Concrete Curing & Curing Compound

Curing for concrete works is very important particularly in hot climate countries such as Malaysia. The temperature at daytime can go as high as 36-37 deg Celsius in fine unclouded weather. My experiences show that, if curing not properly carried out, concrete cracks tend to occur in form of hairline cracks. For example in my recent project of five storey building, the contractor failed to carry out proper curing (for the first few days after concreting) for wide-area slab (for floor) and therefore concrete cracks have occurred.


Hairline cracks about to form just about an hour after concrete casting in hot weather (when concrete surface about to dry and lose its moisture).

Concrete cracks observed in the concrete surface due to poorly carried-out curing. It is observed that some cracks had openings of about 2mm-3mm widths and depths of 30mm-35mm (measuring by penetrating wire that used in re-bars tying works into the cracks; this is rough estimates and therefore not accurate due to nature of wire itself which is quite rigid and its bigger size to enter finer cracks).

concrete cracks observed on the concrete surface

Contractor for this project has failed to carry out proper curing as required in specifications. The contractor failed to commit their promise to use gunnysacks with frequent water spraying on it as a method chosen for concrete curing.

During recent site inspection, the client has not satisfied with this condition. Finally the contractor has opted to use curing compound for concrete curing.

The contractor has chosen curing compound ‘Fosroc Concure’. For comparison, I have carried out simple experiment and marked the areas of slab to be implemented both with curing compound and without curing compound (side by side). Concrete works then carried out in the morning (around 9.30am) with fine unclouded weather. The following is the results you can see:

Concrete surface after curing compound applied-less cracks observed; very fine and negligible (at left side, however the application of curing compound causing the concrete surface relatively a bit darker compared to non-applied-curing -compound area at right side). At right side where concrete surface is without curing compound; concrete cracks occurred; visible, larger than hairline cracks occured at the curing compound area and so glaring that can be seen from quite a distance. This photo taken at 3^rd day after concrete casting for floor slab.

However, a fine tune still needs to be carried out in order to set a proper timing to apply curing compound so that its intended use can be optimally used as per its manual. This is because it is observed that few concrete cracks still happened there (only minor negligible hairline cracks). It is believed that this occurred due to delay in applying the curing compound material.