Pan American Materials Congress: Materials for Infrastructure: Session II
Sponsored by: Third Pan American Materials Congress Organizing Committee
Program Organizers: Henry Colorado, Universidad de Antioquia; Oliverio Rodriguez, Centro de Investigacion en Química Aplicada

Thursday 2:00 PM
March 2, 2017
Room: Palomar
Location: Marriott Marquis Hotel

Session Chair: Henry Colorado, Universidad de Antioquia

2:00 PM  Invited
Jigs, Hydro-cyclones and Sensor-based Sorting to Value Recycled Aggregates: Régis Paranhos1; Carlos Sampaio2; Bogdan Cazacliu3; Raul Neto1; Maria Liendo1; 1Unipampa; 2UFRGS; 3IFSTTAR
    The proposition of this paper is to introduce a sorting platform aiming to increase quality on recycled aggregates by supplementary use of mineral processing techniques and more sorting. The difficulty of liberation is discussed and the methodology currently used in mineral processing is proposed. Jigs, hydro-cyclones and sensor-based sorting are equipments considered as having good performances to sort recycled aggregates. Based on current process in recycling platforms, the new process with supplementary sorting of the concrete recycled is presented. The gain in density and the reduction in water absorption were linked with rates of replaced aggregates and costs with transport and discharge. Replacing a lower quality aggregate by another with medium quality leads an expected gain in density about 4%. On the other hand, if replaced by superior quality, the expected gain will be 8.4%. As consequence, 34% on reduction in water absorption could be obtained too.

2:30 PM  
Effect of C5H11NO2S on Reinforcing-steel Corrosion in Concrete Immersed in Industrial/Microbial Simulating-environment: Joshua Okeniyi1; Abiodun Abioye1; Zechariah Adikpewun1; Adeola Otesanya1; Michael Eleshin1; Olugbenga Omotosho1; Olanrewaju GAbriel1; Oluyori Adeoye1; 1Covenant University
    In this paper, C5H11NO2S (Methionine) effect on reinforcing-steel corrosion in concrete immersed in 0.5 M H2SO4, simulating industrial/microbial environment, was studied by electrochemical techniques of open circuit potential and corrosion rate. The corrosion test-data were subjected to statistical distribution and tests of significance analyses prescribed by ASTM G16-95 R04. From this, analyzed results showed that the corrosion rate test-data followed the Weibull more than the Normal while the corrosion potential test-data followed both distributions. In spite of these, both the corrosion potential and the corrosion rate models still find agreements in corrosion criteria classification for the tested samples. Samples with C5H11NO2S admixture exhibited corrosion rate reductions compared to the control samples. By this, 0.25% C5H11NO2S admixture (i.e. wt% cement) exhibited optimal inhibition efficiency, η = 87.95±7.64%, on steel-rebar corrosion in the 0.5 M H2SO4-immersed concrete. Experimental data fitted Flory-Huggins adsorption isotherm that indicated physisorption as the prevailing mechanism of C5H11NO2S corrosion-protection on the reinforcing-steel in the industrial/microbial simulating-environment.

2:50 PM  
Development of Co-B-SiC Coatings for Use on Aeronautical and Automobile Industries: Alma Martínez1; Gabriel Trejo1; 1CIDETEQ
    The low corrosion and wear resistance, and low microhardness on structures, engines and pieces is a large and expensive problem for the aeronautical and automobile industries. There are some coatings that could offer these properties are Cr and Ni coatings. These coatings has good resistance corrosion and hardness. But recently due the European laws about the uses of Cr(VI) coatings is necessary find the new materials to replace the uses of Cr(VI). Cobalt-boron (Co-B) alloys could offer these properties because has excellent hard, wear resistant, relatively high fracture toughness, excellent chemical resistance and thermal stability. Co-B alloys for uses on coatings has been study recently because Co-B coatings has a thermal stability an good corrosion resistance, and the uses of SiC offer the hardness necessary to use in structures and parts of aircraft and automobile.

3:10 PM  Invited
Colombian Natural Fibers for Structural Materials: Henry Colorado1; Juan M Velez2; 1Universidad de Antioquia; 2Universidad Nacional de Colombia
     This presentation is about the most significant natural fibers from Colombia and its use in structural applications. Fique, luffa, and coconut fibers are presented.Characterization was conducted by Thermo Gravimetric Analysis, optical and Electron Microscopy, and X-ray diffraction. Some tests in cement based materials are presented with the corresponding materials characterization but also including flexural, porosity and density tests.

3:40 PM Break

4:00 PM  
Anticorrosion and Adsorption Mechanism of Rhizophora Mangle L Leaf-extract on Steel-reinforcement in 3.5% NaCl-immersed Concrete: Joshua Okeniyi1; Olugbenga Omotosho1; Cleophas Loto1; Abimbola Popoola2; 1Covenant University, Ota, Nigeria; 2Tshwane University of Technology, Pretoria
    In this paper, the anticorrosion and adsorption mechanism of Rhizophora mangle L leaf-extract on steel-reinforcement in concrete immersed in 3.5% NaCl test-environment was studied. Open circuit potential, macrocell current and corrosion rate measurements were obtained from steel-reinforced concrete samples that have different concentrations of the leaf-extract as admixtures, and that were immersed, for corrosion tests, in the saline/marine simulating-environment. From the corrosion test-data, the ratio of standard deviation of the corrosion potential to the standard deviation of the corrosion current was used for modelling corrosion noise resistance. Analyses of these test-results showed that the corrosion rate from linear polarization resistance exhibited very good correlation with the noise resistance model, for the leaf-extract concentrations employed in the study. Further analyses showed that Rhizophora mangle L leaf-extract concentration exhibited excellent corrosion inhibition efficiency performance on the steel-reinforcement embedded in the concretes. Also data of anticorrosion performance followed the Langmuir adsorption isotherm model, which indicated that the prevalent corrosion-protection, by the Rhizophora mangle L leaf-extract on steel-reinforcement in the 3.5% NaCl-immersed concrete samples, was through physisorption mechanism.

4:20 PM  
Cassia Fistula Leaf-extract Effect on Corrosion-inhibition of Stainless-steel in 0.5 M HCl: Olugbenga Omotosho1; Joshua Okeniyi1; Cleophas Loto1; Abimbola Popoola2; Omokolade Ajibola1; Adebanji Ogbiye1; 1Covenant University, Ota; 2Tshwane University of Technology, Pretoria, South Africa
    This paper investigates Cassia fistula leaf-extract effects on the corrosion-inhibition of stainless-steel in 0.5 M HCl. Measurements of corrosion rate were obtained through linear sweep voltametry (LSV) technique, at the ambient temperature of 28°C from stainless-steel specimens immersed in the acidic medium, containing differ-ent Cassia fistula leaf-extract concentrations. Results showed that inhibition effectiveness on stainless-steel corrosion increases with increasing concentration of the leaf-extract. The 10 g/L Cassia fistula leaf-extract, the highest concentration of the leaf-extract employed in the study, exhibited optimal inhibition efficiency η = 88.46% on the stainless-steel metal. Adsorption isotherm modelling shows that the experimental data followed the Flory-Huggins isotherm with excellent model efficiency, r2 = 90.27%, and the Langmuir model with very good model efficiency, r2 = 78.83%. Other isotherm parameters indicate favourable adsorption and suggest phy-sisorption as the prevalent mechanism of corrosion-protection by the leaf-extract on stainless-steel in the acidic chloride environment.