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Home > Publications > 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.
Showing 1-5 of 303 Abstracts search results
December 1, 2023
Ali Abu-Yosef, Stalin Armijos-Moya, and Randall Poston
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.
Zachary W. Coleman and Anton K. Schindler
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.
Ben Wang, Abdeldjelil Belarbi, Mina Dawood, and Bora Gencturk
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.
Zhenwen Xu and Dongming Yan
External bonding with fiber-reinforced polymer (FRP) offers a
potential solution to mitigate the detrimental effects caused by
load impact and corrosion, which can weaken the bond strength
of reinforced concrete structures. However, existing models need
to be improved in addressing the FRP confinement mechanism and
failure modes. As a solution, the proposed model employs stress
intensity factor (SIF)-based criteria to determine the internal pressure exerted on the steel-concrete interface during various stages of comprehensive concrete cracking. Critical parameters are evaluated using weight function theory and a finite element model.
A bond-slip model is introduced for the FRP-concrete interface
and reasonable assumptions on failure plane characteristics. The
internal pressure model employed demonstrates that FRP confinement has the ability to generate dual peaks in stress distribution and modify their magnitude as the confinement level increases. The proposed predictive model demonstrates superior performance in failure modes, test methods, and wrap methods for assessing bond strength with FRP confinement. The accuracy of this model is indicated by an integral absolute error (IAE) of 9.6% based on 125 experimental data, surpassing the performance of the other
three existing models. Moreover, a new confinement parameter
is introduced and validated, showing an upper bound of 0.44 for
enhancing FRP bond strength. Additionally, a general expression
validating the bond strength model with FRP confinement is established, allowing for the prediction of bond length.
November 13, 2023
Igor Lapiro, Rami Eid, Konstantin Kovler
The penetration of chloride ions causes a degradation of the reinforcement bars, which directly affects the service life of the element. In this study, four different alternatives for the construction of an RC caisson parapet beam are investigated: conventional RC, the addition of a corrosion inhibitor to concrete, and the use of GFRP and galvanized steel instead of steel bars. The durability of the RC element under a marine environment was studied based on both measurements performed in situ 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 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 the 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, as long as no cracks occur. Furthermore, it was found that the potential measured using the half-cell method in all the alternatives slowly increased in 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.
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