Record the orientation (horizontal, vertically up\/down) \u2014 rebound values must be corrected for impact direction.<\/li>\n<\/ol>\nCalculation & Reporting<\/h2>\n
Report the median rebound number per EN 12504-2. Discard the set if more than 20% of readings differ from the median by more than 30%. Strength estimation requires a correlation curve established against cores or cubes from the same concrete.<\/p>\n
Acceptance Criteria<\/h2>\n
Rebound numbers for normal structural concrete typically range 25–50. Values are affected by carbonation (up to +50% overestimate on old surfaces), moisture and aggregate type \u2014 grind carbonated layers and correlate before judging strength compliance.<\/p>\n
Frequently Asked Questions<\/h2>\nHow accurate is the rebound hammer for strength?<\/h3>\n
With a mix-specific correlation, ±15–20% at best. Without correlation it should only rank areas of the same structure for uniformity or locate suspect zones for coring.<\/p>\n
How often should the hammer be calibrated?<\/h3>\n
Verify on the steel anvil each day of use; return the hammer for servicing and recalibration after roughly 2,000 impacts or whenever anvil readings drift outside the manufacturer’s band.<\/p>\n
Recommended Apparatus<\/h2>\n
NL Scientific manufactures the Rock Test Hammer<\/a> for this method. Browse the full Concrete Testing Equipment<\/a> range or request a quotation<\/a> from our engineers.<\/p>\n
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