The method of using 6″ diameter by 12″ long wire mesh cylinders has not been used regularly in several years. The most accepted means of taking samples is as specified in ACI 506 documents which generally require a sample panel of approximately 18″X18″ by 4″ thick from which cores are taken. The cores should be taken at a minimum distance from the edge of the thickness of the panel to yield fair test results. ACI 506.4R-94 references under testing of shotcrete, ASTM C 1140-03 (Standard Practice for Preparing and Testing Specimens from Shotcrete Test Panels. Also ASTM C42/C 42M-03 (Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete. Standard 18″X18″X4″ panels are typically made. ASTM C 1140-03 states a 24″X24″X4″, cores are to be taken 1 core diameter plus one inch from any side of the test panel.