Moisture Content Measurement

The Federal Highway Administration allows for the use of slag from the steel-making industry as a construction aggregate material. When crushed and screened for use in hot-mix asphalt applications, slag moisture must meet specific requirements to ensure minimal expansion in the hot-mix asphalt upon application. Volume changes to the slag from the hydration of unslaked lime and magnesia must be measured and controlled. If stockpiled too long, the slag will overhydrate, causing excessive and difficult-to-break lumps. Insufficient time in storage does not allow for the drainage of excess moisture. Measuring slag moisture throughout the stockpiling process is critical to ensuring that it is optimal for use in hot-mix asphalt.