MARS - A Software Dedicated to Advanced Concrete Modeling

CreepModuleUD uses below aging function to compute va,

va=sdc+(1.0-sdc)*pow(ad,nrd)

where ad is AgingDegree.

Since AgingDegree is a function of CementHydration Degree and CementHydration Degree Rate, ad = 0 at time 0 and at the first step. So at the first step, va = 0, which results in the strains to have infinity/nan values:
depsvN = (dGammaN/va);
depsvM = (dGammaM/va);
depsvL = (dGammaL/va);

It runs with TotalReaction Degree since it becomes nonzero starting at the first step. However if we want to continue using AgingDegree for creep, the calculation of va and the strains should initiate after the first step. Alternatively, let AgingDegree have an initial value at step one.

You need to contact the author of the creep module to fix this logic.

The adopted solution is to use the SolidificationDegreeConstant and assign it a nonzero value.