Concrete is the most widely used construction material in the world, and its rise to this position has played a major part in the shaping of civilisation from as long ago as 7000 BC. It is the second most-used substance by man, after water!

It was known to the Romans, the Egyptians and to even earlier Neolithic civilisations. The foundations of the Colosseum in Rome were made of dense concrete (in 82AD), while lightweight concrete was used in some of the arches and vaults.

After the collapse of the Roman Empire its secrets were almost lost, only to be rediscovered in more recent times. Indeed its modern development spans no more than 175 years; 1824 is the date on the patent for the manufacture of the first Portland cement, one of the most important milestones in concrete’s history.

Concrete is a building material composed of cement, crushed rock or gravel, sand and water, often with chemical admixtures and other materials; this mixture eventually hardens into a stone-like material.

Anyone involved in the maintenance of reinforced concrete structures cannot be unaware of the substantial increase in the amount of repair work now being carried out.

This may merely reflect the fact that a large number of reinforced concrete structures are now coming-of-age although certain changes in materials have been identified over the past twenty years or so which might be partially responsible in some cases.

From our experience it is true to say that 90% of the problems that will be experienced in concrete repair will involve steel reinforcement corrosion as a primary problem. For the most part this will have been caused entirely by simple carbonation/low cover and/or the presence of chloride salts either from calcium chloride used as an accelerator, or even from de-icing salt.

However, in some cases, some other more subtle defect may be present, such as a shrinkable aggregate, alkali silica reaction, frost attack, sulfate attack, structural cracks or a whole variety of other possibilities.

It must be borne in mind that many of these phenomena may reveal themselves first of all in areas of low cover and carbonated concrete, perhaps because microcracking from one or other of these causes has permitted carbonation to advance more rapidly than might otherwise have been the case.

In such cases, it is all too easy to look at the effects of the problem, and not the cause; steel corrosion is the SYMPTOM, not the CAUSE. Attempting to repair concrete by simply addressing the symptom may simply mean that the problem recurs in a relatively short space of time.

Actual structural failure, or even structural cracking is only rarely encountered but it is important to differentiate between cracking from structural and other causes. Such an assessment should only be carried out by a structural engineer, but an initial inspection by a concrete repair contractor and further testing may highlight other (much more likely) causes of cracking.

A concrete repair specialist will know when the advice of a structural engineer is required.