M.Tech Structural Special Concrete — practice questions

1. Density is the defining property that separates light weight from conventional concrete. 2. Conventional concrete sits in the 2100–2500 kg/m³ band, dominating dead load on a structure. 3. Light weight concrete is engineered to occupy 300–1850 kg/m³, reducing foundation loads. 4. The lower density brings lower thermal conductivity and reduced air conditioning load. 5. 2600 kg/m³ and above would describe high density radiation shielding concrete, not light weight. _Source: IGNOU Concrete Technology, Unit 11 "Special Concrete" (Light Weight, Aerated, No-Fines, High Density, Fibre Reinforced, Polymer Concrete)._

1. Fly ash from coal combustion is pelletised, then sintered at 1000–1200 °C to produce a light weight aggregate. 2. The resulting aggregate is sold in the United Kingdom under the trade name Lytag. 3. Haydite, Leca and Agilite are trade names for bloated clay aggregates patented in Western countries. 4. Lytag has high strength-to-density ratio and relatively low drying shrinkage. 5. So fly ash routes to Lytag, while clay routes to Haydite, Leca and Agilite. _Source: IGNOU Concrete Technology, Unit 11 "Special Concrete" (Light Weight, Aerated, No-Fines, High Density, Fibre Reinforced, Polymer Concrete)._

1. Conventional concrete typically shrinks at about 400 × 10⁻⁶ over its drying life. 2. No-fines concrete contains less paste because point-to-point contact reduces paste demand. 3. The unit reports a drying shrinkage of about 200 × 10⁻⁶ for no-fines concrete. 4. This value is roughly half of conventional concrete's shrinkage. 5. However, the rate of shrinkage is higher: 50–80 percent finishes in about ten days. _Source: IGNOU Concrete Technology, Unit 11 "Special Concrete" (Light Weight, Aerated, No-Fines, High Density, Fibre Reinforced, Polymer Concrete)._