ACI ASTM C138

ACI ASTM C138 ASTM C138 is utilized to determine the density (unit weight), yield, and air content (gravimetric) of concrete. A decrease in density may suggest several possibilities, including changes in materials (lower specific gravity), increased water content, higher air content, alterations in ingredient proportions, or reduced cement content. If the reduction in concrete density is attributed to an increase in air content, it may enhance the concrete's durability against freezing and thawing. However, this could negatively impact its strength, resistance to abrasion, chemical attack, shrinkage, and susceptibility to cracking. Density tests should be applied to both lightweight and heavyweight concretes. Changes in density may influence various characteristics, such as pumpability, placeability, finishability, and the overall strength of different types of concrete. Yield refers to the quantity of concrete generated from a mixture that comprises specific amounts of the component materials. - A = air content (percentage of voids) in the concrete - C = actual cement content (in pounds per cubic yard) - Cb = mass of cement within the batch (in pounds) - D = density (unit weight) of concrete (in pounds per cubic foot) - M = total mass of all materials in the batch (in pounds) - Mc = mass of the measuring container filled with concrete (in pounds) - Mm = mass of the measuring container - Ry = relative yield - T = theoretical density of concrete calculated on an air-free basis (in pounds per cubic foot) - Y = yield, indicating the volume of concrete produced per batch (in cubic yards) - Yd = volume of concrete intended to be produced by the batch (in cubic yards) - Yf = volume of concrete produced per batch (in cubic feet) - V = total absolute volume of the component materials in the batch (in cubic feet) - Vm = volume of the measuring container (in cubic feet) To ensure accuracy, a balance or scale must be precise to 0.1 pounds or 0.3% of the test load, whichever is larger, applicable at all points within its usable range. The useable range should extend from the mass of the empty measuring container to the mass of the container when filled, up to 160 pounds per cubic foot. Concrete with a slump exceeding 3 inches should be compacted using a tamping rod. For concrete having a slump between 1 and 3 inches, either a tamping rod or vibration may be applied for consolidation. Concrete with a slump less than 1 inch should be consolidated through vibration. rod each layer 25 times when _____or smaller measures are used. ️14L rod 50 times when____measures are used ️28L and one stroke per______for larger measures ️3 square inches how to determine density (unit weight) ️D=(Mc-Mm)/Vm How to determine theoretical density ️T=M/V how to determine yield in cubic yards ️Y(yd3)=M/(DX27) How to determine yield in cubic meters ️Y(m3)=M/D how to determine relative yeild ️Ry=Y/Yd How to determine the cement content ️C=Cb/Y how to determine the air content ️A=[(T-D)/T]X 100 What MUST be reported ️1. Id of concrete represented by the sample