23. Cement and Concrete

Question 1

Define concrete

Answer 1

A composite material consisting of aggregate particles bound together in a solid body by cement

Question 2

Define cement

Answer 2

a ceramic that by chemical reaction binds particulate aggregrates into a cohesive structure

Question 3

define aggregate

Answer 3

granular material which provides the majority of the volume of concrete. It is used as a filler, providing dimensional stability and wear resistance

Question 4

Cement hardens by reacting with ____

Answer 4

water

Question 5

Lower water content in cement is desirable because….

Answer 5

less shrinkage and potential for
crack formation, which results
in higher mechanical strength

Question 6

Is concrete stronger in tensile or compressive?

Answer 6

compressive

Question 7

is the reaction between cement and water endo or exothermic?

Answer 7

exothermic

Question 8

What are the 3 components used to make clinker?

Answer 8

limestone, clay, and iron oxide

Question 9

What are the products of limestone, clay, and iron oxide in the cement making process?

Answer 9

clinker and CO2

Question 10

Cement is made of a combination of ___ and ____

Answer 10

clinker and gypsum

Question 11

Name the 3 primary CO2 producers in the cement making process and the % of the total they contribute

Answer 11

50% released from chemical reaction
40% from burning fuel to heat kiln
10% from mechanical process such as gringing

Question 12

The hardening reaction involves formation of

interpenetrating ______

Answer 12

spines

Question 13

in general the compressive strength of concrete increases with ____ and ____ ____ in the atmosphere

Answer 13

time

moisture content

Question 14

What happens if too little water is added to cement?

Answer 14

unreacted cements remains which comprimises the strength

Question 15

What happens if too much water is added to cement

Answer 15

the unreacted water remains in little pores and qill lead to cracks

Question 16

air entrainment (really small bubbles) decreases the strength of the concrete but ___ durability because…

Answer 16

increases
little air pockets may fill with water but since the air can compress the water doesnt do as much damage in its freeze thaw cycles

Question 17

Why does rebar have a patterned surface?

Answer 17

to help create a good bond with the concrete

Question 18

Can the load still be transfered from the concrete to the rebar if they are no longer bonded?

Answer 18

no

Question 19

rebar handles the ____ forces while the concrete handles the ____ forces

Answer 19

tensile

compressive