Summary
Highlights
Construction materials are broadly classified by their use, production method, and chemical composition. Usage-based classification includes structural materials (wood, reinforced concrete, steel, masonry), decorative/finishing materials (glazing, windows, fireproofing, finishing, insulation), and facility materials (plumbing, electrical, gas, cooling). Production-based classification categorizes materials into natural (wood, stone, soil) and artificial (cement, concrete, synthetic resins, glass). Chemical composition classifies them into inorganic (metals like steel, aluminum; non-metals like stone, aggregates, cement, concrete) and organic materials (natural like wood, asphalt; synthetic resins like paints, plastics).
This section explains key mechanical properties: elasticity (returns to original shape after external force is removed, like a spring), plasticity (retains deformation after external force is removed, like bent wire), and viscosity (resistance to deformation or tendency for parts to stick together, like honey). The stress-strain curve is introduced as a tool to understand mechanical properties, select appropriate materials, and predict structural performance. Important points on the curve include the proportional limit, elastic limit, ultimate tensile strength, and fracture point.
Stress is defined as the internal resistance force per unit area when an external force is applied. Strain is the change in length relative to the original length. The elastic modulus (Young's modulus) is the ratio of stress to strain within the elastic range, following Hooke's Law. Poisson's ratio describes the ratio of transverse strain to axial strain when a material is stretched or compressed.
Strength refers to a material's capacity to resist external forces. Creep is the time-dependent increase in deformation under constant stress, excluding elastic and drying shrinkage. Factors increasing creep include high cement content, small cross-sectional area, early loading, longer sustained load, higher temperature, low humidity, and high stress. Relaxation is the decrease in stress over time when a material is held at a constant strain.
Key physical properties covered are density (mass per unit volume, with water at 4°C as a reference) and specific gravity (ratio of a material's density to the density of water at 4°C, without units). Specific heat (heat required to raise the temperature of 1g of substance by 1°C), thermal conductivity, flash point, and ignition point are also briefly mentioned.
The video concludes by mentioning the importance of Korean Industrial Standards (KS) for construction materials, highlighting that different countries have different standards due to variations in climate and preferred materials. KS standards are organized into basic and information sections, further categorized into three main areas.