ACI Concrete Field Testing Technician - Grade I Practice Exam 2025 - Free Concrete Field Testing Practice Questions and Study Guide

The correct answer is governed by ASTM C172, which is the Standard Practice for Sampling Freshly Mixed Concrete. This standard specifically outlines the procedures and precautions necessary for sampling concrete to ensure that the sample is representative of the batch.

Sampling is a critical step before conducting tests such as the slump test because it directly affects the reliability and accuracy of the test results. The standard includes important guidelines on how to collect and handle samples, including the quantity of concrete needed, methods to prevent contamination, and the timing of the sample collection in relation to the placement of concrete.

Understanding ASTM C172 is essential for any technician performing field tests on concrete, as it ensures adherence to best practices and compliance with industry standards. The other options, while related to concrete testing and specifications, focus on different aspects: C150 pertains to cement specifications, C31 deals with making and curing specimens for strength tests, and C39 describes the testing of the compressive strength of concrete cylinders. Therefore, none of those standards provide the specific guidance on sampling needed for conducting a slump test.