Minimum Cement Content

Question of the Week (5/31/2010): What should be the minimum cement content for pervious concrete?

Poll Results:
700 lbs. ld/yd3 …………… 0%
600 lbs. ld/yd3 …………… 38%
500 lbs. ld/yd3 …………… 12%
None of the Above………. 50%

The NRMCA Pervious Concrete Certification program correctly states that “500 to 600 ld/yd3 would be a good starting point…..and further fine tuning can be accomplished by the concrete producer”. 

In the early days of pervious concrete promotion, statements were made about proportioning mixes, specifically 600 lbs/CY as a good starting point. This idea seems to have carried itself along and wound up in many documents about pervious concrete and ultimately in the minds of specifiers.  And what started as a "starting point" became a "minimum" in the conservative mind.  Not surprisingly, the poll result reflects this mindset.....38% chose 600 ld/yd3.

You need cement to make pervious concrete, however, caution should be taken when specifying minimum cement content. The producer needs the freedom to develop his mix design based on locally available materials and its' available gradations. Although I typically work with mix designs containing 500-600 ld/yd3, some aggregate gradations I’ve worked with required less than 500 ld/yd3. In fact there are some mixes (high sand) that require less than 400 ld/yd3!

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Be sure and take part in the new Poll: What is Your Preferred Joint for Pervious Concrete?