Concrete is a mixture of sand, aggregate, Portland cement and moisture, which is poured over compacted clay or soil, crushed rock, and a vapor retardant barrier. It cures slowly and continues to release and absorb moisture throughout its use-life. When contacted by Category 1 water, concrete absorbs moisture over time and releases it slowly. Concrete can resist microbial growth and amplification because it is inorganic, relatively cold and alkaline, although microbials can eventually grow and amplify on soil films. Read More »