Am I sinful if I do not stop my work as a construction worker, and I sweat a great deal until the time for prayer expires, so I combine the prayers and perform them after their prescribed time has passed, due to my excessive sweating which I am ashamed to meet Allah with?

It is not permissible to delay the prayer beyond its appointed time, for Allah Almighty says: (Indeed, prayer has been decreed upon the believers a book [due at] fixed times) [An-Nisa: 103]. Delaying it is one of the gravest prohibitions. Scholars have interpreted the squandering of prayer in Allah Almighty's saying: (Then succeeded them successors who neglected prayer and pursued desires; so they are going to meet ghayy) [Maryam: 59] as delaying it beyond its appointed times.

Your sweating profusely and not wanting to meet Allah in that condition is not an acceptable excuse to delay the prayer until its time has passed. What is required for the prayer to be valid is purity from minor and major impurities, and from filth on the clothes, body, and place, and perfect cleanliness is not a condition. If you are unable to clean your body and wear clean clothes, then you must pray in that condition and not abandon the prayer until its time has passed.