# Concrete and Reinforcing Steel

## 18 important questions on Concrete and Reinforcing Steel

### What are the main components of hardened concrete?

### How is compression strength of concrete found?

### Why is NSC heterogeneous?

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### Why is the HSC stress strain response curve linear and brittle?

### What is the typical compression strength of beams and slabs?

### Why does concrete density influence the elastic modulus?

### The modulus of elasticity intersects the non-linear stress strain curve at which level?

### At what compression stress is the linear approximation given by modulus of elasticity an unsafe estimate?

### How is tension strength measured?

### Why is bending tension higher than direct tension strength

### For 30 MPa concrete what are the bending and direct tension strengths?

- Direct tension = 0.33*sqrt(30)

### What physical phenomena cause creep and shrinkage?

### How large can creep strain become as a portion of elastic strain?

### What three factors influence creep AND shrinkage

- Humidity level/temperature

- Strength of paste

- Aggregate to cement ratio

### What factor only influences creep and not shrinkage?

### Why do reinforcing bars have deformations

### What is the linear portion of the stress strain curve of steel?

### What is strain hardening?

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