Examining the Effects of Mixer Type and Temperature on the Properties of Ultra-High Performance Concrete
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EXAMINING THE EFFECTS OF MIXER TYPE AND TEMPERATURE ON THE PROPERTIES OF ULTRA-HIGH PERFORMANCE CONCRETE MBTC-3012 By Andrew M. Tackett & W. Micah Hale The contents of this report reflect the views of the author, who is responsible for the facts and accuracy of the information presented herein. This document is disseminated under the sponsorship of the Department of Transportation, University Transportation Centers Program, in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof. ABSTRACT Ultra-High Performance Concrete (UHPC) is a highly advanced material that has been created as a result of many years of concrete research and development. UHPC addresses a number of concerns that plague most concrete types by taking advantage of today’s latest technology in order to produce this innovative product. Although UHPC is known for producing many beneficial qualities for concrete users, because of the unique makeup of the material, there are some areas that remain unexplored. For instance, the mixer typically specified to batch UHPC is a high shear/energy mixer (e.g. pan). Currently, little information is known as to whether a beneficial or negative impact may be experienced in concrete properties (e.g. flow, strength, MOE) when a lower shear/energy mixer (e.g. drum/ready-mix truck) is used. Another point of interest that has not been explored is the effect on fresh concrete temperature produced when the dry constituent mixing materials (also referred to as premix), such as portland cement, aggregate, silica fume, and ground quartz, are placed at some specific temperature and batched with ice as a replacement for mixing water. Because of these two uncertainties, the goal of this thesis is to rectify such unknowns. Two studies were fashioned addressing the issues listed in the previous paragraph. Both studies documented UHPC fresh (flow and temperature) and hardened properties (modulus of elasticity and compressive strength) to gather information for analysis purposes. The influence of ice on resultant batch temperature could not be determined for the small pan made batches. The drum mixed batches, with their larger volume of materials, proved more beneficial for analysis. Flows for both mixers were erratic over time, but were generally within the acceptable specifications; this fact was dependent upon the type of mixer used. Two different curing procedures were used during the research period. The type of curing regimen used largely influenced UHPC hardened properties. Depending upon the type of curing method used, a stark difference in ultimate strength and MOE values could be observed. TABLE OF CONTENTS CHAPTER 1 INTRODUCTION ...................................................................................................... 1 1.1 GENERAL ........................................................................................................................ 1 1.2 OBJECTIVES ................................................................................................................... 1 1.3 SCOPE ............................................................................................................................. 3 CHAPTER 2 LITERATURE REVIEW ............................................................................................ 4 2.1 GENERAL ........................................................................................................................ 4 2.2 HISTORY OF EARLY CONCRETE ................................................................................. 4 2.3 UHPC ............................................................................................................................... 5 2.3.1 Fibers ........................................................................................................................... 8 2.3.2 UHPC Types .............................................................................................................. 10 2.4 MIXERS.......................................................................................................................... 16 2.4.1 Batch Mixers............................................................................................................... 16 2.4.2 Continuous Mixers ..................................................................................................... 18 2.4.3 Differences between Batch and Continuous Mixers .................................................. 18 2.5 CONCRETE MIXING ..................................................................................................... 19 2.6 CONCRETE TEMPERATURE ....................................................................................... 21 2.6.1 Preventing High Fresh Concrete Temperatures ........................................................ 22 2.6.2 Effect of Concrete Temperature on Admixture Performance ..................................... 23 2.7 CONCLUSION ............................................................................................................... 24 CHAPTER 3 EXPERIMENTAL PROCEDURES AND RESEARCH PROGRAM ....................... 25 3.1 GENERAL ...................................................................................................................... 25 3.2 SCOPE ........................................................................................................................... 25 3.3 TEMPERATURE STUDY ............................................................................................... 26 vi 3.3.1 Premix Temperature Conditions ................................................................................ 27 3.4 MIXER STUDY ............................................................................................................... 29 3.4.1 Hobart®/Blakeslee® Pan Mixer Information .............................................................. 30 3.4.2 Stone® Rotating Drum Information ............................................................................ 30 3.4.3 Ready-Mix Truck Information ..................................................................................... 31 3.5 MATERIALS ................................................................................................................... 31 3.5.1 Superplasticizer .......................................................................................................... 31 3.5.2 Premix ........................................................................................................................ 31 3.5.3 Fibers ......................................................................................................................... 31 3.6 PRECISION.................................................................................................................... 31 3.7 THERMOCOUPLE TEMPERATURE RECORDING ..................................................... 32 3.7.1 Fiber and Premix Resistance to Changes in Temperature ........................................ 32 3.7.2 UHPC Heat Evolution ................................................................................................. 33 3.8 BATCHING METHODS .................................................................................................. 34 3.8.1 Full Batch Method ...................................................................................................... 34 3.8.2 Half Batch Method ...................................................................................................... 38 3.9 SAMPLING ..................................................................................................................... 40 3.10 CASTING AND CURING ............................................................................................... 41 3.11 FRESH CONCRETE TESTS ......................................................................................... 41 3.11.1 Temperature ........................................................................................................... 41 3.11.2 Flow ........................................................................................................................ 42 3.12 HARDENED CONCRETE TESTS ................................................................................. 43 3.12.1 Compressive Strength ............................................................................................ 43 vii 3.12.2 Modulus of Elasticity .............................................................................................. 43 CHAPTER 4 RESULTS AND ANALYSIS ................................................................................... 45 4.1 GENERAL ...................................................................................................................... 45 4.2 TEMPERATURE STUDY ............................................................................................... 45 4.2.1 Fresh Concrete Properties ......................................................................................... 45 4.2.2 Hardened Concrete Properties .................................................................................. 62 4.3 MIXER STUDY ............................................................................................................... 68 4.3.1 Mixture Homogeneity ................................................................................................. 68 4.3.2 Mixing Time ................................................................................................................ 70 4.3.3