In the present work a modification was made on three equations to represent the
experiment data which results for Iraqi petroleum and natural asphalt. The equations
have been developed for estimating the chemical composition and physical properties
of asphalt cement at different temperature and aging time. The standard deviations of
all equations were calculated.
The modified correlation related to the aging time and temperature with penetration
index and durability index of aged petroleum and natural asphalts were developed.
The first equation represents the relationship between the durability index with aging
time and temperature.

log_e(DI)=a₁+0.0123(2log_e T-a₃(1/30.t²+1/2.t))

The second equation represents the relationship between the penetration index with
aging time and temperature.

Log(PI)_e=b₁-0.2013(T-(b₃+b₄t))²
The third equation represents the relationship between the durability index with
penetration index.

Log_elog_e(PI)=a-0.5627log_e(DI)
The values of penetration index and durability index for all aged samples were
compared with predicted values. These correlations give a percent of error in the
range of 1.2 to 7.4%.