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8. Segregation

The chapter outlines the behavior and properties of fresh concrete, addressing critical phenomena such as segregation, bleeding, slump loss, and re-tempering. It emphasizes the importance of understanding these aspects for effective handling, placement, and finishing on construction sites. Additionally, various control measures and practices are discussed, alongside the use of admixtures, to optimize the characteristics of fresh concrete.

Sections

Segregation

Segregation in fresh concrete refers to the separation of its components, leading to non-uniform compositions that can negatively impact structure quality.

1 Section Overview

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1.1 Definition

Fresh concrete's properties are essential for quality and strength, influenced by phenomena such as segregation and bleeding.

1.2 Types of Segregation

This section explains the concept of segregation in fresh concrete, outlining its types, causes, effects, and prevention methods.

1.3 Causes

This section discusses the causes of issues affecting fresh concrete, including segregation, bleeding, slump loss, and re-tempering.

1.4 Effects

This section outlines the effects of segregation, bleeding, slump loss, and re-tempering on the properties and performance of fresh concrete.

1.5 Prevention Methods

This section discusses methods to prevent issues such as segregation, bleeding, slump loss, and re-tempering in fresh concrete.

Bleeding

This section defines bleeding in concrete, outlines its types, causes, effects, and control measures.

2 Section Overview

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2.1 Definition

This section defines fresh concrete and discusses its critical properties, including segregation, bleeding, slump loss, and re-tempering.

2.2 Types of Bleeding

This section discusses the definition, types, causes, effects, and control measures of bleeding in fresh concrete.

2.3 Causes

This section highlights the causes, effects, and prevention methods for the phenomena of segregation, bleeding, slump loss, and re-tempering in fresh concrete.

2.4 Effects

This section discusses critical behaviors of fresh concrete, including segregation, bleeding, slump loss, and re-tempering, and their effects on the final concrete quality.

2.5 Control Measures

This section outlines the control measures needed to address issues such as segregation, bleeding, slump loss, and re-tempering in fresh concrete.

Slump Loss

Slump loss refers to the reduction in workability of fresh concrete over time, impacting placement and compaction.

3 Section Overview

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3.1 Definition

This section introduces the fundamental concepts of fresh concrete, covering critical phenomena affecting its performance, such as segregation, bleeding, slump loss, and re-tempering.

3.2 Typical Timeline

This section details the typical timeline and factors influencing the behavior of fresh concrete, including segregation, bleeding, slump loss, and re-tempering.

3.3 Causes

This section elucidates the significant causes of issues in fresh concrete, including segregation, bleeding, slump loss, and re-tempering, which affect the final hardened concrete quality.

3.4 Effects

This section discusses the effects of segregation, bleeding, slump loss, and re-tempering on fresh concrete, emphasizing their impacts on strength, durability, and performance.

3.5 Control Measures

Control measures for fresh concrete address segregation, bleeding, slump loss, and re-tempering to ensure quality and durability.

Re-tempering

Re-tempering involves the re-introduction of water to regain workability in concrete that has started to set.

4 Section Overview

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4.1 Definition

This section introduces the crucial concepts related to fresh concrete, including segregation, bleeding, slump loss, and re-tempering, emphasizing their effects on concrete quality.

4.2 Context

This section examines significant properties of fresh concrete, including segregation, bleeding, slump loss, and re-tempering, which impact the quality and durability of hardened structures.

4.3 Consequences

This section discusses the adverse effects of segregation, bleeding, slump loss, and re-tempering on fresh concrete, emphasizing their significance for construction quality.

4.4 IS Code Guidelines

This section addresses guidelines for managing fresh concrete behaviors according to IS codes, focusing on segregation, bleeding, slump loss, and re-tempering.

4.5 Alternatives to Re-tempering

This section discusses various alternatives to re-tempering concrete, emphasizing methods that maintain concrete workability without compromising its quality.

Field Practices to Minimize Defects in Fresh Concrete

This section outlines essential field practices aimed at minimizing defects in fresh concrete, emphasizing effective handling, placement, and supervision.

5 Section Overview

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5.1 Site Handling and Transportation

Effective handling and transportation methods are crucial in fresh concrete management to prevent issues like slump loss, segregation, and bleeding.

5.2 Placing Techniques

Placing techniques in concrete work are vital for ensuring proper handling and compaction of fresh concrete, influencing its overall durability and strength.

5.3 Timing and Supervision

Proper timing and supervision during concrete placement are crucial for ensuring quality and preventing issues like slump loss.

Testing of Fresh Concrete Properties

This section discusses the critical properties of fresh concrete, including segregation, bleeding, slump loss, and re-tempering, emphasizing their impact on construction quality.

6 Section Overview

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6.1 Slump Test (IS 1199:1959)

The slump test measures the workability of fresh concrete, indicating its consistency and ease of placement.

6.2 Bleeding Test

The bleeding test measures the amount of water rising to the surface of freshly mixed concrete, which affects its quality and workability.

6.3 Segregation Resistance Test

This section discusses the segregation resistance test, an important evaluation for fresh concrete, focusing on the separation of its components.

6.4 Temperature and Setting Time

This section discusses the effect of temperature on the setting time of fresh concrete and its consequences on concrete quality.

Role of Admixtures in Controlling Fresh Concrete Behavior

Admixtures are essential additives that improve the workability, durability, and overall performance of fresh concrete during its initial phase.

7 Section Overview

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7.1 Plasticizers and Superplasticizers

Plasticizers and superplasticizers are crucial additives that improve the workability and fluidity of fresh concrete without increasing water content.

7.2 Air-Entraining Agents

Air-entraining agents are admixtures that improve the workability and durability of fresh concrete by introducing microscopic air bubbles, thus enhancing its performance.

7.3 Retarders

Retarders are essential admixtures that delay the setting time of fresh concrete, helping to manage workability under certain conditions.

7.4 Viscosity-Modifying Admixtures (VMAs)

Viscosity-modifying admixtures (VMAs) are added to concrete to enhance its performance by controlling segregation and bleeding.

Guidelines from Indian Standards and Codes

This section discusses the impact of various factors on fresh concrete, including segregation, bleeding, slump loss, and re-tempering, and provides guidelines from Indian standards.

8 Section Overview

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Effects on Hardened Concrete and Long-term Durability

Improper behavior in fresh concrete significantly impacts the long-term strength and durability of hardened concrete structures.

9 Section Overview

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Learning Objectives

  • Fresh concrete properties significantly impact the quality and durability of hardened concrete.

  • Segregation and bleeding are critical issues that can affect the performance of concrete.

  • Proper handling and site practices can minimize defects in fresh concrete.

Key Concepts

Segregation

The separation of concrete's constituents, leading to a non-uniform composition and reduced strength.

Bleeding

The phenomenon where water rises to the surface of freshly placed concrete, caused by the settlement of solid particles.

Slump Loss

The reduction in workability of fresh concrete over time, making placement and compaction challenging.

Re-tempering

The practice of adding water to concrete after initial setting has begun, often weakening the mix.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting

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