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Book: Pages: Concrete Technology, A.M. NEVILLE 94 - 100 CONC 203 | Concrete Technology Unit# 6: “Compressive Strength of Concrete” 1 Unit#2.

Objectives 2 ❑To understand compressive strength and its importance. ❑Identify factors affecting strength. ❑To learn about testing methods. ❑Prepare for and conduct experimental work..

➢ Definition: Compressive strength is the capacity of a material to withstand axial loads without failure. ➢ Role in Construction: Essential for ensuring that concrete structures can support the loads they will encounter. ➢ Importance: High compressive strength indicates a well-designed and constructed concrete mix, crucial for structural safety and performance. 3 7.1 Introduction to Concrete Compressive Strength.

➢ Structural Integrity: Ensures that structures can withstand applied loads without collapsing. ➢ Design Considerations: Influences material selection, thickness of members, and overall structural design. ➢ Safety Factor: Compressive strength must exceed the anticipated loads, providing a safety margin for unforeseen conditions. 4 7.2 Importance of Compressive Strength.

5 7.3 Factors Affecting Compressive Strength Factors Affecting Compressive Strength of Concrete Material Properties Concrete Mix Design Curing Processes Roles of Additives (Admixtures).

1. Concrete Mix Design Overview: ➢ Importance: The right mix design is crucial for achieving the desired compressive strength. 6 7.3 Factors Affecting Compressive Strength.

2. Curing Conditions: ➢ Importance of Curing: Curing maintains moisture and temperature, essential for the hydration process and strength gain. ➢ Curing Methods: ✓ Water Curing ✓ Membrane Curing ✓ Wet Covers (Burlap) 7 7.3 Factors Affecting Compressive Strength Why Curing of Concrete.

2. Curing Conditions: ➢ Curing Methods Water Curing: Immersing or spraying concrete with water. 8 7.3 Factors Affecting Compressive Strength.

2. Curing Conditions: ➢ Curing Methods Membrane Curing: Applying curing compounds that form a moisture-retaining film. 9 7.3 Factors Affecting Compressive Strength.

2. Curing Conditions: ➢ Curing Methods Wet Covers: Using wet burlap or other materials to retain moisture. 10 7.3 Factors Affecting Compressive Strength.

2. Curing Conditions: ➢ Duration for Curing of Concrete (7 Days): For most concrete mixes, curing for at least 7 days is recommended for achieving a significant portion of the strength, typically around 65% of the design compressive strength. 11 7.3 Factors Affecting Compressive Strength 0 20 40 60 80 100 120 Continously in Air 3 7 14 28 Copressive Strength in % Days Cured.

2. Curing Conditions: ➢ Duration for Curing of Concrete (28 Days): The standard period for assessing the compressive strength of concrete is typically 28 days. By this time, the concrete should achieve about 100% of its design strength under normal conditions. 12 7.3 Factors Affecting Compressive Strength 0 20 40 60 80 100 120 Continously in Air 3 7 14 28 Copressive Strength in % Days Cured.

3. Material Properties ➢ Cement: Different types of cement (e.g., Ordinary Portland Cement, High-Performance Cement) can influence the final strength. ➢ Aggregates: Size and Shape: Well-graded aggregates improve workability and packing density. 13 7.3 Factors Affecting Compressive Strength.

3. Material Properties ➢ Aggregates: Cleanliness: Contaminants can weaken the bond between cement and aggregates. ➢ Water Quality: Clean, potable water should be used to avoid adverse chemical reactions. 14 7.3 Factors Affecting Compressive Strength.

4. Role of Additives(Admixtures) ➢ Plasticizers: Increase compressive strength by reducing the water-cement ratio and improving workability. ➢ Retarders: Delay the setting time, potentially allowing better curing and long-term compressive strength. ➢ Accelerators: Speed up early strength gain but may slightly reduce long-term compressive strength if overused. 15 7.3 Factors Affecting Compressive Strength.

7. Role of Additives(Admixtures) ➢ Influence on Strength: Additives can enhance compressive strength and durability when used appropriately. 16 7.3 Factors Affecting Compressive Strength.

17 Formative Assessment Scan the QR Code and Let’s rock with this Assessment https://www.proprofs.com/quiz- school/ugc/story.php?title=ndexnzgymqc85h.

➢ Normal Strength Concrete provides adequate compressive strength for various applications while maintaining a standard density suitable for most structural uses. ➢ High-Strength Concrete offers enhanced compressive strength compared to normal-strength concrete, making it ideal for demanding structural applications. 18 7.4 Types of Concrete ➢ Lightweight Concrete: Typically has lower compressive strength compared to normal-weight concrete but offers reduced density for applications where weight reduction is crucial..

➢ Design Considerations: Engineers must consider compressive strength when designing beams, columns, and slabs. ➢ Failure Inadequate compressive strength can lead to structural failure, such as crushing of concrete elements. ➢ Safety and Compliance: Adherence to codes and standards is crucial to ensure safety and performance in construction. 19 7.5 Structural Implications.

➢ Importance of Testing: Ensures that the concrete used meets specified strength requirements. ➢ Standard Testing Methods: ASTM C39: Standard test method for compressive strength of cylindrical concrete specimens. The test method can also be applied to concrete cubes. 20 7.6 Overview of Testing Methods.

➢ Overview of Common Tests: ➢ Compression Test: Most widely used to determine compressive strength. ➢ Flexural Strength Test: Assesses the tensile strength of concrete. ➢ Importance of Consistency: Testing should be performed consistently to ensure reliable results. 21 7.7 Standard Testing Methods Compression Test Flexural Test.

➢ Safety Measures: Emphasize the importance of personal protective equipment (PPE) during experiments. 22 7.8 Safety Measures for Compression Testing Machine.

➢ Purpose of Experimental Work: To validate theoretical knowledge and understand practical implications of compressive strength. ➢ Overview of Procedures: Step-by-step guide on conducting experiments. ➢ Data Collection: Importance of meticulous data collection for analysis. 23 7.9 Experimental Work Overview.

➢ Definition: A machine designed to apply axial loads to concrete samples until failure occurs. ➢ Operation: Samples are placed in the machine, and loads are applied at a controlled rate. ➢ Calibration: Regular calibration of the testing machine is essential for accurate results. 24 7.10 Compression Testing Machine.

➢ Do you know about Axial Loads? ➢ What other types of Loads? 25 Interactive Class Assessment A Quick Class Interactive Assessment.

26 Formative Assessment Scan the QR Code and Let’s rock with this Assessment https://www.proprofs.com/quiz-school/ugc/story.php?title=lesson-2- concrete-compressive-strengthz6.

➢ After 24 hours of pouring, we demold the samples and Immerse in water for curing process for the specified time (7 Days or 28 Days) 27 7.11 Demolding of Concrete Samples.

➢ Curing Techniques: Apply chosen curing methods immediately after casting. ➢ Monitoring Conditions: Check moisture levels and temperature to ensure effective curing. ➢ Duration: Maintain curing conditions for the specified duration (minimum of 7 days). 28 7.12 Curing Concrete Samples.

➢ Testing Procedure: Place the cured sample (after 7 or 28 days) in the compression testing machine. ➢ Loading Rate: Apply load at a specified rate (e.g., 0.25 MPa/s) to ensure controlled failure. ➢ Recording Results: Monitor and record the maximum load applied at the time of failure. 29 7.13 Conducting the Test.

➢ Reading Results: Compressive strength is calculated as the maximum load divided by the cross-sectional area of the sample. Fc (Compressive Strength) = 𝑭𝒐𝒓𝒄𝒆(𝑴𝒂𝒙 𝑳𝒐𝒂𝒅) 𝑪𝒓𝒐𝒔𝒔−𝑺𝒆𝒄𝒕𝒊𝒐𝒏 𝑨𝒓𝒆𝒂 (N/mm2 ) 30 7.14 Interpreting Test Results.

Question 1: A concrete cube has a side length of 150 mm. If the applied load during testing is 500 kN, what is the compressive strength of the concrete? Solution: 1) Calculate the area: A = 150mm x 150mm = 22,500 mm² 2) Calculate Compressive Strength 𝑪𝒐𝒎𝒑𝒓𝒆𝒔𝒔𝒊𝒗𝒆 𝑺𝒕𝒓𝒆𝒏𝒈𝒕𝒉 = 𝑳𝒐𝒂𝒅 𝑨𝒓𝒆𝒂 = 𝟓𝟎𝟎,𝟎𝟎𝟎 𝑵 𝟐𝟐,𝟓𝟎𝟎 mm² = 𝟐𝟐. 𝟐𝟐 𝑴𝑷𝒂 31 7.15 Practice Examples for Compressive Strength of Concrete 150 mm.

➢ Do you know about Pascal (Pa) Unit? ➢ What is the relation of MPa (Mega Pascal) and N/ mm²? 32 Interactive Class Assessment A Quick Class Interactive Assessment.

Question 2: A cylindrical concrete sample has a diameter of 100 mm and a height of 200 mm. If the applied load during testing is 300,000 N, calculate the compressive strength of the cylinder in MPa. Solution: 1) Calculate the area: A = πr² = (3.14)(50)² = 7850 mm² 2) Calculate Compressive Strength 𝐶𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑖𝑣𝑒 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ = 𝐿𝑜𝑎𝑑 𝐴𝑟𝑒𝑎 = 300,000 𝑁 7,850 mm² = 38.2 𝑀𝑃𝑎 33 7.15 Practice Examples for Compressive Strength of Concrete 200 mm 100 mm.

Question 3: A concrete cube has a side length of 150 mm. If the applied load during testing is 750,000 N, what is the compressive strength of the concrete in MPa? 34 7.15 Practice Examples for Compressive Strength of Concrete 150 mm Let’s make it interesting, Do it by yourself.

Question 4: A cylindrical concrete sample has a diameter of 150 mm and a height of 300 mm. If the applied load during testing is 900,000 N, calculate the compressive strength of the cylinder in MPa. 35 7.15 Practice Examples for Compressive Strength of Concrete 300 mm 150 mm Can you do this by yourself.

➢ Significance: Results should be compared to design specifications and standards. ➢ Quality Control: Use results to assess the quality of concrete produced. 36 7.16 Interpreting Test Results.

➢ Overview of Influential Factors: Sample Size and Shape: Different shapes can yield different strength results. Testing Conditions: Temperature and humidity during testing can affect results. ➢ Controlled Environment: Ensuring consistent testing conditions is crucial for reliability. 37 7.17 Factors Influencing Test Results.

➢ Common Problems: Inconsistent strength results, sample failure before testing, improper curing. ➢ Troubleshooting Tips: Ensure proper mixing, casting, and curing techniques are followed. ➢ Preventative Measures: Regular equipment maintenance and adherence to procedures can minimize issues. 38 7.18 Common Issues and Troubleshooting.

➢ Real-World Examples: Case 1: Structural Collapse Due to Low Compressive Strength. ➢ Project: Sampoong Department Store Collapse (South Korea, 1995) ➢ Cause of Failure: The concrete used in the supporting columns had not been adequately tested, and the compressive strength was far below the required specifications. 39 7.19 Case Studies.

➢ Real-World Examples: Case 2: Successful High-Performance Concrete Project ➢ Project: Project: Burj Khalifa (Dubai, UAE) ➢ Successful Project: Burj Khalifa, currently the world’s tallest building, required a high-performance concrete mix to support its immense height and loads. The foundation and structural elements needed exceptional compressive strength to ensure safety and stability. 40 7.19 Case Studies.

7.20 Overview of Lecture by Video Presentation 41.

Summary.

7.21 Conclusion Summary 43 ➢ Compressive Strength is Critical: It ensures the load-bearing capacity and structural integrity of concrete. ➢ Key Factors: Mix design, curing conditions, and material quality significantly influence compressive strength. ➢ Testing is Essential: Standardized tests (like cube/cylinder tests) are crucial to verify concrete's strength..

7.21 Conclusion Summary 44 ➢ Quality Control: Consistent testing and monitoring prevent structural failures and ensure safety. ➢ Practical Applications: Meeting compressive strength requirements impacts both safety and project success. ➢ Engineer’s Role: Engineers must rigorously test and verify concrete strength to ensure the durability of structures..

45 Formative Assessment Scan the QR Code and Let’s rock with this Assessment https://www.proprofs.com/quiz- school/ugc/story.php?title=ndexnzgymqc85h.

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