Which of the following factors influence the durability of concrete?
Correct Answer: D. All options are correct
📚 Detailed Explanation: Three Factors That Influence Concrete Durability
Why D (All options) is correct: IS 456:2000 defines durability as the ability of concrete to resist weathering action, chemical attack, abrasion, and any other process of deterioration, retaining its form, quality, and serviceability throughout its design service life. All three listed categories are explicitly part of this definition.
Three Categories of Durability Attack
| Category | Specific Attack | Effect on Concrete | IS 456 Exposure Class |
|---|---|---|---|
| A. Abrasion | Mechanical wear by traffic | Surface erosion; loss of cover | Increases with exposure class |
| Erosion by water-borne particles | Hydraulic structures; dams; spillways | Surface abrasion → reduced cover depth | |
| Impact loading | Machine foundations; floors | Spalling and surface wear | |
| B. Chemical action | Acid attack (acids, CO2) | Dissolves Ca(OH)2; weakens paste | Very severe / extreme |
| Sulfate attack | C3A + sulfate → ettringite → expansion → cracking | Very severe | |
| Chloride attack | Cl¹¯ depassivates steel; corrosion; spalling | Severe/very severe (marine) | |
| C. Weathering | Freeze-thaw cycles | Water expands 9% on freezing; spalling | Moderate (frost areas) |
| Thermal cycling | Differential expansion/contraction; cracking | Moderate to severe | |
| Carbonation | CO2 lowers pH → depassivates reinforcement | Mild to moderate |
IS 456:2000 Exposure Classification for Durability Design
| Exposure Class | Condition | Max w/c | Min Cement (kg/m³) | Min Concrete Grade |
|---|---|---|---|---|
| Mild | Indoor, dry | 0.55 | 300 | M20 |
| Moderate | Humid; sheltered | 0.50 | 300 | M25 |
| Severe | Marine; industrial | 0.45 | 320 | M30 |
| Very severe | Seawater; de-icing salts | 0.45 | 340 | M35 |
| Extreme | Abrasive; very aggressive chemicals | 0.40 | 360 | M40 |
- Concrete durability is influenced by abrasion, chemical action, and weathering (all three).
- IS 456:2000 defines five exposure classes from Mild to Extreme.
- Durability requirements (min grade, max w/c, min cement) increase with exposure severity.