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2019

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Articles 271 - 300 of 1769

Full-Text Articles in Civil and Environmental Engineering

New Model For Natural Carbonation Prediction In Reinforced Concrete – Concept And Validation On Chemical Admixtures, Stephen O. Ekolu, M Raats Nov 2019

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 …

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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 Nov 2019

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 …

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The Influence Of Waste Glass Powder On The Chloride Binding Capacity Of Fly Ash/Cement Hardened Paste, Jh Yan, Tingyu Hao Nov 2019

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. …

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Alkali Reactive Carbonate Rocks: Is It Alkali Silica Reaction (Asr) Or Alkali Carbonate Reaction (Acr)?, Mengesha Beyene, Rc Meininger Nov 2019

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 …

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Study Of The Deterioration Of Concrete Incorporating Sulfide-Bearing Aggregates, Josée Duchesne, Benoit Fournier, Julie Francoeur Nov 2019

Study Of The Deterioration Of Concrete Incorporating Sulfide-Bearing Aggregates, Josée Duchesne, Benoit Fournier, Julie Francoeur

International Conference on Durability of Concrete Structures

In the Trois-Rivières area (Québec, Canada), several hundred foundations of private houses, apartment and public buildings were built using concrete incorporating an anorthositic gabbro coarse aggregate containing sulfide minerals. A large number of those concrete structures developed serious deterioration within 3 to 5 years after their construction, which triggered, in many cases, their demolition/replacement. To help understanding the deterioration mechanisms and the conditions most prone to the development of premature damage, as well as quantifying the rate of deterioration, concrete blocks, 1 m x 1 m x 0.225 mm in size, were extracted from housing foundations just prior to their …

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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 Nov 2019

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 …

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Influence Of Mineralogical Nature Of Aggregates On Acid Resistance Of Mortar, K P. Ramaswamy, Manu Santhanam Nov 2019

Influence Of Mineralogical Nature Of Aggregates On Acid Resistance Of Mortar, K P. Ramaswamy, Manu Santhanam

International Conference on Durability of Concrete Structures

Cement-based materials being alkaline in nature are often subjected to rapid deterioration on exposure to the aggressive acidic environments. Acids penetrate into the cement matrix causing calcium leaching and deterioration of phases leading to alteration in the microstructure. Currently, there are hardly any codes or standards available for evaluating the durability of materials to acid attack. Moreover, the literature addressing the material resistance is quite inconclusive. This paper aims to evaluate the influence of mineralogical nature of aggregates on the degradation kinetics of cement mortar when exposed to inorganic and organic acid solutions by performing a static accelerated leaching test. …

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Comparison Of Alkali-Silica Chemical Reaction Of Reactive Glass And Chert Aggregate, Yuka Morinaga, Elakneswaran Yogarajah, Toyoharu Nawa, Lalita Yongchaitrakul, Eiji Iwatsuki Nov 2019

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 …

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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 Nov 2019

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 …

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Workability And Freeze-Thawing Performance Of Fiber Reinforced Expansive Self-Consolidating Concrete, Qi Cao, Qq Gao Nov 2019

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 …

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Polymer Binder, Impact On The Pull-Out Force Of Macro Fibers In Sprayed Concrete, Klaus Bonin, Christina Neumaier Nov 2019

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 …

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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 Nov 2019

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 …

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Post-Cracking Behavior Of Cementitious Composite Incorporating Nano-Silica And Basalt Fiber Pellets, Ahmed Bedwiy, Mohamed T. Bassuoni, Ehab El-Salakawy Nov 2019

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 …

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Long Term Permeability And Acid Resistance Of Selfcompacting Concretes With Micro And Nano Mineral Additions, Gonzalo Barluenga, Cynthia Guardia, Javier Puentes, Nelson Flores Nov 2019

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 …

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Transport Properties And Strength Development Of Blended Cement Mortars Containing Nano-Silica, Ali Akbar Ramezanianpour, Sajjad Mirvalad, Mehrdad Mortezaei Nov 2019

Transport Properties And Strength Development Of Blended Cement Mortars Containing Nano-Silica, Ali Akbar Ramezanianpour, Sajjad Mirvalad, Mehrdad Mortezaei

International Conference on Durability of Concrete Structures

In the present study, the mechanical properties and durability of blended cement mortars containing nanosilica and natural pozzolans is investigated. Trass and pumice, two different Iranian natural pozzolan, are used in the experiments. For cement blends preparation, nano-silica replacement levels of 2, 3 and 4% by mass of cement was considered; each mixture contained one of the natural pozzolans with a fixed replacement percentage of 15. The Standard mortar samples were made with w/cm ratio of 0.485; the flow of all mortars ranged from 14 to 16 cm. All prepared mortars’ samples were cured in saturated limewater until the test …

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Effect Of Nanosilica On The Sulfate Attack Resistivity Of Cement Mortar, Pengkun Hou, Zh Guo, Q Yu, N Xie, X Cheng, Sp Shah Nov 2019

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 …

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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 Nov 2019

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 …

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Enhancement Of Durability Characteristics Of Geopolymer Concrete With Manufactured Sand, Abdul Aleem, T Shanmuga Priya Nov 2019

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 …

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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 Nov 2019

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 …

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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 Nov 2019

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 …

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Strength And Durability Of Hybrid Fibre Reinforced Binary Blend Geopolymer Concrete, Namasivayam Ganesan, P V Indira, R Sahana Nov 2019

Strength And Durability Of Hybrid Fibre Reinforced Binary Blend Geopolymer Concrete, Namasivayam Ganesan, P V Indira, R Sahana

International Conference on Durability of Concrete Structures

This paper deals with an investigation on the influence of hybrid fibres on the strength and durability of binary blend geopolymer concrete. Geopolymer concrete was prepared using Fly ash and GGBS as source material and mix design was carried out as per the guidelines of Professor Rangan of Curtin University, Australia. Different fly ash-GGBS proportions namely 50-50%, 60-40%, 70-30%, 80-20% and 90-10% were considered. The tests on Geopolymer concrete reveal that the compressive strength increases as the percentage of GGBS increases up to 30%. Hence the combination of 70% fly ash and 30% GGBS was considered as a base material. …

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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 Nov 2019

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. …

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Impact Of Water Content On The Performance Of Alkali-Activated Slag Concretes, Susan A. Bernal, John L. Provis, Jannie S.J. Van Deventer Nov 2019

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 …

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Internal Curing By Sap In Ultra-High Strength Concrete With Cement-Silica Fume-Fly Ash Binder, Jianhui Liu, Caijun Shi, Xianwei Ma Nov 2019

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 …

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Design Of Ternary Blend High-Volume Fly Ash Concrete Mixes Using Hydrated Lime, Chamila Gunasekara, David Law, Sujeeva Setunge Nov 2019

Design Of Ternary Blend High-Volume Fly Ash Concrete Mixes Using Hydrated Lime, Chamila Gunasekara, David Law, Sujeeva Setunge

International Conference on Durability of Concrete Structures

The increase of carbon emission due to annual growth of Portland cement (PC) production has enforced research into the development of sustainable green concrete using a range of readily available industrial waste materials. The present study is focused on developing two high volume fly ash (HVFA) concretes with cement replacement levels 65% (HVFA‒65) and 80% (HVFA‒80). Initially, the required lime for both HVFA concrete mixes were determined, and then the optimized mix design identified, based on 28-day strength, by varying the fly ash‒lime combination. The optimized mixes achieved a compressive strength of 53MPa and 40MPa, for HVFA‒65 and HVFA‒80 concretes, …

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Compressive Strength, Free Expansion And Shrinkage Of Expansive Concrete Containing Fly Ash, Warangkana Saengsoy, Rachot Chatchawan, Somnuk Tangtermsirikul Nov 2019

Compressive Strength, Free Expansion And Shrinkage Of Expansive Concrete Containing Fly Ash, Warangkana Saengsoy, Rachot Chatchawan, Somnuk Tangtermsirikul

International Conference on Durability of Concrete Structures

This study is aimed to investigate effect of fly ash on compressive strength, free expansion and shrinkage of expansive concrete. High CaO and low CaO fly ashes are used in this study. The replacement percentages of total binders by fly ash are 0 and 30% by weight. The replacements of expansive additive are 0, 20 and 30 kg/m3 of concrete. The test results revealed that the use of fly ash especially the high CaO fly ash can enhance expansion of expansive concrete at early age. The use of fly ash also reduces shrinkage at long term of the expansive …

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Carbonation In Alternative Cementitious Materials: Implications On Durability And Mechanical Properties, Prasanth Alapati, Kimberly E. Kurtis Dr. Nov 2019

Carbonation In Alternative Cementitious Materials: Implications On Durability And Mechanical Properties, Prasanth Alapati, Kimberly E. Kurtis Dr.

International Conference on Durability of Concrete Structures

Understanding the rate and implications of carbonation on strength and durability in alternative cementitious materials (ACMs) is critical in designing ‘green’ concretes for intended service lives. In this paper, three commercially available ACMs, including one calcium aluminate cement (CAC), one calcium sulfoaluminate belite cement (CSA), and one alkali-activated binder using class C fly ash (AA), were evaluated against one portland cement (OPC). Thermogravimetric analysis (TGA) and x-ray diffraction (XRD) techniques were used to understand the effect of carbonation on ACM paste composition. Water sorption tests on both carbonated and uncarbonated cement mortar showed a significant reduction in porosity of this …

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Effects Of Temperature And Curing Duration On The Stability Of Slag Cements In Combined Chloride-Sulphate Environments, Joseph Onah Ukpata, P. A. M. Basheer, Leon Black Nov 2019

Effects Of Temperature And Curing Duration On The Stability Of Slag Cements In Combined Chloride-Sulphate Environments, Joseph Onah Ukpata, P. A. M. Basheer, Leon Black

International Conference on Durability of Concrete Structures

This experimental study investigates the effects of temperature and curing duration on the stability of slag blended cement systems exposed at 20 °C and 38 °C to combined sodium chloride (30 g/L) – sodium sulphate (3 g/L) solutions. Two slags, designated as slag 1 and 2, having CaO/SiO2 ratios of 1.05 and 0.94, were respectively blended with Portland cement CEM I 52.5R at 30 wt.% replacement level. Mortar prisms and cubes with w/b ratio of 0.5 and binder/aggregate ratio of 1:3 were then prepared for length and mass changes. The samples were cured in lime water for either 7 …

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Impact Of Chemical Compositions On Mechanical Properties Of Modified Asphalt Binders, Mohammad Nazmul Hassan Nov 2019

Impact Of Chemical Compositions On Mechanical Properties Of Modified Asphalt Binders, Mohammad Nazmul Hassan

Student Theses and Dissertations

Modified asphalt binders offer better mechanical performance in field conditions. According to many researchers, nanoclay modified asphalt binders can be a cheaper alternative of currently practiced polymer modified binders. The primary purpose of this study was to observe any changes in asphalt chemistries due to nanoclay modification and explore any correlations that may exist between chemical compositions and mechanical properties. Changes in chemical fractions were found to be source variant. Insoluble Asphaltene contents were observed to increase significantly after aging, whereas the Saturate contents decreased. Correlations were observed between mechanistic properties and chemical compositions. Moreover, aggregate-binder compatibility evaluation showed nanoclay …

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Effects Of Reservoir Conditions And Trace Co-Contaminant Gases On Geological Carbon Sequestration, Ram Kumar Nov 2019

Effects Of Reservoir Conditions And Trace Co-Contaminant Gases On Geological Carbon Sequestration, Ram Kumar

USF Tampa Graduate Theses and Dissertations

Geological carbon sequestration in a saline formation is a promising technology for large-scale carbon dioxide (CO2) mitigation. Several factors such as temperature, pressure, salinity, hydraulic conductivity, and mineralogy of a formation affect the CO2 sequestration in saline formations. These factors can vary widely depending upon the type of formation or the degree of heterogeneity within a formation. In addition to these properties of the repositories, the CO2-rich flue gas streams captured from point sources often contains small amounts of impurities such as sulfur oxides (SOx) and nitrogen oxides (NOx), which may have serious implications on the chemistry of the repositories …

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