How Concrete Absorbs Moisture

And how to Stop It

Moisture is the single most important factor behind the deterioration of concrete. Without it, most damage mechanisms simply don’t occur. Yet concrete’s porous structure readily absorbs water through microcracks and capillaries – allowing frost, chlorides, and contaminants to penetrate deep into the material. Understanding how this happens is key to understanding why concrete needs protection. This section explains how water travels through concrete and how Komsol’s mineral-based technology stops it – from within.

The Capillary Structure of Concrete

Concrete is primarily composed of cement, gravel or crushed stone, sand, water, and air. During the curing process, water is removed from the mix, forming a fine-meshed network of interconnected channels and pores – known as the capillary system. Once fully cured, concrete typically contains around 20% air. The higher the water-to-cement ratio (WCR) in the mix, the more porous the hardened concrete becomes – resulting in increased air content and reduced density.

Shrinkage and the Formation of Cracks

Cracking occurs in all concrete, though to varying degrees and extents. One common cause is plastic shrinkage, which results from two simultaneous movements of water within the concrete mass: internal water migration toward the surface (dewatering), and surface evaporation. When evaporation outpaces internal water transport, the surface dries too quickly, increasing the risk of cracking. Some cracks are visible to the naked eye, while others require a microscope to detect. Spraying a fine mist of water over the surface often reveals microcracks clearly during the drying process.

Capillary Absorption and Liquid Transport

When concrete is exposed to water or other liquids, the fluid is drawn into the material through its capillaries, microcracks, and larger cracks by means of capillary action. The narrower the capillaries, the stronger the capillary pull. This transport occurs both horizontally and vertically – and can penetrate deep into the structure.

Crystallisation-Based Protection

Komsol Seal penetrates deep into the concrete’s capillaries, microcracks, and pores. Inside the structure, it reacts with calcium and minerals to form a dense, crystalline calcium silicate hydrate (C-S-H). This crystalline matrix blocks the transport of water while remaining vapor-permeable – allowing internal moisture to escape through diffusion. Because the protection forms within the concrete rather than on the surface, it is highly resistant to external influences such as abrasion, freeze-thaw cycles, and mechanical wear.

Proven Penetration and Crack Sealing Performance

Two physical experiments demonstrate the penetration capabilities of our silicate impregnation technology. In the tests, one concrete cube was treated from the top (simulating a floor), and another from below (simulating a ceiling). The treatment filled and sealed microcracks along their entire length – up to 200 mm – with an average penetration depth of 30 mm in solid (free from cracks) concrete with a water-cement ratio (w/c) of 0.7.