Title: Behavior of Type K Shrinkage Compensating Concrete Under Various Forms of Mechanical Restraint
Author(s): Chris Ramseyer and Seth Roswurm
Publication: Symposium Paper
Appears on pages(s): 1-18
Keywords: Shrinkage compensating concrete, restrained expansion, Type K concrete, ettringite, expansive concrete, vibrating wire strain gage
Shrinkage compensating concrete is one of the most common products currently used to mitigate the influence of drying shrinkage cracking in slabs, beams and other structural components. Type K expansive concretes have proved effective for prevention of structural and aesthetic damage due to tensile cracking in many modern applications. However, the ACI 223R-10 technical guide still indicates that a shrinkage compensating slab cannot expand adequately if it is surrounded on all sides by mature reinforced concrete. The objective of this project was to
investigate whether the presence of a stiff external restraint condition, which may be provided by adjoining concrete, prevents a Type K expansive concrete slab from compensating for shrinkage.
To investigate this behavior, the field condition of a slab-to-slab interaction was simulated using a steel restraint system with varying degrees of stiffness and amounts of Type K expansive cement component. Test frames were instrumented to evaluate the force and displacement responses of the Type K expansive concrete to the different boundary conditions provided by varying the steel restraint system. The results of this investigation support a conclusion contrary to that currently found in the ACI 223R-10 guiding document. This study concludes that a Type
K expansive cement concrete does not suffer a severe reduction in shrinkage compensation in the presence of a very stiff boundary condition.