ABSTRACT
This chapter discusses concrete strength variability due to variations in mixing water and air contents.
Compared to other ingredients, there are several sources (and potential errors) by which mixing water is incorporated in a concrete mixture. These sources and ways to ensure that the batchwater is within tolerance of the designed amount are discussed in a later chapter. ASTM C94 and ACI 117 state that the total mixing water should be within ±3% of the quantity required by the mixture proportion. ASTM C94 also requires that the added water should be within ±1% of the design total mixing water. These standards do not establish accuracy requirements for individual sources of water, such as for water added from the water tank on the concrete truck. The NRMCA Plant and Truck Certification inspection process has accuracy requirements for water measurement in the plant and for water tanks that are based on target quantities.
