IS 14959 (Part 2) : 2000Method of Test determination of water-soluble and acid-soluble chlorides in mortar and concrete, Part 2: Hardened mortar and concrete

IS 14959 Part 2:2000 is the **method for determining water-soluble and acid-soluble chlorides in *hardened* mortar and concrete — the forensic / condition-assessment counterpart to Part 1. It is used to diagnose chloride-induced corrosion in existing structures**: how much chloride is present, and how it varies with depth toward the reinforcement.

It sits in the structural-assessment stack:

• IS 456 — durability / chloride limits (the benchmark) · IS 14959 Part 1 — chlorides in fresh concrete (the prevention companion)
• IS 516 Part 5 — NDT (UPV, rebound) · IS 3085 — permeability (the transport property behind ingress)

Once concrete is hardened and in service, chloride that has ingressed from the environment (marine spray, de-icing, contaminated ground) accumulates with time and migrates inward. Part 2 quantifies it on samples taken at successive depths (drilled powder / cores), giving:

• A chloride-vs-depth profile — is the chloride front near or past the reinforcement (where it depassivates steel and initiates corrosion once it exceeds the threshold)?
• Acid-soluble (total) vs water-soluble (free) content at each depth — the free fraction drives corrosion risk
• Input to residual-life and repair decisions — patch repair, realkalisation/desalination, cathodic protection, or replacement

The engineering point: Part 2 is diagnosis, not prevention — by the time you run it the chloride is already in the structure. Its value is locating *how far the front has reached* relative to the steel, which converts a vague 'the concrete looks spalled' into a quantified, depth-resolved corrosion assessment that a repair strategy can be designed against.

Scenario: a coastal/marine RCC structure showing rust staining and spalling.

Step 1 — combine with NDT: map the suspect zones with UPV/rebound and cover survey first (target the worst areas).

Step 2 — depth sampling: extract drilled-powder samples or cores and section them at successive depths toward the rebar.

Step 3 — test (IS 14959 Part 2): determine acid-soluble and water-soluble chloride at each depth → a chloride-vs-depth profile.

Step 4 — compare to threshold: is the chloride at rebar depth above the corrosion-initiation threshold / the IS 456 benchmark? How steep is the front (how fast is it advancing)?

Step 5 — design the intervention: profile + cover + corrosion survey → choose patch repair, chloride extraction, coatings/CP, or replacement, and set a monitoring interval.

The profile turns visible distress into a quantified diagnosis; without it, repairs are guesses about where the chloride actually is.

1. Single bulk sample instead of a depth profile. The whole diagnostic value is the chloride-vs-depth trend toward the steel — one averaged number hides it.

2. Treating it as prevention. Part 2 is forensic; the chloride is already in the structure — prevention is Part 1 on the fresh mix.

3. Reporting only total or only free chloride. Both matter — total vs the IS 456 benchmark, free for corrosion-risk interpretation.

4. Sampling away from the distress / not combined with cover & NDT. Chloride results must be read with cover depth and corrosion survey to mean anything.

5. No threshold/residual-life interpretation. Numbers without comparison to the corrosion-initiation threshold and front advance don't drive a repair decision.

• IS 14959 Part 1 — chlorides in fresh concrete (prevention companion)
• IS 456 — chloride limits / durability benchmark
• IS 516 Part 5 Sec 1 — UPV NDT (zone mapping for sampling) · IS 516 Part 5 Sec 2 — rebound
• IS 3085 — permeability (controls the ingress rate this test measures the result of)

IS 14959 Part 2 is reaffirmed and is a core tool of concrete forensic engineering — repair and rehabilitation of chloride-attacked structures (marine, coastal, de-icing, contaminated ground) is a large and growing part of practice, and a depth-resolved chloride profile is what turns visible spalling into an actionable diagnosis. The recurring error is taking one bulk sample: the entire point is the chloride-vs-depth profile relative to the reinforcement — how close the front is and how fast it is moving — read together with cover depth and a corrosion survey. It is diagnosis, not prevention; the cheap stop is Part 1 on the fresh mix, and Part 2 is what you run when that stop was missed and you now have to quantify the damage and design the intervention.