Rating: ⭐⭐⭐⭐½ (4.5/5)
High. At roughly $50–$80 (ACI member pricing), it pays for itself the first time it saves you from wrongly rejecting a slab. aci 214.4r-10 pdf
ACI 318 (Building Code) and ASTM C42 (Standard Test Method for Obtaining Cores). Pro Tip for PDF users: Make sure you get the official ACI PDF (watermarked). Some third-party scan copies of this particular 2010 edition have illegible figures in Appendix B. The searchable text feature in the official PDF is worth the extra cost. Rating: ⭐⭐⭐⭐½ (4