Podcast
Questions and Answers
Aggregate should be washed for a better bonding between paste and ______
Aggregate should be washed for a better bonding between paste and ______
aggregate
It is mainly the aggregate that provide strength to concrete especially coarse aggregates which act just like bones in the ______
It is mainly the aggregate that provide strength to concrete especially coarse aggregates which act just like bones in the ______
body
Rough and angular aggregate provides better bonding and high ______
Rough and angular aggregate provides better bonding and high ______
strength
It is water cement ratio that basically governs the property of ______
It is water cement ratio that basically governs the property of ______
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Type of cement affect the hydration process and therefore strength of ______
Type of cement affect the hydration process and therefore strength of ______
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Amount of cementing material It is the paste that holds or binds all the ingredients.Thus, greater amount of cementing material greater will be ______
Amount of cementing material It is the paste that holds or binds all the ingredients.Thus, greater amount of cementing material greater will be ______
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Rough and angular aggregates is preferable as they provide greater ______
Rough and angular aggregates is preferable as they provide greater ______
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Chemical admixtures like plasticizers reduce the water cement ratio and increase the strength of concrete at same water cement ______
Chemical admixtures like plasticizers reduce the water cement ratio and increase the strength of concrete at same water cement ______
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Mineral admixtures affect the strength at later stage and increase the strength by increasing the amount of ______ material
Mineral admixtures affect the strength at later stage and increase the strength by increasing the amount of ______ material
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The strength of concrete is basically referred to compressive strength and it depends upon three factors. 1.Paste Strength It is mainly due to the binding properties of cement that the ingredients are compacted ______ together
The strength of concrete is basically referred to compressive strength and it depends upon three factors. 1.Paste Strength It is mainly due to the binding properties of cement that the ingredients are compacted ______ together
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Study Notes
Heat of Hydration
- Concrete undergoes nonlinear temperature distributions during setting and hardening due to heat of hydration, potentially causing tensile stresses that exceed young concrete strength and lead to cracking.
Accelerated Setting Time
- Concrete remains fluid until the cement sets and then progressively hardens over time.
Workability
- Workability refers to the ease and homogeneity of mixing, placing, consolidating, and finishing freshly mixed concrete.
Water Reduction
- Decreasing the water-to-cement ratio leads to increased concrete strength, with a direct relationship between water reduction and strength improvement.
Types of Admixtures
- Chemical Admixtures: Water-soluble compounds used to modify concrete properties.
- Mineral Admixtures: Finely ground solid materials that enhance concrete performance.
Water-Reducing Admixtures / Plasticizers
- Purpose includes achieving higher strength by reducing water-cement ratio while maintaining workability, decreasing cement content to lower heat of hydration, and enhancing workability for easier placement.
- Effective water reduction typically ranges from 5% to less than 12%.
- Common admixtures include ligno-sulphonates and hydrocarbolic acid salts, with plasticizers usually derived from lignosulphonate.
Mixing
- Concrete must be uniformly mixed to ensure even distribution of cement, water, aggregates, and admixtures.
- Mixing is usually done with machines for consistent results.
Proportioning and Mixing Concrete
- Concrete mixes should be designed for easy placement while minimizing costs.
- Properties of concrete evolve over time; care during initial curing can enhance durability later.
Deterioration of Concrete
- Over time, concrete can deteriorate due to various physical and chemical attacks.
Fresh Concrete
- Known as "Green Concrete," this stage allows for shaping and molding while still in a plastic state.
- Consistency denotes the ease of flow of fresh concrete.
Water to Cement Ratio
- An increased water-to-cement ratio results in decreased strength and durability of hardened concrete.
- To enhance strength and durability, it is crucial to reduce the water-to-cement ratio in the mix.
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Description
Test your knowledge on the different types of concrete admixtures, heat of hydration phenomenon, setting time acceleration, and workability properties of concrete. Understand how these factors affect the overall quality and strength of concrete structures.
