This article provides guidance on concrete pumps for contractors looking to expand their services into shotcrete. It discusses the use of rotary gunite machines for dry-mix shotcrete and four pump types that are available for delivering wet-mix concrete: swing tube piston, squeeze tube (peristaltic), rotor stator (progressive cavity), and hydraulic ball valve pumps.

The nominee for ACI President in 2021-2022 is Cary S. Kopczynski, CEO and Senior Principal of Cary Kopczynski & Company, Seattle, WA, USA. If elected during membership balloting, he will serve a 1-year term as ACI President that begins at the conclusion of the ACI Concrete Convention Spring 2021 and ends at the conclusion of the ACI Convention Spring 2022

The American Concrete Institute showcases the contributions and efforts of its global membership and the concrete industry worldwide through its varied honors and awards program.

The Concrete Product and Service Guide comprises company names, URLs, and key phone numbers. We have maintained most of the product categories from previous guides, and we have added services, including industry associations, consulting firms, contractors, and testing agencies.

Q: Last winter, we placed concrete grade beams for an industrial building. A technician from the owner’s testing agency took test cylinders but left them unprotected in the cold weather for a week. At 28 days, the average cylinder compressive strength was 2750 psi. Because this was far below the specified f_c^′ of 6000 psi, the engineer required three cores to be taken to evaluate the in-place concrete strength. The individual core compressive strengths were 4940, 4970, and 5370 psi, resulting in an average strength of 5090 psi (84.8% of f_c^′). The engineer rejected the concrete on the basis that the ACI 318-19 Code¹ requires the average core strength to equal 85% of the specified strength. In this case, 0.85 f_c^′ = 5100 psi, so isn’t the average core strength of 5090 psi close enough?