I spent much of my working life in architecture and surveying, saw lots of problems with concrete and I concur with much of what was said in the article ‘Many residential buildings under construction to face problems in 30 years due to untested, defective concrete’ (March 29). However, I would like to make some observations.

The quality of concrete is determined by the mix design and the alkalinity of the concrete is of paramount importance in the protection of steel reinforcement.

The standard tests carried out on the concrete being used on any construction basically only determine whether that sample is consistent with the attributes expected from each test cube.

The crushing strength of each test cube is determined and from this all other attributes are inferred.

In the design of reinforced concrete structures it is most important to protect the reinforcement by ensuring not only that the concrete is sufficiently alkaline to help protect the steel but that there is sufficient cover to the steel to minimise the chance of moisture affecting it. The usual minimum cover required is 25mm.

One serious problem with concrete production methods involves the, perhaps unwitting, use of salty sand in the manufacture of the concrete. Salt in the mix leads to early and aggressive corrosion of steel reinforcement when moisture is present.

Few buildings on Malta are high enough for there to be any serious worry about the strength of well-designed and manufactured concrete. However, even the best of concrete designs can fail badly if there is insufficient cover to the reinforcing steel or salty sand has been used in the manufacture of the concrete.