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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 2815 Abstracts search results
December 1, 2023
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.
Hongbo Zhu, Yilu Zhang, Hongxiang Gou, Liang Ren, and Qing Chen
To improve the added application value of an industrial waste stone
powder (SP), the optimizing mechanism of SP for the structure and
composition of hydrothermal synthetic hardened cement stone was
investigated in this paper. Cement was partially replaced by SP,
silica fume (SF), or ground-granulated blast-furnace slag (GGBS),
and then the microstructure with different SP content was tested
through X-ray diffraction, thermogravimetric analysis (TG-DTG),
mercury intrusion porosimetry (MIP), and scanning electronic
microscopy. The findings indicate that the incorporation of SP in
autoclaved products significantly enhanced compressive and flexural
strengths. As the proportion of SP in cement was increased, a
corresponding increase in the content of tobermorite within autoclaved cement mortar was observed. This increase in tobermorite concentration results in an initial rise followed by a subsequent decline in both compressive and flexural strengths. The maximum compressive and flexural strengths were achieved at an SP content of 15%. In addition, the mechanical strength was further improved by adding SP+GGBS or SP+SF. The strengthening mechanism of SP reveals that the change in the ratio of calcium and silicon ions (C/S) caused by SP in the sample was conducive to the formation of tobermorite and strength increase. Meanwhile, an increase in the quantity and a decrease in the crystal size of tobermorite were observed with an increase in the content of stone powder, resulting in a more compact microstructure of the sample. Moreover, the mechanical strength of cement composites doping SP+GGBS or SP+SF was further improved through superposition effects of SP and GGBS or SF with high activity. Currently, it is mainly applied to pipe pile products, and the strengthening effect of SP increases its use value. Meanwhile, the study of SP strengthening mechanism has laid a theoretical foundation for its application in high-strength autoclave and improved the relevant theory.
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.
Rita Maria Ghantous, Margaret N. Goodwin, Mehdi Khanzadeh Moradllo, Sean Quinn, Vahit Aktan, O. Burkan Isgor, Steven Reese, and W. Jason Weiss
Carbonatable calcium silicate cement (CSC) is a promising
approach to reducing the carbon footprint associated with concrete
production. Carbonatable CSC gains strength by reacting with
carbon dioxide (CO2). While the concept of carbonation is well
known, more information on the curing process is needed. This
study focuses on studying the impact of drying time, carbonation
duration, and degree of saturation (DOS) on the carbonation reaction
of CSC mortar. Samples were exposed to different drying durations
at controlled environmental conditions to reach various DOSs
ranging from 100 to 0%. The samples were then exposed to carbonation under the same environmental conditions for different durations. Neutron radiography (NR) was performed on the samples
during drying to determine the DOS corresponding to various
drying durations. NR was also used during the carbonation period
to determine the degree of carbonation (DOC) in real time. The
impact of carbonation on the diffusivity of water vapor (Dh) and
pore size distribution of CSC-based samples was examined using
dynamic vapor sorption (DVS). It was concluded that the carbonation reaction increased as the DOS decreased from 100 to 40%. The carbonation reaction ceased for samples with DOS values less than 6% DOS. It was also concluded that as the DOC increased,
the pore structure was refined, which led to a decrease in the Dh of
the CSC mortar samples.
R. M. Ghantous, V. Bui, S. Schaef, B. Fronczek, C. B. Jablonski, S. R. Reese, and W. J. Weiss
This study uses neutron radiography (NR) and visual inspection to
quantify water penetration in concrete samples exposed to water
pressure on one face. It provides experimental data regarding the
impact of mixture proportions on the hydraulic permeability of
concrete. Specifically, it illustrates the influence of water-cement
ratio (w/c), curing duration, entrained air content, and coarse
aggregate (CA) size and volume on water transport. In addition,
this paper quantifies the impact of permeability-reducing admixtures (PRAs) on water transport in concrete. It was observed that decreasing the w/c and/or increasing the curing duration reduced the fluid transport. Liquid and powder PRAs efficiently reduced fluid transport in concrete without impacting the compressive strength. The liquid PRA showed more consistent results, likely due to better dispersion than the powder PRA. Fluid ingress in concrete samples appears to increase with entrained air content due to a lower degree of saturation (DOS) at the start of the test. Increasing the CA volume fraction or decreasing the CA size will increase the fluid transport in concrete due to an increase in the connectivity of the interfacial transition zone. The influence of entrained air content, curing duration, CA volume fraction, and CA size was less noticeable on mixtures with PRAs due to the higher density and low permeability of these samples compared to control samples.
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