Source: https://guthlabs.ai/docs/instruments/water-cement-ratio-strength-estimator/mechanism/

instrument mechanism / verified-clean

# Water-Cement Ratio ↔ Strength Estimator mechanism

The inspectable method record for Water-Cement Ratio ↔ Strength Estimator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The supplied honest label is directionally appropriate but incomplete. The instrument should identify the exact ACI edition/table, air-content condition, strength units, interpolation policy, and whether it reports an approximate table-associated strength or a maximum allowable w/c. Without those specifications and the actual table data, the implementation cannot receive an unconditional PASS.

- Abrams' law is named but no explicit equation or calibrated constants are supplied, so that method cannot be independently verified.

- The cited ACI lookup table is an allowable maximum water-cement ratio table for mixture proportioning, not a universal strength-prediction equation; treating its inverse as the required w/c ratio is technically misleading.

- ACI table values depend on the selected table edition, air-entrainment condition, and mixture assumptions. The spec does not identify these choices.

- Linear interpolation between discrete ACI table rows is not explicitly authorized by ACI and should be labeled as an approximation if implemented.

- A target strength alone does not uniquely determine a required w/c ratio because strength also depends on cement type, aggregate, curing, age, air content, admixtures, and testing procedure.

## Units and conventions

- w/c is a dimensionless mass ratio: mass of water divided by mass of cementitious material.

- The worked lookup convention is ACI 211.1-91, Table 6.3.4(a), non-air-entrained concrete, with compressive strength in psi and 28-day test age.

- For SI display, 1 psi = 0.006894757293 MPa.

- The ACI entries are treated as maximum w/c ratios associated with nominal 28-day compressive-strength classes, not guaranteed measured strengths.

- The target-strength input unit must be explicitly selected as psi or MPa; the original spec does not specify one.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "mode": "strength_from_wc",
    "wc_ratio": 0.58
  },
  "expected_outputs": {
    "estimated_fc_psi": 3000,
    "estimated_fc_mpa": 20.6843
  },
  "reference_data": {
    "rows": [
      {
        "fc_psi": 2500,
        "max_wc_ratio": 0.62
      },
      {
        "fc_psi": 3000,
        "max_wc_ratio": 0.58
      }
    ],
    "source_convention": "ACI 211.1-91 (reapproved 2009), Table 6.3.4(a), non-air-entrained concrete; US customary textbook table values"
  },
  "working": "Exact table lookup: w/c = 0.58 corresponds to f'c = 3000 psi. Convert units: 3000 psi × 0.006894757293 MPa/psi = 20.684271879 MPa ≈ 20.6843 MPa."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification does not provide the actual ACI table, table version, air-entrainment basis, interpolation rule, or valid input range. Consequently, boundary results and inverse results are not uniquely determined. An extreme target such as 1,000,000,000,000 psi must be rejected; returning an extrapolated w/c value would be a failure.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/water-cement-ratio-strength-estimator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/water-cement-ratio-strength-estimator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/water-cement-ratio-strength-estimator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`