Civil Engineering Commons^™

Interaction Of Cementitious Systems With Chemical Admixtures, Natallia Shanahan

USF Tampa Graduate Theses and Dissertations

The use of supplementary cementitious materials (SCMs) in commercial construction have been increasing over the last several decades as climate change and sustainability has been gaining global attention. Incorporation of SCMs into concrete mixtures provides several environmental benefits. Since most SCMs are waste by-products of other industries, their use in concrete reduces waste disposal. Additionally, cements substitution with SCMs reduces the carbon footprint of the construction industry. Cement production generates large amounts of CO₂ emissions; the use of SCMs reduces the amount of cement in a concrete mixture thereby reducing emissions from its production.

In addition to SCMs, modern …

Sustainability At U.S. Urban Water Utilities: A Framework To Assess Key Attributes, Matthew Paul Ries

USF Tampa Graduate Theses and Dissertations

Urban water utilities in the United States face challenges due to a combination of external drivers. These include urbanization and population growth, which are stressing a system of aging infrastructure. Compliance with increasing regulations is also a challenge in a fiscally-constrained economic environment. A changing climate threatens infrastructure and past assumptions for water supply and quality. Urban utilities provide clean water and sanitation services to over 80% of the country’s population and its industrial centers. Therefore, the sustainability of these water utilities are crucial to the country’s and the public’s well-being.

New operating models are emerging for a “utility of …

An Investigation Of Motor Vehicle Driver Inattention And Its Effects At Highway–Rail Grade Crossings, Shanshan Zhao

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

The relationship between accident injury severity and drivers’ inattentive behavior requires an in-depth investigation – this is especially needed in the case of motor vehicle drivers at highway-rail grade crossings (HRGCs). The relationship between drivers’ personality/ socioeconomic characteristics and inattentive behavior at HRGCs is another topic requiring research. Past educational programs about safe driving at HRGCs have often not been designed to target people who may be in urgent need of such information, which may limit the effectiveness of those programs.

This dissertation thus focuses on the following four objectives: to investigate the association between motor vehicle inattentive driving and …

Forest Soil Carbon And Nitrogen Cycles Under Biomass Harvest: Stability, Transient Response, And Feedback, Anthony J. Parolari, Amilcare Porporato

Civil and Environmental Engineering Faculty Research and Publications

Biomass harvest generates an imbalance in forest carbon (C) and nitrogen (N) cycles and the nonlinear biogeochemical responses may have long-term consequences for soil fertility and sustainable management. We analyze these dynamics and characterize the impact of biomass harvest and N fertilization on soil biogeochemistry and ecosystem yield with an ecosystem model of intermediate complexity that couples plant and soil C and N cycles. Two harvest schemes are modeled: continuous harvest at low intensity and periodic clear-cut harvest. Continuously-harvested systems sustain N harvest at steady-state under net mineralization conditions, which depends on the C:N ratio and respiration rate of decomposers. …

Quantitative Risk Evaluation Of Obstacle Limitation Surfaces For Final Approaches At Airports, Amila Silva, Alexandre G. De Barros

Journal of Aviation Technology and Engineering

Obstacle limitation surfaces (OLS) are the main safeguard against objects that can pose a hazard to aircraft operations at and around airports. The standard dimensions of the most of those surfaces were estimated using the pilot’s experience at the time when they were included in the standard documents. As a result, some of these standards may have been overestimated, while others may not provide an adequate level of safety. With airports moving to the Safety Management System (SMS) approach to design and operations safety, proper evaluation of the level of safety provided by OLS at specific sites becomes important to …

Probability Model Of Corrosion-Induced Cracking Time In Chloride-Contaminated Reinforced Concrete, Chunhua Lu, Jinmu Yang, Ronggui Liu

International Conference on Durability of Concrete Structures

Corrosion-induced concrete cover cracking caused by chloride ion is an important indication of durability limit state for marine reinforced concrete (RC) structures and can ultimately determine the structural service life. In this paper, considering the random nature of factors affecting the corrosion cracking process, a probabilistic model which expands on the deterministic model of cover cracking time is developed by using Monte Carlo simulation technique. The results showed that the time to corrosion cracking can be modelled by the Weibull distribution. Finally, the probabilistic analysis for the cracking time is applied to an in-site RC bridge girder with four different …

Progress Of Carbonation In Chloride Contaminated Concretes, Yaocheng Wang, P. A.M. Basheer, S. Nanukuttan, Y. Bai

International Conference on Durability of Concrete Structures

Concretes used in marine environment are generally under the cyclic effect of CO₂ and chloride ions (Cl^-). To date, the influence of carbonation on ingress of chloride ions in concretes has been widely studied; in comparison, study on the influence of Cl^- on the progress of carbonation is limited. During the study, concretes were exposed to independent and combined mechanisms of carbonation and chloride ingress regimes. Profiles of apparent pH and chloride concentration were used to indicate the progress of carbonation and ingress of Cl^- in concretes. From the apparent pH profile, a carbonation front …

Carbon Fiber As Anode Material For Cathodic Prevention In Cementitious Materials, Emma Qingnan Zhang, Luping Tang, Thomas Zack

International Conference on Durability of Concrete Structures

Cathodic prevention (CPre) technique is a promising method and has been used for the past two decades to prevent steel from corrosion in concrete structures. However, wide application of this technique has been restricted due to high costs of anode materials. In order to lower the cost and further improve this technique, carbon fiber composite anode has been introduced as an alternative anode material with affordable price and other outstanding properties. This paper presents the study of using carbon fiber mesh as anode material for long-term cathodic prevention system and the effect of accelerated current on macro- and microstructure of …

Investigation Of A Novel 3d Non-Destructive Evaluation For Corrosion Process In Reinforced Concrete, Guohao Fang, Biqin Dong, Ningxu Han, Feng Xing

International Conference on Durability of Concrete Structures

X-ray computed microtomography (X-ray μCT) method is proposed to trace the corrosion features of steel bar in cementitious materials. Three-dimensional corrosion morphology (including morphology of steel corrosion, corrosion products and cracks formation) are characterized and reconstructed. Experimental results demonstrate that X-ray μCT can track time-dependent development of corrosion products and the subsequent initiation and propagation of corrosion-induced cracks. In addition, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) are used to morphologically and chemically analyze the corrosion result. The microscopic analysis result is found to be in a very good agreement with the image analysis measured by X-ray μCT. …

An Experimental Study On Effect Of Steel Corrosion On The Bond–Slip Performance Of Reinforced Concrete, Xiaolin Zhang, Xuebing Liang, Hancheng Huang, Haijun Zhou

International Conference on Durability of Concrete Structures

This paper studied the effects of reinforcement corrosion on bond performance between rebar and concrete. Tests were carried out to evaluate the degradation of bond between reinforcing steel and concrete for different corrosion levels of reinforcing steel. A series of 20 specimens of different concrete strength with various reinforcing steel corrosion levels were designed and manufactured. Each specimen was casted as a 200-mm concrete cube, and a steel rebar was centrally embedded with two stirrups around it. The steel rebar were corroded using an electrochemical accelerated corrosion technique. The corrosion crack opening width and length were recorded after the corrosion …

Threshold Chloride Concentration Of Stainless Steels In Simulated Concrete Pore Solution, Hailong Wang, Jiayan Ling, Xiaoyan Sun

International Conference on Durability of Concrete Structures

To evaluate whether stainless steel can replace carbon steel as rebar in reinforced concrete structures exposed to aggressive environment, the threshold chloride concentration of carbon steel, austenitic and duplex stainless steels were experimentally studied in this paper. The solutions with pH ranging from 9.5 to 13.6 were used herein to simulate the pore liquids in both alkaline and carbonated concretes. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were carried out in the solutions with chloride concentration ranging from 0 to 5.0M and at a temperature around 25°C. The activation of pitting corrosion was determined when corrosion current increased and …

Corrosion-Induced Concrete Cracking Model Considering Corrosion-Filled Paste, Jianfeng Dong, Yuxi Zhao, Yingyao Wu, Weiliang Jin

International Conference on Durability of Concrete Structures

A T_CP–T_CL model is established to describe the relationship between the thickness of the corrosion-filled paste (CP) and that of the corrosion layer (CL). This model can describe the phenomenon that the corrosion filling in the concrete pores and accumulating at the steel/concrete interface occur synchronously. Based on the T_CP–T_CL model, a corrosion-induced concrete cracking model, which can quantitatively consider corrosion-filled paste at concrete/steel interface, is proposed. Combined with damage analysis in corrosion-induced cracking process of concrete cover, the model is developed to describe the quantity of steel corrosion required to crack …

The Compressive Strength Of Cement–Slag–Calcium Sulphoaluminate Ternary System, Hu Shi, Jun Wang, Zhuqing Yu, Xiaodong Shen

International Conference on Durability of Concrete Structures

At present, there is an increasing interest on the use of calcium sulphoaluminate (C₄A₃$) in cement. In this paper, pure mineral of sulphoaluminate (C₄A₃$) was prepared in laboratory. Different dosages of steel slag and C₄A₃$ were blended into cement. The aim of this paper is to investigate the compressive strength of this ternary system. The test results show that the addition of C₄A₃$ can improve the strength of cement. Larger C₄A₃$ dosage (7%) may reduce the 28 days strength. The …

Potential For Alkali–Silica Reaction In Radiation Shielding Concrete Containing Special Aggregates, Daria Jóźwiak-Niedźwiedzka, Michał A. Glinicki, Karolina Gibas

International Conference on Durability of Concrete Structures

In the present study, the potential for the alkali–silica reaction (ASR) in radiation shielding concrete containing special aggregates is presented. The tests were performed on two kinds of aggregate: (1) high-density aggregate to absorb the gamma radiation (barite, magnetite, and hematite) and (2) mineral with high bound water content to attenuate the neutron flux (serpentinite). The optical microscopy in transparent light on thin sections, XRD and XRF method, was used to assess the mineral composition of aggregates. ASTM C1260 test method for potential alkali reactivity of aggregates was applied also to investigate the effect of different content and crystal size …

Effect Of Superabsorbent Polymers (Sap) On Fresh State Mortars With Ground Granulated Blast-Furnace Slag (Ggbs), Fernando Do Couto Rosa Almeida, Agnieszka Joanna Klemm

International Conference on Durability of Concrete Structures

Although cementitious materials are the main construction materials and worldwide produced, there is still a major concern about their sustainability and durability, especially in terms of conserving resources, reducing wastes, and decreasing the environmental impacts of repair and replacement. In general, cementitious materials are very susceptible to cracking provoked by autogenous shrinkage due to their associated self-desiccation process. The problem is even more critical in concrete with blended cements, including Portland cement with ground granulated blast-furnace slag (GGBS). The current paper evaluates efficiency of superabsorbent polymers (SAP) as internal curing agents; shrinkage reduction in mortars with different levels of cement …

Designing Repeatable Self-Healing Into Cementitious Materials, Mo Li, Shuai Fan

International Conference on Durability of Concrete Structures

Designing self-healing into cementitious materials can open a new world of opportunities for resilient concrete infrastructure under service loading conditions. The self-healing process should be robust as well as repeatable, allowing for self-repair after multiple damage events. The repeatability poses great challenges when self-healing strategies mainly rely on the formation of low-strength calcium carbonate healing product, complicated by the localized cracking behavior of cementitious materials. This study aims at formulating a new cementitious material system with designed physical and chemical characteristics that favour repeatable self-healing. Advanced experimental methods, coupled with micromechanics theory, are adopted to probe and design repeatable self-healing …

Progress In Durability Study Of Frp Materials, Zeng-Zhu Zhu, Ying-Wu Zhou, Li-Li Sui, Feng Xing, Jia Du

International Conference on Durability of Concrete Structures

During the past decades, FRP strengthened RC structures have attracted worldwide interest in both application and research. Nowadays, as more and more infrastructures are being suffered from severe corrosions due to harsh and extreme environments, the durability of FRP strengthened RC structures has generally emerged as the most important issue in research. Thus, the paper presents the latest progress in durability study of the FRP materials through an in-depth review and analysis on existing extensive investigations. The time-dependent performances of two types of FRP materials of carbon FRP (CFRP) and glass FRP (GFRP) under severe environments of humidity, high temperature, …

Durability-Based Optimal Design Methodology For Rc Members In Corrosive Environment, Saeid A. Alghamdi, Shamsad Ahmad, Adamu Lawan

International Conference on Durability of Concrete Structures

No abstract provided.

Investigation Of The Spatial Variability Of Steel Weight Loss And Corrosion Cracking: A Novel X-Ray Technique, Sopokhem Lim, Haitao Jiang, Mitsuyoshi Akiyama

International Conference on Durability of Concrete Structures

The performance of corrosion-affected RC members depends strongly on localized damages of reinforcement. Therefore, modeling the spatial variability of steel corrosion is very important for the assessment of the remaining service life of corroded structures or time for maintenance. To study the changes of spatial variability of steel weight loss over time, a continuous monitoring is necessary. In this paper, a novel procedure of X-ray technique application in monitoring the spatial growth of a corroded bar in a RC specimen is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. The relationship of …

Influence Of Concrete Moisture Condition On Half-Cell Potential Measurement, Sylvia Kessler, Christoph Gehlen

International Conference on Durability of Concrete Structures

The detection of on-going corrosion is one of the main issues during inspection of reinforced concrete structures. The half-cell potential measurement method is the most common and established non-destructive technique to support this task. But a lot of infrastructures are exposed to rain or seawater, which can cause heterogeneous moisture condition within one component. In turn, this can have influence on the potential mapping results, and as a consequence, the interpretability of the half-cell potential measurement is impaired. This paper focuses on the influence of concrete moisture condition on half-cell potential measurement. Laboratory and practical tests’ results are analyzed qualitatively …