Abstract
Historically, Caltrans Material Engineering and Testing Services has relied on construction experience and testing of post-installed concrete anchors to provide design and construction guidance. With AASHTO’s recent adoption of ACI 318-19 Chapter 17: Anchoring to Concrete there is the need to update Caltrans design guidance and construction specifications for consistency with new code requirements. This is critical for the bridge application of post-installed anchors known as Drill and Bond Dowels.The main objective of this 2-part research program is to evaluate single Drill and Bond Dowels through 54 static tension tests in uncracked concrete specimens subjected to variable bonding materials, mixing, and hole cleaning. This Part 1 thesis focuses on: 1) construction including drilling, mixing, bonding, and material testing, and 2) testing including developing a test matrix, test setup, test protocol, limited description of specimen behavior, failure modes, and Part 1 test results. A subsequent Part 2 thesis will address test results comprehensively, including a full summary of specimen behavior, the entire body of test data for Parts 1 and 2, data analysis in comparison to ACI 318-19 and BDA 5-81, and final design recommendations.
The test matrix was designed to evaluate Drill and Bond Dowels for both construction and static tension testing. #5 rebar with various embedment depths (5db -10db) were subjected to reduced (50%) and full (100%) manufacturer-recommended hole preparation. MasterEmaco T 545 (ME) and Elephant Armor (EA) were selected as the bonding material based on field surveys for the most common Drill and Bond Dowels.
Construction and testing revealed that blowing out a drilled hole with compressed air is sufficient for hole preparation as the tensile capacity did not increase when more extensive hole cleaning efforts such as brushing were used per ACI 355.4. Although ME and EA both meet the Caltrans 2023 Standard Specifications for Bonding Materials, this experimental program demonstrated that, due to reduced flowability, dowels are not as easily inserted into a hole using EA. While EA exhibited tensile capacities within 9% of ME, its more difficult mixing and placement produced substantially greater variability in capacity. Based on these limited test results, it is recommended that a mortar flowability test requirement, ASTM C1437-20 “Standard for Flow of Hydraulic Cement Mortar” be added to Caltrans specification for Drill and Bond Dowels.