LAB IN YOUR GRASP - KARAKTERISASI MATERIAL BETON : 19 MIX DESIGN BETON 25 MPa DENGAN METODE DOE

Summary

In this video, Panglima Rizal and Zikri Fikriansyah guide viewers through the process of designing concrete with a compressive strength of 25 MPA. They discuss essential factors such as material data, water-cement ratios, and aggregate percentages. The video explores calculations using the dos method for determining cement, water, and aggregate requirements based on specific gravity and absorption rates. Viewers are also introduced to techniques for adjusting material conditions and ensuring a balanced mix for optimum concrete performance. A detailed and practical explanation of concrete mix design principles is provided, ideal for students or professionals in civil engineering.

Takeaways

• 😀 The script discusses the process of designing concrete with a compressive strength of 25 MPA, using a specific engineering method.
• 😀 The concrete design method follows the standard guidelines, including using material data like fine aggregate, coarse aggregate, specific gravity, and absorption.
• 😀 The first step in the design process is determining the average compressive strength (SCR) using standard deviation or provided tables like SNI 28284.
• 😀 For a compressive strength of 25 MPA, the formula Ffnc + 8.3 is used, assuming a standard deviation of 4, resulting in a compressive strength of 30.36 MPA.
• 😀 The next step involves determining the water-cement factor (EFS), considering the type of cement (Type 1 or PCC cement) and the aggregate used.
• 😀 A chart is used to determine the relationship between cement type and compressive strength, which shows that the required compressive strength is 37 MPA for Type 1 cement.
• 😀 The water-cement factor is determined to be 0.56 using the graph, which influences the concrete's final compressive strength.
• 😀 The script also discusses how to calculate the cement content and free water content, leading to a total requirement of 366 kg of water per cubic meter.
• 😀 For determining the aggregate requirements, the percentage of fine and coarse aggregate is calculated using size tables and a standard method.
• 😀 The script highlights the importance of adjusting water content based on the moisture conditions of the aggregates to ensure proper reaction with the cement.
• 😀 Finally, the concrete mix is balanced to maintain a consistent volume of 1 cubic meter, accounting for adjustments in water content and aggregate conditions.

Q & A

What is the main focus of the video?

The video focuses on explaining the process of concrete mix design, specifically aiming for a compressive strength of 25 MPA using the DOS method.

What is the first step in the concrete mix design process?

The first step is determining the average compressive strength (SCR) using the standard deviation from existing data or referencing SNI 2828-4 (2013) if no data is available.

How is the compressive strength determined in this method?

The compressive strength is determined using the formula **FFNC + 8.3** for a 25 MPA mix, with an average compressive strength of approximately 30.36 MPA based on the standard deviation of 4.

What is the significance of the water-cement ratio in concrete mix design?

The water-cement ratio determines the required amount of water relative to cement for a concrete mix. It affects the strength and durability of the concrete. In this case, it was calculated based on Type 1 cement and crushed stone.

What issue is mentioned regarding the availability of Type 1 cement?

Type 1 cement, which is Ordinary Portland Cement (PC), is no longer widely available on the market. It is often replaced by Portland Composite Cement (PCC), which may affect the accuracy of the provided compressive strength data.

How is the cement content calculated in this process?

Cement content is calculated based on the free water content, aggregate type, and the mix's required compressive strength. The video uses a specific formula to determine that the cement content is 205 kg per cubic meter.

What role do aggregate sizes play in the mix design process?

The size of aggregates, such as fine aggregates (sand) and coarse aggregates (stone), affects the volume and proportions in the concrete mix. For this design, the maximum aggregate size was set to 20 mm.

What is the process for determining the amount of fine and coarse aggregates?

The percentage of fine and coarse aggregates is determined using a table based on the maximum aggregate size and other factors like specific gravity. In this case, fine aggregates make up 42% and coarse aggregates 58%.

Why is it important to adjust for the moisture content of aggregates?

Adjusting for moisture content ensures that the water in the mix reacts appropriately with the cement. If aggregates are too dry or too wet, the concrete mix can be compromised, affecting its strength and durability.

How is the final water content adjusted in the mix?

The final water content is adjusted based on the moisture conditions of the aggregates. For this mix, fine aggregates required an additional 12 kg of water due to dryness, while coarse aggregates required a reduction of 6.8 kg due to their wet condition.

What are the final adjusted values for the concrete mix components?

The final values per cubic meter of concrete are: water = 210 kg, cement = 366 kg, fine aggregates = 758 kg, and coarse aggregates = 1052 kg.