Forensic petrographic assessment of hardened concrete (ASTM C856)
Hardened Concrete Petrographic Assessment (ASTM C856)
Petrographic assessment of hardened concrete applies principles derived from ASTM C856. This assessment is important because it provides detailed information about the microstructure of the concrete, including the type and amount of cement, the size and shape of the aggregate, and the presence of any defects or deficiencies. This information can be used to assess the quality and durability of the concrete, as well as to identify the cause of any problems or perceived deleterious defects that may have occurred during its production or service life. Petrographic assessment can also be used to evaluate the effectiveness of different concrete mixtures and curing methods, and to optimize the design of new concrete structures.
Petrographic Assessment of Alkali Silica Reactivity (ASR) in Concrete Structures
Petrographic analysis of concrete affected by Alkali-Silica Reaction (ASR) can help identify the type and extent of ASR damage and determine the underlying causes of the reaction. This analysis involves microscopically examining thin sections of concrete samples to observe the presence of ASR gel and its effects on the concrete matrix. The examination can reveal the size, shape, and distribution of the gel, as well as its interaction with the aggregates and the concrete matrix. Petrographic analysis can also determine the type of reactive silica present in the aggregate and the degree of expansion caused by the ASR reaction. This information can be used to make informed decisions on the need for repairs, the selection of appropriate repair methods, and the expected service life of the structure.
https://cdn.ymaws.com/concretenz.org.nz/resource/resmgr/docs/conf/2017/19.pdf
Petrographic Assessment of Fire Damage in Concrete Structures
Petrographic assessment of fire-damaged concrete can help determine the extent of damage to the structure by analysing the microstructural changes in the concrete after exposure to high temperatures. This analysis can reveal the presence of cracking, spalling, formation of new minerals, and loss of matrix strength and stiffness, which can provide a quantitative evaluation of the damage. The information obtained through petrographic assessment can then be used to determine the need for repairs, the appropriate repair methods, and the expected service life of the structure. Additionally, the assessment can provide insight into the fire resistance of the concrete and guide future fire protection measures.
http://www.ciaconference.com.au/concrete2021/pdf/full-paper_46.pdf
Typical crack pattern of the alkali-silica reaction (ASR). The gel exudations through the concrete cracks have a characteristic yellow color and a high pH. The fatty aspect of the exudations imbibing the concrete porosity along the cracks is also a distinctive feature of ASR - Wikipedia
17th EMABM, University of Toronto, Toronto, Canada, May 20-23, 2019, Fire Damaged Concrete from a Petrographer’s perspective, Derek Cong Et. Al.