Concrete Technology Quiz

Aggregate is the primary ingredient of concrete, which is made up of gravel, sand, and crushed stone. It provides strength and stability to the concrete mixture. Aggregates are inert materials, meaning they do not chemically react with other components.

Admixtures are chemical additives that enhance the performance of concrete. They modify specific properties such as setting time, workability, water resistance, and strength.

Water is a key component in the concrete mixing process. It interacts with cement to initiate a chemical reaction called hydration, which hardens the concrete.

Cement is the main binding agent in concrete. It is a fine powder that reacts with water, forming a paste that binds together the aggregates.

The amount of water used in concrete affects its workability. It's a balance between ease of mixing and a strong final product. Too much water weakens concrete, too little makes it difficult to work with.

The final strength of concrete is affected by the quality of its ingredients, mixing ratios, and curing conditions. Properly cured concrete develops maximum strength over time.

Concrete requires a controlled environment to cure properly. It should be kept moist and at a stable temperature for optimal hydration and strength development.

Concrete has a naturally high compressive strength, meaning it can withstand significant forces pushing down on it. However, it has low tensile strength, which means it can be easily stretched.

Materials that are added to concrete during mixing, affecting its properties.

Air-entraining agents increase the concrete's ability to withstand freezing and thawing cycles.

Aggregate with particles greater than 3/16 inch.

Coarse aggregate grades are determined by the percentage of particles that pass through specific sieves.

Different grades of coarse aggregate are classified based on the size of the particles.

A 1-1/2 inch aggregate will have most of its particles pass through a 1-1/2 inch sieve, but be caught by a 1-inch sieve.

The percentage of material passing through each sieve determines the grade.

Coarse aggregate is usually locally sourced due to its weight and high shipping costs.

Concrete that has a compressive strength between 3,000 and 5,000 psi, often used in general construction projects.

Concrete made with lightweight aggregates like shale or perlite, used where structural strength is not a top priority.

Concrete made with dense aggregates like hematite or steel shot, primarily used for radiation shielding.

Concrete with a compressive strength exceeding 6,000 psi, often used in high-load applications.

The amount of time a concrete mix remains workable before hardening.

The process of maintaining moisture and temperature conditions for concrete to gain strength.

The ability of concrete to withstand pressure applied directly to its surface.

The ability of concrete to withstand stretching or pulling forces.

Describes how easily concrete flows. Measured by how much the concrete mixture settles after being removed from a cone.

Tests the strength of cured concrete by measuring the force needed to crush a sample.

Measures the strength of cured concrete by bending a sample until it breaks. Used when concrete is subjected to bending forces.

Concrete is strengthened by adding steel bars, wires, or welded wire fabric that can withstand the tensile forces.

The ability of a material to withstand pulling or stretching forces. Concrete is weak in tension.

The ability of a material to withstand crushing forces. Concrete is strong in compression.

Concrete is weak in tension and needs reinforcement to withstand pulling forces.

A mixture of cement, aggregates, water, and sometimes admixtures to create a strong building material.

Reinforced concrete involves adding steel bars (reinforcement) to concrete to improve its tensile strength, which is its ability to resist pulling forces.

Reinforced concrete has advantages like high compressive strength, good fire/water resistance, rigidity, long lifespan, and low maintenance. It's also versatile and uses local materials.

Concrete's main disadvantage is its low tensile strength, requiring steel reinforcement. It also needs forms to hold it in place while hardening, and can be heavy.

Reinforced concrete is commonly used in structural elements like footings, floor slabs, walls, piers, beams, columns, and even arches. It is also widely used in building construction.

The steel bars (reinforcement) are placed within the forms before concrete is poured. This ensures the steel is embedded inside the hardened concrete for strength.

Forms are needed to hold the concrete in place while it hardens. Falsework or shoring may be required to support the forms for roofs, walls, and similar structures until the concrete gains enough strength.

Reducing water content in concrete increases compressive and flexural strength. It also improves water tightness, weather resistance, bond between layers, and reduces volume change from wetting and drying.

The water-cement ratio represents the weight of water used in a concrete mixture compared to the weight of cement. This ratio is crucial for determining the strength and durability of the concrete.

A slump test is a way to measure the consistency of fresh concrete by checking how much it slumps when placed in a cone-shaped mold. It helps to ensure that the concrete mix has the right amount of water.

Concrete must be mixed thoroughly to achieve a uniform mixture and avoid weak spots. Uniform color and texture indicate proper mixing.

Evenly mixing concrete ingredients ensures that its strength is consistent throughout the batch. Sampling from different areas should show similar characteristics.

Hand mixing concrete is possible for small batches using a wheelbarrow, hoe, and shovel. It requires careful attention to ensure a strong mix.

The first step in hand mixing concrete is measuring the fine and coarse aggregates into a neat pile on a flat surface. This ensures the right proportions are used.

After measuring the aggregates, pour the cement into a crater formed at the top of the pile. This helps ensure even distribution of the cement.