CONCRETE 3

Question 1

adding to much water will reduce strength of concrete and can cause

Answer 1

segregation

Question 2

1 : 3 : 6

Answer 2

34L

Question 3

1 : 2 : 4

Answer 3

30L

Question 4

1 : 1 1/2 : 3

Answer 4

27L

Question 5

1 : 1 : 2

Answer 5

25L

Question 6

When freshly mixed
concrete is checked to ensure that
the specified slump is being attained
consistently.

Answer 6

slump test

Question 7

A standard slump cone
is ___ and ___ in diameter at the
bottom and __ on top
which is open on both ends

Answer 7

12 inches high (0.30)
8 inches (0.20)
4 inches (0.10)

Question 8

Common quality-control test of
concrete, based on 7- and 28-days
curing periods.

Answer 8

compressive strength test

Question 9

Standard size.is ___ high and___ diameter. Filling is done the
same way as the slump test but
taken out from the mold in ___ hours.

Answer 9

12 inch
6 inch
24 hours

Question 10

compressive strsses

Answer 10

2,000 psi, 2,500 psi, 3,000 psi.

Question 11

concrete additives

Answer 11

1. To speed up the initial set of concrete . 2. To retard the initial set.
2. To make the concrete more resistant to
   deterioration due to repeated freezing and thawing cycles. ·
3. To prevent bleeding of water to the surface of concrete.
4. To improve the workability of the mix.
5. To improve the hardness or denseness to the concrete surface.
6. To render the concrete more watertight.

Question 12

concrete additives 2

Answer 12

8. To improve the bond between two concrete surfaces.
9. To inhibit the set of cement paste. 10.To produce a colored surface.
   11.To produce a non-skid surface.
   12.To prevent the evaporation of water from the newly placed concrete.
   13.To help develop all the potential strength of a given water-cement paste.
   14.To decrease the weight of concrete per cubic foot

Question 13

An admixture which is used to speed up the initial set of concrete. Such a material may be added to the mix to increase the rate of early-strength development for several reasons. For example, this will allow earlier removal of forms and in some cases reduce the whole curing period.

Answer 13

accelerators

Question 14

to delay or extend the setting time of the cement paste in concrete. In hot weather hydration is accelerated by the heat, thus cutting down the time available to place, consolidate, and finish the concrete. High temperatures, low humidity and wind cause rapid evaporation of water from the mix during summer. This drying of the concrete leads to cracking and crazing of the surface.

Answer 14

retarders

Question 15

A material used to reduce the amount of ·water necessary to produce a concrete of given consistency or to increase the slump for a given water content. A typical one is made from the metallic. salts of ligninsulfonic acids.

Answer 15

water reducing admixtures

Question 16

Water under pressure and in contact with one surface of the concrete can be forced through channels between the inner and outer surfaces. A measure of the amount of water passing in this way is a measure of permeability; any admixture used to reduce this flow is really a permeability reducer

Answer 16

concrete waterproofers