New Model For Natural Carbonation Prediction In Reinforced Concrete – Concept And Validation On Chemical Admixtures,
2019
University of Johannesburg
New Model For Natural Carbonation Prediction In Reinforced Concrete – Concept And Validation On Chemical Admixtures, Stephen O. Ekolu, M Raats
International Conference on Durability of Concrete Structures
A new model for prediction of natural carbonation in reinforced concrete structures has recently been developed and presented in (Ekolu, 2018). For brevity, the model is referred to as ESS model. It employs concrete strength as the primary property depicting core carbonation behaviour of any given concrete while other factors induce secondary influence. Chemical admixtures in concrete significantly influence concrete behaviour. Using experimental data from the literature (Dan-Herrera et al., 2015), the model behaviour is verified under use of various types of chemical admixtures of concrete including internal curing, shrinkage reducing, viscosity modifying, and high range water reducing admixtures. Class …
Absorption, Porosity, Capillarity And Chloride Diffusion In Ultra High Performance Concretes,
2019
Universitat Politècnica de València
Absorption, Porosity, Capillarity And Chloride Diffusion In Ultra High Performance Concretes, José Manuel Gandia-Romero, José Enrique Ramón-Zamora, Isabel Gasch, Manuel Valcuende, Rafael Calabuig, Victor Calvet, Pedro Serna
International Conference on Durability of Concrete Structures
Concrete durability performance can be assessed by a number of parameters, among which permeability properties are key. In this experimental work, the permeability to water and the diffusion of chlorides in Ultra High Performance Concrete (UHPC) are studied. To this end, three types of concrete were made: two Ultra High Performance (one with fibers and one without fibers) and a Conventional Concrete (CC) of w/c ratio equal to 0.5. The compressive strength of Ultra High Performance Concretes was 130 MPa, and that of conventional concrete was 50 MPa. All of them were cured at a temperature of 20°C and RH …
The Influence Of Waste Glass Powder On The Chloride Binding Capacity Of Fly Ash/Cement Hardened Paste,
2019
Purdue University
The Influence Of Waste Glass Powder On The Chloride Binding Capacity Of Fly Ash/Cement Hardened Paste, Jh Yan, Tingyu Hao
International Conference on Durability of Concrete Structures
The potential of using waste glass powder to increase the chloride binding capacity of fly ash/cement hardened paste was investigated. When only fly ash replacing cement, the chloride binding capacity was raised within 28d when the fly ash replacement level was in the range from 30-50% by mass. But at a longer age of 60 to 90d, the binding performance was increased at the replacement level of 10-30wt%. The chloride binding capacity of glass powder-fly ash-cement system was increased by adding glass powder of 2% and 4% by mass at 7d while those at larger addition and longer age reduced. …
Alkali Reactive Carbonate Rocks: Is It Alkali Silica Reaction (Asr) Or Alkali Carbonate Reaction (Acr)?,
2019
SES Group & Associates, LLC
Alkali Reactive Carbonate Rocks: Is It Alkali Silica Reaction (Asr) Or Alkali Carbonate Reaction (Acr)?, Mengesha Beyene, Rc Meininger
International Conference on Durability of Concrete Structures
The root cause of distress in two different concrete structures made from carbonate coarse aggregates that fit the textural and compositional criteria cited for ACR was found to be caused by ASR, not ACR. Stereo-optical examination and transmitted polarized light microscopy (PLM) analysis showed that the concretes contain some dark gray, fine-grained argillaceous dolomitic coarse aggregates in which secondary white deposit filling the cracks extending from these aggregates into the paste (as well as lining air voids) is ASR gel. Back scattered electron (BSE) imaging with EDS spectra and x-ray elemental mappings, clearly confirm that the white secondary deposits consist …
Impact Of Portlandite On Alkali-Silica Reaction Of Pyrex Glass And Blastfurnace Slag Aggregate,
2019
Hokkaido University
Impact Of Portlandite On Alkali-Silica Reaction Of Pyrex Glass And Blastfurnace Slag Aggregate, Natsumi Noguchi, Tomohiro Kajio, Yuka Morinaga, Yogarajah Elakneswaran, T Nawa, Toshiki Ayano
International Conference on Durability of Concrete Structures
In this study, it is investigated the effect of Ca ion on dissolution and reaction products in alkaline environment using Pyrex glass showing ASR expansion and blast furnace slag fine aggregate suppressing ASR. It is reported that Ca plays a role in the dissolution and polymerization of silica, and is therefore an important factor in ASR. For each sample, calculation of dissolution rate and analysis of solid phase product by 29Si MAS NMR and XRD/Rietveld analysis, and liquid phase analysis by ICP-AES were performed. As a result, it was confirmed that addition of Ca has an influence on dissolution behavior …
Comparison Of Alkali-Silica Chemical Reaction Of Reactive Glass And Chert Aggregate,
2019
Hokkaido University
Comparison Of Alkali-Silica Chemical Reaction Of Reactive Glass And Chert Aggregate, Yuka Morinaga, Elakneswaran Yogarajah, Toyoharu Nawa, Lalita Yongchaitrakul, Eiji Iwatsuki
International Conference on Durability of Concrete Structures
Alkali silica reaction (ASR) is one of the most important factors of deterioration of Concrete. However, there are a lot of unknown points about ASR such as mechanism of ASR and pessimum effect. We investigate to the mechanism of Alkali silica chemical reaction by using two different aggregates, early type expanded aggregate and delayed type expanded aggregate. Experiments were used to investigate ASR by reaction between reactive silica and alkali ions with or without calcium ions. Two phases of reacted samples (liquid and solid) are presented. In the absence of calcium hydroxide (CH), reactive materials with specified sizes (Yorochert, and …
Performance Of Concrete Made With A Calcined Clay – Limestone-Portland Cement Exposed To Natural Conditions,
2019
universidad central marta abreu de las villas
Performance Of Concrete Made With A Calcined Clay – Limestone-Portland Cement Exposed To Natural Conditions, Fernando Martirena, Ernesto Díaz, Dayran Rocha, Hamed Maraghechi, Karen Louise Scrivener
International Conference on Durability of Concrete Structures
This work presents the results of an investigation carried out to assess durability of concrete made with a calcined clay- limestone-Portland cement with 47% of clinker, hereafter named LC3, produced during an industrial trial in 2013. LC3 was used to cast concrete blocks and later expose them at a natural location at the northern coast of Cuba. Reference concrete was cast with Cuban Portland cement having 88% of clinker. Throughout three years (2015, 2016, 2017) concrete cores were systematically taken and the specimens were subjected to a testing program that included Formation factor, chloride profiling, surface resistivity, air permeability and …
Workability And Freeze-Thawing Performance Of Fiber Reinforced Expansive Self-Consolidating Concrete,
2019
Dalian University of Technology
Workability And Freeze-Thawing Performance Of Fiber Reinforced Expansive Self-Consolidating Concrete, Qi Cao, Qq Gao
International Conference on Durability of Concrete Structures
The aim of this study is to investigate the workability and freeze-thawing performance of fiber reinforced expansive self-consolidating concrete (ESCC). Fibers and expansive agent were used to decrease shrinkage, control cracks and enhance microstructure of the concrete. Steel fibers with three volume fractions (0.25%, 0.50%, 0.75%) of the total volume of concrete and monofilament polypropylene fibers with two volume fractions (0.05%, 0.10%) were used in the test. The freeze-thawing performance was determined by rapid freezing and thawing test. Results indicated that polypropylene fiber shows more sensitivity on slump flow than steel fiber but less impact on T500. The relative dynamic …
Polymer Binder, Impact On The Pull-Out Force Of Macro Fibers In Sprayed Concrete,
2019
Wacker Chemie AG
Polymer Binder, Impact On The Pull-Out Force Of Macro Fibers In Sprayed Concrete, Klaus Bonin, Christina Neumaier
International Conference on Durability of Concrete Structures
Macro-fibers have been used in sprayed concrete for many years now, particularly to prevent cracks from developing in the concrete due to deformation energy. These fibers can be made of steel or plastics and are provided for the Application. The type of fiber to be used is selected based on the building project’s requirements. Usually, the fibers are added to the sprayed concrete in the standard application’s mixture, regardless of whether the concrete is wet or dry (fiber-reinforced concrete or FRC). FRC’s functional principle is to mechanically anchor the steel or polymer fibers in the dense matrix of the binder …
Strength And Durability Performance Of Ultra-High-Performance Cementitious Composite Enhanced With Carbon Nanofibres,
2019
Universiti Kebangsaan Malaysia
Strength And Durability Performance Of Ultra-High-Performance Cementitious Composite Enhanced With Carbon Nanofibres, Jlg Nim, Sudharshan Naidu Raman, Mfm Zain, R Hamid, Fc Lai
International Conference on Durability of Concrete Structures
Ultra-high-performance concrete (UHPC) is known for exhibiting excellent strength and a more durable matrix compared to conventional concrete. Typically UHPC consists of carefully selected constituent materials of: ultrafine graded sand, silica fume (or other alternative binders), steel micro-fibres, and ordinary (or special blends) Portland cement. This study was initiated to synthesize a new blend of Ultra-high-performance cementitious composite (UHPCC) with compressive strength higher than 150 MPa under normal curing conditions, and to investigate the influence of two different sources of carbon nanofibres (CNF) on its strength, durability and microstructure properties. Several mix designs with different CNF percentages were designed, optimised …
Post-Cracking Behavior Of Cementitious Composite Incorporating Nano-Silica And Basalt Fiber Pellets,
2019
University of Manitoba
Post-Cracking Behavior Of Cementitious Composite Incorporating Nano-Silica And Basalt Fiber Pellets, Ahmed Bedwiy, Mohamed T. Bassuoni, Ehab El-Salakawy
International Conference on Durability of Concrete Structures
Recently, fiber reinforced polymers (FRPs) have been increasingly used to reinforce concrete structures in harsh environments, due to their non-corrodible nature. Developing a nonferrous reinforcement system (corrosion-free system) for concrete using FRP bars along with discrete fibers is a promising option for exposed concrete structures in cold regions or marine environments. Incorporating highly efficient non-metallic fibers into any cementitious composite is capable of reducing bleeding, controlling shrinkage cracking, and improving toughness and impact resistance. Therefore, in this study, a new type of basalt fiber pellets with high tensile strength was investigated. This paper reports on the flexural performance of the …
Long Term Permeability And Acid Resistance Of Selfcompacting Concretes With Micro And Nano Mineral Additions,
2019
University of Alcala
Long Term Permeability And Acid Resistance Of Selfcompacting Concretes With Micro And Nano Mineral Additions, Gonzalo Barluenga, Cynthia Guardia, Javier Puentes, Nelson Flores
International Conference on Durability of Concrete Structures
Self-Compacting Concrete (SCC) can incorporate different types of Supplementary cementitious materials (SCM), as filler and other active mineral additions, to increase the amount of paste without increasing the amount of cement. SCM modify the SCC hardened microstructure due to the filler effect, the seeding effect as nucleation points for hydration products and the pozzolanic effect in the case of reactive SCM, as mineral additions (MA). The pore network is also modified which produce changes in the permeability of SCC. It is generally considered that the increase of fine particles improves SCC durability due to the larger compactness of the hardened …
Effect Of Nanosilica On The Sulfate Attack Resistivity Of Cement Mortar,
2019
University of Jinan
Effect Of Nanosilica On The Sulfate Attack Resistivity Of Cement Mortar, Pengkun Hou, Zh Guo, Q Yu, N Xie, X Cheng, Sp Shah
International Conference on Durability of Concrete Structures
The effect of nanosilica on the sulfate attack resistivity of cement mortar was investigated through study on the mechanical property evolution and the length change of the cement mortar under 5 wt.% sodium sulfate for 6 months. Meanwhile, the effects were compared with those of fly ash-replacement mortar. Results showed that by taking the advantages of nanosilica and fly ash in improving the property of cement mortar at early and later ages, the sulfate attack resistance of cement mortar can be enhanced in mechanical property increase and expansion reduction. Further, it implies that a combination of both pozzolans could enhance …
The Synergistic Effect Of Nano-Silica With Slag On Frost Resistance Of Concrete,
2019
University of Jinan
The Synergistic Effect Of Nano-Silica With Slag On Frost Resistance Of Concrete, Yuan Lianwang, Zhou Zonghui, P Du, X Cheng, P Hou, L Zhang, Q Li
International Conference on Durability of Concrete Structures
The frost resistance of concrete is one of the most important factors for its durability. Supplementary cementitious materials could effectively improve the frost resistance of concrete. On this basis, the synergistic effect of nano-silica (NS) with slag on the frost resistance of concrete is better than the single, which was investigated. Nano-silica and slag were employed as a partial substitute of cement. The effect of these on the related indexes, including the mass loss, relative dynamic elastic modulus and porosity of concrete were measured after specified number of freeze and thaw cycles. Results show that the frost resistance of nano-silica …
Enhancement Of Durability Characteristics Of Geopolymer Concrete With Manufactured Sand,
2019
VIT University
Enhancement Of Durability Characteristics Of Geopolymer Concrete With Manufactured Sand, Abdul Aleem, T Shanmuga Priya
International Conference on Durability of Concrete Structures
Geopolymer Concrete is the concrete made without using any quantity of cement. Instead the waste material from the thermal power station called fly ash is used as the binding material. This fly ash reacts with alkaline solution like sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) and forms a gel which binds the fine and coarse aggregates. Similarly another artificial material called manufactured sand (M-Sand) is also used as the fine aggregate against the normal river sand. The durability of Geopolymer Concrete with M-sand was studied by casting cubes of size 100 x 100 x 100 mm. The cube specimens were …
A Preliminary Investigation Into Geopolymer Cement Mortar’S Suitability For Providing Resilient Highway Solutions,
2019
University of Ulster
A Preliminary Investigation Into Geopolymer Cement Mortar’S Suitability For Providing Resilient Highway Solutions, Bryan Magee, A Wilkinson, D Woodward, S Tretsiakova-Mcnally, P Lemoine
International Conference on Durability of Concrete Structures
Despite local and national road authorities striving to provide motorists with a durable and safe infrastructure environment, one in six UK roads are currently classed as being in poor condition. In terms of safety, Department for Transport statistics continue to report high numbers of road fatalities; 1,780 in 2015, representing a 3% increase from the previous year. As such, research focused on developing resilient and cost effective planned/preventative highway maintenance solutions remains highly topical. Reported in this paper is research aimed at developing high performance, low impact solutions for both highway repair and skid resistance enhancement. A metakaolin/alkali silicate-based geopolymer …
Comparison Of Lithomarge And Cement-Based Mortars Performance In Aggressive Aqueous Environments,
2019
Queen’s University Belfast
Comparison Of Lithomarge And Cement-Based Mortars Performance In Aggressive Aqueous Environments, Jacek Kwasny, Timothy A. Aiken, Marios N. Soutsos, Andrew J. Mcintosh, David J. Cleland
International Conference on Durability of Concrete Structures
The resistance of room temperature cured geopolymer mortar (GPM) against chemical attacks, i.e. sodium and magnesium sulfate solutions, and sulfuric and hydrochloric acid solutions, was evaluated. GPM was formulated using a lithomarge precursor (low-purity kaolin) to achieve 28-day characteristic compressive strength of 60 MPa. Its performance was compared with an equivalent Portland cement mortar (PCM) having the same paste volume and strength grade. 28-day old bar samples were stored in 0.352 mol/L sulfate solutions for 52 weeks whereas 28-day old cube samples were exposed for 8 weeks to acid solutions with concentration of 0.52 mol/L. GPM showed superior performance against …
Influence Of Sulfide On The Onset Of Chloride-Induced Corrosion Of Steel Reinforcement In Alkali-Activated Slags.,
2019
The University of Sheffield
Influence Of Sulfide On The Onset Of Chloride-Induced Corrosion Of Steel Reinforcement In Alkali-Activated Slags., Maria Criado, Shishir Mundra, Susan Andrea Bernal, John Lloyd Provis
International Conference on Durability of Concrete Structures
In alkali-activated slags (AAS), where ground granulated blast furnace slag is used as the main precursor, the presence of reduced sulfur species yields a highly reducing pore solution environment. This study investigates the influence of sulfide on steel passivation in alkali-activated slag mortars immersed in alkaline (1 M NaOH) and alkaline chloride-rich (1 M NaOH with 5 M NaCl) solutions, and the dependency of chloride-induced pitting on the immersion time and the concentration of sulfide in simulated alkali-activated slag pore solutions (containing 0.80 M OH- and 0 M, 0.01 M and 0.45 M HS- ) by means of electrochemical techniques. …
Impact Of Water Content On The Performance Of Alkali-Activated Slag Concretes,
2019
Department of Materials Science and Engineering, The University of Sheffield, UK
Impact Of Water Content On The Performance Of Alkali-Activated Slag Concretes, Susan A. Bernal, John L. Provis, Jannie S.J. Van Deventer
International Conference on Durability of Concrete Structures
In this study, we report the effect of varying the water/binder (w/b) ratio on the performance of sodium silicate activated concretes. Compressive strength development and water transport properties of these concretes were assessed, along with their resistance to carbonation. The results demonstrate that varying the water content within a reasonable range induced negligible changes in the compressive strengths of these concretes, when a constant paste content was used. A direct correlation between the w/b ratio and the amount of permeable voids in the concretes was not identified. The carbonation behaviour of these concretes changes prominently depending on the CO2 concentration …
Internal Curing By Sap In Ultra-High Strength Concrete With Cement-Silica Fume-Fly Ash Binder,
2019
College of Civil Engineering, Hunan University
Internal Curing By Sap In Ultra-High Strength Concrete With Cement-Silica Fume-Fly Ash Binder, Jianhui Liu, Caijun Shi, Xianwei Ma
International Conference on Durability of Concrete Structures
Super-absorbed polymer (SAP) is an effective internal curing materials for reducing autogenous shrinkage and improving cracking resistance of ultra-high-strength concrete (UHSC). This study investigated the compressive strength, shrinkage properties of UHSC with cement–silica fume–fly ash binder. The composition of the binder was designed using seven-batch factorial design method. The relationships between the binder composition and the properties were expressed in contours. Results showed that, silica fume could improve the compressive strength and total shrinkage of UHSC. However fly ash reduced the compressive strength and total shrinkage of UHSC to certain extent. On the other hand, under the internal curing of …
