Lightweight Aggregate Particle Shape Effect on Structural Concrete*


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Title: Lightweight Aggregate Particle Shape Effect on Structural Concrete*

Author(s): Milton H. Wills, Jr.

Publication: Journal Proceedings

Volume: 71

Issue: 3

Appears on pages(s): 134-142

Keywords: aggregate shape and texturs: compressive strength: flexural strength; lightweight aggregate concretes: lightweight aggregates: mortars (material) ; splitting tensile strength; void cement ratio: voids; water; water-cement ratio.

Date: 3/1/1974

An exploratory investigation of six lightweight fine aggregates was conducted in an effort to extend the concept, developed with normal weight fine aqqreqates or sands, that one of the most important properties of fine aggregates is their particle shape features--angularity and texture as measured by loose void content. They affect mixing water requirements, water-cement ratio and, consequently, most of the strength characteristics of mortar having a constant cement-aggregate ratio. For a range of 10 percent in loose void content, compressive strength varied about 2000 psi (150 kgf/cm). The lightweight fine aggregates were generally found to have high void contents and mortar mixing water requirements; therefore, they had lower strengths when compared to natural sand mortars. Further extending the results of this exploratory work, each of the lightweight fine aggregates, as well as that from a seventh source, and their coarse companions, were combined with the same natural quartrite, sand and gravel. Concrete was designed to contain 517 lb (235 kg) of cement, to have a 3 to 4 in. (8 to IO cm) slump and no entrained air. As indicated, fine and coarse aggregate were seen to influence mixing water requirements depending on their shape features as measured by void cotent. Both compressive and flexural strength responded to these changes in mixing water content as a function of water-cement ratio. This concept leads to a more accurate design of structural Iightweight concrete according to normal weight pro-cedures.