Repair mortar

Concrete is a very versatile and durable building material when constructed using advanced technology. Unfortunately, however, in the past, and even now, the construction industry has been severely damaged by a disregard for basic principles of concrete and structural concrete application. Over the past 30 years, the cost of repairing concrete buildings has increased significantly in all industrialized countries. In Germany, the cost of repairing structural concrete buildings has increased significantly. In Germany, approximately 20% of the total cost of structural concrete construction is spent on repair and maintenance of existing buildings. Carbon dioxide and other corrosive media in the air (e.g., sulfur dioxide, acid rain) cause carbonation saturation of concrete, resulting in steel bars rusting and structural concrete deterioration. Rusted steel bars increase in size and crack the cladding concrete, damaging the structure. 

In the construction industry, concrete repair work can be divided into two categories: 

1) Repair of concrete that does not contain steel bars and has no load-bearing effect. Repair mortar is normally used for repairs only for aesthetic reasons (aesthetic repair work). 

2) The purpose of repairing damaged load-bearing reinforced concrete structures is to maintain and re-establish their structural stability and functionality. It is carried out in stages using various mortars and is part of the "concrete repair system" (typical applications: repair and restoration of bridges, parking lots, tunnels, etc.). 

Mortar for exterior decoration and aesthetic repairs is based on dry-mix mortar. Usually cement-based mortars are used for interior and exterior decoration, while gypsum-based dry-mix mortars are only used for certain special interior decorations (aesthetic repairs), such as filling small holes, gaps, cracks and caves to restore the original dimensions. 

In order to ensure reliable and durable repair of structural concrete, the concrete repair system must restore the anti-corrosion protection of the steel bars (alkaline environment), decorate the appearance of the concrete structure, restore its load-bearing function and finally restore the protective function. Thereby restoring the durability of the entire building (protecting the building against weathering and environmental damage caused by CO2, SO2, CI2, antifreeze salts, etc.).

For the repair of structural concrete, three types of mortars are currently used: cement-based concrete mortars (CC; mainly used as shotcrete mortars), polymer (modified) cement as prepackaged dry-mix mortars concrete (PCC) and epoxy cement concrete (ECC). Today, PCC mortar is mainly used for repairing concrete structures. In wet shotcrete processing and even dry shotcrete processing, these mortars can be applied by hand or by machine. Dry-mix mortars with various properties and functions become an integral part of the concrete repair system: 

- Primer coatings and tackifiers for steel bars (polymer modified cement mortars or epoxy resin-based coatings )

-Tackified mud (primer coating or primer) for repairing concrete (polymer modified cement-based mud)

-Repair and surface renovation mortar (polymer Modified cement-based mortar)

-Fine aggregate smoothing mortar (polymer-modified cement-based mortar containing fine aggregate)

-Protective and finishing coating (latex paint, crack repair, cement waterproof sealant, etc.). 

So far, the main national guidelines and regulations adopted by organizations relate to the requirements for concrete repair systems. Concrete repair systems receive official approval based on relevant legislation and routine quality surveillance by independent testing agencies.

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