Forensic Chemistry: Cement, Mortar and Concrete XRD Phase Analysis

UGC-NET Forensic Science Unit VII advanced drill covering the forensic characterisation of Portland cement systems by X-ray diffraction (XRD), SEM-EDX, FTIR, and oxide chemistry. Questions test IS 269, IS 1489, IS 12269, and IS 455 composition limits for OPC, PPC, and PSC; the four clinker phases alite (C3S, 50-70%%), belite (C2S, 15-30%%), aluminate (C3A, 5-10%%), and ferrite (C4AF, 5-15%%); hydration products CSH gel (Ca/Si approximately 1.7), portlandite (Ca(OH)2, XRD at 18.0 degrees 2-theta), and ettringite (AFt, XRD at 9.1 degrees 2-theta, FTIR at 1110 cm-1); fly-ash classification (Class C vs Class F per ASTM C618); silica fume specifications (ASTM C1240); GGBS hydraulic activity (IS 12089); and the Bogue calculation versus Rietveld XRD refinement for quantitative phase analysis.

Indian forensic science context runs through every sub-topic. CFSL Chandigarh's trace-evidence section uses the three-peak XRD fingerprint (ettringite 9.1 degrees, portlandite 18.0 degrees, alite 32.2 degrees) to confirm OPC-based mortar in IED pipe-bomb debris. SERC Chennai applies petrographic thin-section analysis and compressive-core testing under IS 456:2000 in structural-failure investigations. Construction fraud patterns -- substandard w/c ratio, cement-poor mixes, oversized aggregate, and adulteration with Class C fly-ash or off-spec GGBS -- are framed against IS 456:2000 Clauses 5.3 and 9, IS 12269:2013 chemical limits, and IS 455:2015 GGBS content limits. The 30-35 degrees 2-theta clinker XRD window (alite 32.2, belite 32.7, C3A 33.2, C4AF 33.8) and free-lime detection at 37.3 degrees 2-theta are tested as forensic evidence thresholds.

Topics covered:

• OPC, PPC, PSC composition limits under IS 269, IS 1489, IS 455, IS 12269
• Clinker phase ranges: C3S (50-70%%), C2S (15-30%%), C3A (5-10%%), C4AF (5-15%%)
• Hydration products: CSH gel (Ca/Si 1.7), portlandite (18.0 degrees 2-theta), ettringite (9.1 degrees 2-theta)
• Fly-ash Class C vs Class F (ASTM C618 SAF thresholds); silica fume (ASTM C1240)
• GGBS composition and IS 12089 hydraulic activity index (80%% at 28 days)
• XRD 2-theta peak map: ettringite 9.1, portlandite 18.0, alite 32.2, belite 32.7, C3A 33.2, C4AF 33.8
• SEM-EDX phase ID (Ca/Si for CSH; Ca+Al+S for ettringite); FTIR ettringite fingerprint (1110, 3300-3450, 870 cm-1)
• IED post-blast, building-collapse, and construction-fraud forensic interpretation

Calibrated for UGC-NET Paper II Unit VII top-decile candidates and NFSU MSc Forensic Chemistry entrance examinees. Allow 30 minutes.