Resources & Guides / Building Codes & Standards / ASTM & UL Standards / ASTM C330
ASTM C330
Standard Specification for Lightweight Aggregates for Structural Concrete
Overview
ASTM C330 provides requirements for aggregates used to produce structural concrete with lower density than conventional concrete. These aggregates are typically manufactured by heating shale, clay, slate, or slag in a rotary kiln until they expand, creating a porous, low-density particle structure. The primary objective is to significantly reduce the dead load of concrete structures while maintaining specified compressive strength (generally 2,500 psi or greater).
Key Performance Metrics
- Dry loose unit weight: 35-70 lb/ft³ determines final concrete density
- Proven concrete-making properties for specified strength targets
- Maximum drying shrinkage and popout resistance requirements
- Limits on deleterious substances like organic matter and clay lumps
Strategic Applications
In high-rise buildings, lightweight concrete reduces cumulative dead load on columns and foundations, allowing smaller structural members and more economical foundation systems. For long-span bridge decks, the reduced weight enables more slender designs. Lightweight concrete on metal deck systems achieves higher fire-resistance ratings for given slab thickness compared to normal-weight concrete, potentially eliminating costly fireproofing.
Internal Curing Advantage
A significant but often underappreciated benefit is the ability to facilitate "internal curing." The porous structure of lightweight aggregates allows them to absorb and hold water. During cement hydration, this stored water releases back into the paste, effectively curing concrete from inside out. This results in more complete hydration, lower permeability, and reduced plastic shrinkage cracking - particularly valuable for large slabs exposed to rapid surface drying.