<P> It is uncertain when Roman concrete was developed , but it was clearly in widespread and customary use from about 150 BC ; some scholars believe it was developed a century before that . </P>
<P> It is uncertain when Roman concrete was developed , but it was clearly in widespread and customary use from about 150 BC ; some scholars believe it was developed a century before that . </P>
when was the earliest use we know about for concrete
when was the earliest use we know about for concrete
about 150 BC
about 150 BC