Restrained Shrinkage Testing of High-Performance Concrete Modified with Structural Lightweight Aggregate


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Title: Restrained Shrinkage Testing of High-Performance Concrete Modified with Structural Lightweight Aggregate

Author(s): D. Cusson, T. Hoogeveen, and L. Mitchell

Publication: Special Publication

Volume: 228


Appears on pages(s): 1353-1372

Keywords: autogenous shrinkage; high-performance concrete; high-strength concrete; internal drying; restained shrinkage; self-desiccation; tensile creep; thermal shrinkage

Date: 6/1/2005

A comprehensive research program at the National Research Council Canada is underway to develop low-shrinkage high-performance concrete for the design of cost-effective and sustainable concrete structures. This paper presents the structural laboratory testing of large prismatic high-performance concrete (HPC) specimens under restrained shrinkage and tensile creep. A systematic testing approach is presented, including a description of the theoretical background and the experimental apparatus used. The structural behaviour of two different HPC mix designs are compared and documented. The control concrete had a water-cement ratio of 0.34 and a cement-sand-aggregate ratio of 1:2:2. A slight variation of this mix design included 6% sand replacement by pre-soaked porous expanded shale lightweight aggregate. One of the objectives of this study is to determine whether the addition of this type of aggregate could effectively reduce autogenous shrinkage due to internal drying in HPC. Test results show that 6% sand replacement by pre-soaked porous lightweight aggregate reduces autogenous shrinkage moderately. This moderate shrinkage reduction was accompanied by a moderate increase in tensile creep. The results also reveal that most internal drying and autogenous shrinkage developed shortly after setting in both concrete mixes. This observation suggests that solutions to preventing autogenous shrinkage cracking in HPC will involve techniques that should be effective shortly after setting.