Expert sees no major difference between 32.5, 42.5 cement grades

Following the ongoing controversy on cement application and standardisation, Uzo Nwankwo, an Imperial College-trained structural engineer, has said that cement grades 32.5, 42.5 and 52.5, are all the same except for minor changes in characteristics.

“All cement are one and the same but for minor changes in the characteristics,’’ he says.

According to him, the recent controversy over 32.5 cement grade is entirely unnecessary as the grade is suitable for all construction activities in Nigeria where the structural engineer has specified a concrete grade of 30Mpa or less, adding that higher grades of 42.5 and 52.5 have their special uses and should occupy a niche in the market, to be sought by those who need them.

He further states that grade 33 (ie. 32.5) meets the structural requirements of small-scale consumers, while grade 43 (42.5) may be utilised for pre-cast concrete just as grade 53 (52.5) may be used by builders of heavy infrastructure such as bridges, fly-overs, large span structures and high rise structures.

“The common man’s perception that grade 53 cement is the best cement is not only due to the aggressive marketing strategies of the cement manufacturers but also on the presumption that the heat generated during the hardening of the concrete is an index of its quality,’’ he says.

He adds that the 32.5 does not cause building collapses, but attributed such disasters to poor design, construction practices and compaction, improper placement of reinforcing steel, haphazard water cement ratio, gambling in the name of construction, among others.

“If a structural engineer specifies a concrete strength of 20Mpa and proceeds to design the entire structure with this in mind, it will stand the test of time,’’ he adds.

Recall that the Standards Organisation of Nigeria (SON) recently published a directive that cement with strength rating 52.5R be used for bridges; 42.5R for casting of columns, beams, slabs and for moulding blocks, and 32.5 for plastering only.