Effect of Specimen Shape and Size on the Compressive Strength of Foamed Concrete

Abstract

-Lightweight concrete, in the form of foamed concrete, is a versatile material that primarily consists of a cement based mortar, mixed with at least 20% volume of air. Its dry density is typically below 1600 kg/m 3 with a maximum compressive strength of 15MPa. The ASTM standard provision specifies a correction factor for concrete strength of between 14 and 42Mpa, in order to compensate for a reduced strength, when the aspect height-to-diameter ratio of a specimen is less than 2.0. However, the CEB-FIP provision specifically mentions a ratio of 150mm dia. x 300mm cylinder strength to 150 mm cube strength; though, both provision requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength to lightweight concrete (in this case, foamed concrete). The focus of this work is to study the effect of specimen size and shape on the axial compressive strength of concrete. Specimens of various sizes and shapes were cast with square and circular cross-sections i.e., cubes, prisms, and cylinders. Their compression strength behaviours at 7 and 28 days were investigated. The results indicate that, as the CEB-FIP provision specified, even for foamed concrete, 100mm cubes (l/d = 1.0) produce a comparable compressive strength with 100mm dia. x 200mm cylinders (l/d = 2.0).

Freeze casting – A review of processing, microstructure and properties via the open data repository, FreezeCasting.net

“…Increased aspect ratios are reported to have a larger, negative effect on the compressive strength of bar-shaped specimens vs. cylinders [511]. Increased aspect ratio has also been reported to increase the compressive strength of cylinders and decrease the compressive strength of bars [512]. The over-representation of cylinder specimens for camphene relative to other fluids may be partially responsible for the reverse trend of A for camphene.…”

Size effect at testing strength properties of concrete

“…When testing the strength properties of concrete, the shape and dimensions of tested specimens are crucially important. The influence of a specimen's size on concrete compressive strength has been described in depth ([4]- [7]). The specimens which are the most often used in testing compressive strength of concrete are 150 mm, 100 mm and 200 mm cubes, and cylinders 150 mm in diameter and 300 mm long.…”