Durability

Resistance to deleterious reactions

Sulphates occur naturally in the ground and can sometimes have a harmful effect on concrete, causing it to crack and disintegrate.
The main reactions are known as ettringite and thaumasite. The use of Regen in concrete greatly increases resistance to sulphate attack. This is well recognised by codes and standards. In the latest version of the British Standard for concrete (BS8500), the only option recommended for the most severe sulphate exposure is a concrete with a cement replacement of at least 66 per cent Regen.

Heat of hydration

The hydration of cement is an exothermic reaction. The use of Regen reduces the heat of hydration. High temperatures in concrete can generate stresses that could result in early-age thermal cracking. This cracking is known to have caused issues with some structures, and so the use of Regen is recognised as an effective solution to the problem.

The percentage of Regen used directly affects the heat of hydration; a replacement level of around 70% is recommended for large pours. A temperature reduction of up to 40% can be achieved with a 70% replacement level.

Setting times

Concrete produced with a proportion of Regen has a slightly longer setting time than cement-only concrete. In practice, these extended setting times give greater opportunity for working the concrete, and provide more flexibility on site to compensate for any delivery delays or adverse working conditions.

A concrete containing 50% Regen will have a setting time of approximately half an hour longer than cement-only concrete, although this can be affected by the water/cement ratio and ambient temperature. We recommend carrying out tests to ensure the correct mix ratios.