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Home > Publications > International Concrete Abstracts Portal
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_01
September 20, 2019
Joshua Hogancamp, Cesario Tavares, and Zachary Grasley
The current state of the art in fiber-reinforced cement-based materials indicates that adding multiple fiber types or sizes primarily creates a superpositioned behavior state: the behavior from each fiber type separately is added to the composite behavior of the material. Carbon nanofibers (CNFs) and milled carbon microfibers (MCMFs) can increase cracking resistance in cement-based materials by bridging cracks, although CNFs bridge cracks significantly smaller than cracks bridged by MCMFs. This research suggests that multi-scale fiber reinforcement (CNFs with MCMFs) might add compounded benefits to cracking resistance. Tests evaluating cracking resistance were performed utilizing a restrained-ring drying shrinkage test with Portland cement mortars. The CNFs and/or MCMFs were pre-mixed with cement using a sonication/distillation technique and/or rotary tumbling. Concentrations of CNFs and MCMFs were tested up to 5% and 6% by mass of cement, respectively. Restrained ring tests on mortar with high concentrations of CNFs or MCMFs reveal delayed cracking time by factors up to 6.4 or 2.6, respectively. Combining CNFs with MCMFs delayed cracking by a factor of at least 52. The increase in cracking resistance is attributed to the combined effects of bridging cracks of multiple sizes.
10.14359/51720211
SP-335_02
Maria S. Konsta-Gdoutos, Panagiotis A. Danoglidis, and Surendra P. Shah
The piezoresistive response and self-sensing ability of carbon nanotube reinforced mortar sensors have been investigated. The study aims on optimizing the development of a self-sensing nanoreinforced cement-based sensor for monitoring and evaluating the condition of concrete elements, in real time applications. It has been shown that the piezoresistive response of the nanomodified mortars was substantially enhanced just by adding a low amount of carbon nanotubes (CNTs), 0.1 wt%. Resistance measurements, using direct current (DC) and alternating current (AC), were conducted under the application of cyclic or monotonic compressive loading. The results show the sensor’s great ability to detect crack propagation and damage accumulation at all stages of deformation up to failure.
10.14359/51720212
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
SP-335_04
Douglas Hendrix, Nabil Bassim, and Kay Wille
There is significant potential for the use of nanoparticles in cementitious materials, especially in ultra-high performance concrete. These nanoparticles can further increase packing density, accelerate the pozzolanic reaction or can be used to induce new properties to the material, such as air purification or self-cleaning. Little is known about the interaction mechanisms between nanoparticles in cementitious materials, including their dispersion quality. The characterization of these nanoparticles can be challenging, especially when these nanoparticles interact with cementitious materials and their reaction products during hydration. Thorough characterization of the nanoparticle system is essential to understand how to optimize mixing constituents, procedures, and parameters.
10.14359/51720214
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