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Preventative measures
Published in Brian Cherry, Green Warren, Corrosion and Protection of Reinforced Concrete, 2021
Water borne coatings are lattices of organic polymers in water generally described in AS/NZS 4548 ‘Guide to long-life coatings for concrete and masonry’ (Standards Australia, 1999), for example. They are generally applied by a roller or by spray gun to surfaces that have been sealed for the following coats. The sealer is the first coat applied to a new concrete surface and is often a low solids content polymer solution that penetrates the pores of the concrete and provide moisture barriers in them. The second coat then often consists of a high solids emulsion of a similar polymer. These coatings are required to have sufficient elasticity to be able to bridge cracks and provide an adequate resistance to water permeability. They also act as anti-carbonation coatings and chloride ion barriers. Tests for all these properties are included in AS/NZS 4548.5 (Standards Australia, 1999), for example.
Methods for Protecting Steel Reinforcements
Published in Mohamed Abdallah El-Reedy, Steel-Reinforced Concrete Structures, 2017
The successful performance of coating or sealers depends not only on the quality of the materials used, but also on the application. The concrete surface should be clean and sound. Weak and cracked concrete should be removed, holes should be filled, and, if necessary, a leveling coat should be applied. If the membrane applied has a polymeric composition, the surface should be dry. Silane treatments can be done in wet concrete. This is needed to facilitate better penetration of the liquid compound into the pores. Coating should usually be applied in two layers to obtain a continuous film without pinholes. The service life of the membranes or sealers ranges between 15 and 20 years. Thus, continuous maintenance and follow-up are necessary, apart from additional treatments.
Fatigue of steel bridge infrastructure
Published in Hyun-Moo Koh, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Health Monitoring and Informatics, 2008
Hyun-Moo Koh, Dan M. Frangopol
Other polymer concrete material systems such as Methyl Methacrylate (MMA) have been developed to obtain high strength in one hour in ambient temperatures from �415 deg C to 40 deg C. These materials have been successfully used for concrete patching, bearing pads, joint headers and closure pours. Other development has lead to High Molecular Weight Methacrylate (HMWM) polymer sealers that can heal/seal small cracks in existing concrete surfaces and are applied using only the force of gravity and do not require pressure injection.
Extending the Life of Historic Concrete Arch Bridges: State of the Art
Published in Structural Engineering International, 2019
Arne P. Johnson, Gary J. Klein, John S. Lawler
Since freeze-thaw damage and reinforcing steel corrosion are moisture-driven mechanisms, addressing uncontrolled drainage and leaking expansion joints is the first step in slowing this deterioration. However, precipitation and condensation may still be sufficient to promote deterioration. Depending on historic preservation implications (see below), ingress of moisture can be further limited by application of surface treatments, such as penetrating sealers or film-forming coatings. Clear penetrating sealers (e.g. silane sealers) may help repel water from concrete surfaces and in fine cracks, but do not bridge or fill larger cracks. High performance, film-forming coatings provide a higher level of protection and can bridge cracks. Acrylic- or silicone-based coatings are more vapor permeable than other concrete coatings, allowing the structure to dry.
Crack healing in concrete by microbially induced calcium carbonate precipitation as assessed through electromechanical impedance technique
Published in European Journal of Environmental and Civil Engineering, 2023
Kamal Anand, Shweta Goyal, M. Sudhakara Reddy
Various existing techniques for repairing the cracks include manual application of chemical (Sisomphon et al., 2012) and polymeric sealers (Van Tittelboom et al., 2011). These techniques maintain the strength and durability of the concrete structure to a certain extent, but require regular examination and maintenance post repairing. Recently microbially induced calcium carbonate precipitation (MICCP) has drawn much attention due to sustainability, good compatibility with concrete and has proven to be promising technique (De Belie et al., 2018; Kan et al., 2019). MICCP via urea hydrolysis involves a series of complex biochemical reactions, that are driven by urease and carbonic anhydrase enzymes. The detailed mechanism is well reported by the various researchers (Joshi et al., 2017; Tripathi et al., 2019). A number of investigators have used bacteria as a measure of eco-friendly crack healing agent (Rong et al., 2020; J. Xu & Wang, 2018). The results revealed that bacteria could produce calcium carbonate (CaCO3) precipitation insides the cracks and block them, thus the mechanical properties of the concrete could be restored to a certain extent (Ramachandran et al., 2001). The primary focus of the research has been on the use of various bacterial strains to enhance the mechanical, durability properties and crack healing of concrete (Achal et al., 2011; Alazhari et al., 2018; De Muynck et al., 2008; Sierra-Beltran et al., 2014; Vahabi et al., 2015). In addition to the variety of bacteria, the use of carrier material for the survival and protection of bacteria in the high alkaline concrete environment is of prime interest (Jonkers et al., 2010). A good carrier material should be insoluble, non-toxic; both for the immobilized material and the environment; easily accessible, inexpensive and stable (Dzionek et al., 2016). Moreover, good carrier material should create the optimum environment for bacterial growth and metabolism (Jiang et al., 2020). Researchers have used several carrier materials to increase the viability of bacterial cells in concrete. Previous studies reported the use of perlite (Alazhari et al., 2018), polyurea (Zamani et al., 2020), zeolite (Bhaskar et al., 2017), diatomaceous earth (J. Y. Wang et al., 2012) and graphite nanoplatelets (Khaliq & Ehsan, 2016) as potential carriers for the bacteria in concrete. In order to use the process of MICCP in crack healing in real structures, it is preferable to use the carrier material that is known to be synergistic with concrete. One such material which has the potential to be used as an effective carrier material because of its already established synergy with constituent of concrete is flyash (FA). The use of FA in concrete industry has already shown the engineering, environmental and economic benefits in the past few decades (Thomas, 2007; Xu & Shi, 2018). In the present study, the effectiveness of FA based inoculum in healing the cracks is explored.