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2007-2009 PCA Research and Technical Reports
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Item Code: MS375
Date of Publication: 2009
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This listing is updated monthly and is a compilation of completed publications from PCA's Research and Technical Services programs for the past two years. Reports are listed by title and code number. There are 125 research reports referenced in this edition.
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ECRA CCS Project - Report about Phase II
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Item Code: SN3022a
Date of Publication: 2009
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Climate protection seems to be one of the most important items on the worldwide agenda. All states are challenged to reduce their CO2 emissions dramatically, focussing on the major CO2 sources in their countries to contribute to ambitious reduction targets being worked out on a global level. It is unclear today, how these targets can be reached. In the long run, energy efficiency and the utilization of renewables seem to be the most sustainable way to tackle the global greenhouse gas emissions.
The European Community's objective is to limit the atmospheric temperature increase caused by climate change to 2 degrees C. This can only be achieved, when the global CO2 emissions could be reduced by 50% until 2050. However, it is obviously not possible to reduce the EU or world CO2 emissions by 50% in 2050 with energy efficiency and renewables alone. Therefore also carbon capture and storage of CO2 (CCS) is looked at as an option to contribute to the portfolio of reduction measures. CCS could provide 19% of the needed reduction in 2050. The European policy goal is to make CCS applicable by 2020. However, it is unclear if CCS implementation will be technically feasible and economically viable at that time.
Phase II of the CCS research project was started at the end of 2007 and was completed in summer 2009. The main objective in this phase was to perform a feasibility study of CO2 capture for the clinker burning process which focuses on oxyfuel and post-combustion measures. Apart from technical investigations and assessments, an economic analysis will also be included in the report.
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Effect of Temperature and Relative Humidity on Long-Term Expansion and Periclase Hydration
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Item Code: SN2801
Date of Publication: 2009
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The research reported in this paper in conjunction with the prior literature review deal with a long-existing problem associated with ASTM C 151 “Standard Test Method for Soundness of Cement by the Autoclave Expansion Test” (AET): Whether cements with less than 6% MgO that expand more than 0.8% in the AET are, indeed, potentially harmful or, instead, pose no significant risk to future concrete performance.
A total of 11 cement and clinker samples were characterized for their Blaine fineness, chemical composition, mineralogical make up, free lime content, periclase amount and particle size, and for its AET expansion performance. Total MgO contents ranged from 3.0% to 5.3%. Four cements that exceeded the AET expansion limit of 0.8% were selected for further study that included variables of 1 and 2 curing days, boiling water conditions (modified Le Chatelier method), and the combination of boiling water followed by autoclaving conditions. In addition, three of these cement samples were selected for further testing that included expansion and weight change monitoring of paste specimens made with and without each of the fly ash, metakaolin, and slag pozzolanic materials (ranging from 25% to 30% cement replacement level). Paste specimens were cured for 30 days and stored under water, in air at 15%, 50%, and 100% relative humidity, and at room (23°C) and elevated (50°C) temperatures, for periods of time of up to 3 years.
The results indicate that paste specimens made with certain cement samples show significantly lower AET expansion when cured for 2 days as opposed to 1 day, or when boiled in water before being autoclaved. Long-term performance results under accelerated and normal conditions do not show more than 0.25% paste expansion. The addition of pozzolanic materials only reduces marginally the relatively small expansion observed. Results of this research indicate that the expansion of cement paste appears to correlate with the amount and particle size of periclase.
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Evaluation of Alkali Silica Reactivity (ASR) Mortar Bar Testing (ASTM C1260 and C1567) at 14 days and 28 days
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Item Code: IS549
Date of Publication: 2009
Price: $0.00
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Concrete technologists looking to evaluate the potential for alkali silica reaction (ASR), a chemical reaction between certain reactive minerals in some aggregate and alkalies in the pore solution of concrete, often use accelerated tests. Standard accelerated tests use expansion of mortar bars after 14-days in an aggressive exposure environment to evaluate ASR potential. It has been suggested that these tests should be evaluated at 28 days rather than 14 days. However, this is not good practice for two reasons:
- Correlation between the 28-day versions of the accelerated tests and concrete prism tests expansion is notably less than for the 14-day tests, and
- The 28-day test provides estimates of SCM contents that are approximately 1.5 times higher than actually required for effective ASR mitigation.
Thus, not only is the 28-day duration overly-conservative and more time consuming, it provides recommendations for potentially inefficient concrete mix designs, which may be unacceptable from an engineering perspective. This short report summarizes data on this question.
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A Compilation of Five Papers on Studies of Bond Between Concrete and Steel and Related Factors
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Item Code: RX229
Date of Publication: 1952
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This is a compilation of five papers on studies of bond between concrete and steel and related factors. The paper presents data from studies made at the Research Laboratory of the Portland Cement Association, designed to show the effect of some of the many factors influencing the results of pull-out bond tests. It represents a progress report in an extensive investigation of bond resistance. Data presented cover the influence of the following factors on the loads developed in pull-out specimens; type of bar surface, length of embedment, type of lug on deformed bars, position of lug, consistency of concrete, thickness of concrete around the bar, position of the bar with respect to the placing of the concrete, leakage of water from the molds immediately after placing. Results are given for concrete of different cement contents and ages at time of test. Load-slip curves are presented based on measurements at both the loaded and the free end of the bar. Comparison is given between data from the present investigation and those obtained in earlier studies. This report is also found on DVD021.
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Abnormal Concrete Performance in the Presence of Admixtures
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Item Code: RP333
Date of Publication: 1995
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Reviews cement and admixture chemistry and interactions relative to stiffening mechanisms. Discusses test methods that relate early stiffening and slump loss behavior of concrete when pastes of the same compositions as in concretes are tested at the same temperature. Discusses methods of pretesting cement/admixture combinations for compatibility as a means to prevent early stiffening problems. This report is also found on DVD021.
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Application of Infrared Imaging to Fresh Concrete: Monitoring Internal Vibration
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Item Code: SN2806
Date of Publication: 2004
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The primary purpose of this research was to evaluate the use of infrared imaging cameras as a quality control tool to be used during concrete consolidation via internal vibration. The goal of this research was to monitor the surface of concrete slabs during and after consolidation by internal Vibration. This was done in insulated slab forms to limit lateral heat loss and mimic larger sections of concrete. Concrete and concrete-making materials were also vibrated in a calorimeter and the amount of heat transferred from the internal vibrator to the surrounding material was quantified.
The heat generation rate of internal vibrators was also investigated along with the effect of surface finish on the apparent temperature of fresh and hardened concrete.
This technology was tested under field conditions during site visits to precast concrete plants. Based on the data collected over the course of this research, and the field observations made, recommendations are given for using this technology as a qualitative tool to locate vibrator insertion points in a mass of concrete following the vibration process. This report is also found on DVD021. This thesis was developed as part of the educational requirements at Cornell University under a fellowship grant from the PCA Education Foundation.
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Assessment of Confinement Models for Reinforced Concrete Columns Subjected to Seismic Loading
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Item Code: SN3085
Date of Publication: 2006
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This thesis was developed as part of the educational requirements the University of British Columbia under a fellowship grant from the PCA Education Foundation.
The aim of this research project was to investigate the performance of the current ACI 318 confining steel requirements and compare them to other codes and proposed models to determine their suitability for a performance based design equation for implementation in Chapter 21 of ACI 318.
For both the rectangular and circular column evaluations, the ACI model was determined to be the least desirable of all models investigated. Based on the evaluation techniques developed, specific models were selected as recommended alternatives to the current ACI requirements. The recommended models minimize the potential of a column experiencing lateral strength degradation before reaching the prescribed lateral drift limit.
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Behavior of Inorganic Materials in Fire
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Item Code: RD067
Date of Publication: 1979
Price: $0.00
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Provides information on changes in strength, elastic, and thermal properties due to increasing temperatures for various concretes, steels, and concrete masonry. Also gives some thermal-property information for common brick, gypsum, ceiling tile, plasterboard, and asbestos board. This report is also found on DVD021.
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Bleeding
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Item Code: RP328
Date of Publication: 1994
Price: $15.00
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Provides comprehensive information on the effects of bleeding water on concrete properties, effects of construction practices and concrete ingredients on bleeding, test methods, and methods to properly control bleeding without detrimentally affecting the concrete.
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Calcium Chloride as an Admixture in Concrete
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Item Code: LS013
Date of Publication: 1924
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Calcium chloride, when used within certain limiting percentages, gave increased strength to concrete and mortar. The increase in strength was approximately in proportion to the amount of CaCl2 used up to a certain "optimum" percentage, 2 to 4%; the strength increase became less with larger additions. With 2 or 3% of CaCl2, the compressive strengths were increased about 100 to 200 lbs. per sq. in. For richer mixes and drier consistancies the strength increase was greater and for leaner mixes and wetter concrete it was less. This report is also found on DVD021.
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Cement Soundness and the Autoclave Expansion Test--An Update of the Literature
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Item Code: SN2651
Date of Publication: 2005
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This report updates previous literature reviews on the autoclave expansion test (ASTM C 151) and will be valuable to cement and concrete technologists interested in the applying or interpreting the results of this test. A standard cement test, ASTM C 151 detects potential unsoundness in concrete as a result of expansion due to free lime or magnesia in cement. Topics included in the review include correlation with concrete unsoundness; effects of iron and other cement raw mix components; effects of periclase (MgO) size, distribution, and crystallinity; temperature effects; cement fineness; and effects of pozzolans.This report is also found on DVD021.
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Chemical Path of Ettringite Formation in Heat Cured Mortar and Its Relationship to Expansion: A Literature Review
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Item Code: RD136
Date of Publication: 2005
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The issues related to delayed ettringite formation (DEF) have received much attention since this particular concrete deterioration process was first reported. Despite many attempts to develop a fundamental understanding, the mechanism involved is still unclear and remains controversial. A large number of literature sources dealing with various aspects of this phenomenon are currently available, but such information is scattered and discrepancies in interpretation may lead to further confusion. The literature review presented here aims to present each aspect of DEF-related issues in a comprehensive manner to help readers develop an overview. The text comprises two major sections. The first part reveals the work performed to date, including ongoing controversies and discrepancies associated with DEF-related expansion. The second part focuses on various factors that control the expansive behavior and their mutual relationships. Throughout the text, the combined influence of the physical and chemical characteristics is the main emphasis. This review highlights the basic, essential concept that has been missing in previous approaches, i.e. the influence of physical changes and their relation to chemical reactions. This report is also found on DVD021.
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Chemical Path of Ettringite Formation in Heat-Cured Mortar and Its Relationship to Expansion
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Item Code: SN2526
Date of Publication: 2005
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In order to provide a better understanding of the DEF phenomenon, the present study investigated mortar systems made with various mixing and curing parameters for detailed changes in pore solution chemistry and solid phase development, while corresponding changes in physical properties were also closely monitored. This holistic approach enabled the development of a correlation between the chemical and physical changes which occur in the DEF-affected mortars. The present study revealed that relationships exist between the physical properties and expansive behavior. The normal aging process of the cementitious systems involves dissolution of uniformly distributed fine ettringite crystals within the hardened cement paste and subsequent recrystallization as innocuous crystals in the largest accessible spaces. This process, known as Ostwald ripening, facilitates relaxation of any expansive pressure developed within the paste. Ostwald ripening is impeded in a well-compacted, dense microstructure containing few flaws due to the low diffusion rate of the system. Therefore, alteration of the mortar parameters to enhance microstructure for improved mechanical strength increases the risk of DEF-related expansion. This report is also found on DVD021.
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Clinker Microstructure and Grindability: Updated Literature Review
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Item Code: SN2967
Date of Publication: 2007
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Much of the available literature on the relationship between clinker microstructure and grindability agree that the primary influential factors are alite and belite crystal size and content. Specifically, smaller crystals and more alite (less belite) result in easier to grind clinker. Numerous equations are found in literature to predict clinker grindability based on its microstructure, and although the equations vary somewhat, the relationship to alite and belite content and size previously described are consistent.
On a related topic, some literature was found on clinker microstructure and grindability with the focus on the influence of trace elements, this topic arising likely due to the increased use of alternate raw materials and fuels.
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