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Application Of Ultrasonic Measurements For The Evaluation Of Steel Fiber Reinforced Concrete, Belayhun Gebretsadik, Kazem Jdidirendi, Visar Farhangi, Moses Karakouzian

Civil and Environmental Engineering and Construction Faculty Research

This study investigates the feasibility of the application of ultrasonic measurement to characterize Steel-Fiber-Reinforced Concrete (SFRC). Specifically, the effects of steel fiber content, age, moisture content, and fiber orientation on Ultrasonic-Pulse-Velocity (UPV) were investigated. In this regard, beam and cylindrical samples were fabricated with different steel fiber contents. The result indicated that for beam specimens the UPV increases with the addition of fiber up to 2% and decreases for higher fiber percentages. Additionally, the fiber orientation within the beam specimens influences the UPV measurements. For cylindrical samples, the rate of UPV decreased with the addition of steel fiber reinforcement. In …

Galena Creek Bridge Structural Health Monitoring Instrumentation And Modeling, Leopold Falkensammer

UNLV Theses, Dissertations, Professional Papers, and Capstones

Structural health monitoring (SHM) of an instrumented structure provides numerous benefits when assessing the long-term condition of the structure against degradation, or the short-term condition after an extreme event, such as an earthquake. The Nevada Department of Transportation (NDOT) has an interest in expanding the use of SHM for such assessments. Accordingly, the objective of the current study is to develop and implement a permanent SHM system for the Galena Creek Bridge, the largest concrete cathedral arch bridge in the world, to monitor its response to routine traffic and seismic activity. Completed in 2012, the bridge connects Reno and Carson …

Coir Fiber Reinforced Concrete, Jose De La Serna, Moses Karakouzian

AANAPISI Poster Presentations

This poster exhibits the testing and research done on general Portland Cement Concrete with the addition of coir (coconut) fibers as reinforcement. Using the fundamental constituents of cement (water, cement, fine and coarse aggregate) and processed coir fiber, concrete specimens were batched to test for compressive and flexural strengths (per appropriate ASTM standards). Cylindrical and rectangular beam specimens were subjected to loadings until failure occurred. The capacity and modes of failures of the specimens were observed. It was determined that:

• The addition of processed coir fibers decreases the overall strength of general Portland Cement Concrete. • The tested concrete’s …

Alkali-~Activated Fly Ash Binders: Feasibility As A Sustainable Alternative To Ordinary Portland Cement For Pre-~Cast Systems, Kimberly Sierra

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fresh, load-dependent, transport, and durability properties of alkali-activated fly ash mortars were studied. The influences of activator concentration, solution-to-binder ratio, curing condition, activator type, and sodium silicate-to-total solution ratio on the properties of the studied alkali-activated mortars were examined. This study was divided in two phases. The first phase dealt with the use of sodium hydroxide as the sole activator. The second phase of the study was divided into two parts, both of which used a combination of sodium hydroxide and sodium silicate as the activator solution. Part I of phase II used elevated temperature curing conditions, whereas part II …

Transport Properties Of Nano-Silica Contained Self-Consolidating Concrete, Borhan Moradi

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this research study, transport properties of various self-consolidating concretes (SCCs) containing nano-particles (SiO2) were investigated. Nano-silica replaced a portion of the cementitious materials at different replacement levels ranging from 1.5 to 7.5% by weight. For the purpose of this investigation, flow, bulk, and transport properties of SCCs were studied. The investigated transport properties were absorption, water penetration, rapid chloride permeability, capillary absorption, rapid migration, and chloride diffusion. Transport properties of nano-silica SCCs were also compared to those of equivalent silica fume (micro silica) contained concretes, as well as those of control mixture (concrete without nano or micro silica).

Test …

Mechanical And Transport Properties Of Alkali-Activated Natural Pozzolans As Sustainable Binders, Brittany Radke

Calvert Undergraduate Research Awards

OPC production accounts for 5 to 7% of the global carbon dioxide (CO₂) emissions, contributing to global warming. The desire to reduce CO₂ emissions and produce more durable concrete has given impetus to search for new binders. It is suggested that alkali-activated natural pozzolans have the potential for use as a sustainable replacement for OPC in concrete.

The current study presented herein evaluated fresh, mechanical, and transport properties of alkali-activated natural pozzolan mortars containing various concentrations of sodium hydroxide solutions as an alkaline activator. To this aim, alkali-activated natural pozzolan mortars were made with concentrations of sodium …

Structural Performance Of Reinforced Concrete Flat Plat Buildings Subjected To Fire, Sara Jean George

UNLV Theses, Dissertations, Professional Papers, and Capstones

Reinforced concrete structures are typically considered to have inherent resistance to fire. However, several concrete structures around the world have experienced partial or total collapse under fire. Reinforced concrete flat-plate is a type of structural system widely used for office and residential buildings. Flat plate construction is prone to punching shear failure at slab-column connections which may lead to a catastrophic progressive collapse. The slabs of flat-plates generally have very thin concrete cover leaving steel reinforcement more sensitive to thermal loads. Little is known in the engineering community about the structural performance of flat-plate structures subjected to fire. Through a …

Investigating The Use Of Pozzolans In Portland Cement Concrete And Inorganic Polymer Mortar, Omar Abdelmalek Saleh

UNLV Theses, Dissertations, Professional Papers, and Capstones

The use of pozzolans offers promising signs for a change in the cement industry. Pozzolan in its natural and artificial forms can be used to improve cement properties or to synthesize new cement. This study investigates the use of pozzolans in portland cement concrete and inorganic polymer mortar (geopolymer mortar).

This thesis is divided into two phases. Phase 1 investigates the use of natural pozzolan as a partial replacement of portland cement in concrete. In this phase two types of class N pozzolan are used separately to develop concrete mixtures contain different percentages of class N pozzolan. Fresh concrete properties …

Recycling Waste Latex Paint In Overlays, Rigid Pavements, And Pervious Concrete, Oscar Inez Quiroz

UNLV Theses, Dissertations, Professional Papers, and Capstones

With over 16 million gallons of latex paint (WLP) being disposed every year it is the largest by volume, liquid hazardous waste in the United States. WLP is difficult to recycle and hazardous to the environment due to the volatile organic compounds it contains. Several methods exist for disposing WLP including paint swaps, combustion, drying and discarding in a landfill, and by placing pigments in cement. Many communities are moving to dispose WLP by drying and placing in a landfill due to the reduced cost. However, this is the least preferred technique for the environment because it creates a need …

Air Void Characteristics Of Air-Entrained Self-Consolidating Concrete, Mary Ellen Barfield

UNLV Retrospective Theses & Dissertations

The purpose of this study was to determine the influence of admixture source, slump flow, hauling time and remediation on the air void characteristics of air-entrained self-consolidating concrete (SCC). The first phase of the investigation focused on the effects of four different admixture manufacturers and three distinct slump flows on the fresh flow properties and air void characteristics of SCC. The second phase evaluated the effects of eight hauling times and two forms of remediation on the air void characteristics of three SCC mixtures. The type of high range water reducing admixture and the type of air-entraining agent used significantly …

Parametric Study Of Self -Consolidating Concrete, Hamidou Diawara

UNLV Retrospective Theses & Dissertations

The research investigation presented herein was intended to study the influence of parameters, such as aggregate size, admixture source, hauling time, and temperature on the fresh and hardened properties of three distinct groups of self-consolidating concretes (SCC). Within each group, the selected SCCs were made with a constant water-to-cementitious materials ratio, a uniform cementitious materials (cement and fly ash) content, and a constant coarse-to-fine aggregate ratio that provided the optimum aggregate gradation. Three coarse aggregate sizes (ASTM C 33 #8, #7, and #67) obtained from two different quarries were investigated. Four sources of polycarboxylate-based high range water-reducing admixtures (HRWRA) and …

Nonlinear Model For Reinforced Concrete Under Cyclic Loading, Aly Said, M. Elmorsi, M. Nehdi

Civil and Environmental Engineering and Construction Faculty Research

Most of the available shear models for reinforced concrete rely on empirical formulations. In this study, a rational shear stress function is used to define the shear stress–strain envelope for reinforced concrete. Cyclic rules are proposed to define the loading, unloading and reloading relationships for reinforced concrete under shear stress reversals. A normal stress function describing the cyclic relationship of concrete under axial stress is also introduced. The proposed functions are verified using experimental data of reinforced concrete panels tested under monotonic and cyclic loading. Subsequently, the normal and shear stress functions along with their cyclic rules are integrated in …

Feasibility For The Use Of Non-Contact Ultrasound For Application With Asphalt Concrete Materials, Michael Robert Dunning

UNLV Retrospective Theses & Dissertations

The quality control of the production of asphalt concrete and the subsequent placement for roadway pavement requires the extensive use of laboratory and field-testing. These tests determine mix properties such as gradation, binder content, air void content, and percent compaction. The amount of time it takes to perform these tests generates time delays in the information transfer from the laboratory to the construction and plant inspectors. The lack of timeliness of a test result may result in placement of an inferior product being placed. Thus, there would be a great benefit for the application of a rapid test method during …

Using The Concrete-Representational-Abstract Teaching Sequence To Increase Algebra Problem-Solving Skills, Kyle B Konold

UNLV Retrospective Theses & Dissertations

Researchers have demonstrated the effectiveness of using direct instruction, learning strategy instruction and the concrete-representational-abstract teaching sequence for teaching a variety of basic math skills, but little research has been conducted related to their effectiveness for teaching more complex skills such as algebra. This study investigated the effects of teaching secondary school students with and without mild disabilities a strategy for solving algebra equations and word problems using the concrete-representational-abstract (CRA) teaching sequence. There were 169 secondary students who participated in this study. Of the 169 participants, 79 were male and 90 were female, they ranged in age from 11 …

Characterization Of Steel Fiber And/Or Polymer Concrete Mixes And Applications To Slender Rectangular And I -Beams, Ashraf Ibrahim Ahmed

UNLV Retrospective Theses & Dissertations

This dissertation presents results from experimental studies related to polymer modified concrete, steel fiber reinforced concrete, and steel fiber/polymer modified concrete. As a first stage of this research, the properties of different concrete mixes were characterized. These mixes were: plain concrete, steel fiber concrete with fiber volume fraction of 1%, polymer modified concrete with 1% to 7.5% solids of polymer, and steel fiber/polymer modified concrete with 1% to 7.5% polymer solids and I% steel fiber fraction. Concrete cylinders and 4 x 4 inches beams were tested under compressive, tensile, flexural, and bar pull-out loadings; In the second phase of this …

Evaluation Of Ultrasound Method For Determining Aggregate Gradations In Asphaltic Concrete Mixes, Michael Robert Dunning

UNLV Retrospective Theses & Dissertations

The purpose of this study is to evaluate a geotechnical method, ultrasound, to detect aggregate gradation differences in asphaltic concrete pavements. Empirical data had previously been used to suggest that the more coarse the gradation, the less incidence's of rutting. It is my thesis that the more coarse the gradation, the higher the velocity of a sound wave through the asphalt concrete. This being the case, the velocity measure can be used in a design or field quality control procedure as a correlation to a performance test to choose a coarse gradation that has non-rutting field performance properties. Tests were …

Evaluation Of Rutting Resistance Of Coarse Graded Aggregate Asphaltic Concrete Mixes In Clark County, Nevada, Jerold Dewayne Stegeman

UNLV Retrospective Theses & Dissertations

The purpose of this study is to evaluate the effectiveness of utilizing coarse aggregates in asphaltic concrete pavements for reducing rutting in Clark County, Nevada. Previous specifications used for asphaltic concrete mix designs in the Clark County area allowed for a wide range of aggregate gradations. The aggregate gradations in the asphaltic concrete mixes produced from these specifications tended to be on the finer side of the range. The pavements constructed based on the specifications were observed to be tender and susceptible to rutting. Paving projects were initiated which demonstrated that coarser aggregates in the asphalt mixes appeared to reduce …