A complete guide to identifying, testing, documenting, and resolving non-compliant concrete deliveries and in-place failures
Handling non-compliant concrete correctly in 2026 protects structural integrity, minimises legal exposure, and ensures regulatory compliance. This guide covers how to identify non-compliance at the point of delivery and after placement, the testing and assessment options available, decision-making frameworks, remediation pathways, and the documentation required to manage non-compliant concrete situations from first detection to final resolution.
A systematic approach to identifying, assessing, and resolving non-compliant concrete for contractors, site managers, and quality engineers in 2026
Non-compliant concrete is any concrete that fails to meet one or more of the specified requirements at the point of delivery, during placement, or upon testing of hardened specimens. Non-compliance can be identified at the truck — through incorrect mix design, excess water addition, slump out of range, or load age exceeding 90 minutes — or after placement, when 28-day cylinder or cube test results fall below the specified characteristic compressive strength (f'c or fcu). The consequences range from a simple rejected load to costly in-situ investigation, structural reassessment, demolition, and replacement of hardened concrete elements.
Incorrectly handling non-compliant concrete — whether by accepting a deficient load, failing to document a rejection, or not following a structured assessment process after low strength results — creates serious legal, financial, and structural risks. Under most national building codes and concrete standards (AS 1379, EN 206, ACI 301), the principal contractor and the concrete producer share obligations to supply, test, and accept only conforming concrete. Accepting non-compliant material without documented assessment transfers liability for any future structural deficiency to the contractor. A structured, documented process for handling non-compliant concrete is the essential protection against these risks in 2026.
The management of non-compliant concrete is governed by concrete product standards and construction specifications. Key references include AS 1379 (Specification and supply of concrete — Australia), EN 206 (Concrete — Specification, performance, production, and conformity — Europe/UK), ACI 301 (Specifications for Structural Concrete — USA), and ACI 318 (Building Code Requirements for Structural Concrete). Project-specific specifications — typically referencing one of these standards — define the acceptance criteria, testing frequency, conformity assessment methods, and the procedure to follow when non-conformance is detected. Engineers, contractors, and concrete producers should all be familiar with the applicable standard before works commence in 2026.
Handling non-compliant concrete requires distinguishing between the different types of non-conformance, as each triggers a different response. Pre-placement non-compliance — detected at the truck before or during discharge — is always simpler and less costly to manage than post-placement non-compliance, where the concrete has already been placed and partially or fully hardened. Understanding the type of non-compliance determines the urgency, the testing required, and the remediation options available.
The most financially significant form of non-compliance is a low compressive strength result from 28-day test cylinders or cubes. This is because by the time the result is known, the concrete has been in place for four weeks, formwork has typically been stripped, and subsequent construction may have proceeded on the basis of the element being structurally adequate. The structured response to a low strength result is one of the most important procedures in handling non-compliant concrete, and is described in detail in this guide. For context on how the existing structure should be assessed when in-situ investigation is required, see our guide on assessing existing concrete structures.
When non-compliance is detected — at delivery or through test results — work must stop, the engineer must be notified, and no further construction must proceed on the affected element until a written assessment is completed and a disposition decision is documented.
The first and most straightforward point of intervention in handling non-compliant concrete is at the point of delivery, before the concrete is discharged. Site personnel authorised to accept concrete deliveries must check each delivery docket against the specification and conduct field tests before authorising discharge. A load that fails any acceptance criterion at this stage must be rejected — it is always far simpler and less costly to reject a non-conforming load before placement than to deal with hardened non-compliant concrete in a structure.
Before any concrete is discharged, the delivery docket must be checked for: correct mix design code matching the specification; specified grade (f'c or fcu) and exposure class; correct aggregate size and cement type; batch plant identification and batch number; water-to-cement ratio not exceeding the specified maximum; admixture types and dosages consistent with the approved mix; time of batching; total water added including any water-in-aggregate corrections; and confirmation that no additional water has been added after batching without documented authorisation. Any discrepancy between the docket and the approved mix design is grounds for rejection before field testing even begins.
Concrete that has exceeded its maximum permissible age at the point of discharge must be rejected. Under AS 1379 and most project specifications, the maximum time from water first contacting cement to completion of discharge is 90 minutes in standard conditions, reducing to 60–70 minutes in hot weather (ambient temperature above 30°C or concrete temperature above 35°C). Concrete temperature at discharge must be checked with a calibrated thermometer — maximum concrete temperature at delivery is typically 32°C, with lower limits on hot-weather pours and higher specification elements. Loads exceeding these limits must be returned to the plant without discharge, regardless of the slump reading.
Slump testing (AS 1012.3.1 / ASTM C143 / EN 12350-2) at the point of delivery determines whether workability is within the specified tolerance. Slump must be within ± 20 mm of the target or within the specified range. If slump is below the minimum, the load may have lost workability due to age or temperature — it must be rejected. If slump exceeds the maximum, water or admixture may have been added — check the delivery docket for any post-batch water additions and reject if total w/c ratio exceeds the specified maximum. Never add water to a delivered load to adjust slump without documented engineer approval and verification that the w/c ratio limit will not be exceeded.
Adding water to a delivered concrete load to increase slump is one of the most common and most damaging practices on construction sites in 2026. Every litre of additional water beyond the design w/c ratio reduces compressive strength, increases shrinkage cracking, and compromises durability. Under AS 1379, EN 206, and ACI 301, water addition after batching is only permissible if: the maximum w/c ratio specified will not be exceeded after the addition; the concrete has not been partially discharged; the addition is properly documented on the delivery docket; and the truck drum is rotated at full speed for a minimum of 30 drum revolutions after addition. In practice, authorising water addition on site without these conditions being met voids the conformity of the load and transfers full liability for the resulting concrete quality to the contractor who authorised the addition.
When 28-day compressive strength test results from standard cylinders or cubes fall below the specified characteristic strength (f'c or fcu), a formal non-conformance response process must be initiated immediately. The first step is to not panic and not demolish — low cylinder results do not automatically mean the in-situ concrete is structurally deficient. Standard test cylinders are cured under ideal laboratory conditions and consistently produce lower strengths than well-compacted, properly cured in-situ concrete in a real structure. A structured investigation is always required before any disposition decision is made.
The following procedure applies whenever non-compliance is detected — either at delivery or through test results. It must be implemented immediately, fully documented, and completed before any further construction loads are applied to the affected element.
As soon as non-compliance is detected, notify the structural engineer, project manager, and concrete supplier in writing — email or NCR (Non-Conformance Report) — within 24 hours. Preserve all delivery dockets, batch tickets, field test records, and cylinder/cube test reports for the affected pour. Do not strip formwork, apply loads, or proceed with construction on the affected element until written clearance is received from the engineer.
Raise an NCR referencing the pour date, element location (grid reference, pour strip, slab zone), mix design code, specified strength, actual test result, and the name of the person who identified the non-conformance. The NCR must be logged in the project's quality management system and assigned a unique reference number. All subsequent actions — testing, assessment, disposition decision — must be recorded against the NCR reference number to create a complete audit trail.
Where standard cylinder results are low, the engineer will typically direct that in-situ cores be extracted from the affected element per AS 1012.14 / ASTM C42 / EN 12504-1. A minimum of three cores must be taken from the suspect area, at locations selected by the engineer to be representative of the poured element and avoiding reinforcing bars. Cores must be taken by a NATA-accredited (or equivalent) laboratory and tested in a certified laboratory. Supplementary non-destructive testing — rebound hammer (Schmidt hammer) per AS 1012.21 / ASTM C805, or ultrasonic pulse velocity (UPV) per AS 1012.22 / ASTM C597 — may also be directed as a means of mapping the uniformity and extent of low-strength concrete across the pour area.
The structural engineer reviews the core test results alongside the original cylinder data, the mix design records, the curing history of the element, and any NDT results. They assess whether the in-situ concrete strength is structurally adequate for the design loads. If average core strength is ≥ 0.85 × f'c and no individual core is below 0.75 × f'c, acceptance without structural intervention is typically justified under ACI 318 and AS 1379. If core results remain below these thresholds, a full structural capacity assessment is required — comparing the actual measured strength to the demand from factored design loads at the critical section of the element.
The structural engineer must issue a written disposition — Accept, Conditionally Accept, Remediate, or Reject and Replace — based on the complete test evidence and structural assessment. The disposition must be signed by a registered/chartered structural engineer. "Accept as is" dispositions must document the basis for acceptance, any monitoring requirements, and any restrictions on future loading. "Remediate" dispositions must specify the strengthening method, the performance standard to be achieved, and how compliance will be verified. "Reject and Replace" dispositions trigger a demolition and re-pour sequence, with all costs typically recoverable from the concrete supplier where supplier non-conformance is proven.
Execute the engineer's disposition — whether monitoring, remediation, or demolition and replacement. For remediation works, verify that the strengthening system has achieved its design performance through appropriate testing (pull-off tests for FRP, load testing for structural elements, core testing for concrete overlay). For demolition and replacement, the replacement pour must use a verified mix design, be independently witnessed, and be tested at the required frequency with results reviewed by the engineer before any construction proceeds on the element.
Close the NCR only when: all testing is complete and results are on file; the engineer's written disposition is attached; all remediation or replacement works are complete and verified; the root cause of the non-conformance has been identified and corrective action implemented to prevent recurrence; and the concrete supplier has been formally notified of the non-conformance outcome and any claims for remediation costs have been initiated. The closed NCR package must be retained as part of the permanent project quality records for the design life of the structure.
Where the structural engineer determines that the in-situ concrete does not meet strength requirements but demolition and replacement is disproportionate, several remediation options are available. The selection depends on the structural element type, the magnitude of the strength deficiency, the applied loads, and the acceptable long-term risk profile for the structure.
Fibre reinforced polymer (FRP) wrapping or bonding is the most commonly specified remediation for non-compliant concrete in columns and beams. CFRP or GFRP jacketing of columns increases compressive strength and ductility, compensating for low in-situ concrete strength. FRP flexural strengthening of beams and slabs adds tensile capacity where the reduced concrete strength has lowered the moment capacity below the design demand. FRP remediation requires a project-specific design by a structural engineer and must be installed by a qualified applicator with full quality control documentation.
Where the non-compliant element has excess structural capacity relative to the actual design loads — for example, a slab designed conservatively for a live load that will never be achieved — the engineer may accept the reduced-strength concrete by imposing a formal permanent load restriction. The restriction must be documented in the building's structural records, communicated to the building owner, registered on the building certificate where required, and physically posted on the structure if the load restriction affects operational use of the building or car park in 2026.
Demolition and replacement of the non-compliant element is required when: core test results confirm the in-situ strength is significantly below requirements; the structural assessment shows the element cannot safely carry design loads even with remediation; or the cost of remediation exceeds the cost of replacement. Demolition must be carefully sequenced to maintain structural stability of adjacent elements and must be completed under a separate safe work method statement. All costs are recoverable from the concrete supplier where batching records, batch plant audits, or cylinder retest data confirm that the non-conformance was caused by a supplier error in mix production.
The table below summarises the most common types of non-compliant concrete situations, the tests used to confirm non-compliance, the standard acceptance criteria, and the typical disposition pathway.
| Non-Compliance Type | Detection Point | Test Method | Acceptance Criterion | Typical Disposition |
|---|---|---|---|---|
| Excess slump at delivery | Truck — before discharge | AS 1012.3.1 / ASTM C143 | Within ± 20 mm of target | Reject load — return to plant |
| Load age exceeded | Truck — docket check | Docket review, clock check | ≤ 90 min water–discharge | Reject load — return to plant |
| Wrong mix design supplied | Truck — docket check | Docket vs specification | Exact mix code match | Reject load — new order required |
| Excess concrete temperature | Truck — thermometer | AS 1012.17 / ASTM C1064 | ≤ 32°C at discharge | Reject or hold — retest after cooling |
| Low 7-day cylinder result | Laboratory — 7 days | AS 1012.9 / ASTM C39 | 7-day typically ≥ 70% of f'c | Alert engineer — await 28-day result |
| Low 28-day cylinder result | Laboratory — 28 days | AS 1012.9 / ASTM C39 | Per AS 1379 / ACI 318 / EN 206 | NCR → cores → engineer disposition |
| Core results low (85% rule) | In-situ — cores extracted | AS 1012.14 / ASTM C42 | Avg ≥ 0.85f'c; min ≥ 0.75f'c | Structural assessment → remediation |
| Core results critically low | In-situ — cores extracted | AS 1012.14 / ASTM C42 | Below 0.75f'c individual core | Engineer review → demolish / replace |
| Air content out of range | Truck — pressure meter | AS 1012.4.1 / ASTM C231 | Per specification (typically 4–7%) | Reject if freeze-thaw critical; assess if not |
Every non-conformance event for handling non-compliant concrete must include a root cause analysis to prevent recurrence on the same project and on future projects. Common root causes include: incorrect water additions at the plant (calibration error in water meters or aggregate moisture corrections); wrong mix design selected at batching (human error in entering mix code); cement or SCM supply change not communicated to the site team; poor cylinder making or curing practice on site producing unrepresentative test specimens; delayed delivery due to traffic causing load age non-conformance; and hot weather reducing slump and increasing w/c drift. The corrective action plan must address the specific root cause and be implemented before the next pour of the same element type proceeds.
Effective management of non-conformance records for concrete works requires a structured quality management system (QMS) that logs every NCR, tracks its status from detection through to closure, and retains all supporting documentation permanently. Project QMS requirements are typically specified in the contract documents and may reference AS/NZS ISO 9001, ISO 17025 (laboratory accreditation), or project-specific quality plans. The QMS must be in place before concrete works commence — not established reactively after a non-conformance event. All NCRs and their supporting test records must be included in the project's operation and maintenance (O&M) manual handed to the building owner at practical completion.
Concrete Assessment Guide →All compressive strength testing of concrete cylinders and cores used for conformity assessment and non-conformance investigation in 2026 must be performed by a NATA-accredited laboratory in Australia, a UKAS-accredited laboratory in the UK, or an equivalent nationally accredited facility in other jurisdictions. Non-accredited testing — including on-site cylinder testing by unqualified personnel — is not accepted for conformity assessment under AS 1379, EN 206, or ACI 318. Contractors must confirm laboratory accreditation scope before commencing a project and must use the same accredited laboratory consistently throughout the pour programme to ensure data comparability across the test record.
Air-Entrained Concrete Guide →The supply of concrete that fails to meet specified requirements is a breach of the concrete supply contract and may also constitute a breach of statutory implied warranties under consumer and building legislation. In 2026, concrete suppliers in Australia are subject to the Australian Consumer Law (ACL) guarantees of acceptable quality, fitness for purpose, and compliance with description. Similar protections apply under the Sale of Goods Act (UK) and UCC Article 2 (USA). Contractors who detect non-compliant concrete must formally notify the supplier in writing within the notice periods specified in the supply contract and must not take any action — including demolition — that could be construed as mitigating their loss without first giving the supplier an opportunity to inspect. Legal advice should be sought before any demolition of non-compliant concrete is commenced where supplier liability is being pursued.
Foundation Backfill Guide →