‘Shelf life of cement shouldn’t be more than 3 months’

What is the institute doing to ensure cement manufacturers keep to specifications and standards? I believe that the Nigerian public is entitled to asking questions about the quality of construction materials that are being used. There’re many questions that need to be answered by both cement manufacturers and those in charge of regulations and specifications […]

What is the institute doing to ensure cement manufacturers keep to specifications and standards?
I believe that the Nigerian public is entitled to asking questions about the quality of construction materials that are being used. There’re many questions that need to be answered by both cement manufacturers and those in charge of regulations and specifications which include NBRRI.
But primarily, the Standards Organization of Nigeria, SON has regulatory duty. SON’s mandate covers a wide array of specializations, disciplines and materials. It will depend on the goodwill of research and development from specialized research institutions, like ours, and possibly our laboratories and those of the tertiary education sector, to provide it data in areas where it is its responsibility to set standards and undertake regulation.
However, on the issue of cement quality in Nigeria, we have spoken in public fora organized by the Cement Manufacturers Association of Nigeria (CMAN). We have also made similar initiatives in public fora of the Standards Organization of Nigeria relating  to the quality of construction materials where we have given our views on Nigerian cement and other construction materials, like sandcrete blocks and concrete. Cement generally, as example, is in classes and fundamentally there are five classes of cement all over the world.
There’re cement class 1, cement class 2, cement class 3, cement class 4 and cement class 5.
Cement class 1 is the most popular and the Ordinary Portland Cements, OPCs ubiquitously applied in the Nigerian construction industry belong to this class. Cement class 2 is also Portland cement but is modified so that it has a low heat of hydration because Class 1 releases high heat during the process of transforming from liquid to plastic paste and the hardening phase through the process called hydration.
The reason is that in many circumstances, high heat of hydration is not to the advantage of concrete and the structure because though it results in higher early strength, it leads to cracking, lower ultimate strength and the processes for its production are not energy efficient, as a result of which this second type of cement was brought into contention.
Comparing and contrasting the other three types, class 3 is for high early strength designed for specialized rapid strength requirements. Unfortunately, as is typical with higher early strength, it leads to low final strength and high heat of hydration.
Class 4 are cements that have partial replacement up to 55 percent with Pozzolana, a material that NBRRI is now promoting and championing in Nigeria. It has its own advantages when you wish to improve on the degree of imperviousness of structures. It also gives higher workability and has pronounced appeal as it relates to affordability — because of lower costs. Type 5 are composite cements which are primarily developed to provide resistance to leaching in saline environments associated with sea water, and they are known as sulfate resisting cements for special purpose conditions.
Since cement classes 3 and 5 are for special conditions, they are not commonly available for everyday and common applications, while class 4 cements are just being championed by the Nigerian Building and Roads Research Institute.

What classes then are used in Nigeria?
It is both classes 1 and 2 that the cement manufacturers claim are being produced for the Nigerian construction industry. Their application depends on the circumstances whether it is class 1 or 2, each is also further re-categorized theoretically and practically according to the strength class.
Therefore, classes 1 and 2 cement, depending on chemical proportioning of the four primary compounds constituting cement, and smaller additives, each has strength classes 32.5 and 42.5, in Nigeria and also class 52.5 unavailable internationally. The problem in Nigeria is vividly that the cement companies do not explicitly state the cement specifications on their bags, if they know it at all, or they’re making errors of haphazard production, or they’re making the matter some sort of trade secret in order to maximize profit and evade enforcement.
I recommend that the bag should contain details to state whether it is cement class 1 or class 2 and also the strength class, whether 32.5 or 42.5 (kPA). Where special cement needs to be used, additional details should be provided. These are the issues that Nigerians are complaining about.
In a nutshell, there’re definite questions of quality that Nigerians need clarifications on from the manufacturers of cement. Also regulators like SON, certification agencies like NBRRI and research and development groups should provide information.

You talked about strength?
Definitely, strength is a quality matter and there is the need for quality control at the production source. Quality control is not an issue of arbitrariness. When cement companies are working towards a set of specifications, they need to be guided about the chemical composition of the cement, the calcining conditions, including incinerating temperatures, milling, etc.
What factors could lead to deterioration of cement?
One of the most important factors, related to deterioration, is the level and period of exposure. Basically, the shelf life of cement should not be more than three months, given proper compliance with storage processes so that they are not unduly open to humidity and very high pressure from over-stacking. I don’t know if anybody is observing these at all because the cements we buy don’t even carry manufacture date and quite many would have started caking, losing some of their potent cementisious abilities while still in the warehouses.
 If cement is exposed to damp weather, it is likely to deteriorate much faster; if it is stacked more than 10 bags, which exist all over the place anyway, the undue pressure will have its deteriorating effect. These are rule-of-thumb laws made for a purpose, not arbitrarily, to protect even the most ordinary user.

Is there any area of partnership with other regulatory bodies to ensure that cement is produced to standards?
We partner and synergize in most of our activities with universities, SON, cognate professional bodies, many other government agencies. We’re available for certification purposes and I recall vividly in one of our public outings, the CEO of SON made a proposal to visit our laboratories with a view to utilizing them for their monitoring activities. We have given the go ahead. Therefore, NBRRI is very open to collaboration and complementation for the benefit of Nigerians.
Are you saying there is a specification?
There’re sets of specifications: what is generally referred to as the Nigeria Industrial Standards, NIS, related to cement. There’re documents on the shelve and without any ambiguity you can trace them to SON. These specify many of these limits that have or may not have already been mentioned in our discussions.  
These specifications are there and some of NBRRI’s presentations have comprehensively analyzed them and compared and contrasted with other countries’ specifications, like South Africa, India, US, UK based on which opinions were made. It is also important to note that these specifications are between 40-50 years and long overdue for reviews, which can only succeed through collaborations and research.