When to design per App. Strength design method for anchorage to concrete i. Design equations check 5 different failure modes Steel capacity Tension and Shear. Nsa Nominal tensile strength of an anchor group n Number of anchors Ase,N Effective cross sectional area of anchor in tension futa Specific ultimate tensile strength of anchor. D-9 N Centroid of anchors. D-7 kc Coefficient for basic concrete breakout strength Found in either App.
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The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts. Showing of 10 Abstracts search results. Publication: Symposium Papers. Volume: Abstract: The detrimental influence of chlorides on the corrosion of reinforcing steel in concrete has been widely documented.
The literature clearly shows that chloride concentration at the steel level must exceed a critical chloride threshold to initiate active corrosion of reinforcement embedded in concrete. It is now well accepted that this critical chloride threshold is not a unique value, but rather a range that depends on several factors. Regardless, placing concrete with chloride concentrations above the critical chloride threshold for a particular situation would result in active corrosion of the reinforcement and is therefore undesirable.
Unnecessarily restrictive limits, however, can lead to preclusion of some otherwise acceptable materials or require use of supplemental materials or alternative mixture designs that may increase costs or impact sustainability. Thus, there is a need from a practical standpoint to establish conservative, yet reasonable, limits so that the effects of corrosion can be managed without undue restrictions.
ACI documents place limits on the amount of chlorides that can be incorporated into new concrete — these limits are referred to as the allowable admixed chloride limits. Documents published by ACI Committees and currently recommend limiting admixed chlorides based on a mass percentage of the portland cement in the concrete mixture. Other documents, such as ACI , limit the admixed chlorides based on weight percentage of cement.
With the movement of the industry towards greener systems, the inclusion of supplementary cementitious materials SCMs as part of the cement could be beneficial. SCMs, however, when used in large quantities, have been reported to decrease the pH of the pore solution, which may lower the critical chloride threshold values. If the critical chloride threshold values for concrete systems containing only portland cement are different than the critical chloride threshold values for systems containing portland cement and SCMs, the published allowable admixed chloride limits may not be applicable.
A further complication in establishing values exists due to performance-based cements in which the specific amounts of SCMs might not be known to the specifier. This special publication SP , based on two technical sessions held during the Fall Concrete Convention and Exposition in Denver, CO, November , , addresses challenges associated with allowable admixed chloride limits, critical chloride thresholds, testing for the critical chloride threshold, binding of chlorides in different systems, and how admixed chlorides influence service life.
Authors and presenters from North America and Europe provided a variety of perspectives, experiences, and opinions. Based on the presentations, the open discussion that followed the presentations, and the papers in this SP, evidence indicates that allowable chloride limits should be based on cementitious materials content including both portland cement and SCMs. However, because research on the amount of chlorides required to initiate corrosion in systems containing high SCM replacement levels suggests that there may be upper limits at which the inclusion is appropriate, it was suggested that it may be appropriate to place limits on the replacement percentages of SCMs used for calculations of cement content when determining allowable admixed chloride limits.
Although the Denver sessions and the papers in this SP provide a significant move forward on better defining allowable chloride limits and likely allow for refinement of current recommendations in ACI documents, more research is needed. On behalf of ACI Committees and , the editors sincerely thank all authors and presenters for their efforts and contributions to the presentations, open forum, and this SP volume.
Special thanks are extended to the peer reviewers of the manuscripts for their constructive comments and recommendations. The editors are also indebted to the ACI staff for their assistance in organizing the sessions, organizing the open forum, and in preparing this volume. The editors earnestly hope that this symposium and SP volume will serve as a valuable resource to those searching for data, guidance, and better clarity on allowable admixed chloride limits in concrete.
Author s : Francisco J. Presuel-Moreno, Eric I. Abstract: The aim of this study was to determine the chloride threshold concentration of carbon steel rebar embedded in high performance concrete under exposure conditions relevant to the substructure of coastal bridge in Florida.
The experiments were based upon a series of reinforced and non-reinforced concrete specimens that contained 1 20, 35 and 50 percent cement replacement by fly ash, 2 6, 15 and 27 percent cement replacement by silica fume, and 3 control specimens no pozzolanic admixture.
The specimens have been exposed to one week wet - one week dry ponding cycle with natural seawater since January, Rebar potential values were monitored with time in order to determine when corrosion initiated. The rebar of several specimens activated after Cores were obtained to determine the extent of chloride ingress, the apparent diffusion coefficient Dapp and concrete resistivity. The chloride concentration above the rebar trace was also measured on most of the terminated specimens.
The value for Dapp was correlated against the corresponding measured resistivity. Specimens with 50 percent FA had the lowest Dapp but also the lowest chloride threshold. Author s : Vahid Jafari Azad and O. Burkan Isgor. Abstract: A thermodynamic modeling investigation was conducted to quantify free and bound chloride concentrations, and pore solution pH, in mixtures produced with different types of blended cements and admixed chlorides.
Specifically, the validity of using total cementitious materials content, instead of cement content, as the basis for allowable admixed chloride limits in new construction was evaluated. The effects of replacing OPC with two types of fly ash class C and F and one type of slag at different replacement levels were investigated.
Author s : Kyle Stanish. Abstract: The corrosion-initiation threshold for corrosion is a key parameter that controls the expected service life of a concrete structure. Different methods of establishing threshold values that consider different components of concrete mixtures can have a significant impact on anticipated service life. This impact is evaluated using typical concrete mixtures that are used in structures exposed to chloride-laden environments across the United States.
The often synergistic impact of including supplementary cementing materials SCMs in a concrete mixture and corrosion-initiation thresholds is examined, where the reduction of diffusion values with time can lead to a greater impact that would be expected from variation in corrosion-initiation thresholds alone. Author s : David Trejo and Cody Tibbits. Abstract: Chloride—induced corrosion of embedded metals in reinforced concrete structures is dependent on the quantity of chlorides in the concrete material.
Because of this, most ACI documents limit the amount of chlorides in the concrete for new reinforced concrete structures. Most documents in the United States limit the chlorides as a function of cement content, generally accepted to be the portland cement content.
Significant changes have occurred in the cement and concrete industries, such as performance based specifications for cement e. The allowable chloride limits published by ACI Committee specifically states that the allowable limits are based on portland cement content. ACI specifies limits based on weight of cement but is not clear on what determines cement portland cement only or all cementitious materials?
Significant research has been performed to assess the influence of SCMs on transport properties but limited research has been performed on assessing the influence of SCMs on the critical chloride corrosion threshold of steel in concrete.
This paper reports on research investigating the influence of SCMs replacement types and quantities on the diffusivity and critical chloride corrosion threshold. The reinforcing steel for all specimens was conventional steel reinforcement meeting ASTM A specifications. Results indicate that the diffusivity of the mixtures containing SCMs was significantly lower than the mixture with portland cement as the only binder. The results also indicate that the critical chloride threshold levels for mixtures containing SCMs is significantly lower than the critical chloride threshold of mixtures containing only portland cement as the binder.
An analysis of time to corrosion indicates that although the mean time to corrosion can be lower for systems containing SCMs, t-tests indicate that the null hypothesis that the means of the time to corrosion of the systems are equal cannot be rejected. This indicates that although there is a significant reduction positive influence in diffusivity when using SCMs, there is also a significant reduction negative influence in critical chloride threshold.
The benefits of the reduction in the rate of diffusivity seems to be offset by the detrimental effects of SCMs on critical chloride threshold. Limits on allowable chlorides in concrete for new construction published by ACI were based on concretes containing only portland cement as the binder. This research indicates that the ACI published limits may not be applicable to systems containing SCMs and that the limits are less conservative when basing the limits on total cementitious materials content.
ACI Materials Journal. CI Magazine. ACI Collection Online. Symposium Volumes. International Translations. International Concrete Abstracts Portal. July 25, Symposium Papers. The detrimental influence of chlorides on the corrosion of reinforcing steel in concrete has been widely documented. June 1, Author s :. Francisco J. The aim of this study was to determine the chloride threshold concentration of carbon steel rebar embedded in high performance concrete under exposure conditions relevant to the substructure of coastal bridge in Florida.
Vahid Jafari Azad and O. A thermodynamic modeling investigation was conducted to quantify free and bound chloride concentrations, and pore solution pH, in mixtures produced with different types of blended cements and admixed chlorides. Kyle Stanish. The corrosion-initiation threshold for corrosion is a key parameter that controls the expected service life of a concrete structure. David Trejo and Cody Tibbits. Chloride—induced corrosion of embedded metals in reinforced concrete structures is dependent on the quantity of chlorides in the concrete material.
Request an unlock code for Superuser or Staff access. Unlock Code:. Please enter this 5 digit unlock code on the web page. Moreno Publication: Symposium Papers Volume: Abstract: The aim of this study was to determine the chloride threshold concentration of carbon steel rebar embedded in high performance concrete under exposure conditions relevant to the substructure of coastal bridge in Florida.
Burkan Isgor Publication: Symposium Papers Volume: Abstract: A thermodynamic modeling investigation was conducted to quantify free and bound chloride concentrations, and pore solution pH, in mixtures produced with different types of blended cements and admixed chlorides.
International Concrete Abstracts Portal
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318-08 Building Code Requirements for Structural Concrete (ACI 318-08)
ACI 318-08, Appendix D