ABOUT THE INTERNATIONAL CONCRETE ABSTRACTS PORTAL

  • 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.

International Concrete Abstracts Portal

Showing 1-5 of 303 Abstracts search results

Document: 

22-133

Date: 

January 1, 2024

Author(s):

David Trejo and Gokul Dev Vasudevan

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

Inconsistencies in standards and codes result in confusion, increased costs, and do not promote the efficient use of concrete. In addition to inconsistencies, the lack of science-based approaches and data used for defining criteria in these standards and codes can limit the reliability and trust of these requirements. A review of industry documents indicates that inconsistencies and lack of science-based approaches exist across many documents, both throughout the industry and within ACI, relating to the corrosion of steel reinforcement embedded in concrete. This paper proposes to address five key issues to promote science-based standardization of requirements necessary for reinforced concrete systems exposed to corrosive conditions. These five issues include the need for: 1) standardization of chloride testing methods and requirements; 2) standardization of chloride reporting units; 3) standardization of terminology for specifying chlorides in cementitious systems; 4) standardization of exposure classifications for corrosive conditions; and 5) standardization of allowable chloride limits. This paper presents current inconsistencies in guide documents and codes for each of the items listed previously and then proposes an approach to standardize each using either available data and/ or a scientifically based approach. Recommendations for testing, reporting, definition of exposure classifications, and allowable chloride limits are then proposed. It is hoped that the systematic approach used herein will lead to standardization and consistency, less confusion, and will promote the efficient use of durable and economical concrete.

DOI:

10.14359/51739198


Document: 

22-287

Date: 

January 1, 2024

Author(s):

Igor Lapiro, Rami Eid, and Konstantin Kovler

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

The penetration of chloride ions causes degradation of reinforcing bars, which directly affects the service life of the element. In this study, four different alternatives for the construction of a reinforced concrete (RC) caisson parapet beam are investigated: conventional RC, the addition of a corrosion inhibitor to concrete, and the use of glass fiber-reinforced bars (GFRP) and galvanized steel instead of steel bars. The durability of the RC element under marine environment was studied based on measurements performed both in-place and in well-controlled laboratory conditions on specimens prepared in the laboratory, as well as specimens taken from the actual structural element. It was concluded that the exposure of fresh concrete to seawater splash has no effect on mechanical properties. In addition, galvanized rods were found to be a less effective protection strategy compared to the other alternatives studied. GFRP bars, however, provide better protection than the other tested alternatives, although chloride ion penetration in these bars was found to be more accelerated in an alkaline environment compared to a chloride environment. In contrast to the prevailing approach, which considers plain concrete and according to which the electrical resistance of the concrete decreases because of chloride penetration, this study found that electrical resistance in the reinforced element is increased due to an increase in the amount of corrosion products formed between steel and concrete if no cracks occur. Furthermore, it was found that the potential measured using the half-cell method in all the alternatives slowly increased with time, as well as the corrosion risk in the three alternatives with reinforcing steel. The remaining question is whether this change of potential is a direct characteristic of the corrosion risk. Therefore, more research in this direction is needed.

DOI:

10.14359/51740260


Document: 

22-272

Date: 

December 1, 2023

Author(s):

Ali Abu-Yosef, Stalin Armijos-Moya, and Randall Poston

Publication:

Materials Journal

Volume:

120

Issue:

6

Abstract:

Biogenic sulfuric acid attack (BSA) is a biodegradation mechanism that causes accelerated deterioration of concrete sewer systems and wastewater treatment structures. BSA is a multi-stage biological process that deposits sulfuric acid over concrete surfaces. Due to its complex nature, there are no current standards to evaluate the presence, extent, and severity of BSA in concrete structures during service. The authors evaluated the chemical and biological conditions in an operational digester where BSA activity was suspected. The evaluation included microbial culture testing, quantitative polymerase chain reaction (qPCR) analysis of biofilm samples, pH measurements, and petrographic assessment of extracted samples. To evaluate the effect of oxygen on BSA activity, evaluations were performed in strictly anaerobic and oxygen-rich environments inside the same digester. The investigation determined that oxygen injection caused significant changes in the biological and chemical conditions inside the digester. The addition of oxygen promoted BSA activity and the associated production of sulfuric acid, and therefore accelerated concrete deterioration.

DOI:

10.14359/51739147


Document: 

23-083

Date: 

December 1, 2023

Author(s):

Ben Wang, Abdeldjelil Belarbi, Mina Dawood, and Bora Gencturk

Publication:

Materials Journal

Volume:

120

Issue:

6

Abstract:

This paper presents the findings of an experimental study on the corrosion performance of both conventional and corrosionresistant steel reinforcements in normal-strength concrete (NC), high-performance concrete (HPC), and ultra-high-performance concrete (UHPC) columns in an accelerated corrosion-inducing environment for up to 24 months. Half-cell potential (HCP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods were used to assess the corrosion activities and corrosion rates. The reinforcement mass losses were directly measured from the specimens and compared to the results from electrochemical corrosion rate measurements. It was concluded that UHPC completely prevents corrosion of reinforcement embedded inside, while HPC offers higher protection than NC in the experimental period. Based on electrochemical measurements, the average corrosion rate of mild steel and high-chromium steel reinforcement in NC in 24 months were, respectively, 6.6 and 2.8 times that of the same reinforcements in HPC. In addition, corrosion-resistant steel reinforcements including epoxycoated reinforcing bar, high-chromium steel reinforcing bar, and stainless-steel reinforcing bar showed excellent resistance to corrosion compared to conventional mild steel reinforcement. There was no active corrosion observed for epoxy-coated and stainless steel reinforcements during the 24 months of the accelerated aging; the average corrosion rateS of high-chromium steel was 50% of that of mild steel in NC based on the electrochemical corrosion measurements; and the average mass loss of high-chromium steel was 47% and 75% of that of mild steel in NC and HPC, respectively. The results also showed that the LPR method might slightly overestimate the corrosion rate. Finally, pitting corrosion was found to be the dominant type of corrosion in both mild and high-chromium steel reinforcements in NC and HPC columns.

DOI:

10.14359/51739153


Document: 

22-376

Date: 

December 1, 2023

Author(s):

Zachary W. Coleman and Anton K. Schindler

Publication:

Materials Journal

Volume:

120

Issue:

6

Abstract:

In this study, a procedure for interpreting impact-echo data in an automated, simple manner for detecting defects in concrete bridge decks is presented. Such a procedure is needed because it can be challenging for inexperienced impact-echo users to correctly distinguish between sound and defective concrete. This data interpretation procedure was developed considering the statistical nature of impact-echo data in a manner to allow impact-echo users of all skill levels to understand and implement the procedure. The developed method predominantly relies on conducting segmented linear regression analysis of the cumulative probabilities of an impact-echo data set to identify frequency thresholds distinguishing sound concrete from defective concrete. The accuracy of this method was validated using two case studies of five slab specimens and a full-scale bridge deck, each containing various typical defects. The developed procedure was found to be able to predict the condition of the slab specimens containing shallow delaminations without human assistance within 3.1 percentage points of the maximum attainable accuracy. It was also able to correctly predict the condition of the full-scale bridge deck containing delaminations, voids, corrosion damage, concrete deterioration, and poorly constructed concrete within 3.5 percentage points of the maximum attainable accuracy.

DOI:

10.14359/51739149


12345...>>

Results Per Page