Bituminous Materials and Geosynthetics

Introduction

Bituminous materials and geosynthetics are central to the performance, sustainability and constructability of modern pavement, transportation, hydraulic and geotechnical infrastructure. Bitumen provides waterproofing, adhesion and viscoelastic load transfer, while geosynthetics modify soil–water–structure interaction through separation, filtration, drainage, reinforcement and containment.

At postgraduate level, material selection must move beyond description. It requires relating material properties to climate, traffic, stress state, drainage conditions, construction methods, durability and life-cycle risk. This chapter develops that approach for asphalt binders, asphalt mixtures, ageing, modified bitumen, recycling and geosynthetic systems.

Learning Objectives

After completing this chapter, the learner should be able to:

1. Explain the rheological and chemical behaviour of paving bitumen.

2. Evaluate asphalt binders using empirical, rheological and performance-related properties.

3. Analyse mixture volumetrics, stability, durability and moisture susceptibility.

4. Explain short-term and long-term ageing and select mitigation strategies.

5. Compare polymer-modified, rubber-modified and chemically modified binders.

6. Assess recycling options and calculate basic recycled-mixture quantities.

7. Select geotextiles, geogrids, geomembranes and geocomposites for their governing functions.

8. Apply quantitative criteria for filtration, drainage, reinforcement and containment.

9. Integrate material choice with construction quality, sustainability and life-cycle performance.

1. Bitumen as an Engineering Material

Bitumen is a complex hydrocarbon binder containing asphaltenes, resins, aromatic fractions and saturates. Its behaviour is temperature- and time-dependent. At high temperature or slow loading it may flow; at low temperature or rapid loading it behaves more elastically and may crack.

Important terminology includes:

• Penetration: depth, in tenths of a millimetre, penetrated by a standard needle under specified load, time and temperature.
• Softening point: temperature at which a standardized bitumen specimen reaches a specified deformation.
• Ductility: extension before rupture under prescribed conditions.
• Viscosity: resistance to flow; it strongly influences mixing, pumping and compaction.
• Complex modulus, Ga: ratio of stress-amplitude to strain-amplitude under sinusoidal loading.
• Phase angle, a: lag between stress and strain; low values indicate more elastic response.
• Performance grade: classification based on high- and low-temperature performance and climate.

Penetration and softening point are useful quality-control indices, but they do not fully describe behaviour under actual traffic loading. Rheological testing, particularly dynamic shear rheometry, provides a more mechanistic basis for selection.

For oscillatory loading within the linear viscoelastic range,

G* = a/a,

where G* is complex modulus, a is stress amplitude and a is strain amplitude. The storage and loss components are

G' = G cos a, G'' = G sin a,

where a is phase angle. These relationships apply only when the specimen response is approximately linear and sinusoidal testing is controlled adequately.

A high-temperature rutting parameter commonly used in binder evaluation is G/sina. A larger value indicates greater resistance to traffic-induced shear deformation under the relevant test conditions. For fatigue-related assessment, G sina has historically been used, although modern specifications increasingly employ tests that better represent damage evolution. No single binder parameter predicts complete pavement performance.

2. Asphalt Mixture Constituents and Volumetrics

An asphalt mixture consists of coarse aggregate, fine aggregate, mineral filler, bituminous binder and, sometimes, fibres or additives. Aggregate provides load-bearing structure; binder provides cohesion and waterproofing; air voids permit thermal and traffic-related movement but excessive voids accelerate oxidation and water ingress.

The principal volumetric quantities are:

• Air voids, Va: volume of air divided by total compacted mixture volume.
• Voids in mineral aggregate, VMA: intergranular void space between aggregate particles in the compacted mixture, including effective binder volume and air voids.
• Voids filled with asphalt, VFA: percentage of VMA occupied by effective asphalt.

Using percentages by volume, a general relationship is

VMA = Va + VFA-volume occupied by effective binder.

For a mixture containing aggregate mass fraction Ps, compacted bulk specific gravity Gmb and aggregate bulk specific gravity Gsb, the commonly used expression is

VMA = 100[1 − (Gmb Ps/Gsb)].

Here Ps is the aggregate mass fraction expressed as a decimal, and Gmb and Gsb are dimensionless specific gravities measured on compatible bases. The equation assumes that the mixture bulk volume and aggregate bulk volume are represented consistently; it should not be used by substituting binder fraction for aggregate fraction.

The air-void content is

Va = 100(1 − Gmb/Gmm),

where Gmm is the maximum theoretical specific gravity of the loose, air-free mixture. Effective binder volume is then represented through VMA − Va. VFA is

VFA = 100(VMA − Va)/VMA,

provided VMA is expressed as a percentage and VMA is greater than zero.

Worked volumetric example

A compacted mixture has Gmb = 2.35, Gmm = 2.48, aggregate fraction Ps = 0.94 and Gsb = 2.65.

Air voids:

Va = 100(1 − 2.35/2.48) = 100(1 − 0.94758) = 5.24%.

VMA:

VMA = 100[1 − (2.35 × 0.94/2.65)]

= 100[1 − 2.209/2.65]

= 100(1 − 0.83358)

= 16.64%.

Thus the effective asphalt-filled portion of VMA is 16.64 − 5.24 = 11.40 percentage points, and

VFA = 100(11.40/16.64) = 68.5%.

The values are internally consistent: VMA exceeds air voids, and VFA lies between 0 and 100%.

Mixture design must balance stability, durability and workability. Excessively low binder content or low VMA may cause inadequate coating and fatigue cracking. Excessive binder, low air voids or weak aggregate structure may cause bleeding and rutting. Design criteria must be interpreted with traffic, climate, compaction level and aggregate type rather than applied mechanically.

3. Asphalt Mixture Performance

Rutting

Rutting results from densification, shear flow, or instability in the aggregate–binder system. It is controlled by aggregate angularity, gradation, interlock, binder stiffness at service temperature, compaction and construction quality. Heavy slow-moving traffic is especially critical because longer loading duration permits viscoplastic deformation.

Fatigue cracking

Fatigue cracking develops under repeated tensile strain, especially at the bottom of bound layers. It depends on strain magnitude, binder ageing, mixture stiffness, healing, temperature and pavement support. A very stiff mixture may resist rutting but become fatigue-sensitive, illustrating the need for balanced design.

Thermal cracking

Cooling generates contraction. If tensile stress exceeds the mixture’s low-temperature strength, transverse cracking occurs. Binder low-temperature stiffness and relaxation capacity are important selection variables.

Moisture damage

Water may weaken the binder–aggregate bond or promote pore-pressure effects. Evaluation includes tensile strength ratio, conditioned/unconditioned strength comparison, water sensitivity testing and field drainage assessment. Anti-stripping agents, hydrated lime, improved aggregate cleanliness, adequate compaction and drainage can reduce risk.

4. Ageing of Bituminous Materials

Ageing occurs in two principal stages:

1. Short-term ageing: oxidation and volatile loss during mixing, transport and placement.

2. Long-term ageing: continued oxidation and physical hardening during service.

Oxidation increases polarity and molecular association, commonly increasing stiffness and reducing ductility. Physical hardening arises from molecular rearrangement at low temperature and may increase thermal-cracking susceptibility without equivalent chemical oxidation.

Ageing is affected by temperature, oxygen availability, film thickness, ultraviolet exposure, binder chemistry, air voids and permeability. Laboratory simulations use controlled procedures such as rolling thin-film or pressure-ageing methods, but these are approximations rather than exact predictions of field life.

Ageing control includes appropriate binder grade, adequate but not excessive mixing temperature, rapid placement, effective compaction, dense yet stable mixture design, antioxidants where justified, and preventive maintenance. Recycling agents can restore workability and moderate stiffness, but excessive rejuvenation may reduce rutting resistance.

5. Modified Bitumen

Modification is used when conventional binders cannot meet the combined demands of climate, traffic and construction. Common modifiers include:

• Elastomeric polymers, such as styrene–butadiene–styrene, which improve elastic recovery and rut resistance.
• Plastomeric polymers, such as polyethylene or ethylene-based materials, which increase stiffness but may reduce low-temperature flexibility if poorly selected.
• Crumb rubber, which can improve elasticity, crack resistance and resource recovery, with performance depending on rubber size, digestion time and dosage.
• Sulphur and reactive chemicals, which alter viscosity, compatibility or cross-linking.
• Fibres and nanomaterials, which can modify reinforcement, drainage within the mastic, ageing or interfacial behaviour.

Compatibility, storage stability, blending temperature and shear history are essential. A binder that performs well in a laboratory test may segregate in storage or fail during pumping. Selection should therefore include storage-stability testing, viscosity limits, elastic recovery, rheology over the design temperature range and plant-process compatibility.

6. Pavement Recycling

Recycling reduces virgin aggregate and binder demand, conserves landfill capacity and may reduce embodied emissions. The main approaches are:

• Hot central-plant recycling: reclaimed asphalt pavement (RAP) is processed and heated with virgin materials.
• Warm-mix recycling: additives or process changes lower production temperature.
• Cold in-place recycling: existing pavement is milled, mixed with emulsion or foamed bitumen and compacted on site.
• Full-depth reclamation: pavement and part of the underlying material are pulverized and stabilized.
• Reclaimed asphalt shingles and other approved sources: used only after characterization and specification compliance.

RAP binder is usually aged and stiff. Its contribution depends on RAP content, gradation, fractionation, blending efficiency and virgin binder selection. A simple mass balance for total binder is

P_b,total = P_b,virgin + P_b,RAP,

where each term is expressed as a mass percentage of total mixture. If RAP content is r by total mixture mass and RAP binder content is p_R by mass of RAP, then

P_b,RAP = r p_R.

For example, with 25% RAP and 5.2% binder in RAP, the RAP contributes 0.25 × 0.052 = 0.013, or 1.30% of total mixture mass. If the target total binder content is 5.40%, virgin binder required, before accounting for blending or losses, is 5.40 − 1.30 = 4.10% of total mixture mass. This is a mass balance, not a direct prediction of effective binder performance. Binder grade adjustment, blending assumptions and laboratory verification remain necessary.

Risks include variable RAP properties, incomplete blending, excessive stiffness, contaminants, plant segregation and uncertainty in long-term cracking. Best practice includes stockpile separation, representative sampling, ignition or extraction testing, fractionation for high RAP contents, balanced mixture design and production monitoring.

7. Geosynthetic Functions and Material Families

Geosynthetics are polymeric products placed in contact with soil, aggregate, water or waste. Their function—not merely product name—should govern selection.

Geotextiles

Geotextiles are woven or nonwoven fabrics. Wovens generally provide high tensile strength and controlled openings; nonwovens commonly provide greater thickness, filtration capacity and puncture resistance. Functions include separation, filtration, drainage and limited reinforcement.

Geogrids

Geogrids are apertured polymer structures designed primarily for tensile reinforcement and aggregate interlock. Their performance depends on junction strength, rib stiffness, aperture geometry, installation damage resistance and strain compatibility with the soil or aggregate.

Geomembranes

Geomembranes are low-permeability sheets used for containment. Important properties include thickness, tensile and tear resistance, puncture resistance, seam strength, chemical compatibility, stress-crack resistance and permeability. A geomembrane is a barrier, not automatically a drainage layer.

Geocomposites

Geocomposites combine materials, such as a drainage core with geotextile filters or a geomembrane with a protective geotextile. They can reduce construction thickness and integrate several functions, but interfaces, clogging, seam details and installation damage must be checked.

8. Quantitative Selection of Geotextiles

Separation

For separation beneath an aggregate layer, the geotextile must withstand installation stresses and prevent intermixing. Selection should consider subgrade strength, aggregate size, drop height, trafficking during construction and puncture resistance. A product with high tensile strength but inadequate puncture resistance may fail during placement.

Filtration

A filter must retain critical soil particles while allowing water flow. A simplified retention check compares the geotextile apparent opening size, AOS, with a representative soil particle size such as D85:

AOS ≤ C D85,

where C is selected according to soil gradation, density, hydraulic gradient and design standard. Values often used in preliminary design range approximately from 0.5 to 1.0, but the governing specification and soil conditions must control.

Hydraulic compatibility also requires adequate normal permeability:

k_g ≥ F k_s,

where k_g is geotextile permeability normal to the plane, k_s is soil permeability and F is a safety factor accounting for clogging, compression and uncertainty. This is a screening relationship, not a substitute for gradient-ratio or full filtration testing.

A geotextile may retain particles initially but clog under sustained flow. Design must therefore consider critical hydraulic gradient, soil dispersivity, constriction size, confinement and long-term biological or chemical clogging.

Drainage

For in-plane drainage, transmissivity is

a = q/(iW),

where q is flow rate through a specimen, i is hydraulic gradient, and W is specimen width. Units are typically m²/s. The required transmissivity should exceed design discharge capacity after applying reduction factors for compression, creep, intrusion and clogging:

a_design ≥ q_required/(iW) × RF_total.

For example, if a drainage strip must carry q_required = 2.0 × 10⁻⁶ m³/s per metre width at i = 0.10, the ideal required transmissivity is 2.0 × 10⁻⁵ m²/s. With a total reduction factor of 3, the tested product should provide at least 6.0 × 10⁻⁵ m²/s under the relevant normal stress and boundary conditions. The calculation assumes q is expressed per metre width and that the tested transmissivity is measured under representative confinement.

Reinforcement

Geogrid selection requires compatibility between mobilized tensile strain and available tensile resistance. A simplified external stability or allowable tensile check is

T_allow = T_char/(RF_ID RF_DUR RF_ENV RF_C),

where T_char is characteristic tensile strength and the reduction factors account respectively for installation damage, durability, environmental effects and construction or creep uncertainty. The factors must come from testing, standards or defensible project-specific evidence; they should not be invented arbitrarily.

Reinforcement is effective only when aggregate can develop sufficient interlock and the geogrid is placed at the correct elevation. A high-strength grid placed where tensile strain is negligible may provide little benefit. Design should assess bearing-capacity improvement, lateral restraint, trafficking, rut depth, interface friction and long-term creep.

Containment

Geomembrane containment design requires low permeability, chemical compatibility and reliable seams. Leakage is governed not only by membrane permeability but also by defects, wrinkles, penetrations and drainage conditions. A leak-detection drainage layer beneath the membrane can reduce hydraulic head and facilitate monitoring. Protection layers must be designed against puncture from subgrade, aggregate, equipment and differential settlement.

For liquids, Darcy’s law may estimate flow through a porous drainage layer:

Q = k i A,

where Q is discharge, k hydraulic conductivity, i hydraulic gradient and A cross-sectional flow area. This equation applies to saturated porous flow under conditions where Darcy behaviour is valid; it does not describe leakage through a geomembrane defect without a suitable defect-flow model.

9. Integrated Design and Quality Assurance

Material selection should follow a performance-based sequence:

1. Define climate, traffic, loading duration, subgrade, groundwater and design life.

2. Identify the governing distress or geotechnical function.

3. Establish measurable performance criteria.

4. Select candidate materials and test them under representative temperature, stress, confinement and chemistry.

5. Check constructability, availability, compatibility and installation damage.

6. Apply reduction factors and uncertainty management.

7. Verify field quality through sampling, inspection and acceptance testing.

8. Monitor performance and revise maintenance decisions using life-cycle evidence.

Quality assurance should cover binder certificates, storage temperature, mixing temperature, aggregate moisture, gradation, density, joint construction, geosynthetic identification, seam testing, overlap dimensions and protection before covering. Traceability is particularly important for high-consequence containment systems.

10. Illustrative Case Study: Reinforced Road over Weak Subgrade

Background

An access road is required across saturated silty clay with low undrained strength. Seasonal wetting causes pumping and aggregate intrusion. Heavy construction traffic must use the route before final surfacing.

Problem

A conventional aggregate layer is expected to rut during construction and become contaminated by subgrade fines. The design team must select a system providing separation, filtration, drainage and reinforcement without confusing these functions.

Analysis

A nonwoven geotextile is considered for separation and filtration. Laboratory soil testing indicates D85 = 0.18 mm and k_s = 2 × 10⁻⁷ m/s. Using a preliminary retention coefficient C = 0.8 gives:

AOS ≤ 0.8 × 0.18 = 0.144 mm.

If the selected geotextile has AOS = 0.12 mm, it passes this preliminary retention check. If its normal permeability is 3 × 10⁻⁶ m/s, then k_g/k_s = 15, indicating hydraulic capacity greater than the soil under the simplified screening criterion. Clogging and gradient-ratio testing would still be required.

A geogrid is placed above the geotextile within the lower aggregate layer. Its purpose is aggregate interlock and lateral restraint, not filtration. The geogrid is selected using junction strength, aperture size compatible with aggregate grading, installation-damage resistance and allowable tensile capacity after reduction factors.

A geocomposite edge drain is added to intercept infiltrated water. Its transmissivity is checked under the expected overburden stress, not solely from an unconstrained catalogue value. The pavement surface uses a suitably graded and ageing-resistant asphalt mixture; construction density is controlled because low density would accelerate oxidation and water ingress.

Outcome

The combined system reduces soil contamination, maintains drainage and improves construction trafficking. It does not eliminate the need for subgrade improvement or surface drainage. Performance depends on correct placement, overlap, aggregate thickness, outlet maintenance and protection from construction damage.

Learning Points

The case demonstrates that geotextile, geogrid and geocomposite functions are complementary but not interchangeable. Quantitative screening must be followed by testing under project conditions. The least expensive product is not necessarily the least-cost solution when maintenance and failure consequences are included.

11. Limitations, Sustainability and Emerging Practice

Laboratory binder tests cannot reproduce every field ageing, healing and damage mechanism. Mixture volumetrics depend on accurate specific-gravity measurements and representative sampling. Geosynthetic catalogues may report idealized properties that do not include installation damage, creep or confinement.

Environmental assessment should include virgin material extraction, transport, production energy, polymer manufacture, recycling, maintenance and end-of-life. Recycling is beneficial only when material quality, plant energy, transport distance and service life are considered together. Polymer modification may improve durability but increases material complexity and can complicate recycling.

Digital image analysis, automated mixture compaction, machine-learning prediction of binder rheology and sensor-based pavement monitoring are emerging tools. Artificial intelligence should support—not replace—mechanistic understanding, calibrated data, laboratory verification and engineering accountability. Models must be checked for bias arising from limited climates, materials or traffic conditions.

Chapter Summary

Bitumen is a temperature- and time-dependent viscoelastic binder whose selection must reflect climate, traffic and ageing. Asphalt mixture performance depends on aggregate structure, binder properties, volumetrics, moisture resistance, compaction and construction quality. The corrected volumetric relationship is VMA = 100[1 − (GmbPs/Gsb)], with compatible specific-gravity and mass-fraction definitions.

Ageing increases stiffness and may reduce cracking resistance. Polymer, rubber and chemical modification can improve performance but require compatibility and process control. Recycling conserves resources, yet aged RAP binder must be accounted for through mass balance, grade selection and verification rather than assumed complete blending.

Geosynthetic selection is function-based. Geotextiles provide separation and filtration; geogrids primarily reinforce; geomembranes contain; and geocomposites integrate functions. Quantitative design requires opening-size retention, permeability, transmissivity, tensile reduction factors, puncture resistance, chemical compatibility and installation-damage assessment. Successful systems combine material testing, construction quality assurance, drainage design and life-cycle decision-making.

Key Terms

Bitumen: Hydrocarbon binder used in asphalt and waterproofing applications.

Viscoelasticity: Behaviour combining recoverable elastic response and time-dependent viscous response.

Complex modulus: Magnitude of the dynamic stress-to-strain relationship.

Phase angle: Lag between applied stress and resulting strain.

Performance grade: Binder classification based on temperature-related performance requirements.

Rutting: Permanent pavement deformation in wheel paths.

Fatigue cracking: Cracking caused by repeated cyclic tensile stress or strain.

Air voids: Volume of air within compacted asphalt mixture.

VMA: Voids in mineral aggregate, including air and effective binder volume.

VFA: Percentage of VMA occupied by effective asphalt.

Ageing: Chemical and physical change that generally stiffens bituminous materials.

RAP: Reclaimed asphalt pavement used in new mixtures.

Geotextile: Planar polymeric textile used for separation, filtration, drainage or reinforcement.

Geogrid: Apertured polymeric grid used mainly for tensile reinforcement and interlock.

Geomembrane: Low-permeability polymer sheet used for containment.

Geocomposite: Product combining two or more geosynthetic components.

AOS: Apparent opening size of a geotextile.

Transmissivity: In-plane flow capacity per unit hydraulic gradient and width.

Reduction factor: Factor accounting for deterioration or uncertainty in geosynthetic design.

Review Questions

Short Answer Questions

1. Distinguish penetration grading from performance grading of bitumen.

2. Define VMA, air voids and VFA.

3. Explain the difference between short-term and long-term ageing.

4. State two functions of a geotextile and one function of a geogrid.

5. Why must geomembrane seams be tested separately from the membrane sheet?

Long Answer Questions

1. Explain how binder rheology, aggregate structure and compaction collectively influence rutting and fatigue.

2. Discuss the mechanisms of bitumen ageing and the effectiveness and limitations of ageing-control measures.

3. Compare hot recycling, cold in-place recycling and full-depth reclamation.

4. Develop a performance-based procedure for selecting a geotextile filter beneath a drainage layer.

5. Explain the design and quality-assurance requirements of a geomembrane containment system.

Analytical / Application Questions

1. A mixture has Gmb = 2.40, Gmm = 2.52, Ps = 0.935 and Gsb = 2.67. Calculate Va and VMA, then interpret whether the results are internally plausible.

2. A drainage geocomposite must carry 1.5 × 10⁻⁶ m³/s per metre width at hydraulic gradient 0.08. If the total reduction factor is 2.5, calculate the minimum tested transmissivity required.

3. A pavement uses 30% RAP by total mixture mass, with RAP binder content 5.0% and target total binder content 5.6%. Calculate the nominal virgin-binder contribution by mass balance and identify two reasons why the final design cannot rely on this calculation alone.

Multiple Choice Questions with Answers

Question 1

A compacted asphalt mixture has Gmb = 2.35, Gmm = 2.48, Ps = 0.94 and Gsb = 2.65. What are its approximate air voids and VMA?

A. 5.24% and 16.64%

B. 5.24% and 14.87%

C. 4.76% and 16.64%

D. 16.64% and 5.24%

Correct Answer: A. 5.24% and 16.64%

Question 2

A drainage geocomposite must carry 2.0 × 10⁻⁶ m³/s per metre width at i = 0.10. With a total reduction factor of 3, what minimum tested transmissivity is required?

A. 2.0 × 10⁻⁵ m²/s

B. 6.0 × 10⁻⁵ m²/s

C. 6.0 × 10⁻⁶ m²/s

D. 1.5 × 10⁻⁴ m²/s

Correct Answer: B. 6.0 × 10⁻⁵ m²/s

Question 3

For a soil with D85 = 0.18 mm and preliminary C = 0.8, which geotextile AOS satisfies the simplified retention criterion?

A. 0.12 mm

B. 0.18 mm

C. 0.20 mm

D. 0.30 mm

Correct Answer: A. 0.12 mm

Question 4

Which condition most directly increases the risk of rutting in a heavily trafficked asphalt pavement?

A. High aggregate angularity and strong interlock

B. Low-temperature, rapid loading only

C. Weak aggregate structure combined with high service-temperature loading

D. High low-temperature relaxation capacity

Correct Answer: C. Weak aggregate structure combined with high service-temperature loading

Question 5

A mixture contains 25% RAP by total mass and RAP binder content is 5.2%. What is the nominal contribution of RAP binder to total mixture mass?

A. 0.52%

B. 1.30%

C. 5.20%

D. 20.8%

Correct Answer: B. 1.30%

Question 6

Which selection best matches geosynthetic function with product?

A. Geogrid—primary containment barrier

B. Geomembrane—primary tensile aggregate interlock

C. Geotextile—separation and filtration

D. Geocomposite—always a substitute for all drainage design checks

Correct Answer: C. Geotextile—separation and filtration

Question 7

Why may a high-strength geogrid provide little pavement benefit when placed at an unsuitable elevation?

A. Strength is irrelevant to polymer products

B. Reinforcement requires tensile strain and aggregate interaction to mobilize resistance

C. Geogrids function only as filters

D. Geogrids cannot be used with aggregate

Correct Answer: B. Reinforcement requires tensile strain and aggregate interaction to mobilize resistance

Question 8

Which statement most accurately describes RAP binder design?

A. RAP binder can always be ignored because it is inactive

B. A mass balance alone completely predicts blended-binder performance

C. RAP binder contribution must be estimated, but blending, ageing and grade adjustment require verification

D. Higher RAP content always improves fatigue resistance

Correct Answer: C. RAP binder contribution must be estimated, but blending, ageing and grade adjustment require verification

Question 9

For Darcy flow through a saturated porous drainage layer, which variables are required in Q = kiA?

A. Binder penetration, phase angle and air voids

B. Hydraulic conductivity, hydraulic gradient and flow area

C. Tensile strength, AOS and seam strength

D. RAP content, VMA and VFA

Correct Answer: B. Hydraulic conductivity, hydraulic gradient and flow area

Question 10

Which quality-assurance action is most important before covering a geomembrane containment system?

A. Relying only on the manufacturer’s brochure

B. Testing and documenting seams, defects, protection and penetrations

C. Increasing asphalt binder penetration

D. Removing all drainage layers beneath the membrane

Correct Answer: B. Testing and documenting seams, defects, protection and penetrations