Modulus of Elasticity 3

[Butch1224]

How can I determine modulus of elasticity of normal weight concrete for each varying f'c (from casting to 28days)?? How is it related to time??

 

[msquared48]

you can approximate "E" with 59,000(f'c)^1/2

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[DST148]

Modulus of elasticity(MOE) is a function of the density of concrete, strength of concrete, and is sensitive to MOE of aggregates. Modulus of elasticity of concrete develops more rapidly than strength in the short term, with less significant growth beyond 28 days, e.g. strength at 7 days is typically 75% of 28-day strength, however, MOE @ 7 days could be greater than 90% of MOE @ 28 days
Mod. of Elasticity is determined per ASTM C469 "Standard Test Method....."

 

[Butch1224]

Thank you so much for response

 

[WillisV]

@msquared48 it's actually 57,000(f'c)^1/2 per ACI 318 Section 8.5.

But directly to the o.p.s question had to do with the gain of E over time, see the research report linked below, page 32 of the pdf (12 of the report), equation 2.5 which provides a time dependent model.

 

[WillisV]

link:

http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SMO/FDOT_BC354_85_rpt.pdf

 

[msquared48]

You're right Willis. Used it for years.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

Butch1224, as you are probably aware, the information given above is in psi units. If you want MPa, you need to convert. E is also a function of concrete density. The Australian Code gives an approximation of (density in kg/m^3)^1.5 x .043 fcm^0.5, where fcm is the mean value of compressive strength at the appropriate age. Only an approximation, as any expression for concrete E would be, and should be considered +/- 20%. If you want better data on a given concrete, you have to do testing using a method like the one suggested by DST148.

 

[asixth]

I'm pretty sure that ACI 209 will have some equations and likewise ACI 360 or 363 for high strength concrete.