Concrete weighing from 15 to 90 lb/cu ft is classified as?

Concrete that weighs between 15 to 90 lb/cu ft is classified as lightweight insulating concrete. This type of concrete is specifically designed to reduce density while maintaining adequate strength and durability, making it suitable for applications where weight reduction is critical, such as in structural applications, roofing, and insulation. Lightweight insulating concrete often incorporates lightweight aggregates like expanded clay, shale, or pumice, which contribute to its lower density and insulating properties.

In contrast, heavyweight concrete is significantly denser, commonly exceeding 90 lb/cu ft and is often used for radiation shielding. Mass concrete refers to large volumes of concrete that are placed in structures, focusing on thermal control rather than density. No-slump concrete is a specific term for a type of mix that has such a low water-to-cement ratio that it maintains its shape when placed, rather than being fluid like traditional concrete. Thus, option B accurately captures the defining characteristics of concrete in the given weight range.