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A short class with Sarah and her students. The other ways are under More.
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Let's start by discussing basic creep. Basic creep occurs when Concrete is kept in a sealed environment with no moisture exchange. Can anyone tell me why this is significant?
Maybe because it shows how concrete can deform even without additional load?
Exactly! Since no moisture can enter or exit, it builds internal stress. It's essential to remember 'no moisture, no stability.' Now, what do you think the long-term effects on structures might be?
It could lead to cracks or failures in the structure over time, right?
Yes! That's spot on. As they say, 'creep along in silence; it could sink your building!' Let's move to the next type.
Now, let's talk about drying creep, also known as the Pickett Effect. Does anyone know what happens during this process?
Could it be when concrete loses moisture while it's under load?
Yes! Great observation. Drying can enhance creep significantly. Think of it as 'drowning in air' — if it dries out, the stresses increase. Why is it crucial to manage moisture during construction?
So we don't get unexpected deflections or failures later?
Correct! Drying creep is a silent assassin for structures if not controlled. Let's dive deeper into autogenous creep.
Autogenous creep is interesting because it occurs without any moisture movement, especially in high-strength concrete. Can anyone explain why this might happen?
Is it due to chemical reactions happening in the concrete?
Absolutely! Internal chemical shrinkage leads to deformation. This is particularly critical in mixes with a low water-cement ratio. Remember, 'no water, big trouble!' What implications does this have for the design of high-strength concrete?
We need to account for this in our structural designs to prevent unwanted deformation and damage.
Exactly! Understanding these types of creep allows engineers to make educated decisions in material selection and structural integrity. Great job, class!
Basic creep might occur in a concrete wall that is not allowed moisture exchange during curing, leading to unexpected deformations over time.
Drying creep may happen in a concrete slab on a hot, dry day, where rapid moisture loss increases creep and can cause structure instability.
Autogenous creep can be observed in a high-strength concrete beam that shrinks internally due to hydration processes despite being properly sealed.
Creep and dry, if moisture's nigh, concrete will bend, and cracks will vie.
Once there was a concrete wall, sealed tight in a crawl. As time went by, it crept and sighed, until it cracked, oh what a fall!
BDA - Basic, Drying, Autogenous; remember these types of creep.
For Drying Creep, think P-F-W: Pickett Effect, Fast evaporation, Water loss.
Term
What occurs during basic creep?
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What enhances creep significantly?
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What is a characteristic of autogenous creep?
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Gradual increase in strain or deformation in concrete under constant load over time.
Creep occurring in a sealed environment without moisture exchange.
Creep that occurs when concrete loses moisture under load, significantly enhancing deformation.
Creep that occurs due to internal chemical processes in high-strength concrete, even in the absence of moisture.
The section details the various types of creep in concrete, including basic creep, drying creep, and autogenous creep, each resulting from different environmental and material conditions.
This section describes three main types of creep: basic creep occurs in sealed environments; drying creep arises from moisture loss due to applied load; and autogenous creep appears in high-strength concrete without external moisture, all emphasizing the importance of moisture levels and stress conditions.
Understanding the types of creep is essential for engineers designing concrete structures. Creep is the gradual deformation of concrete under constant stress over time. The three predominant types of creep include:
Basic Creep: This type occurs when concrete is loaded in a sealed environment, meaning no moisture exchange takes place. The absence of moisture exchange can exacerbate the creep effect over time, emphasizing the criticality of moisture in material behavior.
Drying Creep (Pickett Effect): Occurs when concrete loses moisture while under load. This type greatly enhances creep due to the additional stress caused by moisture loss. Drying conditions can lead to significant deformations over time, stressing the importance of controlling environmental conditions during curing.
Autogenous Creep: This phenomenon occurs even when no external moisture moves, primarily affecting high-strength concrete with low water-cement ratios. The internal chemical shrinkage leads to additional creep, making it crucial to consider this factor during the design of high-performance concrete structures.
Each type varies based on moisture conditions and stress factors, further influencing the overall behavior of concrete in structural applications, thus highlighting the need for careful planning and design.