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Investigation of methods of preparing horizontal construction joints in concrete. Report 4, Evaluation of high-pressure water jet and joint preparation procedures

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Date

1973-08

Authors

Tynes, W. O. (William O.)
McCleese, William F.

Journal Title

Journal ISSN

Volume Title

Publisher

U.S. Army Engineer Waterways Experiment Station.
Engineer Research and Development Center (U.S.)

Abstract

Description

Technical Report
Abstract: This study was designed to investigate procedures for preparation of horizontal construction joints using a high-pressure water jet, to compare these procedures with the alternative practice of wet sandblasting, and to develop additional information on procedures and methods that have been utilized in horizontal construction joint practice. The investigation was divided into two phases, laboratory and field. One 6-in. maximum size crushed limestone aggregate concrete mixture, with a cement content of 235 lb/cu yd, an air content of 6 ± 1 percent, and a slump of 2 ± 1/2 in. on the portion of the mixture passing the 1 - 1/2- in. sieve, was used to cast specimens for both phases . In the laboratory phase, thirty 3- by 3-ft by 18-in. concrete test specimens were cast for surface cleanup utilizing the high-pressure water jet, and five 3- by 3-ft by 18-in. specimens were cast for surface cleanup utilizing the wet sandblasting method. Two nozzle types and three water pressures (2000, 6000, and 10,000 psi) for each nozzle type were used to determine the effectiveness of the various combinations of nozzle and water pressure in cutting the surface of concrete specimens at each age of 2, 3, 7, 14, and 28 days. Wet sandblasting was used to cut the surface of concrete test specimens at each of the five test ages for comparison with the water jet cleanup. In the field phase, three concrete blocks, 10 by 20 by 5 ft high, were cast in two 30-in. high lifts. The 10- by 20-ft joint plane of the first lift of each block was divided into four equal areas for four different types of cold joint preparation (dry with mortar, dry without mortar, wet with mortar, and wet without mortar). The joint cleanup technique (using the 6000-psi water jet) was common to all three blocks. A series of strength tests (shear, tensile, and flexural) were made of cores drilled from several areas of each block to evaluate the various methods of preparing the horizontal construction joints. Results of the laboratory phase indicate that the 2000-psi pressure is not satisfactory, except possibly for very low strength concrete (less than 1500 psi), and that-the water jet cutting efficiency with 6000- and 10,000-psi pressures is as satisfactory as the wet sandblasting method and requires less cutting time and less cleanup of the concrete surface after cutting. Strength test results of the core specimens of the blocks during the field phase indicate that the dry joint without mortar is equal to the wet joint with mortar.

Keywords

U.S. Army Engineer Waterways Experiment Station, Concrete, Concrete construction, Concrete joint, Methods, Design, Concrete strength, Water jets, Preparation

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