extends from the substructure through to the superstructure and extensively, the external works. In Nigeria, the most common types of walls built till date are made from hollow sandcrete blocks which come in standard widths of 6 and 9-inches (i.e. 150 and 225mm). Although in some parts of the country, there is appreciable use for solid sandcrete blocks.

There is also a growing market for baked Redbricks, Polyblocks, Lateritic Coldbricks, Nvarsform, Hydraform, Ecobrava, etc. as well as hollow and solid concrete blocks made from crushed stones. But put together, they still accounts for less than 50% of the total existing wall forms in modern construction in the local industry. For medium and large sites, it has been observed that the time taken to produce blocks/bricks readily available for use is often mismanaged thereby contributing largely to project overstay. 

On the one hand, contractors have overtime observed that relying on supply of blocks/bricks from a production factory increases the overall project costs and do not always guarantee desired quality and speed of delivery; therefore it becomes imperative or perhaps reasonable to produce on site.

Visits to several estate project sites across the country recently reveal that the old single-or double-mould block machine is still in common use. When asked why they choose to stick to the old ways of doing things, they often lament that they do not have reliable information on how to get mass block/brick production machines and may equally not know how to use them. Working with a unit of the popular single-mold machine, workers are only able to produce some 300-500 blocks per day (i.e. 8-hour construction time). Then the down-times which are pretty-more frequent than the new variants. These low production capacities measured against time spur contractors of sizeable sites to acquire some more units of the same ‘old-clog’ machine just to beat time. But why have 3 units of the same machines with 3 different operators each and their respective 4-man supports to produce say 1000 blocks a day when with just a single gang you can produce 1000 or more blocks a day using a single unit of mass-production machine? Ironically, its penny foolish, pound foolish.

Furthermore, using variants of multi-mould machine erases the cost associated with the use of block palettes (i.e. the sitting table/plank for freshly-molded blocks) which as at December 2016 goes for an average price of 400 Naira per piece. The new machine class literarily lay blocks directly on the floor as it pulls along. In-tune contractors and block makers are fast trading-off their old machines for the new variants. Interestingly, most of these machines possess higher compression potentials and come with automatic mould changing functions. Some users order for those with trio-capacities; for produces blocks, lateritic bricks and concrete pavers together.  For mega projects, machines with installed capacities of 3000 - 5,000 bricks/blocks per day are highly recommended. It is believed that the market for these new machine variants would increase rapidly in coming months.