Polyethylene and polyvinyl chloride resins are used in various parts of building areas for:
🔬 Understanding the Role of Plastics in Construction
Plastics are versatile polymers that have become indispensable in modern construction. However, their role is highly specialized. Unlike steel or concrete, they are generally not used for primary load-bearing applications. Instead, they excel in roles that require durability, chemical resistance, and, most importantly, impermeability to water.
Polyethylene (PE): A common thermoplastic known for its flexibility and excellent moisture resistance. Often produced in the form of sheets or films.
Polyvinyl Chloride (PVC): A rigid and durable thermoplastic that is highly resistant to water, chemicals, and weathering. Used for a vast range of products.
⚖️ Detailed Analysis of the Options
Let's evaluate the primary function of these plastics in building applications.
(c) water proofing
Why it's correct: This is the most common and critical application for both materials.
• Polyethylene is widely used as damp-proof course (DPC) sheeting, vapor barriers under concrete slabs, and protective films to keep materials dry. Its entire purpose is to block the passage of water and water vapor.
• PVC is extensively used for water pipes, drainage systems, window frames, roofing membranes, and waterproof flooring. All these applications rely on its ability to be a durable, long-lasting barrier to water.
Therefore, "water proofing" is the primary function.
(a) structural strength & (b) structural ductility
Why they're incorrect: While some advanced fiber-reinforced plastics can have high strength, standard PE and PVC are not used for primary structural elements like beams, columns, or trusses. Their strength and stiffness are significantly lower than those of steel or concrete. Their role is not to carry the main building loads.
(d) termite proofing
Why it's not the best answer: While it is true that plastics are inorganic and therefore not a food source for termites, this is a secondary benefit, not their primary function. We don't install PVC pipes *mainly* to stop termites; we install them to carry water without leaking. The primary engineering property being utilized is water resistance.
💡 Study Tips for Plastics in Construction
- Think of Common Products: When you see PVC, think of white water pipes. When you see Polyethylene, think of the black plastic sheets used on construction sites. What do they both do? They manage and block water.
- Plastics Seal and Protect: Remember that the main role of common plastics in buildings is to seal joints, protect from weather, and transport fluids. They are part of the building's "skin" and "circulatory system," not its "skeleton."
- Primary vs. Secondary Benefits: Learn to distinguish the main engineering reason for using a material (its primary property) from its other useful side-effects (secondary properties).