Coaching Conversations (ICC Reinforced Concrete)
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The table indicates 4.5% air content for 3/4" agg and F1 exposure. How do you get to a range of 2.5-6.5? The strength would lower it to 3.5% then with the +/- 1.5% tolerance, wouldn't the allowable range would be 2%-5%?
The question is: " The range of air allowable in a 6,000 psi, 3/4 inch aggregate mix of concrete exposure class F1 is:"
Answer 1: 2.5% - 6.5%
Answer 2: 3.5% - 6.5%
Answer 3: 4.5% - 6%
Answer 4: 4.5% - 7.5%
The correct answer is: Answer 1.
My answer was: Answer 2.
These tables actually show a 5.0% air content for F1 and 3/4", so our typical tolerance would make that 3.5% to 6.5%. And remember that the question is asking for what range of air content could possibly be considered acceptable. We see here that there is a scenario in which 6.5% air content is acceptable on the high end.
Then if we apply the allowable 1% air reduction, that would mean that our target air content is 4% and our tolerance would be 25% to 5.5%.
Since this scenario allows a 2.5% on the low end, we get 2.5% to 6.5% as being possibly acceptable.
i cant find any rebar size in B4/S401 at level 6.
The question is: "On Level 6 at approximately D/9, what type of vertical reinforcement goes in the concrete wall?"
Answer 1: #6 at 12 inches oc
Answer 2: #6 at 12 inches oc, each face
Answer 3: #5 at 15 inches oc
Answer 4: #9 at 4 inches oc, alternating faces
The correct answer is: Answer 2.
My answer was: Answer 4.
Look just below Level 6 on the left of detail B4 and you'll see where it says 15" Concrete SW (shear wall) with #6 at 12" oc, EF/EW (each face, each way). It's pointing to reinforcement that runs all the way from Level 5 to Level 9.
thanks for your answer.
For the tolerance to be +- 1.5 wouldn’t the answer be 3.5-6.5 considering the air content is 5.0 for 3/4 aggregate?
The question is: "The range of air allowable in a 6,000 psi, 3/4 inch aggregate mix of concrete exposure class F1 is:"
Answer 1: 2.5% - 6.5%
Answer 2: 3.5% - 6.5%
Answer 3: 4.5% - 6%
Answer 4: 4.5% - 7.5%
The correct answer is: Answer 1.
Hi, Richard. Right, so a mix of 5,000 psi or less would be a 5.0% air for 3/4" aggregate and the 1.5% tolerance would put us at 3.5 to 6.5%. For a 6,000 psi mix though, we are allowed to have a 1% reduction in air, so 4.0%, which would put as at 2.5% to 5.5%. However, we are not obligated to follow the 1% reduction and can keep it at 5% target. Therefore, the entire range of possibly acceptable air content can be as low as 2.5% if we use a 4% air target and as high as 6.5% if we use a 5% target air.
Regarding Module 4 "Clear spacing for bundled bars and lap splices" Can you pls clarify why a bundle of bars 4.5 in thick needs 4.5 in spacing in between bundles....i cant seem to figure that using the code requirements
Let's look at 25.6.1.6 in ACI 318. It tells us that the diameter of the bundle should be considered as db, or bar diameter, when it comes to calculating spacing and cover requirements. Now let's jump back to 25.2.1 where clear spacing between bars needs to be the greatest of 1 inch, 1 bar diameter or 4/3 x the aggregate diameter. Since 4.5 inches is the largest, that's the required spacing between bundled bars.
I didn’t understand why you go with 1 - 1/2” =0.5” instead of 1/3 x 3=1. On the examples you picked the bigger number. During the module example 1, you picked 1” which is bigger than 0.5”. Why not 0.5”?
The question is: "The tolerance on concrete cover of reinforcement for a 14-inch cast-in-place basement wall with a specified cover of 3 inches is:"
Answer 1: Zero tolerance
Answer 2: -1 inch
Answer 3: -3/8 inch
Answer 4: -1/2 inch
The correct answer is: Answer 4.
My answer was: Answer 3.
We go with the least of either 1/3 x cover or 1/2" for members over 8 inches. So, in this case, go with -1/2" because it's more restrictive than 1 inch, which would be 1/3 the cover.
please explain how to get 14 inches.
The question is: "The maximum spacing of lateral ties enclosing #7 longitudinal reinforcement in a 2' x 2' column shall be"
Answer 1: 14 inches
Answer 2: 18 inches
Answer 3: 24 inches
Answer 4: 36 inches
The correct answer is: Answer 1.
My answer was: Answer 2.
Hi, Chris. In this scenario, we choose the least of 16 bar diameters of the #7 bar, 48 bar diameters of the tie, or the smallest dimension member. A #7 bar is 7/8 inch, so multiply that by 16 and we get 14 inches, which is smaller than our 24 inch column dimension and therefore our best answer since we don't have a tie size either.
thank you
on level 10 i see cpb11 not cpb3. cpb3 is on level 9
The question is: "What type of diagonal bars go in the coupling beam at Level 10 at D.5/11?"
Answer 1: (5) #5 bars
Answer 2: (6) #10 bars
Answer 3: (4) #8 bars
Answer 4: (3) #7 bars
The correct answer is: Answer 3.
My answer was: Answer 4.
Hi, Chris. At Level 10, we see a CPB-3 coupling beam that is part of the Level 10 framing and slab. We don't use the CPB-11 because that is actually occurring at the roof level.
I don't know how to get to 2".
The question is: "What is the minimum clear spacing between #11 vertical bars in a boundary element in a wall that will be cast using concrete with 1 inch nominal maximum aggregate?"
Answer 1: 2 inches
Answer 2: 1-1/3 inch
Answer 3: 1-3/8 inch
Answer 4: 1-1/2 inch
The correct answer is: Answer 1.
My answer was: Answer 2.
In this instance, we need to select the largest number of 3 options given. 1.5 db means 1.5 bar diameters, so 1.5 x 1-3/8" gives us 2.06 inches for our answer.
If I look at the column schedule for Column C3B as found at GL: 2/F, the dimensions listed state 20" x 30". However at the enlarged columns listed below between levels 1 and 3, I am led to believe that the column at GL: 2/F between levels 1 thru 3 will be 36" square. Am I correct for inferring this?
The question is: "The column on grid F/2 reduces in size to a ____________________ configuration."
Answer 1: 2 closed and 1 cross tie
Answer 2: 1 closed and 3 cross tie
Answer 3: 1 closed and 2 cross tie
Answer 4: 1 closed and 1 cross tie
The correct answer is: Answer 4.
My answer was: Answer 3.
Hi, Chris. Yeah from levels 1 to 3 we have the architectural enlargement which essentially just adds some more rebar around the 20"x30" structural column to make it 36" x 36".
there is no column at F.8/5 on level 2!
The question is: "How many pieces of steel make up the tie configuration in the Column at gridline F.8/5 on Level 2, four feet above the slab?"
Answer 1: 3 pieces
Answer 2: 2 pieces
Answer 3: 1 piece
Answer 4: 4 pieces
The correct answer is: Answer 2.
Hi, Michael. Although it's not one of the sheets for the question, if you look at S2.20, you'll see a column at F.8/5. This would fall under the "All columns, UNO" section of the schedule on 1/S3.01.
Got it, thanks
Sure thing!
i do not understand where to find information to verify that note 8 matches this condition. how do we know there is 12" of fresh concrete cast below the reinforcement?
The question is: "For the concrete foundation wall on GL E/2.4-4, what is the required lap splice for the horizontal reinforcing, assuming a Class A lap splice?"
Answer 1: 27"
Answer 2: 24"
Answer 3: 21"
Answer 4: 18"
The correct answer is: Answer 2.
My answer was: Answer 4.
Hi, Robert. Unless the wall is shorter than 12 inches, that will mean all horizontal bars except the bottom one can basically be considered top bars.
in the table it doesnt talk about nominal maximum size
The question is: "What is the minimum clear spacing between #11 vertical bars in a boundary element in a wall that will be cast using concrete with 1 inch nominal maximum aggregate?"
Answer 1: 2 inches
Answer 2: 1-1/3 inch
Answer 3: 1-3/8 inch
Answer 4: 1-1/2 inch
The correct answer is: Answer 1.
My answer was: Answer 3.
Hi, Jose. d-agg is the nomenclature for nominal maximum aggregate size. 👍
The W1 in table calls out a water content at N/A
The question is: "Concrete exposed to water with low permeability requirements shall have a maximum w/c ratio of:"
Answer 1: 0.4
Answer 2: 0.45
Answer 3: 0.5
Answer 4: N/A
The correct answer is: Answer 3.
My answer was: Answer 4.
Hi, Frank. ACI 318 and Concrete Manual don't jive completely here, so let's look at ACI 318 first. Table 19.3.1.1 tells us that concrete in contact with water and having low permeability requirements is considered W2. Then when we go to W2 in Table 19.3.2.1, we see the 0.5 requirement.
In Table 12.1 of the CM, they don't identify W1 properly (it should be W2) but they do state concrete in contact with water and having low permeability requirements should have 0.5 w/c ratio.