Saturday, 10 December 2016

Using Dry-Cementized Construction and Re-Use Techniques For Mass Building Construction To Save Cost and Time - Engr. Osaz' ENOBAKHARE

A term of contract for a project may require a contractor to construct a large number of buildings (say 50-100 units) within a short period of time (e.g. 2-3 months). Often than not in such cases even when the conditions are well spelt out, most local contractors readily accept the job without necessarily designing a workable blue-print on how to complete the project within the stipulated period of time, hence few days to the expiration of the deadline, they are still staggering at 30-40% completion.

Project planning is very crucial to the successful delivery of any project but planning a project in isolation of the technique to carry out the actual work itself is effort in futility because it is the work on ground that matters more than the print on paper or soft notes.

For construction projects where pre-fab or pro-fab construction techniques are considered expensive, a smart combination of dry-cementized construction and re-use method could be adopted. 

Most buildings in this part of the world are made from brick and concrete hence a good case for the use of dry-cementized construction. In using this method, the volume or type of cement used in the mix for the concrete elements and components within the structure are increased so that they dry or harden very quickly such as will enable the speedy removal of the formwork. For instance a structural design specification of a minimum concrete mix of 1:2:4 (i.e. 1 part of cement to 2 parts of fine aggregates or sharp sand and 4 parts of coarse aggregates or granite) can be constructed at 1:1½:3 (i.e. 1 part of cement to 1½ parts of fine aggregates to 3 parts of coarse aggregates) which is a more stiffer mix. The idea is to increase the cement content in the mix par aggregates so as to dry quickly while still maintaining the required strength. Alternatively rather than use ordinary Portland cement which is the most common and readily available, rapid hardening cement could be used as a suitable alternative while the original mix is maintained.

Dry-Cementized construction and Re-use Techniques
can be used to save cost on large projects

 Where the common timber/wooden formwork is to be used, the inner surfaces of the timber is lined with water-proof material (e.g. polythene covering) that does not react with the concrete so as to reduce the rotting of the wood; making it suitable for re-use. Practically, a good wood can be re-used for up to 10 times or for 10 buildings. The carpenter fabricates the formwork in such a way that it can be removed and transferred with ease.  This way the cost of extra volumes of cement used will be compensated by the re-use of the timber formwork.

It is very important to note that when adopting this method, a controlled proportion of water is used; a little less than the usual volumes. In the end, the concrete will set faster and the formwork is ready for detaching in about 24 hours for non-suspended elements (e.g. columns) and about 7 days for suspended elements (e.g. upper floors) – saving roughly 48 hours and 14 days for non-suspended and suspended elements respectively.  

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