Construction Materials & Methods Flashcards
9 cards from real CCI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 9 Construction Materials & Methods flashcards as text
What is the primary purpose of using formwork in concrete construction?
Answer: To mold and support concrete until it gains sufficient strength
Formwork is essential in concrete construction as it serves as a temporary mold or container into which fresh concrete is poured. Its primary purpose is to hold the concrete in the desired shape and provide crucial support. This support is maintained until the concrete has cured sufficiently to gain its required strength and become self-supporting.
Why is rebar used in concrete construction?
Answer: To help concrete resist tensile forces
Rebar (reinforcing bar) is used in concrete construction because concrete is exceptionally strong in compression but weak in tension. By embedding steel rebar, which is excellent at resisting pulling forces, into the concrete, the composite material gains significant tensile strength. This allows reinforced concrete to withstand both compressive and tensile stresses, making structures more durable and resistant to cracking.
What is the purpose of curing concrete?
Answer: To prevent cracking and promote strength development
Curing concrete is a critical process that involves maintaining adequate moisture and temperature conditions for a specific period after placement. This is essential for the cement's hydration, which allows the concrete to achieve its full design strength and durability. Proper curing also significantly helps to prevent shrinkage cracking and improves the overall quality of the concrete.
Which material is commonly used as a moisture barrier under concrete slabs?
Answer: Plastic sheeting or polyethylene film
Plastic sheeting or polyethylene film is commonly used as a moisture barrier under concrete slabs. Its purpose is to prevent moisture from the ground, such as water vapor, from migrating upwards through the concrete. This protection is crucial for preventing mold growth, protecting flooring materials, and maintaining indoor air quality.
What is the function of expansion joints in concrete?
Answer: To allow controlled cracking and movement
Expansion joints, also known as isolation or control joints, are intentionally placed in concrete to create weakened planes. Their function is to allow the concrete to expand and contract due to temperature changes and moisture variations without developing uncontrolled, unsightly cracks. This managed movement helps to relieve stress and prevent structural damage to the slab.
What is the typical compressive strength of standard concrete used in construction?
Answer: 3000 to 4000 psi
Standard concrete used in most general construction applications, such as foundations, slabs, and driveways, typically has a specified compressive strength ranging from 3000 to 4000 pounds per square inch (psi). This range provides adequate strength for common structural elements and ensures the durability and load-bearing capacity required for typical building projects.
Why is slump testing important in concrete construction?
Answer: To measure workability and consistency of concrete
Slump testing is a crucial quality control measure for fresh concrete. It directly assesses the concrete's workability, which is its ability to be placed, compacted, and finished without segregation, and its consistency, indicating the water-cement ratio. This test helps ensure the concrete will perform as intended during placement and achieve its specified strength.
Which type of cement is commonly used for general construction?
Answer: Portland cement
Portland cement is the most common type of cement used worldwide for general construction purposes. It serves as the basic ingredient for concrete, mortar, and stucco, known for its versatility, strength, and widespread availability. Its balanced properties make it suitable for a vast array of structural and non-structural applications.
What is a key advantage of using precast concrete components?
Answer: They reduce on-site labor and improve quality control
Precast concrete components are manufactured off-site in a controlled factory environment, which allows for higher quality control, precise dimensions, and faster curing times. Bringing finished components to the site significantly reduces the amount of on-site labor, time, and material waste required. This leads to accelerated project schedules and a more consistent, high-quality product.