Creep & Shrinkage of Concrete
Demand for high-performance concrete mixtures has increased greatly over the past several decades. Volumetric changes in hardened concrete may occur in conventional or high-performance mixtures when subject to environmental (shrinkage) or mechanical (creep) conditions. Shrinkage of concrete can lead to uncontrolled and undesired cracking that can severely affect the structure durability. The deformation of concrete can be significant when elements are subject to long-term stress conditions. Both mechanisms are strongly dependent on the concrete mixture materials and proportions.
CTLGroup uses custom designed frames to perform creep tests. These frames maintain load using disk springs specifically selected to maintain constant load over the range of deformation typically encountered during creep tests. Maximum applied loads to 1 MN are possible using these frames. Creep and shrinkage deformations are measured using externally mounted mechanical gage points and a digital length change comparator with a resolution of 0.001 mm. We have the capacity to conduct over 30 creep and shrinkage tests concurrently.
CTLGroup’s expertise in the volumetric performance of concrete stems from having the largest commercial creep and shrinkage laboratory in North America. Our laboratory holds over thirty high-strength frames for evaluating the creep performance of concrete mixtures with design compressive strengths exceeding 120 MPa. We also have state-of-the-art equipment for conducting autogenous, linear, and restrained shrinkage experiments. Supported by these laboratory services, our concrete and cement-based materials experts have evaluated the creep and shrinkage performance of numerous infrastructure and high-rise buildings in the Middle East, Asia, and North America.
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Understanding early and long-term behavior of concrete is paramount for mitigating cracking and undesired deformations. Projects that require creep and/or shrinkage evaluation include long-span bridge decks, restrained concrete placements, mass foundations, concrete repair, and ultra-high rise construction.
Creep and shrinkage test specimens are very sensitive to ambient temperature and humidity conditions, thus it is imperative that the test environment is maintained at the specified temperature and humidity levels. ASTM C512 “Creep of Concrete in Compression” requires test conditions be maintained at 23±1.5°C and 50±4% relative humidity. CTLGroup’s environmental laboratory for creep and shrinkage is typically at 23±0.5°C and 50±2% RH to assure reliability of test results. Environmental conditions are continuously monitored electronically. Automated alerts are generated to notify laboratory personnel if room conditions deviate from the specified range.
Contact a CTLGroup creep and shrinkage expert today by visiting www.ctlgroup.com/contact