R34 RCA (3/4” Aggregate) is a recycled concrete aggregate that is an alternative to a 3/4" natural stone as determined by the ASTM #57 stone spec. R34 is an aggregate supplement in ready mix concrete specifically for use in inground pools. Its light weight characteristics and compressive strength of 3000 psi make R34 an ideal aggregate supplement. P.Park NJ’s R34 is a green alternative to expensive natural stone which can earn you LEED credits and increase your profits.