Development of Autogenous Shrinkage Deformation and Strength Parameters in Self-Consolidating Concrete with Light and Natural Aggregate

Abstract

The concrete during the curing exhibits volume changes caused by different factors: chemical reactions during hydration, surface drying, external temperature or carbonisation. Each aforementioned factor imposes different type of shrinkage that constitutes to the overall shrinkage of concrete. In case of the concretes with a low water/cement ratio, significant influence on the overall shrinkage has the autogenous shrinkage. This type of shrinkage is a result of self-desiccation that sucks out the water from capillary pores during the hydration. The article presents the results of the test on the autogenous shrinkage performer in accordance with modified ASTM C1581. To reduce the autogenous deformations caused by the shrinkage, the authors implemented internal curing by using presoaked lightweight aggregate. The tests were performed on cement mortars and self-consolidating concretes with water/cement ratio of w/c=0.28. The mortars were made with use of fine natural aggregate 0-2 mm and fly ash lightweight aggregate 0-4mm. To produce concrete authors used natural aggregate 0-2 mm and 2-8 mm and fly ash lightweight aggregates 0-4 mm and 4-8 mm. Designed self-consolidating mixes were tested to determine their rheological properties. The concrete compressive strength and tensile splitting strength was determined after 1, 3, 7 and 28 days. The autogenous deformations were registered every 500 s during 28 days. The shrinkage was determined on slab samples 35×150×1100 mm. The samples simulated linear expansion of ring specimen used in ASTM method. Study analyses the influence of the type of aggregate on the development of autogenous deformations and strength properties of young self-consolidating concretes. Studies have shown that presoaking of the light aggregate changes the development of deformation. Internal curing caused swelling instead of shrinkage during the hydration stage, reducing the overall autogenous shrinkage.