How many years did it take the modern engineers to figure out how the roman concrete was made out of?

Analyze the quotation below in the context of european exploration in the americas. as you read the quote, think about what it says about columbus's motivations to explore. was he interested in gaining knowledge, wealth, or both? how did his motivations influence how he treated the people already living in the americas? i did not try to examine them in detail, because it could not be done in 50 years. for my desire is to see and discover as much as i can before returning to your highnesses, our lord willing, in april. it is true that in the event of finding places where there is gold or spices in quantity i should stop until i had collected as much as i could. i, therefore, proceed in the hope of coming across such places.