5 Causes of Common Concrete Cracks

(5 Causes of Common Concrete Cracks)

Cracks caused by deformation of the foundation

Due to uneven vertical settlement or horizontal displacement of the foundation, additional stress is generated in the structure, exceeding the tensile capacity of the concrete structure, resulting in structural cracking.

 

Cracks caused by corrosion of steel bars

Due to poor concrete quality or insufficient protective layer thickness, the concrete protective layer is eroded by carbon dioxide and carbonized to the steel bars' surface, reducing the concrete's alkalinity around the steel bars. Due to chloride intervention, the chloride ion content around the steel bars is high, which can cause oxidation of the steel bar surface. The film is damaged, and the iron ions in the steel bars react with the oxygen and moisture that invade the concrete. The volume of the rust product, iron hydroxide, increases by about 2 to 4 times the original volume, thus generating expansion stress on the surrounding concrete, causing cracking and peeling of the protective layer of concrete. , cracks occur longitudinally along the steel bars, and rust penetrates the concrete surface. Due to corrosion, the effective cross-sectional area of steel bars is reduced, the binding force between steel bars and concrete is weakened, the structural bearing capacity is reduced, and other forms of cracks will be induced, aggravating the corrosion of steel bars and leading to structural damage.

To prevent corrosion of steel bars, the crack width should be controlled according to the specifications during design, and sufficient protective layer thickness should be used (of course, the protective layer should not be too thick; otherwise, the effective height of the component will be reduced and the crack width will increase when stressed); during construction, the Control the water-cement ratio of the concrete and strengthen vibration to ensure the compactness of the concrete and prevent oxygen intrusion. At the same time, strictly control the amount of chlorine-containing additives. Be especially cautious in coastal areas or other areas with highly corrosive air and groundwater.

 

Cracks caused by frost heave

When the atmospheric temperature is below zero, the water-saturated concrete freezes, the free water turns into ice, and the volume expands by 9%, causing expansion stress in the concrete; at the same time, the supercooled water in the concrete gel pores (freezing temperature is below -78 degrees ) migration and redistribution in the microstructure cause osmotic pressure, which increases the expansion force in the concrete, reduces the strength of the concrete, and causes cracks to appear. In particular, concrete is most severely affected by freezing during its initial setting, and its strength loss can reach 30% to 50% after it matures. During winter construction, frost heave cracks along the direction of the pipeline may occur if insulation measures are not taken after grouting the prestressed tunnels.

Cracks caused by the quality of construction materials

Concrete mainly comprises cement, sand, aggregate, mixing water, and admixtures. Substandard quality materials used to configure the concrete may lead to cracks in the structure.

Cracks caused by quality of construction artistry

During the pouring, component production, mold making, transportation, stacking, assembly, and hoisting of concrete structures, if the construction technology is unreasonable. The construction quality is poor; longitudinal, transverse, oblique, vertical, horizontal, and Various surfaces, deep and penetrating cracks are more likely to occur, especially in slender and thin-walled structures. The location, direction, and width of cracks vary depending on the cause.

 

Supplier

TRUNNANO is a supplier of Cement Anti-crack Agent-Preventing Cracks in Foam Concrete(which is one of concrete additives) with over 12 years experience in nano-building energy conservation and nanotechnology development. It accepts payment via Credit Card, T/T, West Union and Paypal. Trunnano will ship the goods to customers overseas through FedEx, DHL, by air, or by sea. If you are looking for high quality concrete crack reducing admixture, please feel free to contact us and send an inquiry. (sales@cabr-concrete.com).

(5 Causes of Common Concrete Cracks)