Final Flashcards
Rate of loading for running a Compressive strength test is
20-50 psi/second
Rate of loading for running Splitting tensile test is
100-200 psi/minute
Rate of loading for running Rupture tensile test (beam test) test is
125-175 psi/ minute
If a water reducer is added to the concrete mix without changing other ingredients, what will happen to the properties of the concrete?
It will increase the slump or Workability
If a water reducer is added to the concrete mix without changing other ingredients, and the intention of adding the water reducer is to increase the compressive strength of
hardened concrete, how this can be achieved?
Reduce w/c, and keeping the same slump
In making a slump test, the cone should be filled in
3 layers
In making a slump test, each layer should be equal
4 inches
In making a slump test, each layer should be rodded
25 times per layer
Concrete should have the desired ______________ before beginning any other tests.
Slump
A load of 200,000 pounds was recorded from testing a 6 in. x 12 in. concrete cylinder under
compression. The concrete compressive strength is ________psi.
7077.15
f ′c=P/A
Where:
f′c is the compressive strength, P is the load applied, and A is the cross -sectional area.
Given:
P = 200,000lbs
A is a cylinder so area is pi*radius(r)^2
Solve:
Given that the diameter of the cylinder is 6 inches, the radius (r) is (6/2) = 3 inches.
A = pi3^2 = pi9 = 28.27in^2
so
f’c = 200,000/28.27 = 7077.15 psi
The splitting tensile strength of a 6 x 12 in. concrete cylinder is ____ psi for a recorded failure
load of 56520 pounds.
500
The modulus of rupture of a standard beam test specimen (ASTM C78) (6 x 6 x 18 in.) is _____ psi for a recorded failure load of P = 6000 pounds
500
Define High Performance Concrete and how do we achieve HPC Mix?
High-Performance Concrete (HPC) is concrete that meets specific performance and composition requirements. Achieving an HPC mix involves using high-strength materials, careful proportioning, and often incorporating supplementary cementitious materials.
Describe elastic and inelastic deformation?
Elastic deformation refers to reversible, temporary changes in shape under load, like stretching a rubber band. Inelastic deformation, on the other hand, is permanent and occurs when the material undergoes plastic deformation or fractures.
Define toughness of fibrous concrete beams?
The ability to resist damage by holding the broken cement together via fibrous strands
Define pervious concrete and what are the advantages of using this concrete?
Pervious concrete is actually designed to be more porous, allowing water to pass through. It’s often used for stormwater management. The correct definition is: Pervious concrete is a special type of concrete with high porosity that allows water to pass through it, promoting water infiltration and reducing runoff. The advantages include improved stormwater management, reduced flooding, and groundwater recharge.
The property that reflects the ease or difficulty in placing and finishing freshly mixed
concrete, is called:
Workability
The bonding agent used in a concrete mix is:
Cement
A material used for the purpose of delaying the setting time of concrete is:
Retarding admixture
The weight of one gallon of water is:
8.33lbs
The ability of hardened concrete to resist the deterioration caused by weathering, chemicals,
and abrasions is known as:
Durability
The IDOT allowable range for air content in concrete pavement and bridge decks is:
5.0 - 8.0
The most important effect of entrained air in concrete is to:
Increase durability
Air entrainment admixture must be dispersed into the concrete mixer with:
Water
What are the three important factors in curing concrete:
Time, Temperature, Moisture
When curing test cylinders for the first 20 to 24 hours, they must be kept moist and at
temperature between:
60 to 80 deg. F
Test cylinders should be sent to the laboratory for standard curing, within 7 days
False
When test cylinders are being made on a truckload of concrete, what other type test should be
run on the same load of concrete?
Slump Test
A mix design requires 33.5 gallons of metered water per cubic yard. Due to high temperature,
25 pounds of ice per cubic yard will be used. How much metered water is now needed per
cubic yard using the ice?
8.5 gallons per cubic yard.
Solution:
The substitution ratio for ice to water is typically around 1:1 by weight, meaning 1 pound of ice is roughly equivalent to 1 gallon of water. So, the amount of water replaced by the ice is 25 gallons.
To find the adjusted amount of metered water needed, subtract the amount replaced by ice from the original requirement:
Adj Water = Original water - water replaced by ice
Adj water = 335-25 = 8.5 gallons per yrd^3
The amount of slump, as determined by the slump cone, is calculated by measuring the
difference between the height of the mold and the height over the displaced center of the top of the specimen.
True
Using the following information, determine the unit weight of a concrete mixture
* Weight of empty bucket 15.62 lbs
* Weight of full bucket 52.69 lbs
* Volume of bucket 0.33 cu.ft
112.33lbs/ft^3
Solution:
Net weight of the cement:
52.69-15.62 = 37.07lbs
Net volume of the bucket:
Net weight bucket * volume
37.07/0.33 = 112.33lbs/ft^3
The property of fresh concrete, in which the water in the mix tends to rise to the surface while
placing and compacting, is called
Bleeding
The property of the ingredients to separate from each other while placing the concrete is
called
Segregation
Workability of concrete is directly proportional to:
A. Aggregate cement ratio
B. Time of transit
C. Gradation of the aggregate
D. All of above
D. All of above
Air entrainment in the concrete increases
Workability
1% of voids in a concrete mix would reduce its strength by about
5%
Concrete is required for a bridge deck in Chicago. A specified compressive
strength, f’c, of 4,000 psi is required at 28 days using Type I cement. The concrete should
be designed to overcome all the environmental conditions encountered in Chicago,
Category F (Severe Exposure for Freeze and Thaw and Deicing Salt). Refer to the
attached tables of Chapter 12 of PCA Textbook–Use the absolute volumetric method to
answer the following for a mix of 1 cubic yard. The following information is submitted for a
proposed concrete mix:
Cement, Specific Gravity =3.15
Fine aggregate (Natural Sand)
Fineness modulus 2.60
Specific gravity 2.67
Absorption (SSD) 1.5%
Moisture Content 3.5%
Coarse aggregate
1.0 in Nominal maximum size gravel
Specific gravity 2.69
Bulk density 95 lbs./ft3
, Dry rodded
Absorption (SSD) 1.0%
Moisture contentment 2.0%
Concrete
Slump 3 in
Air content 6%
What is the bulk volume of dry-rodded coarse aggregate per unit volume of concrete for nominal
maximum coarse aggregate size of 1.0 in. and a fineness of fine aggregate of 2.80?
0.67
Concrete is required for a bridge deck in Chicago. A specified compressive
strength, f’c, of 4,000 psi is required at 28 days using Type I cement. The concrete should
be designed to overcome all the environmental conditions encountered in Chicago,
Category F (Severe Exposure for Freeze and Thaw and Deicing Salt). Refer to the
attached tables of Chapter 12 of PCA Textbook–Use the absolute volumetric method to
answer the following for a mix of 1 cubic yard. The following information is submitted for a
proposed concrete mix:
Cement, Specific Gravity =3.15
Fine aggregate (Natural Sand)
Fineness modulus 2.60
Specific gravity 2.67
Absorption (SSD) 1.5%
Moisture Content 3.5%
Coarse aggregate
1.0 in Nominal maximum size gravel
Specific gravity 2.69
Bulk density 95 lbs./ft3
, Dry rodded
Absorption (SSD) 1.0%
Moisture contentment 2.0%
Concrete
Slump 3 in
Air content 6%
What is the dry weight of the coarse aggregate in 1 yd3
of concrete?
1719 lbs
Answer:
0.67x95x27= 1719 lbs
Concrete is required for a bridge deck in Chicago. A specified compressive
strength, f’c, of 4,000 psi is required at 28 days using Type I cement. The concrete should
be designed to overcome all the environmental conditions encountered in Chicago,
Category F (Severe Exposure for Freeze and Thaw and Deicing Salt). Refer to the
attached tables of Chapter 12 of PCA Textbook–Use the absolute volumetric method to
answer the following for a mix of 1 cubic yard. The following information is submitted for a
proposed concrete mix:
Cement, Specific Gravity =3.15
Fine aggregate (Natural Sand)
Fineness modulus 2.60
Specific gravity 2.67
Absorption (SSD) 1.5%
Moisture Content 3.5%
Coarse aggregate
1.0 in Nominal maximum size gravel
Specific gravity 2.69
Bulk density 95 lbs./ft3
, Dry rodded
Absorption (SSD) 1.0%
Moisture contentment 2.0%
Concrete
Slump 3 in
Air content 6%
When required strength data are available to establish a standard deviation, for a specified concrete
strength, f’c of 4,000 psi and a standard deviation, S of 50 psi, what is required average compressive
strength f’cr is:
3616.50 psi
Solution:
4000+1.34x50=4067 psi
4000+2.33x50-500=
3616.50 psi
Concrete is required for a bridge deck in Chicago. A specified compressive
strength, f’c, of 4,000 psi is required at 28 days using Type I cement. The concrete should
be designed to overcome all the environmental conditions encountered in Chicago,
Category F (Severe Exposure for Freeze and Thaw and Deicing Salt). Refer to the
attached tables of Chapter 12 of PCA Textbook–Use the absolute volumetric method to
answer the following for a mix of 1 cubic yard. The following information is submitted for a
proposed concrete mix:
Cement, Specific Gravity =3.15
Fine aggregate (Natural Sand)
Fineness modulus 2.60
Specific gravity 2.67
Absorption (SSD) 1.5%
Moisture Content 3.5%
Coarse aggregate
1.0 in Nominal maximum size gravel
Specific gravity 2.69
Bulk density 95 lbs./ft3
, Dry rodded
Absorption (SSD) 1.0%
Moisture contentment 2.0%
Concrete
Slump 3 in
Air content 6%
When required strength data are not available to establish a standard deviation, for a specified
concrete strength of 4,000 psi, what is required average compressive strength f’cr is:
5200 psi
Solution:
4000+1200 = 5200 psi
An air entrained concrete mix to be used in a severe environment. For a nominal maximum coarse aggregate size of 1.0 in. and a slump of 4 inches, what is the
amount of water required is
295 lbs
An air entrained concrete mix to be used in a severe environment. For a nominal maximum coarse aggregate size of 1.0 in. and a slump of 4 inches, what is the
Amount of air content required is
6%
What is the absolute volume of the coarse aggregate in 1 yd3
of concrete?
1719/(2.69x62.4) = 10.24 ft3
The maximum water-cement ratio (w/c) for corrosion protection for reinforced concrete exposed
to severe environment with exposure category F is
0.45
The minimum compressive concrete strength, f’c for corrosion protection for reinforced concrete
exposed to severe environment with exposure category (Class F2 and F3) is
500 psi
What is the weight of cement in 1 yd3
of fresh concrete?
w/c = 0.45,
C = 295/0.45 = 655.5
What is the absolute volume of the cement in 1 yd3
of this fresh concrete?
655.6/(3.15x62.4) = 3.33 ft3
What is the volume of water designed for use in 1 yd3
of fresh concrete?
295/(1x62.4) = 4.72 ft3
What is the absolute volume of sand in 1 yd3
of fresh concrete?
27-10.24-3.33-4.72-0.06x27 = 7.09 ft3
What is the weight of the sand in 1 yd3
of fresh concrete?
7.09x2.67x62.4 = 1181.25 lbs
How much water would the oven-dry weight of the coarse aggregate need to absorb to reach SSD conditions?
0.01x1719 = 17.19 lbs
Consider casting a concrete driveway 40 feet long, 12 feet wide and 6 in. thick. The
proportions of the mix by weight are given as 1:2:3 for cement, sand, and gravel with w/c of 0.50. The
specific gravities of cement, sand, and gravel are 3.15, 2.65, and 2.65 respectively. Entrained air is 6 %.
- How many pounds of cement, water, sand, and gravel are needed?
Weight of cement: 5206.15 lbs
Weight of water:
2603.07 lbs
Weight of sand:
10412.31 lbs
Weight of gravel:
15618.46 lbs
Solution:
Volume of driveway:
40x12x6/12=240 ft3
Absolute volume of air= 0.06x240=14.4 ft3
Adjusted Volume=240-14.4=225.6 ft3
Vmix = (1/3.15) +( 0.5/1) +( 2/2.65) + (3/2.65) = 2.704
Weight of cement:
1 x 225.6 x 62.4)/2.704 = 5206.15 lbs
Weight of water
(0.5 x 225.6 x 62.4)/2.704 = 2603.07 lbs
Weight of sand
(2 x 225.6 x 62.4)/2.704 = 10412.31 lbs
Weight of gravel
(3 x 225.6 x 62.4)/2.704 = 15618.46 lbs
A 6 in x 12 in concrete cylinder failed at an axial compressive force of 125,000 lbf. The ultimate
compressive strength is:
𝑓’c= 𝑃/𝐴 = (125,000/28.27) = 3587.5 psi
A 6 in x 12 in concrete cylinder resisted a transverse force of 45,000 lbf in a split tensile cylinder test.
The concrete tensile strength is:
𝑓’c= 2𝑃/pi*LD
𝑓’c = 2450,000/(3.1412*6) = 398 psi
A 6 x 6 x 21 in unreinforced concrete beam resisted a force of 6500 lbf on 18 in span length. A one-third
point loading test was used, and the fracture occurred within the middle third. The modulus of rupture is:
f = P/12 = 65000/12 = 541.6 psi
Note: for the beam 6621 inches spanned 18 inches.
Given a compressive strength of 6000 psi, the approximate value of the modulus of rupture is:
𝑓𝑟 = 7.5√fc
7.5√7500 = 580.9psi
The following information submitted for a proposed concrete mix.
Cement
Specific Gravity 3.15
Fine aggregate
Fineness modulus 2.70
Specific gravity 2.60
Absorption 2.0%
Coarse aggregate
Specific gravity 2.65
Dry bulk density 100 lb/ft3
Absorption 0.75%
Concrete
Slump 5 in
Water 5.0 gal/sack
Air content 4%
Cement content 7.0 sack mix
Coarse aggregate 0.57 ft3
/ft3 bulk
- What is the dry weight of the coarse aggregate in 1 yd3 of concrete?
- What is the absolute volume of the coarse aggregate in 1 yd3 of concrete?
- What is the water-cement ratio?
- What is the weight of cement in 1 yd3 of fresh concrete?
- What is the absolute volume of fine aggregate in 1 yd3 of fresh concrete?
- What is the SSD weight of the sand in 1 yd3 of fresh concrete?
- What is the absolute volume of the cement in 1 yd3 of this fresh concrete?
- What is the volume of water designed for use in 1 yd3 of fresh concrete?
- If the oven-dry weight of the coarse aggregate were 1600 lb, how much water would it need to absorb to
reach SSD conditions? - The unit weight of this concrete mix is most nearly
Solutions:
1.
𝑉𝐶A = 0.57 ∗ 27 = 15.39𝑓t^3
𝑊𝐶.𝐴 = 15.39𝑓t^3*100 = 1539lbs
- 𝑊𝐶.𝐴 = 1539/(62.4*2.65) = 9.31ft^3
- w/c = 5*(8.33/94) =0.44
- cement = 794=658
water = 0.44658 = 289.52 lbs - VF.A. = 27-(1539/(6242.65)) -(658/62.5 ∗ 3.15) - (298.52/62.41) - (4/100 * 27) = 8.49 ft^3
- WF.A = VF.A. SpG 62.4 =
8.492.6062.4 = 1377.42 lbs - V = 658/(62.4*3.15) = 4.64 ft^3
- V = 289.52/(62.4*1) = 6.46 ft^3
- A.C>=. = 0.75%
Water Absorbed = (0.75/100) *1539 = 11.54 lbs - Density = (weight cement + weight water + Weight Fine Agg. + Weight Course Agg. )/27 =
143.10 lbs / ft^3
A load of 300,000 pounds was recorded from testing a 6 in. x 12 in. concrete cylinder
under compression. The concrete compressive strength is __________psi.
10612
The splitting tensile strength of a 6 x 12 in. concrete cylinder is ___ psi for a recorded failure load of 56000 pounds.
495
The modulus of rupture of a standard beam test specimen (ASTM C78) (6 x 6 x 21 in.) ________ psi for a recorded failure load of P = 7000 pounds
583
The two aspects of bleeding are _______ and _______.
amount of bleeding and rate of bleeding
The shrinkage reading for concrete at 90 days is 0.0007 in/in. For a beam of 30 ft long, what
is the deformation (∆L) due to shrinkage of the beam in inches?
0.0007 x 30 x 12 = 0.252 inches
The approximate value of ultimate shrinkage strain in concrete is
(a)0.003 in/in, (b)0.000780 in/in,
(c) 0.00003 in/in,
(d) 0.03 in/in
(b) 0.000780 in/in,
Consider casting a concrete driveway 40 feet long, 12 feet wide, and 6 in. thick. The mix
proportions by weight are given as 1:2:3 for cement, sand, and gravel with w/c of 0.50. The specific
gravities of cement, sand, and gravel are 3.15, 2.65, and 2.65, respectively. Entrained air is 6 %.
How many pounds of cement, water, sand, and gravel are needed?
Note: 1 ft3 = 7.48 gallons and 1 gallon = 8.33 lbs
Volume of driveway=
40x12x(6/12) =240 ft3
Absolute volume of air = 0.06 x 240 =14.4 ft3
Adjusted Volume =
240 -14.4 =225.6 ft3
Vmix = 1/3.15 + 0.5/1 + 2/2.65 + 3/2.65 = 2.704
Weight of cement = (1/2.704) x 225.6 ft3 x 62.4 lbs/ft3 = 5206.15 lbs
Weight of water = (0.5/2.704) x 225.6 ft3 x 62.4 lbs/ft3 = 2603.07 lbs
`
Weight of sand = (2/2.704) x 225.6 ft3 x 62.4 lbs/ft3 = 10412.31 lbs
Weight of gravel = (3/2.704) x 225.6 ft3 x 62.4 lbs/ft3 = 15618.46 lbs
