The reality, unfortunately, is quite different. There are examples of a very large number of structures made in concrete, which have required expensive rehabilitation or even replacement much ahead of their expected (though unspecified) life span. This is true not only in the underdeveloped and developing countries but also in the developed countries. That is the reason why rehabilitation of concrete has become an industry by itself! Of all the wonders of the world, both the ancient and the modern ones, concrete is conspicuous by its absence!

In the past this state of affairs could be attributed to our limited knowledge of the properties of concrete and specifically about its durability. However, today it can be asserted that we possess adequate theoretical knowledge to produce concrete, which should live up to its potential. Barring the use of new construction materials and chemicals, the effect of almost all the standard ingredient of concrete on its properties are well researched, understood and documented.

However all the research carried out has not proportionally helped us increase our confidence in producing concrete with high level of durability or performance. This can be attributed to the fact that the knowledge, skills and attitude required to produce high performance concrete is often found wanting at the cutting edge level, where it matters the most. That is perhaps why; research is on to develop self-compacting and self-curing concrete.

It is said that after water, concrete is the most produced & consumed material by man!  In India we produce millions of Cum of concrete every year. While we have not reached the level of concrete produced per capita in the advanced countries, the use of concrete is on an upward spiral. With the continued explosion in investment in the infrastructure sector, the production and consumption of concrete can only rise in geometric proportion. We can ill afford to continue to construct structures with poor quality of concrete. There is thus an urgent need to upgrade our ability not only to produce good concrete but also to demonstrate this ability in no uncertain manner.

Factors affecting performance: If we analyze the factors, which influence the performance of concrete, the following list would emerge;

1.       Design and detailing of the structure.
2.       Prescribed specifications
3.       Mix design (proportioning).
4.       Quality of the ingredients.
5.       Production (batching and mixing) of concrete.
6.       Transport and placing concrete.
7.       Compaction, finishing and curing.
8.       Inspection and testing of the process or end product.

Structural design and detailing: These two three factors are in the hands of the owners’ or the consultants’ Engineers. The situation with regard to design and detailing is generally satisfactory, though one comes across cases of so much of reinforcement in a structure that the placement of concrete in the formwork appears to be a miracle. 

While this may not be an alarming situation in itself, what is of concern here is the fact that the much of this knowledge and information is gained by Engineers only after a few years of practice. Training provided to a student of Civil engineering on these aspects, even in the best of our Institutes, does not cover these aspects adequately. As a result, a fresh engineering graduate at the beginning of his career already has a few gaps in his concrete related knowledge.

Concrete specifications: The fact that the specifications laid down in the contracts have a very strong influence on the end product cannot be over emphasized. While the specifications indicate the desire of the owner / specifier with regard to concrete performance, there should be a matching capability to enforce the specifications. 

Quite often, all parties implicitly agree that specifications are not practicable and this leads to a series of compromises. Equally important is the need to have a judicious mix of both process and performance specifications. The moment we incorporate process specifications, the need to provide very objective and high level of supervision emerges. The absence of a common specification across all major owner organization like NHAI, MOST, Railways, NHPC etc. further compounds the problem. This once again leads to the need of a knowledgeable and skilled work force at site.

Concrete mix design: Traditionally the mix proportioning of concrete has been strength based. Even the IS 10262, which contains the recommended method of mix design focuses on the strength, and to a limited extent, workability of concrete. Requirements of durability are covered in a prescriptive manner. 

The emphasis is on the durability of concrete as a material and not on concrete as a ‘structure’. As a result issues such as crack control are not covered by the mix design. The use of slag, fly ash, silica fume (micro silica) and a variety of admixtures are not covered by the traditional methods of mix design. As a result these are effectively used to enhance the performance of concrete only on large projects. The myth that “higher cement content leads to better concrete” continues to prevail and needs to be removed from the minds of the mix designers, specifiers and practicing engineers. We also need to understand the requirement of the concrete mix from performance consideration and not from the point of strength alone. This knowledge needs to be spread to all the practicing engineers.

Concrete making materials: We should realize that cement (and now admixtures) is the only factory made material, which goes into production of concrete. Bulk of concrete comprises of coarse and fine aggregates (sand), which are to be locally obtained. However, contrary to popular belief, aggregates have a very strong influence on almost all properties of concrete. The construction engineers need to understand the importance of this ‘inert’ material and give it as much respect as they give to cement! Fine and coarse aggregates, being either natural materials or produced in crusher plants, exhibit considerable variation in their properties. The ability to prescribe, select and control the quality of aggregates is an important prerequisite to making good concrete.

Production, transportation & placement:  With the increasing mechanization of construction activities, the production and transport of concrete has become mechanized on all but small projects. The one-bag mixers have given way to automatic and mechanized batching plants for producing concrete. The transit mixers, concrete pump; conveyors or cranes have replaced the traditional methods of manual transportation. These changes have definitely helped to improve the quality of the process of mixing, transportation and placing of concrete. While there is scope for further improvement here, it is definitely not as urgent as in other spheres of concrete making.

Compaction, finishing & curing:  Compaction and curing are arguably the two most important aspects that influence the strength and durability of concrete. 

While more powerful and sturdier vibrators have been developed, can we assert that the quality of compaction of concrete has seen a commensurate rise? Has the advent of curing compound lead to better curing of concrete? I am sure the answer will be an emphatic NO (with exceptions to prove the point!). 

The faster pace of construction, easy achievement of cube strength due to better cements and lack of practical measures to check in-situ compaction and curing has ensured that the attitude and skill of the site supervisors/engineers remains the decisive factor in achieving durable concrete. Amongst all the factors that influence the performance of concrete, I submit that these two aspects have the widest gap between “what is” and “what should be”!

Inspection and testing: The purpose of inspection, testing and supervision is to ensure and place on record that the concrete put in place meets the requirements. There are elements of quality control and quality assurance in these activities. However, the difference between the two is more often than not quite confusing even to the concrete quality professionals!.

The process-based specifications are NOT easily amenable to post production checks and controls. The emphasis therefore must shift to breaking down the process into manageable bits and ensuring compliance of each. This is the philosophy behind quality management tools like ISO 9001 and six-sigma. Concrete industry has a lot to catch up with the manufacturing industry if we are to achieve the goal of creating truly ‘quality’ concrete! The importance and significance of human skills is even more critical in this aspect as compared to all other discussed above.

Root Cause: If we critically examine all the factors discussed above, a common thread running through these, the root cause is the human element! 

Whether it is design, specifications, productions or inspection, the contribution (or the lack of it) is all-pervasive. It is said that given the same ingredients (cement, aggregates, water and admixtures) one can either produce a wonderful concrete or utter mess, depending upon the human ingredient!  As the concrete guru Neville says, we have had enough of concrete related research, what we need is the where withal to implement whatever we know of concrete!

The knowledge, related to concrete, imparted to students at the graduate level is limited to a total of 18-20 hours. Considering the fact that concrete accounts for at least half of all construction activities isn’t this grossly inadequate! Without casting any aspersion on the quality of the teaching, it is certain that this teaching must be highly academic in nature, covering the most fundamental aspects.  The level of skills imparted (ability to utilize the knowledge) is even lesser, obviously due to a lack of resources and infrastructure.

If the young engineers do not get the right guidance at their workplace, they can end up having a much fractured knowledge of concrete. What is even worse is the fact that many Engineers pick up wrong information and practices related to concrete construction, which are more difficult to change. The rapidly changing growth of concrete technology only worsens the situation.

The way out: Fortunately, the solution to remedy this situation is relatively simple. What is required is to provide opportunity to the practicing engineers to upgrade their knowledge and skills related to concrete on a continuous basis. Professional Institutions like Indian Concrete Institute and others provide such opportunities. Leading construction companies like L&T and HCC and Government departments like Indian Railways, NHAI, and NPCIL have infrastructure to upgrade the knowledge and skills of its Civil Engineers through in house training programmes.

However, the above activities, either by professional bodies or organizations are not enough. They reach out to a small proportion of Civil Engineers fortunate enough to be employed in these organizations.  We need  to make these training programmes to reach a much wider base of Engineers. This will require uniformity in the contents of the training and education input and also large-scale education of the engineers belonging to the smaller organizations. It will help the cause of concrete construction a great deal if standard exhaustive and practical tests of concrete related knowledge and skills are developed and practicing engineers are able to obtain the qualification of Professional Concrete Engineer or Chartered Concrete Engineer.

Perhaps ConcreteBasics can start such an initiative?

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