---
title: "Why plastics are widely used"
subject: "Civil Engineering Materials"
chapter: 10
key: "semester_3/civil_engineering_materials:why-plastic-used-extensively"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/why-plastic-used-extensively
site: BCT Engineering
---

# Why plastics are widely used

Civil Engineering Materials · Chapter 10: Asphalt, Bitumen, Tar and Miscellaneous Materials

- Asked in: 2078 Bhadra, 2 marks; 2076 Asoj, 3 marks; 2075 Asoj, 2 marks (asked 3 times)
- Video: [Applications of Plastics in Construction | Construction Materials | Civil Engineering](https://www.youtube.com/watch?v=7BYoHwbEN2c) — Polytechnic Class (READBY) 
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/why-plastic-used-extensively
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-10

## Question

Why are plastic materials used extensively as building materials nowadays?

## Short answer

Plastics are lightweight (900–1500 kg/m³), corrosion-resistant, easily moulded, and provide good thermal and electrical insulation. They are low-cost, require little maintenance, and can be produced in any colour, making them ideal for pipes, tanks, doors, windows and damp-proofing.

## Answer

Plastics are synthetic organic materials (polymers) that can be moulded under heat and pressure. They are widely used today for these reasons:

1. **Light weight:** Density is about 900–1500 kg/m³, giving easy handling, transport and lower dead load.
2. **Corrosion and chemical resistance:** Plastics do not rust or rot and resist water, acids and alkalis, so they last longer in pipes, tanks and fittings.
3. **Easy to mould and install:** Complex shapes are made quickly by moulding or extrusion; pipes, sheets and fittings are quickly joined.
4. **Low cost:** Cheaper overall, with low maintenance and mass production.
5. **Good insulation:** Poor conductors of heat and electricity, used for wire insulation, thermal insulation and switches.
6. **Colour and finish:** Can be made in any colour or transparency; needs no painting.
7. **Strength-to-weight ratio** is high when reinforced (e.g. GRP, FRP).
8. **Water-tightness:** Smooth, non-porous surface gives low friction in pipes and waterproofing in membranes.
9. **Recyclable** (thermoplastics) and long life.

Uses: pipes (PVC, HDPE), water tanks, doors and windows (uPVC), flooring, damp-proof sheets, paints, adhesives and insulation.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What benefit does the low density (900-1500 kg/m3) of plastics give?
   A. Easy handling, transport and lower dead load
   B. Higher fire resistance
   C. Better conduction
   D. Higher cost
   Answer: A. Light weight gives easy handling and lower dead load. (Key point: Light weight)

2. Why are plastics good for pipes and tanks?
   A. They conduct heat
   B. They do not rust or rot and resist water, acids and alkalis
   C. They are heavy
   D. They never need joining
   Answer: B. They resist corrosion and chemicals, so last longer. (Key point: Corrosion resistance)

3. Plastics are used for wire insulation because they are what?
   A. Good conductors
   B. Magnetic
   C. Poor conductors of heat and electricity
   D. Transparent only
   Answer: C. They are poor conductors of heat and electricity. (Key point: Insulation)

4. Which plastics are recyclable?
   A. Thermosetting only
   B. Thermoplastics
   C. None
   D. Only GRP
   Answer: B. The answer lists thermoplastics as recyclable. (Key point: Recyclability)

## Related in Civil Engineering Materials

- [Why bricks are widely used](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Awhy-bricks-widely-used) — Civil Engineering Materials, chapter 3, asked 3×
- [Short note: types of plastic materials](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Atypes-of-plastic) — Civil Engineering Materials, chapter 10, asked 2×
- [Why composite materials are used](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Acomposite-materials-why-used) — Civil Engineering Materials, chapter 10, asked 2×
- [Why pozzolanic materials are used](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Awhy-pozzolanic-materials-used) — Civil Engineering Materials, chapter 4, asked 2×
- [Thermoplastics versus thermosetting plastics](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Athermoplastics-vs-thermosetting) — Civil Engineering Materials, chapter 10
- [Classification of plastics with examples](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aplastics-classification-examples) — Civil Engineering Materials, chapter 10

## Related in other subjects

- [Plastic torque of solid shaft is 4/3](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aplastic-torque-solid-shaft-4-3) — Strength of Materials, chapter 6
- [Limiting plastic moment is 1.5 times elastic moment](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aplastic-moment-rectangular-1-5) — Strength of Materials, chapter 7
- [Define plastic moment capacity of beam](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aplastic-moment-capacity-definition) — Strength of Materials, chapter 7
- [Terms used in a pitched roof](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aroof-terminology) — Building Technology, chapter 4, asked 4×