Building Structural & Protective Solutions

Concrete Repair

Concrete Cancer: The term concrete cancer is actually applied to two basic forms of concrete failure, corrosion of the steel reinforcement and carbonation or silica reaction. Moisture penetrating the concrete due to cracks or honey comb voids reacts with the steel reinforcement. A reaction occurs resulting in corrosion or rust. As the corrosion accelerates, pressure is exerted outwards from the steel to the surrounding concrete, Stress increases until the concrete breaks away, otherwise known as spalling. Other circumstances resulting in concrete cancer are attributed to the presents of chloride components combined with reduced alkalinity. Or increased alkalinity will react with atmospheric carbon dioxide; this occurs in particular to coastal or corrosive environments. Rectification of concrete cancer can be archived with many techniques depending on location and symptoms, however all appropriate techniques will require treatment or replacement of the reinforcement steel. A high compressive strength mortar system in then applied. In addition concrete cancer and often be controlled, slowed or delayed by cathodic protection. Cathodic protection is achieved by two distinctive methods the basic and often less evasive application is to introducing an electrochemical cell or sacrificial anode that is more easily corroded. Cells mostly consisting of zinc, magnesium and aluminium will sacrifice over time and may need to be replaced depending on the severity of the conditions. The second method is to introduce a small current through the reinforcement steel thus changing the polarity of the reaction. This process requires the excavation of the reinforcement steel to allow connection and completing a low volt circuit and control panel.

Cracked Concrete: Cracks in concrete can be the result of many conditions; all cracks are caused by stress and subsequent movement. It is therefore analysis of direction of forces or bending moments that will determine the correct methodology for rectification. Ridged or movement joints may be required depending on the location, detail and intention of the remedy. Repairs can be archived by removing and reconstructing sections of concrete elements, filling cracks with epoxy injection or introducing intentional movement joints and application of flexible sealant.

Honey Comb Concrete: irregular voids, cavities and holes in the concrete are defects caused by poor concrete placement, potentially increasing the ability for moisture to penetrate the concrete and cause corrosion. They may also contribute to a weakening of the compressive and tensile strengths of reinforced concrete design. Prevention of moisture penetration and subsequent protection of steel reinforcement is often achieved by application of Hydroscopic migrating silanes. Depending to the age of the structure repairs may require a combination of structural strengthening, spalling and silane application.

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