scholarly journals Developing New and Optimizing Current Test Methods to Evaluate SulphiDe-bearing Aggregate

2021 ◽  
Author(s):  
Mona El-Mosallamy
Keyword(s):  
Oxygen Consumption ◽  
Test Methods ◽  
Minimum Size ◽  
Fine Aggregate ◽  
Reaction Products ◽  
Testing Procedures ◽  
Oxidizing Agents ◽  
Silicate Content ◽  
Bar Test ◽  
Mortar Bar

This research focuses on testing the applicability on aggregates from Ontario of a testing protocol to evaluate the potential oxidation of sulphide-bearing aggregates, optimizing the protocol test methods, and develop new tests based on the obtained results. The protocol comprises of three sequential tests: Total sulphur content, Oxygen Consumption Test and Oxidation Mortar Bar Test. For the oxygen consumption test, using processing equipment with cast iron media, was found to contaminate the samples and produce high consumption. Moreover, controlling the tested aggregate gradation produces higher consumption and more consistent results than using a fine aggregate sample (<150µm) without controlling the minimum size. The oxidation consumption test showed lower expansion values for carbonate aggregates compared to aggregates with high silicate content. Exposing siliceous aggregate, whether alkali-silica reactive or not, to the high pH from the oxidizing solution and the high temperature produces high expansion regardless of the oxidizable sulphide content. As such, new expansion criteria are suggested which takes into consideration the silicate content of the aggregates. The dissertation proposes, based on testing twenty-six aggregates, modifications to: the oxygen consumption test; the expansion criteria of the mortar bar test; and proposes a new oxidation mortar bar test to avoid the limitation of the applicability of the original mortar bar test on siliceous aggregates. In the new testing program, different testing regimes were investigated using different oxidizing agents and environmental conditions that can promote oxidation of sulphide-bearing aggregates, without the promotion of other chemical reactions (Alkali silica reaction products or Friedel’s’ salt). Out of the various investigated tested regimes, two testing procedures showed promising results and recommended for further development and use. Bleach and lime water are used in these tests as the oxidizing agents; however, mortar bars in both regimes are stored at lower temperature compared to that of the original test in the protocol. Based on the expansion results, new expansion criteria are suggested that can detect if the aggregate contains oxidizable sulphides.

scholarly journals Developing New and Optimizing Current Test Methods to Evaluate SulphiDe-bearing Aggregate

2021 ◽  
Author(s):  
Mona El-Mosallamy
Keyword(s):  
Oxygen Consumption ◽  
Test Methods ◽  
Minimum Size ◽  
Fine Aggregate ◽  
Reaction Products ◽  
Testing Procedures ◽  
Oxidizing Agents ◽  
Silicate Content ◽  
Bar Test ◽  
Mortar Bar

This research focuses on testing the applicability on aggregates from Ontario of a testing protocol to evaluate the potential oxidation of sulphide-bearing aggregates, optimizing the protocol test methods, and develop new tests based on the obtained results. The protocol comprises of three sequential tests: Total sulphur content, Oxygen Consumption Test and Oxidation Mortar Bar Test. For the oxygen consumption test, using processing equipment with cast iron media, was found to contaminate the samples and produce high consumption. Moreover, controlling the tested aggregate gradation produces higher consumption and more consistent results than using a fine aggregate sample (<150µm) without controlling the minimum size. The oxidation consumption test showed lower expansion values for carbonate aggregates compared to aggregates with high silicate content. Exposing siliceous aggregate, whether alkali-silica reactive or not, to the high pH from the oxidizing solution and the high temperature produces high expansion regardless of the oxidizable sulphide content. As such, new expansion criteria are suggested which takes into consideration the silicate content of the aggregates. The dissertation proposes, based on testing twenty-six aggregates, modifications to: the oxygen consumption test; the expansion criteria of the mortar bar test; and proposes a new oxidation mortar bar test to avoid the limitation of the applicability of the original mortar bar test on siliceous aggregates. In the new testing program, different testing regimes were investigated using different oxidizing agents and environmental conditions that can promote oxidation of sulphide-bearing aggregates, without the promotion of other chemical reactions (Alkali silica reaction products or Friedel’s’ salt). Out of the various investigated tested regimes, two testing procedures showed promising results and recommended for further development and use. Bleach and lime water are used in these tests as the oxidizing agents; however, mortar bars in both regimes are stored at lower temperature compared to that of the original test in the protocol. Based on the expansion results, new expansion criteria are suggested that can detect if the aggregate contains oxidizable sulphides.

scholarly journals The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates

2021 ◽  
Author(s):  
Medhat Shehata ◽  
Robert Johnson
Keyword(s):  
Test Methods ◽  
Recycled Concrete ◽  
Accelerated Tests ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Supplementary Cementing Materials ◽  
Alkali Silica Reactivity ◽  
Accelerated Mortar Bar Test ◽  
Bar Test ◽  
Mortar Bar

The effectiveness of accelerated tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates was evaluated. The Accelerated Mortar Bar Test was found effective for evaluating potential alkali-reactivity when the test variables, such as crushing method and absorption, are carried out in a well-defined process. The method of crushing was found to have significant impact on the expansion. The Concrete Microbar Test (CMBT) provides good correlation to the expansion of Concrete Prisms incorporating Supplementary Cementing Materials when an expansion limit of 0.10% at 56 days or 0.04% at 28 days were used, based on the limited number of tests carried out here.

scholarly journals The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates

2021 ◽  
Author(s):  
Medhat Shehata ◽  
Robert Johnson
Keyword(s):  
Test Methods ◽  
Recycled Concrete ◽  
Accelerated Tests ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Supplementary Cementing Materials ◽  
Alkali Silica Reactivity ◽  
Accelerated Mortar Bar Test ◽  
Bar Test ◽  
Mortar Bar

The effectiveness of accelerated tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates was evaluated. The Accelerated Mortar Bar Test was found effective for evaluating potential alkali-reactivity when the test variables, such as crushing method and absorption, are carried out in a well-defined process. The method of crushing was found to have significant impact on the expansion. The Concrete Microbar Test (CMBT) provides good correlation to the expansion of Concrete Prisms incorporating Supplementary Cementing Materials when an expansion limit of 0.10% at 56 days or 0.04% at 28 days were used, based on the limited number of tests carried out here.

Wadi gravel – a new concrete aggregate in Qatar: Part 2 –Alkali aggregate reactivity

2019 ◽  
Vol 53 (3) ◽  
pp. 400-412 ◽  
Author(s):  
Ian Sims ◽  
Khaled Hassan ◽  
Murray Reid ◽  
Mohammed bin Saif Al-Kuwari ◽  
Mohamed Attia ◽  
...  
Keyword(s):  
Perceived Risk ◽  
Test Methods ◽  
Petrographic Analysis ◽  
Concrete Aggregate ◽  
Gulf Region ◽  
Rock Types ◽  
Alkali Aggregate Reactivity ◽  
Accelerated Mortar Bar Test ◽  
Bar Test ◽  
Mortar Bar

Deposits of Wadi gravel are available in many parts of the Gulf region, but not widely utilized as aggregate for concrete, mainly due to the possibility of internal sulfate attack, plus the perceived risk of alkali aggregate reactivity (AAR). This paper describes the investigations for AAR of the Wadi gravel in this case, as part of the wider study described in Part 1 of this paper.Wadi gravel from the Mekaines site in Qatar was subjected to petrographic analysis, plus the gel-pat and accelerated mortar-bar test methods. The AAR potential was found to be low to normal. The accelerated mortar-bar test exhibited ‘innocuous’ behaviour after 14 days of immersion in alkali solution. When separately testing the constituent rock types of the Wadi gravel, limestone and quartz returned innocuous results, while rhyolite, granite and quartzite returned potentially alkali silica reactive (ASR) results and some reaction was confirmed using post-expansion petrographic examination.Wadi gravel was classified as potentially reactive in the RILEM AAR-4.1 accelerated concrete prism test, but of ‘low reactivity’ in the BS 812-123 test over the longer period of 12 months. Overcoming the potential problems of gypsum content and AAR successfully provides a valuable local resource of Wadi gravel aggregate for concrete.

Development of a Reproducible Method of Formulating and Testing Drilling Fluids

1969 ◽  
Vol 9 (04) ◽  
pp. 403-411 ◽  
Author(s):  
B.K. Sinha ◽  
Harvey T. Kennedy
Keyword(s):  
Large Scale ◽  
Drilling Fluid ◽  
Flow Characteristics ◽  
Field Testing ◽  
Test Methods ◽  
Water Evaporation ◽  
Fluid Loss ◽  
Drilling Fluids ◽  
Testing Procedures ◽  
Asymptotic Values

Abstract Recommendations are made for obtaining consistent and reproducible test data on drilling fluids having identical composition. Previously, such a procedure has been difficult to accomplish even when the fluids were mixed in similar equipment. A survey of work in this area indicates that previous methods have been unsatisfactory because previous methods have been unsatisfactory because (1) the muds are extremely sensitive to the duration and violence of agitation during a normal mixing routine, and (2) gelling of the muds occurs before the properties can reach constant values. This gelling is caused by water evaporation resulting from the increase in temperature associated with the agitation. The work shows that these problems largely can be overcome by (1) agitating the constituents of the drilling fluid more vigorously, (2) maintaining a fairly constant temperature, and(3) Protecting the fluid from evaporation. When these steps are followed, the fluid properties approach asymptotic values that do not change by prolonged or accelerated agitation or by aging for a month. The time required to reach asymptotic values or a stabilized state is from 2 to 6 hours and is a function of the mud composition. Introduction Preparation of drilling fluids in the laboratory to determine their suitability to meet specific drilling requirements or to serve as a base fluid to evaluate the effectiveness of thinners, dispersants or other additives normally begins with combining measured quantities of the constituents and stirring them for a short time in a low-speed mixer. This is done to obtain a uniform mixture and to hydrate clays. Then the fluid is further agitated in a higher-speed device (Hamilton Beach mixer or Waring blender) to disperse more thoroughly and clay particles The biggest obstacle in the laboratory investigation of drilling fluids has been the lack of a method of producing a mixture by which reproducible results of the measured properties could be obtained. Numerous investigators have encountered this difficulty. Prior to 1929, density was the only property of mud that customarily was measured. The use of Wyoming bentonite on a large scale after 1929 was mainly responsible for the development of more elaborate testing procedures and for the application of the principles of colloid chemistry to the drilling fluids. Ambrose and Loomis in 1931 were among the first to recognize the plastic flow characteristics of drilling fluids, although Bingham in 1916 had observed The same phenomenon with dilute clay suspensions. Marsh introduced the Marsh funnel for field testing in 1931. By this time, non-Newtonian characteristics of drilling fluids were established. The Stormer and MacMichael viscometers were used to study the rheological properties of the fluids. In the 1930's and early 1940's, the work conducted by several investigators contributed toward a better understanding of drilling fluids. In the mid 1930's, fluid-loss and the associated mud-cake-forming properties of drilling fluids were recognized as important to the behavior of these fluids. The other properties of drilling fluids, including gel strength, pH, and sand content soon were recognized. In 1937, API published its first recommended procedure for test methods. Since that time, these procedures have been revised periodically. The latest edition, RP-13B, was published in 1961 However, in spite of the recognized need for a method of mixing that provides drilling fluids with stabilized properties, no such method previously has been described. SPEJ P. 403

scholarly journals Accelerated test methods for evaluating alkali-silica reactivity of recycled concrete aggregates

2021 ◽  
Author(s):  
Robert C Johnson
Keyword(s):  
Binding Capacity ◽  
Recycled Concrete ◽  
Test Duration ◽  
Accelerated Tests ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Alkali Silica Reactivity ◽  
Accelerated Mortar Bar Test ◽  
Bar Test ◽  
Mortar Bar

This thesis reports the findings of a study carried out to determine the effectiveness of Accelerated Tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates. The study evaluated the variability of the Accelerated Mortar Bar Test due to test variables as well as the single and multi-laboratory variation. The variability of the Concrete Microbar Test due to test variables and the correlation to results from Accelerated Mortar Bar and Concrete Prism Test results were also evaluated. The tests were corroborated by comparing the porosity, permeability and alkali binding capacity of samples tested by the accelerated tests. It was found that the Accelerated Mortar Bar Test provides acceptable results when the test variables, such as crushing methods and absorption values, are carried out and evaluated properly. The Concrete Microbar Test was found to underestimate the expansion of reactive aggregates. However, the same test was found to provide good correlation to the expansion results of Concrete Prisms incorporating Supplementary Cementing Materials when the test duration was increased.

How does fly ash mitigate alkali–silica reaction (ASR) in accelerated mortar bar test (ASTM C1567)?

2013 ◽  
Vol 37 ◽  
pp. 143-153 ◽  
Author(s):  
Seyed M.H. Shafaatian ◽  
Alireza Akhavan ◽  
Hamed Maraghechi ◽  
Farshad Rajabipour
Keyword(s):  
Fly Ash ◽  
Alkali Silica Reaction ◽  
Accelerated Mortar Bar Test ◽  
Bar Test ◽  
Mortar Bar

Mode of Action of Fluoride: Application of New Techniques and Test Methods to the Examination of the Mechanism of Action of Topical Fluoride

1994 ◽  
Vol 8 (2) ◽  
pp. 166-174 ◽  
Author(s):  
D.J. White ◽  
D.G.A. Nelson ◽  
R.V. Faller
Keyword(s):  
Acid Resistance ◽  
Test Methods ◽  
Magic Angle Spinning ◽  
Treatment Modalities ◽  
Magic Angle ◽  
Reaction Products ◽  
In Situ Experiments ◽  
Ph Cycling

Modern techniques in dental research continue to assist in the study of the mode of (anticaries) action of topical fluorides. The Plaque Glycolysis and Regrowth Model (PGRM) facilitates the standardized assessments of antimicrobial effects on plaque following use of test formulations in vivo without complications arising from coincident mineral reactivity. In vivo plaque glycolysis testing demonstrates that topically applied fluoride, at conventional levels found in dentifrices, has only modest effects on the metabolic (acid-producing) activity of dental plaque. Any 'plaque' contribution to fluoride efficacy must come from more subtle effects on plaque acidogenicity than those measured in PGRM. The 19-F MAS NMR (Magic Angle Spinning Nuclear Magnetic Resonance) technique provides unambiguous measures of the reaction products of F-enamel interactions. Studies have revealed a new 'reaction product' of fluoride-enamel interactions-designated as Non-Specifically-Adsorbed Fluoride, NSAF. This species, along with FAP (fluoroapatite), FHAP (fluorohydroxyapatite), and CaF2 (calcium fluoride), contributes to the remineralization/ demineralization benefits of fluoride. pH cycling and in situ denture chip studies permit quantitative assessments to be made of the relative benefits of fluoride in promoting remineralization and in inhibiting demineralization. Results from pH cycling/ in situ experiments are strongly supportive of Koulourides' 'Acquired Acid Resistance' concept, describing fluoride's decay-preventive effects. The continued application of new analytical/physical techniques and testing regimens to the study of fluoride anticaries mechanisms may lead to the development of improved fluoride agents/treatment modalities for the prevention of dental caries.

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