SANS 50197 / SANS 10100 is the operating manual for South African concrete specification. Most domestic clients never see it, but the difference between specifying RC30 and RC32/40-XC2-Dmax 20 shows up in service life, cost, and contractor confidence.
The SANS 50197 / SANS 10100 designation
A full concrete specification looks like: RC32/40 XC2 Dmax 20 S3
- RC32/40: Strength class — 32 N/mm² cylinder, 40 N/mm² cube
- XC2: Exposure class — corrosion induced by carbonation, wet-rarely-dry
- Dmax 20: Maximum aggregate size 20mm
- S3: Slump class (workability)
Common South African exposure classes
- X0: No risk — internal dry concrete (interior structure)
- XC1: Permanently dry or permanently wet (foundations below water table)
- XC2: Wet, rarely dry (most foundations, parking)
- XC3/XC4: Moderate humidity / cyclic wet-dry (external walls, exposed)
- XF1–XF4: Freeze-thaw exposure (external slabs)
- XS1–XS3: Marine chloride (coastal sites)
- XD1–XD3: De-icing chloride (car parks, road bridges)
Designated mixes (residential shortcuts)
SANS 50197 / SANS 10100 provides pre-defined mixes for common situations:
- GEN1: Strip foundations, blinding
- GEN3: Footings, oversite, garage floors
- RC25: Reinforced slabs, light residential
- RC32/40: Typical reinforced concrete
- RC40/50: Higher strength, exposed reinforced
- FND2: Sulfate-resistant foundations
- FND3/FND4: Higher sulfate class foundations
Cover requirements
Minimum concrete cover to reinforcement depends on exposure class:
- Internal dry (XC1): 15mm
- XC2 foundations: 30mm
- XC4 external walls: 35mm
- XS3 marine: 50mm+
Inadequate cover is the most common cause of premature deterioration.
Cement replacement
GGBS (ground granulated blast furnace slag) and PFA (pulverised fuel ash) replace a portion of Portland cement:
- GGBS: up to 70% replacement
- PFA: up to 35% replacement
- Benefits: lower embodied carbon, better sulfate resistance, lower heat of hydration
- Trade-offs: slower early strength gain
Common specification mistakes
- Not specifying exposure class
- Wrong slump for the placement method
- Specifying maximum aggregate size larger than possible to place
- Missing sulfate class on contaminated sites
MCFAR specifies concrete to SANS 50197 / SANS 10100 on all projects.
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Request a QuoteFrequently Asked Questions
Can I just order "C25" concrete?
Old terminology — modern designation is RC25/30 or higher. Be specific about exposure class to avoid issues.
Is GGBS concrete really lower carbon?
Yes — substituting 50% GGBS typically halves the embodied carbon of the mix. Specify it explicitly on every project.