Hi, I was unable to locate any equations for these curves in Eurocode, which has left me unsure how to proceed with drawing them. Nonetheless, I appreciate your response.
It's interesting, if not utterly intriguing, to see the the vertical scales of the two graphs are completely different.
The scale of the left graph is log, from 1 to 100 (or the other way 'round, if you like that better). The (unlabelled) scale of the right graph is linear and in 7 divisions.
Nice, and close to the (original) graph that the OP showed.
The original graph contains 3 curves, one each for S, N and R (for different classes of cement). The blue line is a straight line through (0,100) and the point where the red line (for a chosen t0), crosses one of the three curves (corresponding to the cement class). For values of t0 >100, the blue line should be the tangent line at the point (0,100).
Next you choose an h0 value and follow the red and purple lines (depends on the type of concrete, I guess) until the crossing with the blue line, then down to find the corresponding value of phi.
But I think thatNM_10165576 can explain this better.