Water-reducing agents standard deviation

Table 7.2 Air-entrained concrete has a higher standard deviation that plain concrete, but this can be minimized by the use of an air-entraining, water-reducing agent...

The effect produced by the incorporation of a lignosulfonate-based water-reducing agent is shown in Table 7.6. The results were obtained from a series of mixes over an 8-month period by a ready-mix plant used in the production of concrete piles. Since the standard deviation of this particular plant was 5.0 MPa for mixes produced without the use of admixtures, it is evident that the use of the admixture resulted in reduced variability. These results indicate that in high workability mixes with cement contents in the median range, the admixture may cause an increase in the standard deviation. Thus in redesigning the mix to have a lower cement content in this class of concrete, adequate consideration should be given to this difference in standard deviation. Increased uniformity can be attained in this instance... 

Table 7.5 Changes in standard deviations of a ready-mix concrete plant using a hydroxycarboxylic water-reducing agent...

Table 7.6 Seven-day and 28-day strengths and standard deviations for concrete containing a lignosulfonate water-reducing agent produced on a ready-mix concrete piant...

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