ASTM C39 Compressive Strength Flashcards
(24 cards)
What is the rate of loading for cylinders?
35+-7 psi/s
Compressive Strength is rounded to what?
Nearest 10 psi
For averaging multiple compressive strength results, do you average the unrounded result or rounded?
Unrounded
Average compressive strength is rounded to what?
Nearest 10 psi
What is the formula for calculating compressive strength?
fcm= (4Pmax)/(πD^2)
In the Compressive strength formula identify the variables? Fcm, Pmax, D
Fcm = compressive strength, Pmax=max force pounds, D=diameter
Will the compressive force pounds change with different size samples?
Yes
Specimens shall not be tested if any individual diameter of a cylinder differs from any other diameter of the same cylinder by more than ___%.
0.02
The compressive strength of the specimen is calculated by___________.
Dividing the maximum load attained by the cross-sectional area of the specimen.
How often must calibration be completed within?
13 months
When must calibration be completed outside of the 13 months?
When equipment is moved, or accuracy is questioned.
When must capping be used on a sample?
When the specimen is not within plane of 0.002”
How many times must a specimen be measured for diameter?
Two times at about midheight.
What is the diameter rounded to?
0.01 in
What is the test age tolerance for 28 day breaks?
+-20 hours
For unbonded caps, verify the alignment of the specimen after application of load but before reaching _______% of the anticipated strength.
0.1
True or False. Make no adjustment in the rate of movement as the ultimate load is being approached and the stress rate decreases due to cracking in the specimen.
t
What information is recorded after the break?
Maximum load, age of sample, and fracture type
What do you do if the fracture pattern is not one of the typical patterns shown?
Sketch and describe breifly
What do you do if the measure strength is lower than expected?
Examine the fractured concrete and note the prescence of air voids and if fractures pass around agg or through them.
What do you do if a corner fracture occurs?
Continue compressing to be sure the max strength is attained
How many fracture types are there?
6
If reporting the average of two or more tested cylinders, do you use rounded or unrounded individual strength values?
Unrounded
For the final reported strength value, what is the final value rounded to?
The nearest 10 psi.
