how come concrete packaging specify 28th day strength ? whats the reason for it ?
mm zai leh?
You mean cement? Concrete is only made by mixing sand with cement and water.
if im not wrong...
concrete takes 28 days to cure to achieve its max strength...
What does 28 -day strength mean?
Concrete hardens and gains strength as it hydrates. The hydration process continues over a long period of time. It happens rapidly at first and slows down as time goes by. To measure the ultimate strength of concrete would require a wait of several years. This would be impractical, so a time period of 28 days was selected by specification writing authorities as the age that all concrete should be tested. At this age, a substantial percentage of the hydration has taken place.
Courtesy of Portland Cement Association, http://www.cement.org/basics/concretebasics_faqs.asp
Must let it cure first mah.