Investigating the effects of aggregate gradations on the compressive strength and the cost of concrete using two proportioning methods

Abstract

Optimizing aggregate gradation in concrete mixtures has an impact on concrete properties such as strength, durability and sustainability. Many aggregate proportioning methods have been proposed to solve aggregate gradation issues. The Tarantula Curve is a recently developed aggregate proportioning technique that can evaluate aggregate gradations and can give insights of the quality of the gradations. Since the Tarantula Curve have been having great success in the United States in producing concrete mixtures with outstanding performances and lower cost, this work aims to validate the gradation boundaries of the Tarantula Curve using local aggregates in Saudi Arabia by measuring the compressive strength and the workability. This work also provides a comparison between the Tarantula Curve method to the ACI 211. The results showed a reduction in the compressive strength and poor workability when the 20% limit is exceeded for the coarse aggregate retained on a single sieve. Similarly, as the limits of sieve sizes 150 µm and 75 µm were exceeded, the compressive strength decreased, and poor workability performance was observed in the mixtures. Harsher mixtures were produced as the 2.36 mm sieve limit was exceeded. It was found that the Tarantula Curve produced mixtures with a 35% higher in compressive strength and 6% lower in cost as opposed to the ACI 211 mixtures. These data and tests provide recommendations and framework for further comparative testing in the durability testing in the future

Keywords

• tarantula curve
• proportioning aggregates
• aci-211
• concrete economy