Cement composites with expanded graphite as resistance heating elements

2020 ◽  
Vol 54 (25) ◽  
pp. 3821-3831
Author(s):  
Maksymilian Frąc ◽  
Waldemar Pichór ◽  
Paulina Szołdra
Keyword(s):  
Cement Mortar ◽  
Rapid Heating ◽  
Expanded Graphite ◽  
Electrical Current ◽  
Maximum Temperature ◽  
Cement Composites ◽  
Resistance Heating ◽  
Self Heating ◽  
Time Required ◽  
Heating Test

The following paper presents the results of research on cement composites with expanded graphite as resistance heating elements. Samples of cement mortar were prepared with expanded graphite obtained from intercalated graphite by means of rapid heating at 1000℃. Monotonic and cyclic self-heating tests of cement composites with differing contents of expanded graphite were conducted. In the monotonic self-heating test, the electrical current and the surface temperature of the cement composites with expanded graphite were measured at temperatures 23℃ and –10℃ in order to evaluate their capacity to generate heat. The maximum temperature of composites, the time required to raise the temperature by 10℃, and the power density were determined. Five cycles were applied in the cyclic self-heating test to investigate heat-dependent mechanical properties. The results of the research revealed that cement composites with expanded graphite exhibited promising properties for application as resistance heating elements.

scholarly journals Effect of Electrical Injection of Corrosion Inhibitor on the Corrosion of Steel Rebar in Chloride-Contaminated Repair Mortar

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
The Huyen Nguyen ◽  
Tuan Anh Nguyen ◽  
Thien Vuong Nguyen ◽  
Van Khu Le ◽  
Thi Mai Thanh Dinh ◽  
...  
Keyword(s):  
Current Density ◽  
Cement Mortar ◽  
Tetrabutylammonium Bromide ◽  
Electrical Current ◽  
Corrosion Current ◽  
Sodium Borate ◽  
Apparent Diffusion Coefficients ◽  
Steel Rebar ◽  
Repair Mortar ◽  
Vis Spectroscopy

The electrical rehabilitation treatments of repair mortar were performed with tetrabutylammonium bromide salt (TBAB) at an electrical current density of 5 A/m2, using two electrolytes (0.1 M NaOH and 0.1 M Na3BO3solutions), and for two time periods (1 and 4 weeks), respectively. The average organic cation-based inhibitor’s concentration in cement mortars before and after this treatment was quantified using the UV-Vis spectroscopy. The experimental results reveal that the EICI treatment with 0.1 M Na3BO3was more effective in injecting the inhibitor and in improving the chloride penetration resistance and compressive strength of the mortar, relative to using 0.1 M NaOH as electrolyte. In this case, after the 4-week EICI treatment, [TBA+] contents were 2.3 % and 2.4% by mass of cement mortar for uncontaminated and salt-contaminated mortars, respectively. After the 4-week EICI treatment, the apparent diffusion coefficients of chloride anion in cement mortar were decreased by 40% from 1.52 × 10−10 m2/s. The EICI treatment was able to halt the chloride-induced corrosion of the steel rebar by promoting its passivation. The 2-week EICI treatment using sodium hydroxide and sodium borate solutions decreased the corrosion current density of the rebar by 77.8% and 78.5%, respectively, approximately two months after the treatment.

Rapid Polymer/Gas Solution Formation for Continuous Production of Microcellular Plastics

1996 ◽  
Vol 118 (4) ◽  
pp. 639-645 ◽  
Author(s):  
C. B. Park ◽  
N. P. Suh
Keyword(s):  
Rapid Heating ◽  
Continuous Production ◽  
Batch Process ◽  
Bubble Nucleation ◽  
Cycle Times ◽  
Solution Formation ◽  
Microcellular Plastics ◽  
Diffusion Phenomena ◽  
Order Of Magnitude ◽  
Time Required

An extrusion system that can create a polymer/gas solution rapidly for continuous processing of microcellular plastics is presented. Microcellular plastics are characterized by cell densities greater than 109 cells/cm3 and fully grown cells smaller than 10 μm. Previously these microcellular structures have been produced in a batch process by saturating a polymeric material with an inert gas under high pressure followed by inducing a rapid drop in the gas solubility. The diffusion phenomena encountered in this batch processing is typically slow, resulting in long cycle times. In order to produce microcellular plastics at industrial production rates, a means for the rapid solution formation is developed. The processing time required for completing the solution formation in the system was estimated from experimental data and the dispersive mixing theory based on an order-of-magnitude analysis. A means for promoting high bubble nucleation rates in the gas-saturated polymer via rapid heating is also discussed. The feasibility of the continuous production of microcellular plastics by the rapid polymer/gas solution formation and rapid heating was demonstrated through experiments. The paper includes not only a brief treatment of the basic science of the polymer/gas systems, but also the development of an industrially viable technology that fully utilizes the unique properties of microcellular plastics.

scholarly journals Preparation and Mechanical Properties of Graphene Oxide: Cement Nanocomposites

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Fakhim Babak ◽  
Hassani Abolfazl ◽  
Rashidi Alimorad ◽  
Ghodousi Parviz
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Graphene Oxide ◽  
Cement Mortar ◽  
Cement Matrix ◽  
Cement Composites ◽  
Xrd Diffraction ◽  
Calcium Silicate Hydrates ◽  
The Matrix ◽  
Scanning Electron

We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar.

Self-Heating Test to Evaluate Temperature Stabilization in the Rolling Bearing

2013 ◽  
Author(s):  
Rafael V. Carvalho ◽  
Ludmila C. A. Silva ◽  
Milton Amaro ◽  
Alessandro A. Ferreira ◽  
Aparecido M. da Rosa
Keyword(s):  
Rolling Bearing ◽  
Temperature Stabilization ◽  
Self Heating ◽  
Heating Test

Embedded resistive heating in composite scarf repairs

2016 ◽  
Vol 51 (18) ◽  
pp. 2575-2583 ◽  
Author(s):  
Mahdi Ashrafi ◽  
Brandon P Smith ◽  
Santosh Devasia ◽  
Mark E Tuttle
Keyword(s):  
Temperature Distribution ◽  
Outer Surface ◽  
Thermal Gradient ◽  
Thermal Damage ◽  
Electrical Current ◽  
Tensile Tests ◽  
Resistance Heating ◽  
Uniform Temperature ◽  
Uniform Temperature Distribution ◽  
Bond Strengths

Composite scarf repairs were cured using heat generated by passing an electrical current through a woven graphite-epoxy prepreg embedded in the bondline. Resistance heating using the embedded prepreg resulted in a more uniform temperature distribution in the bondline while preventing any potential thermal damage to the surface of the scarf repairs. In contrast, conventional surface heating methods such as heat blankets or heat lamps lead to large through thickness thermal gradient that causes non-uniform temperature in the bondline and overheating the outer surface adjacent to the heater. Composite scarf repair specimens were created using the proposed embedded heating approach and through the use of a heat blanket for circular and rectangular scarf configurations. Tensile tests were performed for rectangular scarf specimens, and it was shown that the bond strengths of all specimens were found to be comparable. The proposed embedded curing technique results in bond strengths that equal or exceed those achieved with external heating and avoids overheating the surface of the scarf repairs.

Piezoresistive properties of cement composites with expanded graphite

2020 ◽  
Vol 19 ◽  
pp. 99-102 ◽  
Author(s):  
Maksymilian Frąc ◽  
Waldemar Pichór
Keyword(s):  
Expanded Graphite ◽  
Cement Composites

Examination of the United Nations self-heating test for sulphides

2019 ◽  
Vol 58 (4) ◽  
pp. 438-444 ◽  
Author(s):  
Sungjae Moon ◽  
Frank Rosenblum ◽  
Yue Hua Tan ◽  
Jan E. Nesset ◽  
Kristian E. Waters ◽  
...  
Keyword(s):  
United Nations ◽  
Self Heating ◽  
The United Nations ◽  
Heating Test

scholarly journals Reuse of Waste Material “Waste Sludge Water” from a Concrete Plant in Cement Composites: A Case Study

2019 ◽  
Vol 9 (21) ◽  
pp. 4519
Author(s):  
Klus ◽  
Václavík ◽  
Dvorský ◽  
Svoboda ◽  
Botula
Keyword(s):  
Cement Mortar ◽  
Fresh Concrete ◽  
Hardened Cement ◽  
Cement Composites ◽  
Complete Replacement ◽  
Economic Problems ◽  
Waste Sludge ◽  
Recycled Waste ◽  
Mixing Water

This paper presents the results of research dealing with the use of recycled waste sludge water from a concrete plant (CP) as partial or complete replacement of mixing water in cement mixtures. The need to recycle waste sludge water generated as a by-product (waste sludge water) during the production of fresh concrete in the concrete plant results from the environmental and economic problems associated with the operation of the concrete plant. Mixing water was replaced with recycled waste sludge water in the amount of 25%, 50%, 75%, and 100%. In order to determine the effect of partial or complete replacement of mixing water with waste sludge water from the concrete plant in the production of cement composites, laboratory tests of waste sludge water were carried out to determine whether the waste sludge water complies with the requirements for mixing water defined in CSN EN 1008. The tests also determined the properties of fresh cement mortar and hardened cement composites. These were tests of the beginning and end of cement mortar setting, and the strength characteristics (flexural strength, compressive strength). The results of these tests show that it is possible to replace the mixing water by waste sludge water from the concrete plant in the amount of up to 25% without significantly affecting the tested properties, in comparison with the formula containing pure mixing water.

scholarly journals Corrosion Behavior of Pre-Rusted Rebars in Cement Mortar Exposed to Harsh Environments

2020 ◽  
Vol 10 (23) ◽  
pp. 8705
Author(s):  
Gankhuyag Burtuujin ◽  
Dasom Son ◽  
Indong Jang ◽  
Chongku Yi ◽  
Hyerin Lee
Keyword(s):  
Corrosion Rate ◽  
Cement Mortar ◽  
Cement Composite ◽  
Harsh Environments ◽  
Experimental Program ◽  
Cement Composites ◽  
X Ray Diffraction ◽  
Half Cell ◽  
Cell Potential ◽  
X Ray

Rebar embedded inside reinforced concrete structures becomes corroded due to various factors. However, few studies have focused on the corrosion of pre-rusted rebar embedded in cement composites, and the findings reported thus far are inconsistent. Therefore, in this study, an experimental program was undertaken to examine the effect of pre-rusting on the further corrosion of reinforcements in cement composites. Pre-rust was induced using two different solutions (CaCl2 and HCl). The corrosion rate in the cement composite was analyzed using the half-cell potential and polarization resistance methods. In addition, scanning electron microscopy with energy-dispersive X-ray analysis and X-ray diffraction analysis were used to examine the morphology of the rust. The results show that the corrosion rate of the rebar embedded in the cement composite can be increased by more than 3.8 times depending on the pre-rust conditions (RE: 0.0009 mm/year, HCl: 0.0035 mm/year). In addition, we found that the corrosion products in the pre-rusted layer were comparable to those of the rebar corroded in the marine atmosphere.

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