ACI Concrete Field Testing Technician Grade 1 Study Guide

ACI Concrete Field Testing Technician Grade 1 Study Guide ASTM C31 / C31M-06 outlines the standard practice for making, curing, protecting, and transporting test specimens in field conditions. ASTM C1064 / C1064M-05 describes the standard test method for measuring the temperature of freshly mixed hydraulic-cement concrete. ASTM C172 -07 establishes the standard practice for sampling freshly mixed concrete from various containers used in its production or transportation. ASTM C143 / C143M-05a provides the standard test method for determining the slump of hydraulic cement concrete in both laboratory and field environments. ASTM C138 / C138M-07 sets the standard test method for measuring the density (unit weight), yield, and air content (gravimetric) of concrete. ASTM C231 -04 specifies the standard test method for assessing the air content of freshly mixed concrete using the pressure method. ASTM C173 / C173M-07 outlines the standard test method for evaluating the air content of freshly mixed concrete with any type of aggregate, whether dense, cellular, or lightweight, by employing the volumetric method. Molds Molds used for producing concrete specimens should be made from steel, cast iron, or other nonabsorbent materials that do not react with concrete. They must be watertight and retain their dimensions and shape under all usage conditions. Cylindrical Specimens Specimens for compressive or splitting tensile strength testing need to be cylinders that are cast and allowed to set vertically. The length should be double that of the diameter, with dimensions such as 4 by 8 inches or 6 by 12 inches. The cylinder's diameter must be at least three times the nominal maximum size of the coarse aggregate. If the nominal maximum size of the coarse aggregate exceeds two inches, the concrete sample should be processed by wet sieving through a two-inch sieve. Beam Specimens Flexural strength specimens must be beams of concrete that are cast and hardened in a horizontal position. The length of these beams should be at least two inches greater than three times the depth being tested. The ratio of width to depth during molding should not exceed 1.5. The standard beam dimensions should be 6 by 6 inches in cross-section, suitable for concrete with a nominal maximum coarse aggregate size of up to two inches. When the maximum size exceeds two inches, the smaller cross-sectional dimension of the beam should be at least three times the nominal maximum size of the coarse aggregate. Tamping Rod The tamping rod should be a round, straight steel rod with a hemispherical tip at one or both ends, matching the rod's diameter. The dimensions depend on the diameter of the cylinder or the width of the beam. For cylinders or beams less than six inches in diameter, the rod should be 3/8 inch in diameter and 12 inches long. For six-inch cylinders, the rod should be 5/8 inch in diameter and 20 inches long, and for nine-inch cylinders, the same diameter but 26 inches long. Tolerances for the rod's length should be plus or minus four inches, and for the diameter, plus or minus 1/16 inch. Vibrators Internal vibrators are recommended for use. The vibrator should operate at a frequency of at least 9,000 vibrations per minute while it is in the concrete. The diameter of a round vibrator must not exceed one fourth the diameter of the cylinder mold or the width of the beam mold. Additionally, the combined length of the vibrator shaft and the vibrating element should extend at least three inches beyond the depth of the section being vibrated. Mallet A mallet with a rubber or rawhide head, weighing between 1.25 and 0.5 pounds, should be used for concrete testing purposes. Sampling Receptacle The sampling receptacle should be a robust metal pan, wheelbarrow, or flat, clean, nonabsorbent board that can easily hold and remix the sample with a shovel or trowel. Temperature Measuring Device The temperature measuring device must accurately measure the temperature of freshly mixed concrete with at least three inches of immersion, within a range of 30 to 120 degrees Fahrenheit. It should be accurate to within plus or minus one degree Fahrenheit and readable with an accuracy of plus or minus 0.5 degrees Fahrenheit. Verification of these devices should be conducted every twelve months. ASTM C1064 Standard Test Method for Temperature Procedure To measure the temperature, freshly mixed concrete should be sampled according to Practice C172. The temperature measuring device must be positioned so that the sensing end is submerged at least three inches deep, with a similar concrete cover in all directions.- Close all voids at surface of the concrete around the temperature device. - Leave the temperature measuring device in the concrete for at least 2 mins but no more than 5 mins. -Then read and record to the nearest 1 degree Feahrenheit. ASTM C172 Standard Test Method For Section 40: - The elapsed time shall not exceed 15 mins. between obtaining the first and final portions of the composite sample. - The sample shall be combined and remixed with a shovel to ensure uniformity. -Sample size is dictated by the maximum aggregate size and should be atleast 28 L (1cubic foot) for strength tests. -Start the test for slump, temperature, and air content within 5 mins. after obtaining sample. -Start molding specimens for strength tests within 15 mins. after obtaining the sample. ASTM C172 Sampling from Stationary Mixers - Sample the concrete