a. What would be the expected change in compressive strength if a specimen was t
ID: 1713857 • Letter: A
Question
a. What would be the expected change in compressive strength if a specimen was tested using the same concrete mix but was larger (say 6 by 12 inch cylinder (note that the force would also be larger)),
b. What would be the expected change in compressive strength if a specimen was tested using the same concrete mix but shorter (say 4 inch diameter by 6 inch tall cylinder),
c. What would be the expected change in compressive strength if a specimen was tested using the same concrete mix but younger (say age of 7 days)
d. What would be the expected change in compressive strength if a specimen was tested using the same concrete mix but, dried in air after removing from the forms, instead of curing in a water bath
e. What would be the expected change in compressive strength if a specimen was tested using the same concrete mix but dried in air for 7 days after curing in water for 21 days, (note total age would be 28 days), instead of curing m the water bath for 28 days
f. What would be the expected change in the 28-day compressive strength if a specimen was tested using the same concrete mix but cured hot water (100 0F)?
g. What is the purpose of the plywood strips? What could be the expected change in the splitting tensile strength if the strips were not used?
h. Use the equation from Item 6.3 to calculate the range of appropriate loading rates (highest allowed loading rate and lowest allowed loading rate) for a specimen with an 8” by 8” square cross section and a 24” span.
Explanation / Answer
a) As the force and area bothe are increasing, there will not be any significance change in compressive strength. Compressive strength= force resisted /area.
b) Here area of the cylinder is decreased and force remain constant. Hence stress on cylinder increases and compressive strength decreses.
c) Compressive strength decreases if we test it for 7 days. Becasue In 7 days we attain only 50% of the whole strength.
d) If we dry in air, compressive strength will be reduced because of th epore resent in water. If it is cured then pore will be occupied by water and compressive strength will inccrease.
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