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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 11 Abstracts search results
Document:
SP335
Date:
October 9, 2019
Author(s):
Mahmoud Reda Taha and Mohamed T. Bassuoni
Publication:
Symposium Papers
Volume:
335
Abstract:
Many of the papers presented in this volume were included in the two-part session Nanotechnology for Improved Concrete Performance, sponsored by ACI Committee 241, Nanotechnology of Concrete at the ACI Convention in Philadelphia, PA, on October 26, 2016. In line with the practice and requirements of the American Concrete Institute, peer review, followed by appropriate response and revision by authors, has been implemented.
DOI:
10.14359/51721384
SP-335_06
September 20, 2019
Su-Jin Lee, Shiho Kawashima, and Jong-Pil Won
In this study, nanosilica was applied to the surface of polypropylene (PP) fibers to introduce self-healing abilities when incorporated into cement-composites. When the fiber is at the site of a crack, the nanosilica can form additional hydration products through pozzolanic reaction to effectively seal the crack. Nanosilica was synthesized onto the fibers through a sol-gel process. Then the fibers were dried at room temperature or 50°C (122°F) to remove the excess solution and adhere the nanosilica particles onto the fiber surface. The existence of nanosilica was confirmed by observing the mass change before and after the sol-gel process, water absorption, soluble matter loss and microscopy. The self-healing performance of cement-composites reinforced with treated and untreated macro and micro PP fibers at dosages of 1.8kg/m3 (3.0lb/yd3) and 0.9kg/m3 (1.5lb/yd3), respectively, were evaluated through flexural strength testing according to ASTM C348. To evaluate strength recovery, samples were loaded to 60% of the peak load to induce cracking. The cracked specimens were cured for 28 days under laboratory conditions to undergo self-healing. A significant recovery in flexural strength (112.8%) was observed by using nanosilica treated micro PP fibers dried at room temperature.
10.14359/51720216
SP-335_05
Sumanta Das, Pu Yang, Sudhanshu S. Singh, James C.E. Mertens, Xianghui Xiao, Nikhilesh Chawla and Narayanan Neithalath
A detailed microstructural and micromechanical study of a fly ash‐based geopolymer paste including: (i) synchrotron x‐ray tomography (XRT) to characterize the pores (size > 0.74 m) that are influential in fluid transport, (ii) mercury intrusion porosimetry (MIP) to capture the volume fraction of smaller pores, (iii) high resolution scanning electron microscopy (SEM) combined with a multi‐label thresholding method to identify and characterize the solid phases in the microstructure, and (iv) nanoindentation to determine the component phase elastic properties using statistical deconvolution techniques, is reported in this paper. The 3D pore structure from XRT is used in a computational fluid transport model to predict the permeability of the material. The pore volume from XRT, solid phase volumes from SEM, and the phase elastic properties are used in a numerical homogenization framework to determine the homogenized macroscale elastic modulus of the composite. The homogenized elastic moduli are in good agreement with the flexural elastic modulus determined on macroscale paste beams. It is shown that the combined use of microstructural and micromechanical characterization tools at multiple scales provides valuable information towards the material design of fly ash‐based geopolymers.
10.14359/51720215
SP-335_09
A. M. Yasien, A. Abayou, and M. T. Bassuoni
In cold regions, freezing temperatures limit the construction season to few months, usually between May and September. The use of nanoparticles, which have high specific surface and vigorous reactivity, may potentially enhance the performance of concrete placed at low temperatures. Therefore, this study focused on developing concrete mixtures incorporating nano-silica which were mixed, placed and cured at -5°C (23°F) without any insulation or protection targeting field applications in late fall and early spring periods. Eight mixtures incorporating general use (GU) cement, fly ash (up to 25%), and nano-silica (up to 4%) were tested for this purpose, with water-to-binder ratios of 0.32 and 0.4. All mixtures contained a combination of calcium nitrate and calcium nitrite as an antifreeze admixture. Testing involved concrete setting time (placement), 7 and 28 days compressive strengths (hardened properties) and resistance to freezing-thawing cycles (durability). Moreover, mercury intrusion porosimetry, thermal analysis and scanning electron microscopy were performed to corroborate the trends from the macro-scale tests. It was found that nano-silica significantly improved the overall performance of concrete placed and cured at -5°C (23°F), which implicates its promising use for construction applications under low temperatures.
10.14359/51720219
SP-335_03
Joshua Hoheneder, Ismael Flores-Vivian and Konstantin Sobolev
Fiber additions in portland cement composites is a regular practice for crack prevention and for increasing the flexural strength. In this research, fiber-reinforced composites (FRC) with polyvinyl alcohol (PVA) fibers and carbon nanofibers (CNF) or carbon nanotubes (CNT) were investigated. Specimens were tested to measure their flexural strength, water absorption and electrical conductivity in water or sodium chloride solution. It was found that the developed composites, depending on applied stress and exposure to chloride solutions, exhibit some electrical conductivity. These dependencies can be characterized by piezoresistive and chemo-resistive coefficients demonstrating that the material possesses self-sensing capabilities. The sensitivity to strain, crack formation, and chloride solutions can be enhanced by incorporating small amounts of CNF or CNT into a composite structure. Conducted research has demonstrated a strong dependency of electrical properties of the composite on crack formation in moist environments. The developed procedure is scalable for industrial application in concrete structures that require nondestructive stress monitoring, integrity under high service loads and stability in harsh environments.
10.14359/51720213
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