Dosagem Concreto - Método IPT/ EPUSP

Summary

The video discusses the process of concrete dosage calculation using the USP method. It explains how to determine the appropriate proportions of cement, aggregates (sand and gravel), and water based on structural and production requirements. The script emphasizes the importance of adjusting the mix to meet workability and strength needs, demonstrating through experimental trials. Various calculations are made for the ideal mortar content, including cement-to-water ratios, aggregate quantities, and testing results over a 28-day period to optimize the concrete's strength and behavior.

Takeaways

• 🔧 The students are presenting a dosage method, focusing on determining the proper proportions of concrete components using USP dosage methods based on structural and production requirements.
• ⚖️ A concrete mix ratio of 1:5 is used, meaning for every one part of cement, five parts of aggregate are added, with the sand-to-gravel ratio depending on rheological parameters.
• 🧪 The dosage table is created before starting the experiments, detailing unitary trace proportions of sand and gravel for each mortar content and its adjustments.
• 📊 An Excel sheet is used to calculate material proportions based on a 40% mortar content, helping to obtain the correct sand and gravel ratios.
• 💧 The water content is calculated using a fixed humidity level of 10%, leading to the determination of the required cement mass for a given water volume.
• 🔬 Once initial calculations are made, experiments are conducted to verify the optimal mortar content, aiming for a workable and strong concrete mix.
• 🏗️ The results are used to create a dosage diagram, aiding in understanding the behavior of different concrete mixtures based on water-cement ratios and aggregate quantities.
• 🔄 The Abrams curve is used to analyze the relationship between water-cement ratios and concrete strength at 28 days, while the Larrabee curve examines the effect of dry mass (aggregates and cement) on fresh concrete.
• 🧱 Different concrete mixtures are tested with varying mortar contents (e.g., 50%) to identify the best ratio for strength and workability.
• 🏆 The best-performing mix had a 1:6.5 ratio, showing the highest resistance and proper balance between cement, aggregates, and water for optimal performance.

Q & A

What is the main focus of the method presented in the transcript?

The method focuses on the dosage of concrete, specifically selecting appropriate proportions of materials based on curve adjustments, structural requirements, and production needs.

How is the concrete dosage initially defined in this method?

The concrete dosage is initially set with a ratio of 1 part cement to 5 parts aggregate, with the proportions of sand and gravel depending on the rheology of the mix.

What is the significance of determining the mortar content in concrete?

Determining the mortar content is crucial for achieving the desired workability and structural properties of the concrete. The ideal mortar content is found experimentally by adjusting the mixture and using a dosage table.

How is the proportion of cement calculated for each liter of water?

The cement proportion is calculated using the formula that relates water content, aggregate proportions, and mortar content. For example, with 4 liters of water, the cement required is 1.42 kg.

What role does the humidity of the materials play in the calculations?

The humidity, fixed at 10%, affects the mass of water in the mixture, which in turn influences the calculation of the required cement and other materials.

What is the purpose of the dosage diagram mentioned in the script?

The dosage diagram helps to model the behavior of concrete mixtures and understand their properties, both fresh and hardened. It visually represents relationships like water-cement ratio and aggregate quantities.

How does the water-cement ratio impact concrete strength according to the script?

The water-cement ratio is inversely proportional to concrete strength, meaning that as the water-cement ratio decreases, the strength of the concrete increases, especially at 28 days of curing.

What are the three types of concrete mixtures mentioned, and how do they differ?

The three mixtures mentioned are a rich mix (1:3.5), a standard mix, and a poor mix (1:6.1). They differ in the proportions of cement, sand, and aggregate, which affects the concrete's workability and strength.

What experimental method is used to determine the ideal material proportions?

A series of calculations and adjustments are made for different mortar contents, and experiments are conducted in the laboratory to evaluate the workability and strength of the mixtures, leading to the identification of ideal material proportions.

What conclusions were drawn regarding the resistance of different concrete mixtures?

The mixture with the highest cement and aggregate content (1:3.5) showed the greatest resistance, while mixtures with less water and sand yielded higher resistance and lower specific mass.