PSI - Issue 14

D. Anupama Krishna et al. / Procedia Structural Integrity 14 (2019) 384–394 A. Krishna et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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(stiffer aggregates produce higher modulus concretes, and the modulus increase with aggregate fineness modulus as long as the mix is workable); and (5) moisture content at time of test (wet specimens produce higher modulus values than dry specimens). Temperature can significantly affect the modulus values. The modulus of elasticity ( ) of various concretes at room temperature varies over a wide range, 5.0× 10 3 to 35.×10 3 MPa , and is dependent mainly on the water-cement ratio in the mixture, the age of concrete, the method of conditioning, and the amount and nature of the aggregates. The modulus of elasticity decreases rapidly with the rise of temperature, and the fractional decline does not depend significantly on the type of aggregate [Cruz (1966)]. Table 6 presents the models for the variation of compressive elastic modulus as a function of temperature from previous studies and present study.

Table 6: Compressive elastic modulus models for concrete at high temperature Literature Models at elevated temperature

E

f 2 ' / '  

Anderberg and Thelandersson (1976)

crT

cT cT

E E E

T E / 550)

(700  

BSI

crT

c

T E C T C E ; 200    

T E E ) 0.28 

) 20 (1 0.0015

(0.87 0.00084

 

 

Xiao, and Konig,( 2004) Li and Purkis (2005)

crT

c

crT

c

c

c c T E E 

  / 740) (800

crT

  

 c

E

T

C T C E    125 

1.

0.00165

1.033,20



Chang et al. (2006)

crT







 c

4.5

E E

T ) ,125 1/ 1.2 18(0.0015  

C T C E    800

2. 3.

 E C T C    600  E C T C    800  c

crT crT

T

  ( 0.00165 ( 0.001282

1.033) ,20 1.0265) ,20



E

T

 



Present study

crT

c

Figure 5 illustrates a comparison of the normalized elastic modulus with temperature for different models with that from the present study. At all temperatures the model exhibits a linear decrease till a temperature of 800 o C. The degradation of the modulus may be attributed to excessive thermal stresses and physical and chemical changes in concrete microstructure.

Fig. 5. Variation of normalized Elastic moduli with temperature from various models.