Dosagem Concreto - Método IPT/ EPUSP

Júlia Evangelista

20 Jul 202212:29

Summary

TLDRThe 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.

Outlines

00:00

🛠️ Concrete Mixture Methodology

This paragraph explains the process of determining the proper proportions for concrete mixtures based on the USP method. It outlines how the dosage method adjusts curves to optimize resistance and workability according to structural and production requirements, using materials available on-site. The mix starts with a 1:5 ratio (cement to aggregate), with adjustments made for sand and gravel proportions. The goal is to find the ideal mortar content through experimental calculations, aided by dosage tables. It also details how water content, cement weight, and material humidity are factored into the process, ultimately leading to precise material calculations for experiments.

05:01

📊 Creating Dosage Diagrams

This section emphasizes the importance of constructing dosage diagrams to model the behavior of concrete mixtures. The diagrams highlight the relationship between water-cement ratios, aggregate content, and concrete resistance, with a focus on the mixture’s age (typically 28 days). It explains how to use the curves for evaluating both fresh and hardened concrete, considering mass dry aggregate ratios and cement use. The paragraph also mentions experimental results, guiding adjustments to cement and aggregate proportions to achieve desired properties in different mixtures.

10:01

📐 Material Proportions and Resistance

The final section focuses on calculating and comparing the proportions of cement, sand, and water for different mixtures based on laboratory results. It delves into the methods for determining the ideal water-cement ratio and evaluates the mixture's specific gravity to find the best composition. Through rule-of-three calculations, the text shows how the ideal balance of materials is achieved for varying concrete strengths and workability. It concludes by noting that the 1:3.5 mixture had the highest cement and aggregate content, yielding the best mechanical resistance, and compares calculated versus actual water usage.

Mindmap

Keywords

💡Dosage Method

The dosage method refers to the process of determining the proportions of different components, such as cement, aggregate, and water, to achieve the desired properties of concrete. In the video, it involves adjusting the curves of strength and workability to meet structural and production requirements, ensuring the correct balance of materials.

💡Teor de Argamassa (Mortar Content)

This refers to the proportion of mortar (cement, water, and sand mixture) used in the concrete mix. The mortar content is crucial for determining the concrete's workability and strength. The video explains how experimental adjustments are made to find the ideal mortar content for different mixes.

💡Water-Cement Ratio

The water-cement ratio is the ratio of the weight of water to the weight of cement in a concrete mix. It is a key factor in determining the strength and durability of the concrete. In the script, this ratio is discussed in relation to its impact on the final concrete strength after 28 days of curing.

💡Aggregates

Aggregates, such as sand and gravel (brita), are the granular materials used in concrete. Their proportions relative to other materials in the concrete mix affect the concrete’s texture, strength, and durability. The video mentions how the proportion between sand and gravel varies depending on the specific requirements of the project.

💡Traço (Concrete Mix Design)

Traço refers to the specific mix ratio of the components in concrete, such as cement, sand, gravel, and water. The script mentions different mix designs, like 1:5 or 1:6.5, each optimized for particular strength or workability requirements. Understanding the right 'traço' is essential for successful concrete production.

💡Abrams’ Law

Abrams' Law describes the inverse relationship between the water-cement ratio and the strength of concrete: as the water-cement ratio decreases, the strength increases. The video references this law when discussing the properties of concrete after 28 days, linking it to the mixture's overall performance.

💡Workability

Workability refers to how easy it is to mix, transport, and place concrete. In the video, achieving the right balance between workability and strength is a key goal of the dosage method. Adjustments to water and aggregate content directly impact workability.

💡Pilot Batch

A pilot batch is a small-scale test of a concrete mix, used to evaluate its properties before full-scale production. In the video, a pilot batch with a ratio of 1:5 is mentioned, serving as an initial experiment to determine the right proportions of cement and aggregates.

💡Diagrama de Dosagem (Dosage Diagram)

A dosage diagram is a tool used to visually represent the relationships between the different components in a concrete mix and their impact on the concrete’s properties. The video mentions how this diagram helps in understanding the behavior of different concrete mixtures, especially in terms of strength and workability.

💡Mass Specific

Mass specific refers to the density or specific weight of materials used in the concrete mix, such as cement, sand, and water. In the video, calculations based on mass specifics are performed to determine the exact quantities of each component needed for a given volume of concrete.

Highlights

The dosage method selects the appropriate proportions of components based on curve adjustments and structural requirements.

The method proposes a pilot ratio of 1 to 5, meaning for each part of cement, five parts of aggregate are added.

The ideal mortar content is determined experimentally using the dosage table, aiming for optimal concrete workability.

The process involves calculating material quantities for different mortar contents and proportions of sand and gravel.

A fixed humidity of 10% is applied to determine the water mass, which helps calculate the amount of cement needed.

For 4 liters of water, the calculated cement quantity is 1.42 kg, contributing to the final concrete mix proportions.

Material quantities are calculated for each mortar content, progressing from 40% as an initial point.

A dosage diagram is created to represent the behavior of the concrete mixture at different stages.

The Abrams curve indicates that concrete strength is inversely proportional to the water-cement ratio over 28 days.

The second quadrant illustrates the interaction between dry mass (aggregates) and the water-cement ratio in fresh concrete.

The cement consumption per cubic meter of concrete is inversely proportional to the dry aggregate-to-cement mass ratio.

Concrete samples are created with a 50% mortar content, and the appropriate material proportions are calculated.

The highest concrete strength is achieved with a 1 to 3.5 ratio, utilizing a proportion of cement and gravel optimized for resistance.

Water and cement quantities are recalculated for 15 liters of water, adjusting the ratios for different material batches.

The best concrete strength is obtained from the 1:3.5 mix, confirmed through laboratory experiments, with adjusted water usage.

Transcripts

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