Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources8 documents: Pilkington North America, National Ready Mixed Concrete Association, Federal Highway Administration, Oak Ridge National Laboratory, USDA Forest Products Laboratory, National Institute of Standards and Technology
Concrete
Normal-weight portland cement concrete, strength class f'c = 4000 psi (28 MPa) per NRMCA CIP 35; density NRMCA CIP 36; thermal conductivity USDA FPL Wood Handbook; service temperature ORNL/NRC review
Glass
Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025)
1
Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)Pilkington North Americaarchived copyGlass · Ultimate tensile strength: typical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probabilityGlass · Flexural strength: mean MOR (same value as tensile)Glass · Young's modulus (stiffness): typicalGlass · Density: typicalGlass · Poisson's ratio: typicalGlass · Thermal conductivity: typical at 75 FGlass · Thermal expansion: typical, 75-575 FGlass · Specific heat: typical at 75 FGlass · Max service temperature: strain point (ASTM C336) - stress-relaxation onset, not a rated service limit
2
CIP 35: Testing Compressive Strength of ConcreteNational Ready Mixed Concrete Associationarchived copyConcrete · Compressive strength: specified compressive strength class (f'c), not a measured typical
CIP 36: Structural Lightweight ConcreteNational Ready Mixed Concrete Associationarchived copyConcrete · Density: range for normalweight concrete
5
The Effect of Elevated Temperature on Concrete Materials and Structures: A Literature Review (ORNL/TM-2005/553)Oak Ridge National Laboratoryarchived copyConcrete · Poisson's ratio: general range at normal ambient conditions (overall 0.11-0.32)Concrete · Max service temperature: code long-term temperature limit (ASME Code, concrete containments)
Thermal Coefficient of Portland Cement ConcreteFederal Highway AdministrationConcrete · Thermal expansion: typical range for portland cement concrete (aggregate dependent)
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Best Practice Guidelines for Structural Fire Resistance Design of Concrete and Steel Buildings (TN 1681)National Institute of Standards and Technologyarchived copyConcrete · Specific heat: typical (NIST guidance for thermal analysis)
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Which is lighter, Concrete or Glass?
Concrete is lighter: 2,320 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Concrete or Glass?
Glass is stiffer: Young's modulus 72 GPa against 25.1 GPa for Concrete, so the same part in Glass deflects less under the same load.
Which is lighter for the same job, Concrete or Glass?
For the same stiffness or strength: Glass is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate.
Part that must be
Concrete
Glass
Stiff rod or tie (tension)
2.66x heavier
lighter
Stiff beam (bending)
1.57x heavier
lighter
Stiff panel or plate
32% heavier
lighter
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Thermal
Which conducts heat better, Concrete or Glass?
Glass conducts heat better: 0.937 W/m·K against 0.9 W/m·K for Concrete.
Which expands less with temperature?
Glass expands less: 8.3 µm/m·K against 10 µm/m·K for Concrete.