Corrosion of reinforcing steel and other embedded metals is the most common cause of concrete deterioration. When steel corrodes, the resulting rust occupies a larger volume than steel, creating tensile stresses in the concrete that can lead to cracking, delamination, and chipping. This can cause major headaches for building owners, so it is important to identify these defects in time and plan appropriate repair strategies. Other causes of concrete degradation include fouling, disintegration, erosion, alkaline aggregate reactions, the freeze/thaw cycle, overloading from new levels or heavy machinery, carbon dioxide in the air, and chemical attack from animal fats, oils, acids, alkalis, and industrial salts. The freeze/thaw cycle affects the soil by causing it to settle differently in warm months than when it is frozen.
This can cause cracks and break concrete foundations. Climate damage often occurs in the form of cracks and potholes. Carbon dioxide in the air can react with calcium hydroxide in the concrete mix, lowering its pH and exposing steel to corrosion. For horizontal surfaces where stagnant water accumulates, freezing and thawing can make the concrete more permeable and widen holes over time. Cracking can be caused by improper preparation of the substrate or subbase, a high water-cement ratio, improper curing methods, poor concrete consolidation, improper reinforcement or insufficient joint spacing, and many other factors. Chemical attack is one of the most common causes of concrete deterioration today. Animal fats, natural and artificial oils, acids, alkalis, and various industrial salts are all harmful to concrete.
Chemical attack occurs due to pollution products and after discharge activity on the surface of the insulator. Concrete degradation can also be caused by fire, aggregate expansion, seawater effects, bacterial corrosion, calcium leaching, physical damage, and chemical damage from carbonation, chlorides, sulfates, and non-distilled water. This process negatively affects concrete exposed to these harmful stimuli. The repair of localized areas of concrete deterioration is an effective way to increase its life expectancy. Paramagnetic defects and optical centers are easily formed but very high fluxes are needed to displace a sufficiently high number of atoms in the crystal lattice of minerals present in concrete before significant mechanical damage is observed. Sulfate attack is one of the most harmful causes of concrete deterioration as it causes softening and decay of the concrete matrix or expansive cracking and other disturbances associated with the formation of ettringite (calcium sulfoaluminate hydrate) and other product reactions inside hardened concrete. As the outer concrete paste wears away due to abrasion or impact from coarse aggregate particles being exposed, further degradation related to the strength of the aggregate-to-paste bond and hardness of the aggregate may occur. To protect your concrete from deterioration it is essential to use proper materials for construction; employ proper curing methods; avoid overloading; guard against freeze/thaw cycles; use proper joint spacing; prevent chemical attack; use proper consolidation; shield against carbon dioxide; protect against sulfates; guard against paramagnetic defects; shield against optical centers; guard against abrasion; protect against impact; use proper reinforcement; use proper substrate preparation; use proper water-cement ratio; use proper aggregate selection; use proper design; use proper placement timing; use proper storage materials; use proper formwork removal timing.
