The Future of Durability Based Concrete Acceptance Testing ACI ReportSai Theja Medi(000746509) | Concrete Engineering | 10/07/17 Table of Contents The Future of Durability Based Concrete Acceptance Testing. 0 1 Presenters and Technical qualifications. 3 2 Durability of concrete. 4 3 Problems. 4 4 Physical Durability. 4 4.1 Freez-Thaw..
4 4.2 Percolation or Permeabilty of water 5 5 Chemical Durability. 5 5.1 corrosion of reinforcement 5 5.2 SULPHATE ATTACK.
. 5 6 Strategies. 5 6.1 super air meter 5 6.1.1 Methodology.
6 6.1.2 Results.
7 6.2 surface resistivty. 8 6.2.
1 METHODOLOGY.. 9 7 RESULTS. 10 8 Journals/Articles. 11 8.
1.1 Journal-I- Tanesi, Jussara & Kim, Haejin & Beyene, Mengesha & Ardani, A. (2015). Super Air Meter for Assessing Air-Void System of Fresh Concrete.
11 8.1.2 Journal-II- Ardani, A & Tanesi, Jussara. (2012). Surface Resistivity Test Evaluation as an Indicator of the Chloride Permeability of Concrete. 11 9 conclusion. 12 10 Reference. 13 Table of figures Figure 1 Freeze-thaw.
. 4Figure 2 Super air meter 6Figure 3Air content versus spacing factor for concretes with different admixture combinations. The data shows that just using air content as a measure of air-void quality can be miss leading. 7Figure 4- A comparison of SAM number versus spacing factor for over 300 mixtures from two different labs with both lab and field concrete. 7Figure 5-The SAM number versus the durability factor from rapid F-T testing.
8Figure 6- surface resistivity meter 8Figure 7-Surface resistivity Principle. 9Figure 8-Relationship between SR test and RCPT. 10Figure 9-Correlation between SR test and RCPT obtained in different studies. 10 1 Presenters and Technical qualifications v Dan DeGraaf, P.E. is the Executive Director for the Michigan Concrete Association.
Dan earned a Bachelor of Science in Civil Engineering from Michigan Technological University and has been with the MCA and the Michigan Concrete Paving Association (now part of the MCA) since July of 2000. Dan has over 23 years of experience in the concrete industry with many private companies, such as the Reith-Reilly Construction Company, in addition to his time with the MCA/MCPA. v John Staton, P.
E. is the Concrete Operations and Materials Engineer in the Construction Field Services Division of the Michigan Department of Transportation (MDOT). John earned a Bachelor of Science in Civil Engineering from Michigan State University and has been with the MDOT since 1987. Prior to that John was a Bridge Engineer for the California Department of Transportation. John is a Registered Engineer in both California and Michigan.v Jeff Elliott, P.E.
is the Vice President of Michigan Operations for TTL Associates, Inc. (TTL), a verified Service Disabled Veteran Owned Small Business (SDVOSB) headquartered in Toledo, Ohio, with branch offices in Plymouth, Michigan and Washington, DC. Jeff earned a Bachelor of Science in Civil Engineering from Lawrence Technological Engineering and has been with TTL since 1993. The Michigan Society of Professional Engineers (MSPE) named Jeff its 2015 “Engineer of the Year”.v 2 Durability of concreteDurability of concrete is defined as the ability of concrete to resist weathering action, chemical attack, and abrasion while maintaining its desired engineering properties.3 ProblemsDurability failures of concrete is affected by factors such as cracking, spalling, loss of strength, or loss of mass. The causes of concrete deterioration can be physical and chemical, and most of the cases it is a combination of both. Similarly looking into the deterioration of concrete it is not easy to ascertain the basic cause that could have initiated the deterioration process.
At a later stage, when the deterioration is advanced the concrete becomes porous, could easily lead gases and salt penetrate solutions which damages the more. It is like a weak human body which is susceptible to all possible virus and infection, i.e to the ingredients found in nature to which the concrete is exposed. Simultaneous or successive attacks of several factors accelerate the process and deterioration increases by manifold due to their synergetic effect. It is not always cumulative.4 Physical Durability4.
1 Freez-ThawConcrete is highly saturated by freeze thaw actions, which is when approximately 91% of its pores are filled by water. When water freezes to ice it occupies 9% higher volume than that of water. If there is no enough space for this expanded volume in a porous, water containing mterial like concrete, freezing may cause tensile stresses in the concrete. tensile stresses to critically saturated concrete from freezing and thawing will commence with the first freeze-thaw cycle and will continue throughout winter seasons resulting in repeated loss of concrete surface. Figure 1 Freeze-thaw 4.
2 Percolation or Permeabilty of waterThe durability of structural concretes is strongly related to the transport of fluids through the material pore structure. Structural concretes can bear cracking by both shrinkage and loading actions. The presence of cracks increases the material permeability and accelerates the ingress of aggressive agents. Accordingly, quantifying the permeability of structural concretes with cracks is of vital importance. Concrete is a rather heterogeneous composite composed of porous cement paste, aggregates, and their interfacial transition zones5 Chemical Durability5.1 corrosion of reinforcementCorrosion of reinforcing steel is the leading cause of degradation in concrete. When steel corrodes, volume of rust will be more than steel volume.
This expansion creates tensile stresses in the concrete, which can eventually cause cracking, delamination, and spalling.5.2 SULPHATE ATTACKA mechanism where sulfate ions attack cement from external source. Such attack can occur when concrete is in contact with sulfate containing water. The often-massive formation of gypsum and ettringite formed during the external sulfate attack may cause concrete to crack and scale. But, studies and examinations concrete show that external sulfate attack is caused by loss of cohesion and strength.6 Strategies6.1 super air meterAir void system play a key role for freeze thaw durability of concrete, however, the current test methods for fresh concrete only allow for determination of total air content.
There is a need for a fresh concrete test method capable of indicating that air void size and distribution are adequate. To address this need, a new test method Super Air Meter (SAM) – was developed by Ley and Tabb.Super Air Meter is a modified version of the typical pressure.
The deformation of the concrete is first investigated The differences between the first and second pressure steps are used to calculate the SAM number.. If the spacing between the voids is too high then this could mean the concrete is susceptible to freeze-thaw deterioration Figure 2 Super air meter 6.
1.1 MethodologyAccording (ASTM 231) super air meter is a latest version of typical pressure method. The first modification is that two sequential pressures are applied to the concrete. at 14.5, 30, and 45 psi concrete deformation is studied, pressure is then released, and the same pressure steps are used again to measure the deformation. Sam number is calculated by difference of first and second pressure.
The SAM number has been correlated to the average size and spacing between air voids in the concrete mixture or a value that is known as the spacing factor. Concrete is susceptible to freeze-thaw deterioration if the spacing between the void is too high. A SAM number of 0.20 has been shown to correctly determine over 90% of the time whether the spacing between the bubbles meets the recommendations of the ACI 201 Concrete Durability Committee. The meter is currently being used in 36 different US States and five foreign countries. The SAM has been specified in Oklahoma, Kansas, Idaho and Michigan on transportation projects.
6.1.2 ResultsFigure 3Air content versus spacing factor for concretes with different admixture combinations. The data shows that just using air content as a measure of air-void quality can be miss leading.Figure 4- A comparison of SAM number versus spacing factor for over 300 mixtures from two different labs with both lab and field concrete.Figure 5-The SAM number versus the durability factor from rapid F-T testingSurface resistivity measurement provides extremely useful information about the state of a concrete structure6.
2 surface resistivtyState of concrete can be measured by surface resistivity. Not only has it been proven to be directly linked to the likelihood of corrosion and the corrosion rate, recent studies have shown that there is a direct correlation between resistivity and chloride diffusion rateFigure 6- surface resistivity meter6.2.1 METHODOLOGYIt works on the principle of the Wenner probe, the Resipod is designed to measure the electrical resistivity of concrete or rock. A current is applied to the two outer probes and the potential difference is measured between the two inner probes. The current is carried by ions in the pore liquid.
Resistivity ? = 2?aV/l k?cm Figure 7-Surface resistivity Principle 7 RESULTS Figure 8-Relationship between SR test and RCPTTable 1- chloride penetrability classificationFigure 9-Correlation between SR test and RCPT obtained in different studies.8 Journals/Articles8.1.1 Journal-I- Tanesi, Jussara & Kim, Haejin & Beyene, Mengesha & Ardani, A. (2015). Super Air Meter for Assessing Air-Void System of Fresh Concrete.
A key factor for freeze-thaw durability of concrete is the air void system; nevertheless, the current test methods for fresh concrete only allow for determination of total air content. There is a need for a fresh concrete test method capable of indicating that air void size and distribution are adequate. In an attempt to address this need, a new test method based on the super air meter (SAM) was developed by Ley and Tabb. This paper presented an investigation of the air void system of 64 mixtures, employing standard fresh and hardened concrete test methods, as well as the SAM test method.
The study focused on mixtures with three different coarse aggregates, three air entraining admixtures, different total air contents levels, and slumps below 3 in. (75 mm), typical of paving concrete. Freeze-thaw tests were carried out on some of the mixtures with marginal air content.
Data from this study at the Federal Highway Administration’s Turner Fairbank Highway Research Center Laboratory showed that the SAM test of fresh concrete was able to provide an indication of air void adequacy in low-slump air entrained concrete; a SAM number of 0.20 psi (1.4 kPa) or above identified mixtures with poor spacing factor.
However, a limit of 4.0 % fresh air content was also able to identify these mixtures as a good correlation between air content and spacing factor was found. 8.
1.2 Journal-II- Ardani, A & Tanesi, Jussara. (2012). Surface Resistivity Test Evaluation as an Indicator of the Chloride Permeability of Concrete.Twenty-five plain, binary, and ternary mixtures containing up to 55 percent class F or class C fly ashes and, in some cases, fine limestone powder and with different aggregate types and maximum sizes were used to evaluate the correlation between the RCPT and the SR test. The results show that the SR test results are highly correlated with the RCPT even for HVFA mixtures and ternary mixtures with finely ground limestone, and a correlation curve was proposed. The SR test was easier and faster to run compared to the RCPT and did not require any specimen preparation. It also presented lower variability than the RCPT 9 Conclusion1.
Using Super Air Meter benefited to check the quality of fresh concrete. we no need wait for 24 or 28 days to know strength of concrete SAM calculates strength in 5-to 10 minutes. However, SAM is not consistent because SAM number keeps on bouncing from Batch to Batch with different admixtures.2. Using Surface Resistivity, we find the durability in minutes.
It is ver simple and easy to use. 10 Reference 1. Tanesi, Jussara & Kim, Haejin & Beyene, Mengesha & Ardani, A. (2015). Super Air Meter for Assessing Air-Void System of Fresh Concrete.2. Durability problems in concrete S Chandra, Chalmers University of Technology, Sweden3.
Ardani, A & Tanesi, Jussara. (2012). Surface Resistivity Test Evaluation as an Indicator of the Chloride Permeability of Concrete.
.4. www.quora.com/What-is-meant-by-durability-of-concrete5. https://failuremechanisms.files.
researchgate.net/publication/274084580_Permeability_of_Cracked_C oncretes_through_Percolation_Approach7. http://www.cement.org/learn/concrete-technology/durability/corrosion-of-embedded-materials8. http://www.
superairmeter.com/info.html9. aci 201.2r-08. guide to durable concrete. american concrete institute, detroit, mi, 200810.
aci 201.2r-08. guide to durable concrete. american concrete institute, detroit, mi, 2008.
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