Pavement Construction, Specifications and Quality Management

Introduction and context

Pavement performance depends not only on structural design but also on the quality and consistency of construction. A theoretically adequate pavement may fail prematurely if materials are contaminated, moisture is uncontrolled, layers are placed at incorrect thickness, compaction is inadequate, joints are poorly formed, or acceptance decisions are based on unreliable tests. Construction quality is therefore an engineering control system linking design assumptions, production processes, field operations, measurement, risk management and contractual decisions.

This chapter examines the production, transport, placement, compaction, paving, curing and joint construction of flexible and rigid pavements. It also explains method specifications, performance specifications, statistical quality assurance, acceptance testing and construction risk control. The emphasis is on decision-making: selecting controls that reduce variability, identifying defects before they become concealed, and using reliable evidence to determine whether completed work satisfies the contract and is likely to perform adequately.

Learning objectives

After studying this chapter, the reader should be able to:

1. Plan the production, transport and placement of pavement materials.

2. Select appropriate construction and compaction procedures for soils, granular layers, asphalt mixtures and concrete.

3. Explain curing and joint-construction requirements for concrete pavements.

4. Distinguish method, end-result and performance specifications.

5. Develop a quality-control and quality-assurance framework using sampling and statistical concepts.

6. Interpret acceptance test results and manage nonconforming work.

7. Identify construction risks and establish practical preventive and corrective controls.

8. Evaluate the application of digital technologies and AI in pavement quality management.

1. Construction as a controlled production system

Pavement construction can be represented as a sequence of linked operations:

inputs → production → transport → placement → compaction or consolidation → curing or cooling → testing → acceptance → maintenance of records.

Inputs include aggregates, binders, water, cementitious materials, admixtures, geosynthetics, equipment and labour. Variability at any stage can affect the final pavement. For example, aggregate gradation may change at the plant, asphalt mixture may cool during transport, or concrete may lose workability before placement. Quality management must therefore control both the final product and the processes that create it.

A useful distinction is between quality control (QC) and quality assurance (QA). QC consists of operational activities performed by the contractor to control production and construction. QA consists of independent or owner-led activities used to verify that the contractor’s system and the completed work comply with requirements. Modern contracts often combine contractor QC, agency verification testing and statistical acceptance.

Quality should be considered in four dimensions:

• Conformance: compliance with specified limits.
• Uniformity: control of variation within and between lots.
• Durability: resistance to deterioration under traffic and environment.
• Constructability: ability to achieve the required result under site conditions.

A construction plan should identify inspection points before work begins. These may include approval of material sources, calibration of plant, trial sections, pre-paving meetings, first-load inspections, density checks, joint inspections and final surface surveys.

2. Material production and handling

2.1 Earthworks and subgrade

Subgrade preparation begins with clearing, removal of unsuitable material, drainage control and treatment of weak zones. The exposed formation should be proof-rolled, where appropriate, using a designated vehicle or roller. Excessive deflection, pumping or rutting indicates inadequate support, high moisture, organic material or insufficient compaction. Such areas should not simply be covered; they require undercutting, stabilization, drainage improvement or other approved treatment.

Soil compaction is governed principally by moisture content, soil type, compactive effort and lift thickness. Laboratory moisture–density testing provides a reference relationship, but field conditions may differ because of soil variability and equipment. A commonly used relative compaction measure is:

\[

R_c=\frac{\gamma_{d,field}}{\gamma_{d,max,reference}}\times100\%

\]

where \(\gamma_{d,field}\) is the field dry unit weight and \(\gamma_{d,max,reference}\) is the maximum dry unit weight from the specified laboratory procedure. The relationship is applicable only when the field and reference tests use compatible soil, procedures and units. It does not by itself prove adequate stiffness, drainage or uniformity.

Water should be added or removed uniformly. Mixing, windrow management and timely compaction are essential. The compacted layer should be protected from trafficking and precipitation until the next operation.

2.2 Aggregate production

Aggregates should be obtained from approved sources and processed to achieve the specified gradation, cleanliness, particle shape, strength and durability. Key controls include:

• separate stockpiles for different sizes and sources;
• firm, well-drained stockpile platforms;
• controlled loading to prevent segregation;
• regular gradation and cleanliness testing;
• protection from contamination by soil, vegetation or debris; and
• reconciliation of production quantities with material test results.

Segregation is a major risk. Coarse particles may roll to the base or edges of a stockpile, while fine material may accumulate elsewhere. Stockpiles should be built in controlled layers rather than by dropping material from excessive heights. Loader operation should avoid digging into the stockpile base.

For granular base and subbase, moisture content and gradation must be controlled before placement. Material that is too dry may not compact; material that is too wet may rut or pump. Blending at the plant is generally more reliable than trying to correct large gradation deficiencies in the field.

2.3 Asphalt mixture production

Asphalt mixture production requires control of aggregate moisture, heating, gradation, binder content, mixing time and discharge temperature. The job-mix formula or approved mix design establishes target proportions, but plant operation must maintain them within specified tolerances.

Important plant controls include aggregate cold-feed calibration, screen inspection, hot-bin balance, binder-meter calibration, storage temperature and production-rate matching. Excessive heating can age the binder and damage the mixture; insufficient heating can prevent coating and compaction. Warm-mix technologies may reduce production temperatures, but their use requires validated plant and field procedures.

Mixture should be stored only under conditions that preserve temperature and prevent drain-down, segregation or contamination. The plant output should be coordinated with paving speed so that trucks do not queue for excessive periods or force the paver to stop.

2.4 Concrete production

Pavement concrete requires control of cementitious materials, aggregate moisture, water–cementitious materials ratio, air content where specified, temperature, admixtures and mixing uniformity. Aggregate moisture corrections are essential because uncorrected surface water changes the effective water content. The water–cementitious materials ratio is commonly expressed as:

\[

w/cm=\frac{m_w}{m_{cm}}

\]

where \(m_w\) is the mass of mixing water and \(m_{cm}\) is the mass of cementitious material. The ratio is meaningful only when the water definition and cementitious-material definition are consistent with the governing specification. Lower values generally improve strength and permeability resistance, but excessively low values may impair workability unless mixture design and consolidation are suitable.

Concrete delivery should be organized to maintain a continuous placing operation. Delays can produce cold joints, uncontrolled finishing and differential set. Site addition of water should be prohibited unless expressly permitted and documented because it may increase the effective water–cementitious materials ratio and reduce durability.

3. Transport, placement and compaction

3.1 Transport planning

Transport is a production-control problem, not merely a logistics activity. Planning should match haul capacity with plant output, paving speed, haul distance, traffic conditions and weather. The plan should specify loading sequence, truck cleanliness, covering requirements, maximum delivery time or temperature loss, communication arrangements and emergency procedures.

For asphalt, truck bodies should be clean and treated only with approved release agents. Loads should be covered when required to reduce heat loss and contamination. For concrete, delivery tickets should record batch time, quantities, admixtures and arrival time. Rehandling should be minimized because it can cause segregation.

3.2 Placement of soil and granular layers

Material should be spread in controlled loose lifts. The compacted thickness must be compatible with the material and equipment; excessively thick lifts may have a dense surface but weak interior. The surface should be shaped to line, level, crossfall and drainage requirements before final compaction.

Compaction normally proceeds from the edges toward the centre on crowned sections, with suitable overlap and a defined rolling pattern. The actual number of passes should be established through a trial section or documented construction experience, then adjusted for moisture, temperature and material changes. Rolling should not cause crushing, shoving or cracking. Vibratory equipment must be operated at an appropriate frequency, amplitude and speed.

3.3 Asphalt paving

Before paving, the underlying surface must be clean, dry where required, stable and properly primed or tack-coated. The tack coat provides bond between layers; inadequate or uneven tack coat can cause slippage and delamination.

The paver should operate at a steady speed with consistent head of material. Frequent stopping creates transverse temperature and density variation. Material should be transferred without segregation, and the screed should be adjusted carefully rather than continually manipulated. Temperature measurements should represent the mixture being placed, not only the truck surface.

Compaction occurs in a planned sequence, commonly including breakdown, intermediate and finish rolling. The allowable time window is governed by mixture temperature, weather, layer thickness and binder characteristics. Rolling must achieve density before the mixture cools below its workable range. Excessive rolling can induce cracking, aggregate breakage or surface distortion.

Joints require special attention. A longitudinal joint should be located, where feasible, away from wheel paths and constructed with adequate overlap, trimming or joint-heating procedures. A transverse joint should be formed with a straight vertical face or other approved geometry. The joint area should be checked for density, alignment, smoothness and bonding.

3.4 Concrete paving

Concrete pavement may be placed by fixed-form or slip-form methods. Before placement, forms, dowels, tie bars, reinforcement, subbase condition and drainage details should be inspected. Dowel alignment is particularly important because misalignment can restrain slab movement and contribute to joint distress.

Concrete should be deposited close to its final position and consolidated without excessive vibration. Over-vibration may cause segregation, while inadequate vibration leaves voids and weak zones. Surface finishing should be limited to operations necessary to achieve the specified profile and texture; adding water to the surface or excessive working of bleed water is unacceptable.

The final texture must provide skid resistance without damaging the surface. Texturing equipment, timing and direction should be compatible with the concrete’s setting characteristics and the required noise and friction performance.

4. Curing and joint construction in concrete pavements

Curing maintains conditions that permit cement hydration and reduce moisture loss and thermal stress. It may involve membrane-forming compounds, wet coverings, plastic sheeting, internal curing or combinations approved for the project. The curing method must be applied at the correct time, at the specified rate and uniformly across the surface and edges.

Curing compound coverage should be verified by application records, visual inspection and, where required, coverage tests. Damage to the curing film must be repaired. Early traffic or construction loading should be prevented until the specified strength, maturity or time requirement is satisfied.

Joints accommodate shrinkage, thermal movement and construction constraints. Principal types include:

• Transverse contraction joints, which control the location of cracking.
• Longitudinal joints, which divide lanes or control longitudinal cracking.
• Expansion or isolation joints, used selectively to separate pavement from fixed structures.
• Construction joints, formed when placement stops or proceeds in stages.

Joint layout should be coordinated with slab dimensions, lane geometry, drainage structures and load-transfer systems. Saw-cut timing is a balance: cutting too early can cause raveling, while cutting too late can allow uncontrolled cracking. Joint width, depth, sealant reservoir, cleanliness and sealant installation must comply with the project specification. Sealant should not be installed in wet, dirty or improperly prepared joints.

5. Specification systems

5.1 Method specifications

A method specification prescribes how the contractor must perform the work. It may state equipment type, lift thickness, rolling pattern, mixing temperature, sequence and number of passes. Method specifications are useful where agency experience is strong, risks are high, or the relationship between process and performance is well established.

Their limitations are reduced contractor flexibility and the possibility that prescribed methods do not suit unusual materials or weather. They may also encourage compliance with procedure rather than achievement of durable performance.

5.2 End-result specifications

An end-result specification defines measurable properties of completed work, such as density, thickness, smoothness, strength, air voids, permeability or ride quality. The contractor selects the means of achieving them. This approach promotes innovation but requires reliable tests, clear sampling procedures and competent technical management.

5.3 Performance-related specifications

A performance-related specification links acceptance characteristics to predicted service performance. It may incorporate factors such as material properties, smoothness, layer thickness, density, rut resistance and environmental durability. Payment or acceptance may use a quality-level model rather than a simple pass/fail limit.

Performance specifications are powerful but demanding. They require validated prediction models, representative tests, accurate measurement and a clear treatment of uncertainty. A measured property should not be included merely because it is easy to test; it should have a demonstrated relationship with pavement performance.

5.4 Selecting a specification

A suitable specification depends on project complexity, agency capability, test reliability, contractor expertise, innovation objectives and consequences of failure. Hybrid specifications are common: they prescribe critical methods, require trial sections and also impose end-result limits. Regardless of type, the contract should define lots, sampling locations, test methods, tolerances, retesting rules, corrective work, payment adjustments and dispute procedures.

6. Quality assurance and statistical acceptance

6.1 Lots, samples and tests

A lot is a defined quantity of work treated as a unit for acceptance. It should be sufficiently homogeneous with respect to material, production process, location and time. Samples should be selected using a documented random or systematic-random procedure. Convenience sampling is dangerous because it can overrepresent accessible or visibly good areas.

The sample mean is:

\[

\bar{x}=\frac{1}{n}\sum_{i=1}^{n}x_i

\]

and the sample standard deviation is:

\[

s=\sqrt{\frac{\sum_{i=1}^{n}(x_i-\bar{x})^2}{n-1}}

\]

where \(x_i\) is an observation and \(n\) is the number of observations. The denominator \(n-1\) is used when estimating population variability from a sample. These statistics describe observed data; they do not automatically prove that the entire lot meets a specification.

For a characteristic with a lower specification limit \(L\), a simple estimated quality index is:

\[

Q_L=\frac{\bar{x}-L}{s}

\]

For an upper limit \(U\):

\[

Q_U=\frac{U-\bar{x}}{s}

\]

These indices are useful only under assumptions of appropriate sampling, meaningful measurements and reasonably stable process behaviour. Contract acceptance should follow the specified statistical procedure, which may use confidence limits, percent-within-limits, risk-based acceptance or pay factors.

6.2 Process control versus acceptance

Process-control tests are frequent and timely; they help the contractor adjust operations. Acceptance tests are used to decide whether completed work complies with the contract. Using one test for both purposes may create conflicts, particularly when rapid decisions are needed but formal acceptance requires independent verification.

Control charts can identify changes in mean or variability. A point outside a control limit is not automatically a specification failure, and a point within the limits does not guarantee conformance. Control charts should be interpreted with engineering knowledge, production events and measurement-system information.

6.3 Measurement-system quality

Before relying on test results, the agency should verify calibration, operator competence, sample handling, equipment maintenance and laboratory precision. Duplicate samples, split-sample comparisons and proficiency testing can identify systematic differences between laboratories. A highly precise but biased test remains unsuitable for acceptance.

6.4 Nonconforming work

When results fail to meet requirements, the response should be structured:

1. Confirm sample identification, test method and calculations.

2. Determine whether the failure is isolated or represents a broader lot.

3. Stop or contain the affected operation where necessary.

4. Investigate causes such as plant settings, moisture, temperature, segregation or equipment malfunction.

5. Conduct authorized additional testing or engineering evaluation.

6. Decide on removal, repair, acceptance with reduced payment, or acceptance without penalty only where justified.

7. Document the decision and preventive action.

Retesting must not become a means of selectively replacing unfavorable results. The contract should define when retesting is permissible and how results are combined.

7. Construction risk control

A pavement risk register should identify the event, cause, consequence, likelihood, severity, existing controls, responsible person, trigger and contingency. Typical risks include:

• unexpected weak subgrade;
• rain during earthwork or paving;
• asphalt cooling below compaction temperature;
• concrete setting before finishing;
• plant breakdown or supply interruption;
• aggregate segregation;
• incorrect joint or dowel alignment;
• contaminated materials;
• inaccurate test results;
• traffic intrusion into the work zone; and
• environmental or community impacts.

Risk control should follow the hierarchy of elimination, substitution, engineering control, administrative control and personal protective equipment. For example, preventing public access through physical separation is more reliable than relying only on warning signs. Construction safety is inseparable from quality: unsafe hurried operations often produce defective work.

Hold points should be established before irreversible work, including covering weak subgrade, placing asphalt over a questionable tack coat, encasing reinforcement, or opening a new concrete slab to traffic. Contingency planning should specify who can stop work and how defective or weather-affected material will be isolated.

8. Digital technologies and AI

Modern projects increasingly use intelligent compaction systems, infrared asphalt-temperature mapping, automated density gauges, machine-control grading, drone surveys, digital delivery tickets and geographic information systems. These tools improve spatial coverage and provide traceability, but they do not eliminate engineering judgment.

AI and machine learning can support anomaly detection, prediction of asphalt cooling, identification of segregation from thermal images, and forecasting of pavement smoothness or density. However, deployment requires representative training data, validation against accepted tests, control of sensor drift and transparent decision rules. AI output should be treated as decision support unless the contract and regulatory framework explicitly recognize it as an acceptance method. Data governance must address ownership, privacy, cybersecurity, auditability and responsibility for incorrect recommendations.

9. Illustrative case: quality management on an urban asphalt project

Background

An urban arterial was being reconstructed with a granular base, asphalt binder course and dense-graded wearing course. The project had night-time paving restrictions, a long haul route and a requirement for smoothness and high joint density.

Problem

Early testing showed acceptable average density but substantial variation near the longitudinal joint. Several trucks also arrived at low temperatures after traffic congestion. The contractor proposed increasing roller passes, but this caused surface displacement in some areas.

Analysis

The project team mapped density and temperature by station rather than relying only on lot averages. The data showed that low density coincided with cold loads and paver stoppages. Joint locations also had lower density because the adjacent lane was not adequately supported during rolling. Increasing passes after cooling was ineffective and distorted the surface.

Approach and solution

The team introduced a thermal-compaction plan. Truck dispatch was synchronized with paving speed, loads were covered, and a contingency diversion route was established. The paver was operated at a more uniform speed. A joint-specific procedure was adopted, including correct overlap, edge support and early joint rolling. Infrared scanning identified cold areas for immediate attention, while acceptance remained based on the contract’s approved density tests. A short trial section verified the revised procedure before production resumed.

Outcome

Temperature variation decreased, paver stops were reduced and joint density became comparable with interior density. The project avoided widespread removal and maintained the required smoothness. The outcome resulted from controlling the process rather than merely increasing end-of-process testing.

Learning points

1. Lot averages can conceal spatially concentrated defects.

2. Temperature and time are critical variables in asphalt compaction.

3. More compaction is not always better; compaction must occur within the workable range.

4. Digital mapping is valuable when linked to timely corrective action.

5. Acceptance testing and process control should remain conceptually distinct.

10. Best-practice framework

A robust pavement construction quality system should:

• convert design assumptions into inspectable construction requirements;
• approve sources, materials, mix designs and equipment before production;
• use trial sections to establish workable procedures;
• define lots, sampling plans and test responsibilities in advance;
• control moisture, temperature, thickness, density and surface geometry;
• protect completed work from traffic and weather;
• use independent verification and calibrated measurement systems;
• record material traceability from source to location;
• apply statistical methods without ignoring engineering context;
• investigate trends before they become specification failures;
• document nonconformance and corrective action transparently; and
• review quality data after construction to improve future specifications.

Ethically, engineers must report unfavorable results, avoid selective sampling, disclose conflicts of interest and protect public safety even when contractual or schedule pressures are strong. Regulatory requirements concerning worker safety, environmental protection, emissions, noise, waste and traffic management must be integrated into the construction plan rather than treated as separate paperwork.

Chapter Summary

Pavement construction is a controlled production system in which material quality, logistics, placement, compaction, curing, joint construction and verification are interdependent. Subgrade and aggregate operations require control of moisture, gradation, segregation and layer thickness. Asphalt quality depends strongly on temperature, continuous paving, tack coat, joint treatment and timely compaction. Concrete quality depends on mixture control, delivery, consolidation, finishing, curing and accurately constructed joints.

Method specifications prescribe procedures, end-result specifications focus on measurable completed properties, and performance-related specifications connect measured characteristics with expected service behaviour. Quality control is contractor-led process management, whereas quality assurance includes verification and acceptance. Statistical acceptance requires properly defined lots, representative sampling, reliable tests and explicit treatment of uncertainty. Risk registers, hold points, contingency plans and transparent nonconformance procedures help prevent defects and protect the public. Digital and AI tools can improve monitoring, but they require validation, governance and accountable engineering judgment.

Key Terms

Quality control: Operational activities used to control production and construction.

Quality assurance: Independent or owner-led activities used to verify quality and compliance.

Method specification: Requirement that prescribes how work must be performed.

End-result specification: Requirement based on measurable properties of completed work.

Performance-related specification: Requirement linking measured characteristics to expected pavement performance.

Lot: Defined quantity of relatively homogeneous work evaluated as a unit.

Acceptance testing: Testing used to decide whether work satisfies contractual requirements.

Relative compaction: Field dry unit weight expressed as a percentage of a specified reference value.

Segregation: Separation of components such as coarse and fine aggregate within a material.

Tack coat: Bituminous application used to bond asphalt layers.

Trial section: Initial controlled construction area used to verify methods and settings.

Curing: Treatment that maintains conditions for concrete hydration and strength development.

Contraction joint: Concrete pavement joint intended to control the location of shrinkage cracking.

Construction joint: Joint formed where concrete placement stops or proceeds in stages.

Quality characteristic: Measurable property used for control or acceptance.

Specification limit: Contractual upper or lower boundary for a quality characteristic.

Control chart: Statistical display used to identify process changes or unusual variation.

Nonconforming work: Work that does not satisfy a specified requirement.

Hold point: Stage at which work must stop until an authorized inspection or decision occurs.

Risk register: Structured record of construction risks, controls, responsibilities and responses.

Review Questions

Short Answer Questions

1. Distinguish quality control from quality assurance in pavement construction.

2. Why is segregation a significant risk in aggregate and asphalt operations?

3. State the purpose of a tack coat.

4. What is the function of curing in concrete pavement construction?

5. Why should acceptance lots be relatively homogeneous?

Long Answer Questions

1. Explain the complete quality-management sequence for an asphalt pavement project from material production to acceptance.

2. Compare method, end-result and performance-related specifications, including their advantages and limitations.

3. Discuss the factors governing compaction of soil, granular material and asphalt mixtures.

4. Explain concrete pavement joint types, curing requirements and common construction risks.

5. Describe how statistical quality assurance and independent verification should be integrated into a pavement contract.

Analytical / Application Questions

1. An asphalt lot has a lower density limit of 94%, a sample mean of 95.5% and a sample standard deviation of 0.8 percentage points. Calculate the lower quality index \(Q_L\) and explain what additional information is required before making a contractual acceptance decision.

2. A concrete paving operation experiences repeated delays because trucks arrive in batches, causing cold joints. Develop a risk-control plan addressing production, transport, placement and emergency response.

3. Field mapping shows that average asphalt density meets the specification, but low-density readings cluster at longitudinal joints. Analyse possible causes and propose a verification and corrective-action programme.

Multiple Choice Questions with Answers

Question 1

Which activity is primarily a quality-control activity?

A. Independent verification of the contractor’s test results

B. Adjusting plant settings to correct aggregate gradation

C. Final contractual acceptance by the owner

D. Audit of the quality-management system by an external agency

Correct Answer: B. Adjusting plant settings to correct aggregate gradation

Question 2

What is the principal purpose of a tack coat?

A. To reduce aggregate moisture in the base

B. To increase concrete air content

C. To bond adjacent asphalt layers

D. To replace compaction of the asphalt layer

Correct Answer: C. To bond adjacent asphalt layers

Question 3

A field dry unit weight is 1.92 Mg/m³ and the specified reference maximum dry unit weight is 2.00 Mg/m³. What is the relative compaction?

A. 92%

B. 94%

C. 96%

D. 98%

Correct Answer: C. 96%

Question 4

Which specification primarily prescribes the construction procedure?

A. Method specification

B. End-result specification

C. Performance-related specification

D. Warranty specification

Correct Answer: A. Method specification

Question 5

Why should asphalt paving proceed at a steady paver speed?

A. To eliminate the need for a tack coat

B. To reduce temperature and density variation caused by stoppages

C. To prevent all aggregate crushing during production

D. To ensure that concrete reaches design strength sooner

Correct Answer: B. To reduce temperature and density variation caused by stoppages

Question 6

Which action best represents representative acceptance sampling?

A. Testing only locations selected by visual inspection

B. Testing only the first truck of each day

C. Selecting locations using a documented random or systematic-random procedure

D. Replacing all low results with additional tests

Correct Answer: C. Selecting locations using a documented random or systematic-random procedure

Question 7

What is a major risk of cutting a concrete contraction joint too late?

A. Uncontrolled cracking may occur before the joint is formed

B. The cement becomes completely inert

C. The slab becomes permanently waterproof

D. Dowel bars automatically lose alignment

Correct Answer: A. Uncontrolled cracking may occur before the joint is formed

Question 8

For a lower specification limit L, which expression defines the simple lower quality index?

A. (L − x̄)/s

B. (x̄ − L)/s

C. s/(x̄ − L)

D. x̄/(L − s)

Correct Answer: B. (x̄ − L)/s

Question 9

Which is an appropriate response to a suspected nonconforming pavement lot?

A. Ignore the result if the project schedule is tight

B. Select only favourable replacement samples

C. Confirm the test and investigate whether the problem is isolated or systematic

D. Open the pavement to traffic immediately

Correct Answer: C. Confirm the test and investigate whether the problem is isolated or systematic

Question 10

What is the most appropriate role of AI-based thermal mapping in pavement construction?

A. It automatically replaces all contractual acceptance tests

B. It provides decision support after validation against accepted measurements

C. It eliminates the need for calibrated sensors

D. It guarantees performance regardless of construction defects

Correct Answer: B. It provides decision support after validation against accepted measurements