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

instrument implementation / implementation-contract

# Water-Cement Ratio ↔ Strength Estimator implementation

A source-bound implementation contract for Water-Cement Ratio ↔ Strength Estimator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-085

**Effect**: Computation or source lookup only

## Input and validation requirements

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.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "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."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/water-cement-ratio-strength-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/water-cement-ratio-strength-estimator/mechanism/>)[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`