Why is my air so high (or low) when I am using the same air dosage I was yesterday?

Everything affects the air in concrete, including slump, temperature, change in aggregate gradations, load size, water additions at the job site, other admixtures, mixing time, and SCMs—just to name a few. The only way to know is to test your air contents regularly. We live in an area where temperature can change dramatically from morning to afternoon. Even with all the other factors remaining constant, the amount of chemical used to achieve the target air could vary throughout the day.