Pavement materials and testing

In short

Pavement materials and testing covers the soil subgrade, aggregates, bitumen and cement that make up a road, and the standard laboratory and field tests that decide whether each is fit for use. Every layer thickness a designer specifies assumes a material of known strength (CBR for subgrade, Marshall stability for bituminous mixes, crushing value for aggregates), so testing is what links design to reality. In India the governing documents are IRC codes, the MoRTH *Specifications for Road and Bridge Works* (Section 500 for bases and bituminous work, Section 900 for quality control tests), IS 73 for paving bitumen and IS 2386/IS 2720 for aggregate and soil tests. It is heavily examined in GATE (Transportation Engineering), state PSC/AE exams and the practical rounds of NHAI, NHIDCL, L&T, Dilip Buildcon, Afcons, GR Infraprojects and highway consultancy interviews, where quality-control questions dominate.

Explained

Subgrade soil and its testing

• Role: the subgrade is the compacted natural soil that finally carries all wheel load spread by the upper layers; its strength fixes total pavement thickness.
• Classification: by IS 1498 (IS soil classification) using grain size and plasticity — GW, GP, SW, SP, ML, CL, MH, CH, OL etc. Good subgrade: well-graded granular; poor: highly plastic clay (CH), expansive black cotton soil, organic soil.
• Index tests (IS 2720): grain-size analysis (sieve + hydrometer), liquid limit, plastic limit, shrinkage limit, plasticity index, specific gravity, free swell index (for expansive soils).
• Compaction — Proctor test (IS 2720 Part 7 light, Part 8 heavy/modified): gives OMC (optimum moisture content) and MDD (maximum dry density). Field compaction is specified as % of MDD — MoRTH requires at least 97% of modified Proctor MDD for embankment top 500 mm and subgrade.
• Field density: sand replacement method (IS 2720 Part 28), core cutter, nuclear density gauge.
• CBR test (IS 2720 Part 16): load a 50 mm plunger into a soaked (4-day) soil specimen at 1.25 mm/min; CBR = (test load / standard load) × 100 at 2.5 mm and 5 mm penetration. The 2.5 mm value normally governs; if the 5 mm value is higher the test is repeated, and if it repeats, the 5 mm value is used.
• Why soaked CBR: IRC 37 design uses the soaked CBR of the top 500 mm of subgrade at 97% MDD, representing the worst (monsoon) condition.
• Other strength tests: plate load test (gives modulus of subgrade reaction k, used for rigid pavement design per IRC 58), resilient modulus (MR, cyclic triaxial — the mechanistic input; IRC 37 permits the correlation MR = 10 × CBR for CBR ≤ 5 and MR = 17.6 × CBR^0.64 for CBR > 5).
• Treatments for weak subgrade: lime stabilisation (clayey soil), cement stabilisation, geotextile/geogrid separation and reinforcement, capping layer, removal and replacement of expansive soil.

Aggregates: properties and tests

• Sources and types: crushed stone (granite, basalt, trap, quartzite, limestone), gravel, slag, and recycled concrete/RAP. Required: hard, tough, durable, angular, clean and preferably hydrophobic (non-acidic) in surface character.
• Strength / toughness:
  • Aggregate crushing value (IS 2386 Part 4): aggregate passing 12.5 mm and retained on 10 mm, in a 150 mm mould loaded to 400 kN in 10 min; ACV = (mass passing 2.36 mm / total mass) × 100. Limits: ≤ 30% for surfacing and bituminous courses, ≤ 45% for non-wearing layers (IS 383); MoRTH fixes limits layer-wise — lower is stronger.
  • Aggregate impact value (IS 2386 Part 4): 15 blows of a 13.5–14 kg hammer falling 380 mm; AIV = % fines passing 2.36 mm. Limits: ≤ 24% for wearing course (bituminous concrete), ≤ 27% for bituminous macadam/base, ≤ 30% for WBM/WMM base, ≤ 40% for granular sub-base and WBM sub-base.
  • Ten percent fines value: load (kN) producing 10% fines — preferred for weak aggregate where ACV > 30.
• Hardness — Los Angeles abrasion (IS 2386 Part 4): aggregate plus steel balls rotated in a drum for 500/1,000 revolutions; abrasion value = % passing 1.70 mm. Limits: ≤ 30% for bituminous concrete wearing course, ≤ 35–40% for base courses, ≤ 40–50% for WBM depending on grading.
• Durability — soundness (IS 2386 Part 5): 5 cycles of sodium or magnesium sulphate; loss ≤ 12% (Na₂SO₄) or 18% (MgSO₄). Used where freeze-thaw or salt attack is expected.
• Shape:
  • Flakiness index: % by weight of particles with thickness < 0.6 × mean size (thickness gauge).
  • Elongation index: % with length > 1.8 × mean size (length gauge).
  • MoRTH limit: combined flakiness and elongation index ≤ 30% for bituminous mixes (flakiness alone ≤ 25% for some layers).
  • Angularity number = 67 − % solid volume (0 for rounded gravel, 0–11 typical for crushed aggregate).
• Water sensitivity:
  • Water absorption (IS 2386 Part 3): ≤ 2% generally for bituminous work.
  • Stripping value / coating and stripping test (IS 6241): retained coating must be more than 95% after 24 h in water at 40 °C. Acidic (siliceous, hydrophilic) aggregates like quartzite strip readily; remedy — antistripping agent, hydrated lime 2% or cement filler.
  • Soundness of fines, clay lumps, deleterious matter: sand equivalent / plasticity of fines; MoRTH limits fines passing 0.075 mm.
• Polishing — Polished Stone Value (PSV): resistance to polishing under traffic; governs skid resistance of the wearing course.
• Specific gravities for mix design: bulk, apparent and effective specific gravity (IS 2386 Part 3) — needed for voids calculations.

Bitumen and modified binders

• What it is: a dark, viscoelastic residue of crude-oil distillation, nearly 100% soluble in carbon disulphide/trichloroethylene; distinct from tar (destructive distillation of coal, now banned for road use because of carcinogenic content).
• Grading in India: IS 73:2013 (and later revisions) uses viscosity grading — VG-10, VG-20, VG-30, VG-40 — replacing the old penetration grades (30/40, 60/70, 80/100). The grade number is the nominal mid-range absolute viscosity at 60 °C in hundreds of poise; the specified minimum is 80 × the grade number (VG-10 ≥ 800, VG-20 ≥ 1,600, VG-30 ≥ 2,400, VG-40 ≥ 3,200 poise).
  • VG-10: spray applications, surface dressing, cold regions. VG-30: the workhorse for paving mixes in most of India. VG-40: heavily trafficked, high-temperature areas, toll plazas, intersections.
• Cutbacks (IS 217 / IS 454): bitumen + volatile solvent — RC (rapid curing, naphtha), MC (medium curing, kerosene), SC (slow curing, diesel/oil). For priming and cold-weather work.
• Emulsions (IS 8887): bitumen droplets in water with an emulsifier — RS, MS, SS (rapid/medium/slow setting), cationic grades are standard in India. Used for tack coat, prime coat, fog seal, cold mix, pothole repair in wet weather.
• Modified binders:
  • PMB (polymer modified bitumen, IS 15462): elastomeric SBS (PMB-E) or plastomeric EVA/PE (PMB-P) — penetration-based grades PMB 40, PMB 70 and PMB 120 in IS 15462:2004, with performance-graded designations in later revisions; improves rutting and fatigue resistance, widens the service temperature range.
  • CRMB (crumb rubber modified bitumen): waste tyre rubber; grades CRMB 50, 55, 60.
  • NRMB (natural rubber modified). Waste plastic coated on aggregate (dry process) is permitted and promoted by IRC SP 98.
• Standard bitumen tests:
  1. Penetration (IS 1203): depth in 0.1 mm that a standard needle (100 g, 5 s, 25 °C) penetrates. Measures consistency; now a secondary requirement under viscosity grading.
  2. Ductility (IS 1208): length in cm to which a briquette stretches before breaking at 27 °C, 50 mm/min. Minimum 40–75 cm depending on grade; measures the binder's ability to stretch without cracking.
  3. Softening point — ring and ball (IS 1205): temperature at which the sample softens enough to let a steel ball fall 25 mm; typically 40–60 °C (VG-30 ≥ 47 °C). Indicates susceptibility to high temperature.
  4. Viscosity (IS 1206): absolute viscosity at 60 °C in poise (capillary viscometer) and kinematic viscosity at 135 °C in centistokes — the basis of VG grading.
  5. Flash and fire point (IS 1209, Pensky-Martens): flash point ≥ 220 °C for VG grades — a safety test.
  6. Specific gravity (IS 1202): about 0.97–1.02; used to convert mass to volume and in voids calculations.
  7. Solubility in trichloroethylene (IS 1216): ≥ 99% — a purity test.
  8. Loss on heating / thin film oven (TFOT, IS 9382) and rolling thin film oven (RTFOT, ASTM D2872): simulates hardening during mixing; retained penetration and viscosity ratio are specified.
  9. Float test, Fraass breaking point, elastic recovery (for PMB), separation test for modified binders.
• Superpave/performance grading (PG grades, AASHTO M320) is used on some NHAI projects and research work; IRC has introduced performance-related binder specifications, but VG grading remains the standard Indian practice.

Bituminous mixes and Marshall mix design

• Mix types (MoRTH Section 500):
  • BC (bituminous concrete): dense wearing course — Grading 1 (19 mm nominal maximum size, 40–50 mm layer) or Grading 2 (13.2 mm, 30–45 mm); minimum binder about 5.2–5.4%.
  • DBM (dense bituminous macadam): base/binder course — Grading 1 (37.5 mm nominal maximum size) or Grading 2 (26.5 mm); minimum binder about 4.0–4.5%.
  • BM (bituminous macadam), SDBC (semi-dense BC), mastic asphalt (very high binder, for bridge decks and junctions), open-graded premix carpet (OGPC) with seal coat, surface dressing, slurry seal, micro-surfacing, SMA (stone matrix asphalt) with fibre, porous/gap-graded mixes.
• Gradation concepts: well-graded (dense) mixes have low air voids and high strength; open-graded mixes drain water but need a seal coat; gap-graded SMA relies on stone-on-stone contact.
• Marshall method (ASTM D6927, formerly D1559 / AASHTO T245, adopted by MoRTH):
  1. Prepare 1,200 g batches at 5 binder contents (0.5% increments) to the specified grading.
  2. Compact in 101.6 mm × 63.5 mm moulds, 75 blows per face for heavy traffic (50 for medium).
  3. Measure bulk density (Gmb), theoretical maximum density (Gmm, ASTM D2041 / Rice test).
  4. Compute Va (air voids), VMA (voids in mineral aggregate), VFB/VFA (voids filled with bitumen).
  5. Test at 60 °C in the Marshall apparatus at 50.8 mm/min: stability (max load, kN) and flow (deformation at max load, in 0.25 mm units).
  6. Plot stability, flow, density, Va, VMA, VFB against binder content; optimum binder content (OBC) is typically the average of the binder contents giving max stability, max density and 4% air voids — then checked against all criteria.
• MoRTH/Marshall criteria (VG-30, 75 blows): stability ≥ 9 kN, flow 2–4 mm (8–16 units), air voids 3–5%, VFB 65–75%, VMA depends on nominal maximum aggregate size (e.g. ≥ 14% for 13.2 mm, ≥ 13% for 19 mm, ≥ 12% for 26.5 mm), dust-to-bitumen ratio 0.6–1.2.
• Other design/performance tests: retained stability after 24 h at 60 °C (≥ 75%), tensile strength ratio (TSR) ≥ 80% for moisture damage, indirect tensile strength, wheel-tracking rut test, resilient modulus, Hveem and Superpave volumetric (gyratory) methods.
• Hot-mix temperatures: mixing about 150–165 °C and rolling above about 90 °C for VG-30; higher for modified binders. Over-heating ages the binder, under-heating causes poor coating and compaction.

Cement concrete pavement materials

• Concrete: PQC (pavement quality concrete) normally M40 with minimum cement content 360 kg/m³ and maximum free w/c about 0.45 (IRC 15, IRC 44, MoRTH Section 600); designed on flexural strength — characteristic 28-day flexural strength 4.5 MPa for PQC.
• DLC (dry lean concrete) sub-base: aggregate-cement mix with low water, minimum cement 150 kg/m³, 7-day compressive strength ≥ 10 MPa, compacted by roller.
• Tests: cube compressive strength (IS 516), flexural strength by beam test (modulus of rupture, 150 × 150 × 700 mm beams), split tensile, slump/compaction factor, modulus of elasticity, cement tests per IS 4031 (fineness, setting time, soundness, strength).
• Relation used in design: flexural strength ≈ 0.7√fck (MPa), per IS 456/IRC 58.
• Cement-treated layers: cement-treated sub-base/base (CTSB/CTB) with 7-day UCS typically 1.5–3.0 MPa (CTSB) and 4.5–7.0 MPa (CTB) as per MoRTH; fly-ash, lime-flyash and RAP-cement bases are now standard options.

Field tests, quality control and distress-related testing

• Compaction and thickness control: field density (sand replacement, nuclear gauge), core cutting of bituminous layers for thickness and density (≥ 98% of Marshall/laboratory density for BC and DBM), level checks.
• Binder content and gradation of a laid mix: extraction by centrifuge/reflux (IS 1201–1220 series, ASTM D2172) and ignition oven; gradation of the recovered aggregate.
• Surface characteristics:
  • Roughness by bump integrator or laser profilometer, reported as IRI (m/km); MoRTH typically requires about 2.0 m/km or better for new NH bituminous surfaces (project-specific).
  • Skid resistance by portable pendulum skid tester (skid number) and sand-patch texture depth.
  • Camber and cross-fall by straight edge and camber board; undulations by 3 m straight edge (≤ 3 mm for BC under MoRTH tolerance).
• Structural evaluation:
  • Benkelman beam deflection (IRC 81): rebound deflection under a dual-wheel 8.17 t axle at 5.6 kg/cm² tyre pressure, corrected for temperature and seasonal variation; characteristic deflection = mean + 1 (or 2) × standard deviation decides overlay thickness.
  • FWD (falling weight deflectometer): impulse load, back-calculates layer moduli — the modern input to IRC 37 and IRC 115 overlay design.
  • GPR for layer thickness, pavement condition survey for cracking, ravelling, rutting, potholes, PCI/distress index.
• Quality assurance framework: MoRTH Section 900 fixes test frequency (for example, one Marshall/density check per 400 t or per day's production for bituminous mixes, aggregate tests per source change) and acceptance criteria; the contractor keeps a field laboratory, the Authority Engineer/Independent Engineer audits it.
• Common field reasons materials fail: segregation during laying, moisture in aggregate, tack coat missing, cold joints, rolling started too late, dust-coated aggregate.

Key points

• Soaked CBR - the strength index of the top 500 mm subgrade at 97% MDD; the direct input to IRC 37 flexible pavement design.
• Proctor test - gives OMC and MDD; field compaction specified as a percentage of modified Proctor MDD.
• Aggregate impact value - toughness; ≤ 24% for wearing course, ≤ 27% base, ≤ 30% WBM/WMM base, ≤ 40% granular sub-base (IS 2386 Part 4).
• Aggregate crushing value - resistance to crushing under gradual load; ≤ 30% for surfacing; ten percent fines value is used for weaker aggregate.
• Los Angeles abrasion - hardness/wear resistance (IS 2386 Part 4); ≤ 30% for BC wearing course, up to 40–50% for lower layers.
• Flakiness + elongation index - combined ≤ 30% for bituminous mixes; flaky particles break under the roller and cause segregation.
• Stripping value test (IS 6241) - retained coating > 95%; acidic aggregates need lime or an antistripping agent.
• Viscosity grading (IS 73) - VG-10/20/30/40 by absolute viscosity at 60 °C; VG-30 for general paving, VG-40 for heavy traffic and hot climates.
• Penetration test - consistency in units of 0.1 mm at 25 °C, 100 g, 5 s; softer bitumen gives a higher penetration.
• Softening point - ring-and-ball temperature for a 25 mm ball drop; higher means better resistance to high-temperature rutting.
• Ductility - stretch in cm at 27 °C; indicates flexibility and resistance to low-temperature cracking.
• Flash point ≥ 220 °C - the safety limit for VG bitumen, by Pensky-Martens closed cup.
• Marshall stability and flow - at 60 °C; MoRTH requires stability ≥ 9 kN and flow 2–4 mm for dense mixes with VG-30.
• Volumetrics - Va 3–5%, VMA by aggregate size, VFB 65–75%; OBC is picked where all criteria are met near 4% air voids.
• PMB and CRMB - polymer and crumb-rubber modified binders (IS 15462) for rutting-prone, heavy-traffic or extreme-temperature sites.
• PQC flexural strength 4.5 MPa - the design strength for concrete pavements (IRC 15/IRC 58); DLC sub-base needs 7-day strength ≥ 10 MPa.
• Benkelman beam / FWD - field deflection measurement used to assess a pavement's residual strength and design an overlay (IRC 81, IRC 115).
• MoRTH Section 900 - the quality-control chapter prescribing test frequency and acceptance; Section 500 gives material specifications.

Formulas and examples

Example 1 — CBR of a subgrade soil. A soaked CBR test gives loads of 62 kg at 2.5 mm and 95 kg at 5.0 mm penetration.

• CBR at 2.5 mm = 62/1,370 × 100 = 4.53%
• CBR at 5.0 mm = 95/2,055 × 100 = 4.62%
• The 5 mm value is higher, so the test is repeated; if it repeats, the design CBR is 4.6% (say 4.5%).
• Design input: MR = 10 × 4.5 = 45 MPa (CBR ≤ 5 correlation of IRC 37). A CBR below 5% usually means the subgrade needs a capping layer or stabilisation.

Example 2 — Aggregate impact value. Oven-dry sample W₁ = 350.0 g; after 15 blows the fraction passing 2.36 mm weighs 71.4 g.

• AIV = 71.4/350.0 × 100 = 20.4%
• 20.4% < 24%, so the aggregate is acceptable for a bituminous concrete wearing course (and for all lower layers).

Example 3 — Marshall volumetrics. A BC specimen has Gmb = 2.385, Gmm = 2.496, binder content Pb = 5.2% by total mass of mix, aggregate bulk specific gravity Gsb = 2.680.

• Ps = 100 − 5.2 = 94.8%
• Va = 100 × (2.496 − 2.385)/2.496 = 100 × 0.111/2.496 = 4.45%
• VMA = 100 − (2.385 × 94.8/2.680) = 100 − (226.098/2.680) = 100 − 84.37 = 15.63%
• VFB = 100 × (15.63 − 4.45)/15.63 = 100 × 11.18/15.63 = 71.5%
• Check: Va 4.45% is inside 3–5%; VFB 71.5% is inside 65–75%; VMA 15.6% exceeds the 14% minimum for 13.2 mm nominal size. The mix satisfies MoRTH volumetric criteria; stability must still be ≥ 9 kN and flow 2–4 mm.

Example 4 — Binder quantity and cost for a BC layer. A 1 km single carriageway, 7.0 m wide, gets a 40 mm BC layer at 5.2% binder by mass of mix; compacted mix density 2.385 t/m³; VG-30 at ₹52,000 per tonne.

• Volume = 1,000 × 7.0 × 0.040 = 280 m³
• Mix mass = 280 × 2.385 = 667.8 t
• Binder = 0.052 × 667.8 = 34.7 t; aggregate (incl. filler) = 667.8 − 34.7 = 633.1 t
• Binder cost = 34.7 × 52,000 ≈ ₹18.05 lakh (rate indicative; use the current schedule of rates).

Example 5 — Blending two aggregates to a target grading. Aggregate A (coarse) has 20% passing 4.75 mm; Aggregate B (fine) has 90% passing 4.75 mm. Target = 50% passing 4.75 mm.

• Let x = fraction of A: 20x + 90(1 − x) = 50 → 90 − 70x = 50 → x = 40/70 = 0.571
• Proportion = 57.1% Aggregate A and 42.9% Aggregate B (then verify every other sieve against the specification band).

Where it is used

• Highway construction contractors (L&T, Afcons, Dilip Buildcon, GR Infraprojects, PNC, Ashoka Buildcon): site laboratories running CBR, Proctor, Marshall, core density and gradation checks daily under MoRTH Section 900.
• NHAI / NHIDCL / state PWD and Authority Engineer roles: acceptance testing, approval of mix designs and job-mix formula, material source approval, measurement of IRI and deflection for handover and toll-eligibility.
• Hot-mix plant and quality-control engineers: controlling bitumen temperature, binder dosing, filler and dust-to-bitumen ratio, calibrating plant against the approved job-mix formula.
• Refineries and binder suppliers (IOCL, BPCL, HPCL, Tiki Tar, Hincol): VG-grade production, emulsions and PMB/CRMB manufacture and certification to IS 73, IS 8887 and IS 15462.
• Consultancy and research: pavement evaluation and overlay design with Benkelman beam/FWD (IRC 81, IRC 115), CRRI and IIT pavement labs, recycled-material research (RAP, waste plastic roads under IRC SP 98, cold mix for PMGSY).
• Rural and urban roads: PMGSY uses CBR-based IRC SP 72 design with WBM/WMM and cold-mix surfacing; municipal corporations rely on mastic asphalt and micro-surfacing for city roads and junctions.

Interview questions

• Q: Why is CBR measured on a soaked sample? A: To represent the weakest condition the subgrade will see — after monsoon saturation — so the pavement is not under-designed for the critical season.
• Q: Why did India shift from penetration grading to viscosity grading of bitumen? A: Penetration is measured only at 25 °C and two binders with the same penetration can behave very differently when hot; viscosity at 60 °C and 135 °C relates directly to in-service pavement temperature and to mixing workability.
• Q: What does Marshall stability represent, and why is the test done at 60 °C? A: It is the maximum load a compacted specimen resists, a measure of resistance to deformation; 60 °C approximates the hottest pavement temperature, when rutting is most likely.
• Q: How do you choose optimum binder content? A: Average the binder contents giving maximum stability, maximum bulk density and 4% air voids, then verify that the mix at that content satisfies all limits on stability, flow, Va, VMA and VFB.
• Q: What is stripping and how is it prevented? A: Loss of the bitumen film from aggregate in the presence of water, typical of acidic/hydrophilic aggregate; prevented with antistripping agents, 2% hydrated lime or cement filler, and by using well-drained, dry aggregate.
• Q: Difference between flakiness index and elongation index? A: Flakiness compares thickness to the mean sieve size (thickness < 0.6 × mean), elongation compares length (length > 1.8 × mean); both describe shape but flaky particles break under rolling while elongated particles cause poor interlock.
• Q: Which test would you use for a weak aggregate where the crushing value exceeds 30%? A: The ten percent fines value test, because the crushing value becomes insensitive and unreliable for weak aggregate.
• Q: Why is a tack coat applied and how is its adequacy checked? A: To bond a new bituminous layer to the existing surface; adequacy is checked by the specified rate of spread (measured by tray test) and uniform coverage without pooling.
• Q: What does the softening point tell a designer in an Indian context? A: The higher the softening point, the better the binder resists bleeding and rutting in summer — which is why VG-40 or modified binders are specified for hot regions, toll plazas and climbing lanes.
• Q: How is the field density of a laid bituminous layer verified? A: By cutting cores and comparing their bulk density with the laboratory Marshall density — normally a minimum of 98% — and also measuring layer thickness from the same cores.
• Q: What is the difference between DLC and PQC? A: DLC is a dry lean concrete sub-base with low cement content, roller-compacted, judged by 7-day compressive strength; PQC is the structural pavement slab, normally M40, designed on 28-day flexural strength of 4.5 MPa.
• Q: Why is the Benkelman beam being replaced by the FWD? A: The beam gives only one surface deflection under a slow-moving truck load; the FWD applies a controlled impulse and records a deflection basin, allowing back-calculation of individual layer moduli for mechanistic overlay design.

Common mistakes

• Using the unsoaked CBR, or the CBR at only 2.5 mm, without checking whether the 5 mm value is higher and repeating the test.
• Confusing aggregate crushing value (gradual 400 kN load) with impact value (15 hammer blows) and quoting the wrong IS limit.
• Treating VG numbers as penetration numbers — VG-30 is not 60/70 by definition; the grades overlap but are defined differently.
• Picking optimum binder content from the stability curve alone and ignoring VMA, VFB and air-void limits, which produces bleeding or rut-prone mixes.
• Mixing up Gmb and Gmm, or using apparent instead of bulk specific gravity of aggregate in VMA, which throws volumetrics off by several per cent.
• Reporting Marshall flow in millimetres when the specification is in 0.25 mm units (or the reverse) — 8–16 units equals 2–4 mm.
• Quoting old codes or guessing current MoRTH limits; specifications are revised (MoRTH Specifications, IS 73, IRC 37, IRC 58 have all been updated), so the layer-wise limit must be read from the edition in force on the project.

Related topics

Highway engineering and pavement design · Highway construction and maintenance · Soil mechanics and foundation engineering · Concrete technology and mix design · Building materials and construction · Traffic engineering