It is vital to know exactly how much moisture is present in aggregate and sand in order to reproduce the proper mix design correctly every time. Knowing the moisture content of aggregate allows the operator to subtract that amount of water from the batch water to maintain the specified water-cement ratio.
In the past, aggregate moisture was measured by drying a known weight of aggregate in an oven and calculating the moisture from the weight loss. It is not feasible to perform this test more than a few times in a given day, so some of the correction for moisture would have to be performed by guesswork, leaving ample opportunity for error.
This problem can be remedied by using an electronic moisture sensor. The sensor is placed inside the aggregate bin, where it can accurately measure the water content for a given amount of aggregate. The sensor must be placed in the direct flow of the aggregate, and measurements made while the aggregate is flowing in order to receive correct data.