1、An ACI Technical Publication SYMPOSIUM VOLUMESP-325Mass Concrete and Thermal Cracking, a Joint ACI-JCI SeminarEditors:Melissa Harrison and Christopher C. FerraroMass Concrete and Thermal Cracking, a Joint ACI-JCI SeminarSP-325Editors:Melissa Harrison and Christopher C. FerraroDiscussion is welcomed
2、for all materials published in this issue and will appear ten months from this journals date if the discussion is received within four months of the papers print publication. Discussion of material received after specified dates will be considered individually for publication or private response. AC
3、I Standards published in ACI Journals for public comment have discussion due dates printed with the Standard.The Institute is not responsible for the statements or opinions expressed in its publications. Institute publications are not able to, nor intended to, supplant individual training, responsib
4、ility, or judgment of the user, or the supplier, of the information presented.The papers in this volume have been reviewed under Institute publication procedures by individuals expert in the subject areas of the papers.Copyright 2018AMERICAN CONCRETE INSTITUTE38800 Country Club Dr.Farmington Hills,
5、Michigan 48331All rights reserved, including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowled
6、ge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.Printed in the United States of AmericaEditorial production: Ryan JayISBN-13: 978-1-64195-020-6First printing, July 2018PrefaceThermal cracking and damage from high internal temperatures during
7、construction are concerns for the mass concrete of dams, bridges, buildings, and power plants. The design, planning and execution of placements which involve mass and thermally controlled concrete must consider hydration of cementitious materials within the concrete mixture to avoid thermal-related
8、distress. Without such considerations, durability, and in some cases, structural integrity can be affected. This Special Publication is intended to help owners, designers, contractors, and concrete suppliers understand and address concerns with mass and thermally controlled concrete.To highlight sta
9、te-of-the-art developments in defining, designing, testing and modeling mass and thermally controlled concrete, American Concrete Institute (ACI) Committee 207 and the Japan Concrete Institute (JCI) held a full-day technical session at the ACI Fall Convention, Cincinnati, Ohio, October 16-20, 2011.
10、This Special Publication (SP) contains eight of the papers presented at the technical session. The subjects of these papers include: (1) defining mass and thermally controlled concrete (2) design and planning considerations for mass concrete; (3) modeling and prediction of in-place concrete temperat
11、ure development, and (4) physical testing of mass concrete. On behalf of ACI Committee 207 and JCI, the editors sincerely thank all authors and presenters for their efforts and contributions to the technical session and this SP volume. Special thanks are given to the reviewers of the original manusc
12、ripts for their constructive comments and suggestions. The editors are also indebted to the ACI staff for their assistance in organizing this session and in preparing this SP. The editors earnestly hope that the information presented at the ACI session and in this SP will facilitate significant impr
13、ovements in defining mass concrete, as well as the design, planning and control of mass concrete. This SP will serve as a valuable resource for researchers and engineers to make such improvements. Editors:Melissa Harrison SCB International, USA Christopher C. Ferraro University of Florida, USATABLE
14、OF CONTENTSSP-3251Planning and Execution of a Mass Concrete Placement Utilizing Insulation RegimenAuthor: Ufuk DilekSP-3252Shear Testing of RCC and Other Concrete BlocksAuthors: Stephen B. Tatro and James K. HindsSP-3253Temperature Predictions of a Ternary Mix Design for Mass Concrete PlacementsAuth
15、ors: Joseph W. Clendenen and Benn B StutrudSP-3254Design Considerations for Raising the Hinze Dam Mass Concrete SpillwayAuthors: Scott Jones, David Hughes, and Orville R. Werner IISP-3255Estimating Maximum Temperature Difference in Mass ConcreteAuthors: Ronald Kozikowski and Bruce SuprenantSP-3256Eq
16、uivalent Age and Physical Properties of Mass Concrete Authors: Christopher C. Ferraro, Mang Tia, and Adrian M. LawrenceSP-3257Proposed Mass Concrete Definition Based on Concrete Constituents and Minimum DimensionAuthors: John Gajda, Jon Feld and Christopher C. FerraroSP-3258Planning and Execution of
17、 a Large Mass Concrete Placement with Different Insulation LevelsAuthors: Boris Haranki, Harini Santhanam, and Ufuk DilekSP-3251 1.1 Planning and Execution of a Mass Concrete Placement utilizing Insulation Regimen Ufuk Dilek Ph.D. , P.E. Concrete Subject Matter Expert The Shaw Group 128 S. Tryon Str
18、eet Suite 600 Charlotte, NC 28202 Tel: 1 (704) 343 46 26 E-Mail: Abstract This paper summarizes the planning and execution stages of a critical mass concrete placement performed during summer months. The subject structure was a critical component of a large heavy industrial facility, consisting of
19、large load bearing elevated flexural members. The planning and execution of this critical mass placement consisted of multiple tasks. A laboratory study was performed for the purpose of making improvements to the mixture proportions existing and currently in use, admixture dosages and investigating
20、placement temperature options. Adiabatic and semi adiabatic temperature rise was also measured during the laboratory study along with set times. Final proportions and admixture dosages were selected as a result of the laboratory phase. Primary outcome was increase in fly ash percentage from the exis
21、ting mix design to control heat of hydration. Based on the findings of the measured adiabatic temperature rise, a thermal control plan was developed adapting the new approach to structural mass concrete placements. A thermal protection/insulation regimen was developed using the mix parameters, expec
22、ted ambient temperatures following placement, member dimensions and formwork/blanket insulation properties. The pre-placement modifications to the mixture proportions and the delivery temperature requirements protected the concrete against high internal temperatures and potential of Delayed Ettringi
23、te Formation (DEF), while the insulation regimen protected the concrete against rapid cooling and occurrence of thermal gradients between core and perimeter. As part of the thermal control plan analysis, target placement temperatures were recommended to control maximum temperatures to prevent occurr
24、ence of DEF, in light of the heat rise of the modified mix. The placement temperature was accomplished by starting the placement at night and the use of ice to draw the temperature down. Upon completion of finishing, a curing compound was applied in lieu of water curing and the placement was insulat
25、ed. The thermal control plan simulation predicted a gradual reduction in the temperature of the placement, within limits of maximum internal temperatures and temperature gradients. The actual placement was monitored for core and perimeter temperatures using maturity probes. Monitoring enabled the te
26、am to react to abrupt changes in temperature if any was to occur. The placement was completed successfully with internal temperatures and gradients controlled within the desired ranges. Keywords: mass concrete, adiabatic heat rise, thermal control plan, fly ash, thermal cracking, heat or hydration U
27、fuk Dilek 1.2 Introduction This paper summarizes the planning and execution stages of a critical mass concrete placement performed during summer months. The subject structure was a critical component of a large heavy industrial facility, consisting of large load bearing elevated flexural members, wi
28、th minimum dimensions in the order of 2.1 meters (7 ft) Figure 1. The planning and execution of this critical mass placement consisted of multiple tasks. Figure 1 Overview of beams showing reinforcement congestion. Planning and execution consist of the following stages: 1. Laboratory Study 2. Develo
29、pment of the Thermal Control Plan and Batching Temperature 3. Post-Placement Thermal Monitoring 4. Curing, Insulation and Protection against Temperature Changes Laboratory Study Subject mass concrete placement was scheduled to occur during summer months. The existing concrete mixtures used on site w
30、ere not utilized to date in a mass concrete placement of this significance and under the summer ambient conditions. Therefore the concrete mixture planned for use was reviewed in light of the placement specifics. A laboratory study was performed to revise the concrete mixture to achieve desirable pe
31、rformance objectives in the mass concrete placement under summer ambient conditions. Existing concrete mixture utilized class F ASTM C 618 (ASTM, 2008) fly ash at a replacement rate of 25% of total cementitious material content. Existing concrete mixtures typically used type A (lignin based) water r
32、educers meeting ASTM C 494 Planning and Execution of a Mass Concrete Placement utilizing Insulation Regimen 1.3 (ASTM, 2010). Lignin based water reducer also offered set control benefits in addition to reduction of water. In addition, as warranted by reinforcement congestion and consolidation challe
33、nges at the bottom of sizeable reinforced concrete members a type F superplasticizer meeting ASTM C 494 (ASTM, 2010) was utilized to achieve a maximum slump of 8 inches. Compressive strength of the concrete mixture (fc) was 4000 psi (27 Mpa) and specification required water-to-cementitious ratio max
34、imum was 0.45 by weight. Variables Used during Laboratory Study During the laboratory study, concrete mixtures with a fly ash replacement rate of 25% and 35% of total cementitious material content were tested. In addition, the dosages of type A and type F water reducers were modified in coordination
35、 to yield the same slump value, while increasing the relative dosage of type A in the mixture and achieving an increase in the time of set. Laboratory study also included concrete mixtures batched at varying temperatures. Temperature of water and aggregates was modified to achieve resulting batch te
36、mperatures ranging between 21 and 32 C (70 and 90 F) enabling evaluation of the changes with temperature, in time of set and retention or loss of slump. A total of 10 concrete trial batches were performed. The laboratory study aimed to identify the combination of factors such as concrete placement t
37、emperature, admixture dosages, fly ash replacement rate prior to the placement. In addition to time of set and slump loss, adiabatic and semi-adiabatic heat rise of concrete mixtures was measured and the information gathered was used in the in-depth planning of the mass concrete placement. Figure 2
38、shows semi adiabatic heat rise measurements performed using proprietary thermal measuring equipment by a national admixture manufacturer. This device mainly contains multiple insulated cylinder housing compartments for 4 x 8 in (10 cm x 20 cm) cylindirical specimens. The housing compartments are equ
39、ipped with themocouples feeding temperature data to the data acquisition hardware and associated software. The measurements are not fully adiabatic as is evident from the eventual decline in temperature. However, a time of set determination made based on the shape of the curve provides an estimate o
40、f the time of set, which can be compared or indexed to times of set determined per ASTM C 403 (ASTM 2008). For this study, the subject device was not used for an absolute determination of time of set but for comparisons between various trial batches with different attributes. In general, the compari
41、sons between mixtures were made on the basis of maximum magnitude of temperature achieved, the occurence time of this peak temperature, and occurence of the flat portions of the curve with respect to admixture dosage and retardation effects as a result of the dosages used. These attributes can be ob
42、served in Figure 2. Ufuk Dilek 1.4 Figure 2 Thermal measurements using Adiacal. Selected Mixture Proportions Based on the findings of the study, the mixture proportions nominated for placement were determined. These proportions are provided in Table 1 below. It was decided to utilize an increase fly
43、 ash replacement rate of 35%. As a consequence of the increased fly ash usage, an (fc) of 4000 psi (27 Mpa) determined at 56 days was utilized in lieu of the typical 28 day mixture design cycle. This increase in length of the design cycle aimed to reduce the earlier heat of hydration which would be
44、more pronounced if the design cycle was kept at 28 days and a more agressive water-to-cementitious ratio was used for the 28 day design. Based on the behavior of mixtures and thermal measurement data, a likely upper limit for placement temperature was initially considered to be 80 F (27 C). Under st
45、andard operating measures, the supplying concrete plant was producing concrete just under 90 F (32 C) during the heat of the summer season. If this temperature limit of 80 F (27 C) was to be confirmed by the thermal control plan development, it would likely be necessary to use manually loaded ice as
46、 a replacement to batch water and that the placement be performed at nighttime. Planning and Execution of a Mass Concrete Placement utilizing Insulation Regimen 1.5 Table 1 Selected Mixture Proportions. Code 1435 1435 Strength 4000 psi 27.6Mpa lb/CYkg/m3 CementType I/II 412 lb 245 Fly Ash 222 lb 132
47、 Fine Aggregate 1112 lb 660 Coarse Agg. (67) 1852 lb 1100 Water 285 lb 169 W/(C+F) 0.45 0.45 Air (%) 3.5 -6.5 3.5 -6.5 Slump w/HRWR 5 to 8 in 12.5-20cm Subsequently, full adiabatic thermal measurements were performed on the final selected proportion. Figure 3 shows this measurement on the mixture co
48、ntaining 35% ash and a mix containing 25% ash for comparison, demonstrating the difference made with increasing the fly ash. An increase of 10% in fly ash results in a reduction of 3 C (5 F). Figure 3 Adiabatic measurements, 35 % fly ash ( left), 25% fly ash (right). DEVELOPMENT OF THE THERMAL CONTR
49、OL PLAN ACI 207 Mass Concrete Committee Report In general, ACI 207 (ACI, 2005) committee report (Guide to Mass Concrete) concentrates on unreinforced, large mass structures, such as dams with typically lower strength requirements than reinforced structural concrete. The guidelines provided for mixture attributes (low heat, use of pozzolan, reduction of cement content etc) are appropriate. The recommended curing method is curing by water therefore aiming rapid removal of heat from the mass concrete structure. Ufuk Dilek 1.6 ACI 207 committee i
