Examination of bond strength of partial depth patches used in rigid pavements.

摘要

There is a constant need to find an economically feasible method of repairing damaged roadways and reopening them to traffic quickly. Partial-depth patching poses a potential solution to this problem for deteriorating concrete found in rigid pavements, but evaluating the bond performance of partial-depth patching materials is crucial before they can be accepted for use in state roadways. The current ASTM standard for evaluating bond strength of patching materials is the slant shear test, but prior research shows that this test can sometimes yield erratic results. A variety of different test methods were used to assess the accuracy of each method, as well as to examine the effects of several variables on patching material-concrete substrate bond performance.;A series of four different tests were performed to evaluate bond strength. First was the slant shear test according to ASTM C 882. A pullout test using a concrete slab that had had 3 in diameter cores removed and replaced with patching materials was also performed to obtain a quantitative measure of bond strength. Small concrete slabs were cast, prepared, and patched to simulate field installation of partial-depth patches and loaded in four point bending. Half of the slab specimens were loaded in static positive bending, while the remaining slabs were loaded cyclically in both positive and negative bending. Specimens were prepared using two different patching materials, Futura-45 and 3U18, and a cement paste bonding agent was applied to half of all samples. The two common field preparation methods, milling vs. saw cutting and chipping, were examined in the slab bending tests. Load-displacement data, strain data, and visual observation were used to evaluate bond strength. Results from the experiments showed that Furura-45 created better bond with base concrete than 3U18 did. The cement paste bonding agent actually served to weaken bond between patching material and substrate. Both types of patch preparation had advantages, but the best bond was found to occur in milled prepared patches patched with a material with a high volume of paste and little coarse aggregate. Slant shear, despite having a fairly large spread in results, was deemed sufficient for evaluating patching material bond strength when compared to more complex evaluation methods.