Concrete Testing, Precast & Specialty Work

Foundations

Slump Test (CSA A23.2-5C)

Application	Target	Range
Footings & foundations	80 mm	55–105 mm
Walls & columns	100 mm	75–125 mm
Pump mix (slabs)	150 mm	110–190 mm
SCC (spread test)	550–750 mm	Per mix design

Procedure

Cone: 305 mm tall, 200 mm base, 100 mm top
Fill 3 equal layers; rod each 25 times (16 mm rod)
Lift cone in 5±2 sec — no twisting
Complete test within 2.5 minutes
Tolerance: ±25 mm (≤100 mm slump), ±40 mm (>100 mm)

Air Content (CSA A23.1 Cl. 4.3.3)

Max Agg. Size	Required (C-1)	Target
20 mm	5–8%	6.5%
14 mm	6–9%	7.0%
10 mm	6–9%	7.5%

Test Methods

Pressure (A23.2-4C): Normal-weight concrete. Standard method.
Volumetric (A23.2-6C): Required for lightweight aggregate.

Temperature (CSA A23.2-17C)

Condition	Limit
Normal placement	10–30°C
Cold weather min.	10°C
Hot weather max.	35°C
Mass concrete max.	70°C internal; ≤20°C differential

Cylinder Sampling (CSA A23.2-3C)

Standard size: 100 × 200 mm (or 150 × 300 mm)
Sample from middle of load (A23.2-1C)
Fill 2 layers; 25 rods each (10 mm rod for 100 mm moulds)
Tap mould 10–15 times after each layer
Initial cure: 16–27°C for 24±8 hrs (insulated box)
Transport to lab within 48 hrs

Break Schedule

Age	Expected	Purpose
7 day	65–75% f'c	Early warning
28 day	100% f'c min	Acceptance
56 day	110–120% f'c	Blended cements

Acceptance (CSA A23.1)

Average of 3 consecutive tests ≥ f'c
No individual test < f'c − 3.5 MPa

Mix Design & w/c Ratios

Exposure	Max w/c
C-1 (exterior, de-icing)	0.40
C-XL (extreme)	0.37
F-1 (interior, dry)	0.55
A-1 (agricultural)	0.45

Key Admixtures

Type	Function
Air entrainment	Freeze-thaw protection (verify every load)
Water reducer (A)	Reduce water 5–12%; maintain slump
Superplasticizer	Reduce water 12–30%; place quickly
Retarder (D)	Delay set 1–4 hrs; hot weather
Accelerator (C)	Speed set; non-chloride near rebar

Rejection Criteria

Slump outside specified tolerance (plant cannot adjust)
Air content outside range
Temperature <10°C or >35°C
Wrong mix code on batch ticket
Load >90 min or >300 drum revolutions (CSA A23.1)
Visible segregation, balling, or contamination
Undocumented water added by driver

Document every rejection: photo of slump + batch ticket, reason, signature.

Hot & Cold Weather Limits

Hot Weather (>27°C)

Evaporation >1.0 kg/m²/hr → protective measures mandatory
Evaporation >0.5 → pay attention
Factors: air temp, concrete temp, RH, wind speed
Use retarder, pre-wet subgrade, fog spray, evaporation retarder

Cold Weather (<5°C)

Concrete ≥10°C at placement
Maintain >10°C for 72 hrs (CSA A23.1 Cl. 7.7.4)
Never let fresh concrete freeze — 50% permanent strength loss
Insulated blankets, heated enclosures, hydronic heat
Cold Weather Plan required 48 hrs before pour

Safety & Regulatory

No water at site without batch plant authorization. Every litre raises w/c, drops strength. Document on ticket or reject.
Calcium chloride: Never >2% by cement weight. Never with post-tensioning or embedded aluminum.
Failed 28-day breaks: Notify PM and structural engineer within 24 hrs. Core testing: avg ≥ 0.85 × f'c, no core < 0.75 × f'c.
Cylinder storage: 16–27°C insulated box. Not in sun. Not in truck bed. Not frozen.

Pro Tips

Cast extra cylinders beyond minimum. If 7-day looks low, you have 14-day and 56-day backups. Extras cost ~$15 each.
Review all break reports within 24 hrs. Any result <90% of f'c at 28 days = immediate escalation.
Test every load — not "first and then we'll see." Testing is how you catch problems before they become buildings.