There are many types of aggregates available that are classed as lightweight, and their properties cover wide ranges. Elastic properties, compressive and tensile strength, time-dependent properties, durability, fire resistance, and other properties of structural lightweight aggregate concrete are dependent on the type of lightweight aggregate utilized in the concrete [1]. Structural lightweight aggregate concrete is defined as concrete which:

(a) is made with lightweight aggregates conforming to ASTM C 330,

(b) has a compressive strength in excess of 2,500 psi (17.25 MPa) at 28 days of age when tested in accordance with methods stated in ASTM C 330, and

(c) has an air dry density not exceeding 115 pcf (1,840 kg/m3) as determined by ASTM C 567 [3]. Job specifications often allow unit weights up to 120 pcf (1,920 kg/m3) or more. High performance lightweight concretes are typically produced using rotary kiln expanded clay, shale, or slate. These lightweight aggregates are relatively “light” in weight (density) due to the cellular structure of the individual aggregate particles.