water and pores

Question 1

w/c ratio

Answer 1

0.36 ~ 0.42

Question 2

w/c above 0.42

Answer 2

; excess capillary pores and water

Question 3

w/c below 0.36

Answer 3

; unhydrated cement

Question 4

theory of 0.36

Answer 4

; there is no extra water left beyond what is required for hydration and some cement unhydrated

Question 5

theory of 0.42

Answer 5

; hydrate all the cement but with little water left

Question 6

Higher w/c

Answer 6

; more capillary pores

Question 7

capillary porosity

Answer 7

; amount is function of w/c and time

; not only porosity but also important for strength and permeability

; water has surface tension and movement like evaporation causes crack and shrinkage

Question 8

Pros and cons of unreacted cement

Answer 8

+ unhydrated cement occurs when low w/c

+ less capillary voids

• expect autogenouse shrinkage

Question 9

Hydration characteristics

Answer 9

; kinetics : how rapidly cement compounds react w/ water

; Fineness : how fineness controls the rate of reaction

; Heat : how much heat is produced , exothermic process

Question 10

C-S-H

Answer 10

; Calcium Silicate Hydrate

; Core compound of strength imparting

; Chem. composition varies

; Main heat producer

Question 11

C-H

Answer 11

; Calcium hydroxide

; Not strength imparting compound

; Vulnerable to sulfate

; Water soluble

; hexagonal crystalized material

Question 12

Micro pores

Answer 12

; in btw C-S-H particles, size of pore is big enough for water to access, vulnerable to freeze -thaw

; surface tension is not large

; chem. reaction with final products occurs

Question 13

Capillary pores

Answer 13

; Excess of the water

; surface tension is low, lager pores, affect permeability

; surface tension is high, smaller pores, affect deformation and cracks due to contraction of pores

Question 14

Inter layer pores

Answer 14

; C-S-H particle has pores with water entrapped

; Surface tension is high and not affect permeability (or shrinkage) , hard to remove water