Construction Materials: Aggregate Quiz
45 Questions
5 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is one consequence of water soluble sulfates in natural aggregates?

  • Improves the workability of the mix
  • Causes expansion and deterioration of cement paste (correct)
  • Acts as a bonding agent between aggregates
  • Increases the strength of concrete

What defines a deleterious chemical reaction between aggregates and cement alkalies?

  • When the reaction is not extensive and does not produce gel material
  • When the reaction causes expansion and cracking of the concrete (correct)
  • When there is no observable expansion or cracking
  • When an increase in water-cement ratio is necessary

Which approach can help mitigate Alkali-aggregate reaction?

  • Using conventional cement with high sodium content
  • Increasing the volume of aggregates in the mix
  • Selecting reactive aggregate
  • Reducing the water-cement ratio (correct)

Which of the following is NOT one of the suggested methods to avoid Alkali-aggregate reactions?

<p>Incorporating a higher percentage of water in the mix (B)</p> Signup and view all the answers

What leads to the formation of highly expansive gel material in concrete?

<p>The reaction of reactive aggregates with cement alkalies (A)</p> Signup and view all the answers

What is the minimum size (d) for fine aggregate?

<p>0 mm (B)</p> Signup and view all the answers

Which of the following aggregate types has a maximum size of 31.5 mm?

<p>8/31.5 (A)</p> Signup and view all the answers

What does the fineness modulus (FM) represent in aggregate grading?

<p>Average particle size (C)</p> Signup and view all the answers

Which of the following is NOT a method used to assess the quality of aggregates?

<p>Compressive strength test (A)</p> Signup and view all the answers

What is the significance of a low Los Angeles coefficient in aggregate testing?

<p>Reflects good resistance to fragmentation (C)</p> Signup and view all the answers

For what type of concrete is aggregate strength most critical?

<p>High-strength concrete (C)</p> Signup and view all the answers

How is the specific surface area of an aggregate defined?

<p>Surface area per unit mass (A)</p> Signup and view all the answers

Which of the following is an example of fine aggregate?

<p>0/4 (B), 0/1 (C)</p> Signup and view all the answers

What defines fresh concrete?

<p>Concrete that can be transported, placed, and compacted. (C)</p> Signup and view all the answers

Which of the following statements about aggregates is true?

<p>Aggregates serve as a strong filler material in concrete. (B)</p> Signup and view all the answers

Which type of concrete has undergone setting but has not yet hardened significantly?

<p>Green Concrete (C)</p> Signup and view all the answers

Which is a characteristic of recycled aggregates?

<p>They are derived from previously used construction materials. (A)</p> Signup and view all the answers

What is the role of admixtures in concrete?

<p>They reduce the water-cement ratio without affecting workability. (D)</p> Signup and view all the answers

Which step in concrete manufacturing involves combining aggregates with cement and water?

<p>Mixing (C)</p> Signup and view all the answers

Natural aggregates are characterized by which of the following?

<p>They are derived from minerals without further processing. (D)</p> Signup and view all the answers

What is the significance of curing in the concrete manufacturing process?

<p>It helps to maintain moisture for proper hydration. (C)</p> Signup and view all the answers

What is the typical range of relative densities for most natural aggregates?

<p>2.40 to 2.90 (B)</p> Signup and view all the answers

Which factor does NOT affect void content in aggregates?

<p>Type of cement used (A)</p> Signup and view all the answers

What does void content in aggregates represent?

<p>The space not occupied by solid matter (C)</p> Signup and view all the answers

What is the moisture content state where aggregates are neither absorbing nor contributing water?

<p>Saturated surface dry (SSD) (A)</p> Signup and view all the answers

How does void content affect the mixing water and cement requirements?

<p>Increases with higher void content (A)</p> Signup and view all the answers

Which aggregate type generally has a higher range for absorption levels?

<p>Coarse aggregate (B)</p> Signup and view all the answers

What state is described as fully absorbent with zero moisture content?

<p>Oven dry (C)</p> Signup and view all the answers

Which of these describes free water within aggregates?

<p>Difference between SSD and wet state moisture content (D)</p> Signup and view all the answers

What is a characteristic of crushed stone compared to natural gravel?

<p>Crushed stone tends to have a rough surface. (C)</p> Signup and view all the answers

Why should flaky and elongated aggregate particles be limited in concrete?

<p>They lead to higher specific surface area and increase voids. (C)</p> Signup and view all the answers

What size is classified as fine aggregate according to the given standards?

<p>D ≤ 4 mm (A)</p> Signup and view all the answers

Which of the following statements about rounded smooth aggregates is true?

<p>They produce lower cement content in concrete mixtures. (D)</p> Signup and view all the answers

What is the main advantage of using manufactured or recycled aggregates?

<p>They provide specific properties needed for certain applications. (D)</p> Signup and view all the answers

What role does surface texture play in aggregate properties?

<p>Surface texture influences the bond strength in the concrete mix. (A)</p> Signup and view all the answers

What is a potential disadvantage of using flaky aggregate particles?

<p>They may crush during manufacturing, increasing fines in the mixture. (C)</p> Signup and view all the answers

Which statement correctly describes the grading of natural gravel?

<p>The grading of natural gravel is not controlled. (C)</p> Signup and view all the answers

What does dry bulk density represent in relation to aggregates?

<p>The mass of 1 m³ of aggregates (D)</p> Signup and view all the answers

Which type of aggregate is classified as lightweight?

<p>Aggregates with bulk density less than 1120 kg/m³ (C)</p> Signup and view all the answers

How is relative density (specific gravity) of aggregates defined?

<p>The ratio of aggregate particle density to the density of distilled water (D)</p> Signup and view all the answers

In concrete mix design, what is the primary use of compacted dry bulk density?

<p>To assess the mass/volume relationships for aggregates (B)</p> Signup and view all the answers

What is the approximate bulk density range for normal weight concrete aggregates?

<p>1200 kg/m³ to 1750 kg/m³ (A)</p> Signup and view all the answers

Which property of aggregates is NOT typically classified under physical properties?

<p>Chemical composition (C)</p> Signup and view all the answers

What does void content refer to in the context of aggregates?

<p>The amount of empty spaces between aggregate particles (B)</p> Signup and view all the answers

The application of concrete aggregates with a bulk density greater than 2100 kg/m³ is primarily for which purpose?

<p>Radiation shielding and counterbalancing (A)</p> Signup and view all the answers

Flashcards

What is concrete?

A composite material made of a bonding agent (cement and water) that holds together granular particles (aggregates) like sand and gravel.

What is fresh concrete?

The state of concrete that is fresh and workable, allowing for transport, placement, and compaction.

What is green concrete?

Concrete that has started to solidify but hasn't fully hardened.

What is hardened concrete?

Concrete that has reached sufficient strength to withstand loads without failing.

Signup and view all the flashcards

What are aggregates?

Granular materials, such as sand, gravel, or crushed stone, used with cement to create concrete or mortar.

Signup and view all the flashcards

What are natural aggregates?

Aggregates from natural sources, like sand and gravel, that have only undergone mechanical processing.

Signup and view all the flashcards

What are manufactured aggregates?

Aggregates made from industrial processes, like Leca (Lightweight Expanded Clay Aggregate), often through thermal modification.

Signup and view all the flashcards

What are recycled aggregates?

Aggregates made from recycled materials, such as crushed concrete, glass, or masonry.

Signup and view all the flashcards

Natural Aggregates

Natural aggregates, like sand and gravel, that have been weathered and rounded.

Signup and view all the flashcards

Crushed Stone

Aggregates produced through crushing, resulting in angular shapes, rough surfaces, and controlled grading.

Signup and view all the flashcards

Fine Aggregate

Particle size less than 4mm. Usually found in concrete.

Signup and view all the flashcards

Coarse Aggregate

Particle size greater than 4mm. Found in concrete.

Signup and view all the flashcards

Flaky Aggregate

Aggregates with a thickness much smaller than their length and width.

Signup and view all the flashcards

Elongated Aggregate

Aggregates with a length much greater than their width and thickness.

Signup and view all the flashcards

Specific Surface Area

The ratio of the surface area of the aggregate to its volume.

Signup and view all the flashcards

Workability of Concrete

The ability of fresh concrete to flow and be placed easily.

Signup and view all the flashcards

Bulk Density of Aggregates

The mass of 1 m³ of aggregates, essential for mix design and calculating mass-volume relationships.

Signup and view all the flashcards

Loose Dry Bulk Density

The mass of dry aggregate in a container without compaction divided by the container's capacity.

Signup and view all the flashcards

Compacted Dry Bulk Density

The mass of compacted dry aggregate in a container divided by the container's capacity.

Signup and view all the flashcards

Relative Density (Specific Gravity)

The ratio of aggregate density to water density at a specific temperature. Represents the density of individual particles.

Signup and view all the flashcards

Bulk density

Represents the mass of a specific volume of aggregate, including the spaces between particles.

Signup and view all the flashcards

Lightweight Aggregate

Aggregates lighter than 1120 kg/m³, used for lightweight concrete.

Signup and view all the flashcards

Normal Weight Aggregate

The most common type of aggregate with a density between 1120 kg/m³ and 1920 kg/m³. Used in standard concrete.

Signup and view all the flashcards

Heavy Weight Aggregate

Aggregate with density exceeding 2100 kg/m³. Used for shielding or counterbalancing.

Signup and view all the flashcards

Void Content

The volume of spaces within a mass of aggregate not filled by solid aggregate particles. These spaces within the aggregate are where cement paste will go.

Signup and view all the flashcards

Absorption

The ability of aggregate particles to absorb water. This is a crucial factor in concrete as it affects the amount of water needed for mixing.

Signup and view all the flashcards

Saturated Surface Dry (SSD)

The state of an aggregate particle where it's fully saturated but no excess water remains on the surface. It is neither absorbing water nor contributing it.

Signup and view all the flashcards

Free Water

The water content in an aggregate particle beyond the SSD state. This water will be released into the concrete mixture.

Signup and view all the flashcards

Moisture Content

The moisture content of an aggregate at the SSD state. This is important for calculating the total water content in concrete.

Signup and view all the flashcards

Dry Bulk Density

The density of an aggregate when it's completely dry. This is used to calculate the void content.

Signup and view all the flashcards

Combined Aggregate Specific Gravity

The specific gravity of a mixture of aggregates. This value is useful when dealing with combined aggregate.

Signup and view all the flashcards

What is alkali-aggregate reactivity?

When certain aggregates react with alkalies in cement, it can cause expansion and cracking in concrete.

Signup and view all the flashcards

How does alkali-aggregate reaction affect concrete?

The reaction between reactive aggregates and cement alkalies creates an expansive gel substance that absorbs water, leading to stresses inside concrete and damage like cracking and popouts.

Signup and view all the flashcards

What can be done to avoid alkali-aggregate reaction?

To prevent alkali-aggregate reaction, you can avoid using reactive aggregates, use low-alkali cement, or employ isolating systems in concrete.

Signup and view all the flashcards

How do sulfates in aggregates affect concrete?

Sulfates, when present in aggregates, can react with the cement, leading to expansion and deterioration of the concrete.

Signup and view all the flashcards

What are the effects of chlorides in aggregates?

Chlorides in aggregates can contribute to efflorescence, which is a white powdery substance that appears on the surface of concrete, and also corrosion of embedded steel.

Signup and view all the flashcards

Fine Aggregate Minimum Size (d)

The smallest possible particle size for a fine aggregate, denoted as "0" for zero.

Signup and view all the flashcards

Fine Aggregate Fineness

A measure of the fineness of a fine aggregate, based on the percentage of particles passing through a 0.500 mm sieve. It indicates the ratio of very fine particles to larger ones.

Signup and view all the flashcards

Fineness Modulus (FM)

A numerical value that indicates the average particle size of a fine aggregate. It is calculated as the sum of the percentages passing each sieve size divided by 100. This value helps understand the overall particle size distribution of the aggregate.

Signup and view all the flashcards

Specific Surface Area (SSA)

A measure of the total surface area of the aggregate per unit mass. It represents the total surface area exposed for bond with the cement paste in concrete.

Signup and view all the flashcards

Resistance to Fragmentation

The ability of an aggregate to resist being broken down by forces like abrasion or impact, crucial for durability, especially in high-wear applications like pavements and industrial floors. It is measured by tests like the Los Angeles abrasion test.

Signup and view all the flashcards

Los Angeles Abrasion Test

A test that measures the abrasion resistance of an aggregate, often used for pavements and industrial floors where the aggregate is subjected to wear.

Signup and view all the flashcards

Los Angeles Coefficient

A numerical value that represents the amount of abrasion an aggregate undergoes in a specified test, like the Los Angeles abrasion test. Lower values indicate greater resistance to fragmentation.

Signup and view all the flashcards

Aggregate Strength

The strength of an aggregate is not always a critical factor in concrete, but it plays a larger role in high-strength concrete. Aggregates typically have compressive strengths ranging from 65 MPa to 270 MPa.

Signup and view all the flashcards

Study Notes

Concrete Technology (CES 251s) Fall 2024

Course Contents

  • Concrete Constituents: Aggregates, Cement, Water, Admixtures
  • Concrete Properties: Fresh Concrete, Hardened Concrete
  • Concrete Mix Design

Introduction

  • Concrete Definition: A composite material fundamentally consisting of a binding medium (hydraulic cement and water) encompassing embedded aggregate particles (coarse and fine).
  • Concrete States:
    • Fresh Concrete: Possesses sufficient workability for transportation, placement, and compaction.
    • Green Concrete: Undergone setting but not hardened significantly.
    • Hardened Concrete: Developed sufficient strength to endure anticipated loads without failure.
  • Concrete Manufacturing Processes: Batching, Mixing, Transporting, Placement (Casting), Compacting (Consolidating), Finishing, Curing.
  • Ready-mixed concrete manufacturing: Details of the process, including different systems, were shown.

Aggregates for Concrete

  • Aggregate Definition: Granular materials (sand, gravel, crushed stone) used with a cementing medium to produce concrete or mortar.

  • Role of aggregates in concrete: Strong filler with relatively low cost compared to cementitious materials; major constituent resisting abrasion and localized impact; affects limiting volumetric changes due to restraint from aggregate and dilution effect.

  • Classification of Aggregates:

    • Source: Natural, Manufactured, Recycled
      • Natural Aggregates: Sand, Gravel, Crushed Stone (processed)
      • Manufactured Aggregates: LECA (Lightweight Aggregate), Slag, Fly ash
      • Recycled Aggregates: Crushed concrete, Crushed masonry, Crushed glass
    • Size: Coarse Aggregate (D > 4 mm, d ≥ 2 mm), Fine Aggregate (D ≤ 4 mm), All-in Aggregate (mixture of coarse and fine aggregates), Filler Aggregates (smaller than 0.063 mm).
    • Shape: Rounded (gravel, sand), Angular (crushed stone), Flaky (small thickness compared to other dimensions), Elongated (length large compared to other dimensions).
    • Surface Texture: Smooth, Rough, Porous

  • Shape and surface texture:

    • Avoiding flaky and elongated aggregates (limiting to 25% of mass); high specific surface area increases voids, cement content, and decreases workability.
    • Rounded smooth aggregates decrease water content demand and improve durability, with limited bond strength.

  • Table (3): Approximate Free-Water Contents (kg/m³) required to give various workability levels based on slump (mm) and vebe time (s), with the max size of aggregate (mm) and concrete type.

  • Table (2): Approximate Compressive Strengths (N/mm²) of concrete mixes made with free-water/cement ratio of 0.5, classifying by cement strength class and type of aggregate (uncrushed and crushed).

  • Bulk Density: Light weight (less than 1120 kg/m³), Normal weight (1120-1920 kg/m³), Heavy weight (over 2100 kg/m³)

  • Relative density (Specific gravity): Ratio of aggregate density to distilled water density at a stated temperature; used in concrete mix proportions computations. Types of aggregates relative density.

  • Void Content: Space between particles not occupied by solid matter in aggregate; calculated using dry bulk density.

  • Physical Properties (continued):

    • Absorption and moisture content: Moisture content of aggregates at SSD state; influence total water content of concrete. Coarse aggregate absorption typical (0.2%-4%); fine aggregate absorption typical (0.2%-2%). Water absorbed by aggregates isn't included in mix design water.
    • Bulking of fine aggregate: Increase in volume of moist fine aggregate due to surface tension in the moisture; moisture content (4-6%) influences the volume of fine aggregates.
    • Clay and Fines Content: Fines (particle size < 0.063 mm), adhere to aggregates, impact bond strength. ECP 203 limits on clay and fine content. How to avoid problems due to clay and fines.
    • Aggregate Size and Grading: Particle size distribution; sieve analysis process to divide aggregate into particle fractions; standard sieves; different sieve sets for coarse and all-in aggregates, fine aggregates, and fillers. ECP203 limits and percentages for coarse aggregate maximum/minimum and fine aggregate maximum/minimum size.

  • Mechanical Properties:

    • Strength: Aggregate strength rarely influences conventional concrete strength, but significant in high-strength concrete; compressive strength ranging.
    • Resistance to Fragmentation: Resistance to abrasion or impact, important in industrial floors and pavements; Los Angeles abrasion test measures this property. ECP203 limits for Los Angeles coefficients.

  • Chemical properties:

    • Salt Contamination: Soluble salts (chlorides) affect embedded steel via efflorescence or corrosion; sulfates attack aluminates and calcium hydroxide leading to expansion and deterioration.
    • Alkali-Aggregate Reactivity (ASR): Deleterious chemical reaction between aggregate constituents and cement alkalies. Avoid alkali-aggregate reaction with appropriate testing and measures.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Description

Test your knowledge on the properties and reactions of aggregates in construction materials. This quiz covers topics such as water soluble sulfates, alkali-aggregate reactions, and aggregate grading. Assess your understanding of the significance of various aggregate properties and their testing methods.

More Like This

Aggregate Properties in Data Analysis
1 questions

Aggregate Properties in Data Analysis

InstructiveGreenTourmaline avatar
InstructiveGreenTourmaline
Aggregate Properties Quiz
16 questions

Aggregate Properties Quiz

UndisputedRomanticism9150 avatar
UndisputedRomanticism9150
Aggregate Characteristics and Properties Quiz
45 questions

Aggregate Characteristics and Properties Quiz

BlissfulCosecant avatar
BlissfulCosecant
Civil Engineering Aggregate Quiz
40 questions

Civil Engineering Aggregate Quiz

MesmerizedMountain7926 avatar
MesmerizedMountain7926
Use Quizgecko on...
Browser
Open
Browser
Browser