Concrete, Render & Mortar
Concrete petrography to determine constituents, quality and current material condition
Concrete, render and mortar degradation can result from a number of different processes from poor mix design to chemical attack. Concrete petrography is a crucial technique for the diagnosis of these processes. Examinations are conducted using visual assessment, thin section examination and where required, scanning electron microscope (SEM) analysis, in accordance with the relevant ASTM and industry standards.
The test methodologies applied to assessment of concrete, render and mortars include:
- ASTM C856-11 Standard Practice for Petrographic Examination of Hardened Concrete.
- Applied Petrography Group, SR1 & SR2, 2008. Codes of practice for the petrographic examination of concrete, mortars, plasters, renders and related materials.
Petrolab assesses concrete for common problems that cause degradation including:
- Alkali silica reaction (ASR)
- Alkali carbonate reaction (ACR)
- External and internal sulphate attack including thaumasite sulphate attack (TSA) and delayed ettringite formation (DEF)
- Fire or chemical attack
- Freeze-thaw damage
- Structural cracking
- Reinforcement corrosion
- Leaching by fluid movement
- Abrasion or erosion due to traffic
- Plastic or drying shrinkage cracking
- Pyrite oxidation within aggregate and formation of gypsum
- In situ oxidation of deleterious aggregate
- Delamination of deleterious aggregate
Petrolab petrographic reports include any of the following as appropriate:
- Type, proportions, grading, shape and condition of aggregate(s)
- Bonding characteristics
- Aggregate shrinkage or expansion
- Presence of deleterious aggregate(s)
- Cement type
- Presence of additives such as fly ash
- Depth of carbonation
- Water / cement ratio
- Approximate cement content calculation
- Degree of hydration
- Total void content
- Presence of air entrainment
- Size and distribution of voids
- Void lining
Scan of concrete core slice with scale.
Photomicrograph showing strong carbonation front within binder.
Photomicrograph showing pulverised fuel ash (PFA) binder.
Photomicrograph showing thaumasite fracturing around limestone aggregate.
Photomicrograph of iron oxide impregnation and fracturing due to reinforcement corrosion.