Micro Cracking

The term microcracking refers to very small cracks that form in concrete but are not visible to the naked eye. They are an inherent characteristic in concrete and not typically detrimental.

Due to the layer of water formed around aggregate surfaces, this forms a high w/c ratio locally, thus creating a thin layer of low strength paste, post hydration. As temperature changes naturally through heat of hydration variations and ambient conditions, this layer fractures, creating microcracks. No loading is required for these to form.

Localised microcracking may also be formed by mechanical impact to the concrete. Examples include: drilling for dowels and anchors, cores and breaking out. Again, these are not typically detrimental, but may sometimes influence the bond of subsequent repair materials.