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|Title:||Effects of axial restraint on length change of expanding mortar bars|
|Authors:||United States. Army. Office of the Chief of Engineers.|
Houston, Billy J.
|Publisher:||Concrete Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical report (U.S. Army Engineer Waterways Experiment Station) ; C-69-8.|
Abstract: An investigation was conducted to determine the effects of axial restraint on length change of mortar prisms tending to, expand due to alkali-silica reaction. Three approaches were taken. The first involved use of external restraint on expansive mortar prisms. Restraining rigs consisted of aluminum rods held in place by stress header plates and load cells for determining stress caused by expansion. Results were questionable for a number of reasons. The next approach involved use of polyester laminated strain gages embedded axially in expansive prisms for determining stress. Restraint was provided by external frames giving restraining loads of 0-100 psi. Prisms were stored at 100 F and 100% RH. Results indicated that restraint does act to reduce expansion; however, accuracy was doubtful because it was discovered that the polyester cover of the strain gages expanded when exposed to 100 F and l00% RH even with no external stress transferred to it. The third approach involved use of axially embedded calibrated steel restraining rods (1/4-, 3/8-, and 1/2-in.-diam) with end plates screwed on the ends of each rod, Stress developed on the end plates at 1-yr age was greater with the larger rods because the smaller rods elongated more under tensile stress and relieved some of the end-plate pressure. Linear expansion was reduced 80, 90, and 94% by the three restraints. Tests of cubes sawed from the prism after 1-yr exposure indicated that restraint had-little- or no effect on compressive strength. Strains and stresses expected in the restrained specimens were estimated by an approximative analysis involving linear superposition of measured unrestrained expansion values and elastic and creep behavior of nonexpanding reference prisms. Measured strains ranged only between 16 and 52% of the calculated or theoretical values, indicating that such calculations are at best only useful in giving a very conservative.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|
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