Keyhole Technology Research
Core Reinstatement Materials
The Science of Utilibond - Permanent Keyhole Pavement Bonding Compound
The successful adhesive and cohesive bonding performance of Utilibond in these tests is due both to the fineness of its granular structure and proprietary additives that contribute to lower surface tension when in liquid form and accelerated strength gain during hydration.
When initially mixed, Utilibond has a low viscosity and a low surface tension that allows capillary forces to draw it very close to the surface structure of the concrete and fully
engage the underlying substrate where its very high density and super-fast strength gain result in a very strong bond capable of supporting 52,600 lbs in less than 30 minutes.
When used for reinstatement of cores, these properties result in a waterproof joint that reintegrates the core with the roadway to restore the structural performance of the original roadway as a load bearing system, as was found by the experimentation and observations of Golder Associates.
Gas Technology Institute: Evaluation of Bonding Strength
Objective: An ongoing project is being carried out at Southern California Gas Company (SoCal Gas) to support the development of the keyhole operations process. A major objective of this work was the development of a reliable method for the replacement of the intact cores. Up to this stage, grouting has been used in the field with mixed success. Two major concerns in grouting, as applied to the core replacement process were:
The mixing of the grout and the measurement process was arbitrary and overly complicated for use by field crew.
The bond strength between the core and the surrounding pavement was inconsistent and the cores separated in some cases.
This report addresses these issues and presents the laboratory and field-testing programs which evaluated the strength of several grouts, and the mixing procedure. The implementation of this research should result in a successful and consistent installation process.
Laboratory Testing of Utilibond Used in Pavement Core Reinstatement
A laboratory-testing program was carried out in order to evaluate the mix properties, mixing time, and interface shear strength of the Utilibond grout all at a one-hour curing time and constant temperature. The grout is used for intact pavement-core replacement during keyhole operations.
Performance of Bonding Compounds Evaluation: University of Illinois at Urbana Champaign
Introduction: This study measured the evolution of strength and evaluated the performance of three bonding compound materials. The parameters of interest included compressive strength, slant shear bond strength, and core punch out load. The measurements were taken within the two hour period after casting to characterize early performance.
Bond strength was evaluated using procedures adapted from ASTM C882 -99 "Standard Test Method for Bond Strength of Epoxy-Resin Systems Used With Concrete by Slant Shear," compressive strength was determined using ASTM C109 “Standard Test Method for Compressive Strength of Hydraulic Cement Mortar, " and a nonstandard test referred to as the “Core Punch Out Test" was used to simulate field performance of the bonding materials.
This report describes the procedures and results of each test.