President, G.N.A. Engineers/Consultants, Minneapolis, Minn.
Sales engineer, Set Products, Inc., Maximent Division, Macedonia, Ohio
The past theory of the action of shrinkage-compensating cements is discussed and recent findings that refute the internal compressive stress concept are presented in favor of the American Concrete Institute (ACI) Committee 223 net positive elastic strain behavior (spring action theory) for the proper functioning of concrete with shrinkage-compensating expansive cement.
A method of using less than the minimum ACI-223 committee recommendation of 0.15% steel is presented based on two past research studies.
Examples of typical installations are shown along with some interesting concepts that deal with curvature control (curling/warping) as a result of reversed differential shrinkage/expansion strains. A case for using less than the minimum ACI-318 recommendation of 0.188% steel is also presented for this type of concrete in structural reinforced concrete. The proper type of expansion/isolation joints are presented that exclude current ASTM materials.
This paper provides the design engineer with a summary of the current research and thinking for design concepts for the use of this material that is fundamentally different than conventional concrete. It also describes the working relationship of ASTM Specification for Expansive Hydraulic Cement (C 845) and ASTM Test for Restrained Expansion of Shrinkage-Compensating Concrete (C 878), respectively, covering shrinkage-compensating expansive cement and its concrete prism for measuring expansion strains.
Paper ID: CCA10196J