Showing papers in "Advances in Civil Engineering Materials in 2016"

Utilization of Sustainable Materials for Soil Stabilization: State-of-the-Art

Abstract: Most of the challenging soil deposits necessitate their stabilization either by adopting mechanical modification, which includes soil replacement, compaction, surcharge loading and piling or chemical alteration by using lime, cement, and chemical additives. These methods of stabilization are oriented towards improving certain defined properties such as plasticity, swell potential, strength, and density of the soil mass. Besides, one of the most crucial challenges that is faced is “stabilization induced cracking of the fine-grained soils,” which turns out to be the basic reason for the failure of the soil mass and subsequent failure of the structures. However, concerns such as non-availability of the ideal soil for replacement of the native soil and even inaccessibility of the site and laborious soil-stabilizer mixing methods necessitate exploring suitable alternatives for stabilization of such soil deposits that adds up to the vows of the practicing engineers. A few other pressing issues which need to be addressed are the adverse effects caused by these additives on the environment (viz., release of greenhouse gases and/or subsequent leaching of chemicals into the ground water). In such a scenario, application of industrial by products (viz., fly ash, cement kiln dust, blast furnace slag, rice husk ash, silica fumes, red mud, and textile waste), which could be defined as “sustainable materials,” find a special place in the modern-day soil stabilization and modification exercise. Keeping this in view, a critical synthesis of the literature has been presented in this paper, which showcases superiority of the sustainable materials over the conventionally used soil stabilizers and the need for conducting further research to make these materials an easy and choicest replacement over the former.

Review of the performance of high-strength rubberized concrete and its potential structural applications

Abstract: Partially replacing concrete aggregates with recycled materials could help to combat the decreasing availability of some natural resources (like natural sand) and at the same time help to utilize growing quantities of waste material like used tires. This idea has been put into practice to develop a more sustainable concrete material called rubberized concrete or crumbed rubber concrete (CRC). CRC has improved structural ductility and impact resistance but can have lower strength than traditional concrete. Most research to date has focused on low strength CRC and its non-structural applications. However, recent research has shown that high-strength CRC (HSCRC) can be achieved through rubber pre-treatment, using various additives, optimal rubber content, or good grading of combined rubber sizes. This paper reviews the research undertaken to date in HSCRC (defined as compressive strength over 30 MPa), focusing primarily on the material properties but also considering the potential structural applications of HSCRC. Finally, the future research necessary to prove the viability of HSCRC for structural reinforced concrete applications is discussed.

Electrical Properties of Cementitious Systems: Formation Factor Determination and the Influence of Conditioning Procedures

Abstract: The number of people wanting to use electrical tests to determine the transport properties of concrete has increased with advancements in the portability of hand-held testing devices. Electrical measurements are an attractive test method to quantify transport properties of cement-based materials since they can be performed rapidly. There is a high potential for using these tests in quality control or mixture qualification. However, electrical measurements can be significantly influenced by curing and storage conditions, which can impact the degree of saturation, degree of hydration, sample temperature, and pore solution chemistry. This study proposed a general equation that described the electrical resistivity measurements in cementitious systems and possible methods to account for some of these conditioning-induced changes. It is proposed that these tests are useful in the determination of the formation factor, a numerical quantification that describes the microstructure. A comparison of the formation factor obtained from rapid electrical measurements using the Nernst-Einstein relationship was compared to a migration test with the goal of proposing a curing methodology for rapid electrical tests that allows for the determination of a true transport property.

Toward a Specification for Transport Properties of Concrete Based on the Formation Factor of a Sealed Specimen

Abstract: This paper proposes that the formation factor can be used in performance-based specifications as a fundamental measure of the transport properties of concrete. The formation factor can be measured using a concrete cylinder that is sealed until the age of testing and in either the sealed or fully saturated condition at the time of testing. The proposed method is rapid, easy to perform, fundamentally related to service life models, and is applicable to a wide range of binder compositions. The formation factor is defined herein as the ratio of the electrical resistivity of the bulk sample and the resistivity of the pore solution. The role of temperature, pore solution dilution, and moisture conditioning on the measured results is discussed. The paper then provides a relationship between the formation factor and service life for bridge decks and illustrates how this approach could be used for both a specification and for quality control/quality acceptance. It is recommended that the testing method be standardized, though the performance limits of the formation factor may be dependent on the type and geometry of the structure, the location of the structure, the exposure conditions, and the risk associated with damage to the structure.

Using Low-Temperature Differential Scanning Calorimetry to Quantify Calcium Oxychloride Formation for Cementitious Materials in the Presence of Calcium Chloride

Abstract: Whereas many concrete pavements have exhibited service lives of 30 to 50 years, a portion of these pavements in regions that are exposed to snow, ice, and salt have shown premature distress at the joints. This distress has been observed to occur between 5 and 20 years and requires extensive repair of an otherwise well-functioning pavement. Although there are several potential mechanisms that can lead to this deterioration, a reaction can occur between calcium chloride coming from deicing salt (CaCl2) and the tricalcium aluminate (C3A) and/or calcium hydroxide (CH) in the cementitious matrix. This paper describes the development of a test method that can be used to evaluate the potential for a cementitious binder to react with the calcium chloride deicing salts to form calcium oxychloride (the reaction between CaCl2 and CH). The test method enables the quantity of calcium oxychloride to be determined for each binder system. The results indicate that the amount of calcium oxychloride can be reduced with the replacement of cement with supplementary cementitious materials (fly ash, slag, silica fume, etc.). It is anticipated that the proposed test method could be used to better understand the role of binder chemistry on the calcium oxide formation and to optimize the binder composition to reduce the calcium chloride formation to an acceptable level and ultimately reduce the risk for deterioration.

Potential of Uncultivated, Harmful and Abundant Weed as a Natural Geo-Reinforcement Material

Abstract: Extensive research has been conducted to investigate the utility of agricultural products such as coir, jute, bamboo, and sisal as limited life geotextiles (LLG). These agricultural products have extensive use in automotive industry, paper industry, fishing nets, and shipping rigs. As an alternative, this study demonstrates the usefulness of an abundant, harmful (for environment, eco-tourism, and bio-diversity) weed species Eichhornia crassipes (Water hyacinth (WH)) for manufacturing LLG. Biochemical composition (cellulose, hemicellulose, lignin, and ash content) of WH fiber as well as tensile strength of WH filaments and woven geotextiles were determined. It was found that the tensile strength of woven geotextiles made from WH is higher or comparable to those fibers from the agricultural products. The efficacy of WH geotextile for short term strength improvement was demonstrated by comparing the CBR value of geotextile reinforced soil with that of unreinforced soil. CBR values of soil reinforced with WH geotextile were found to be higher (8.48 ± 0.2 %) as compared to unreinforced soil (6.13 ± 0.07 %). The result obtained from this study is encouraging for promoting the utility of WH LLG in road infrastructure projects.

Shear Behavior of Synthetic Fiber Reinforced Concrete

Abstract: This paper presented a comprehensive experimental study on the shear capacity of zero-slump, dry-cast synthetic fiber-reinforced concrete (SYN-FRC) by using Japan Society of Civil Engineers (JSCE) G-553 test method. In adjacent with shear test, flexural and compression behavior of concrete determined based on ASTM C1609/C1609M-12 and ASTM C39/C39M-16b, respectively. In order to investigate the effect of different concrete compressive strengths on material properties of synthetic fiber-reinforced concrete, two different compressive strengths, 28 MPa (4000 psi) and 34 MPa (5000 psi), were selected. The test results demonstrated that the application of synthetic fibers in concrete yielded to significant improvements in material properties of concrete such as shear strength, shear toughness, flexural strength and flexural toughness. These enhancements were greater at higher synthetic fiber dosage rates.

The Influence of Aggregate Lithological Nature on Pavement Texture Polishing: A Comparative Investigation on a Test Site in Southern Italy

Abstract: Pavement surface performance plays a key role in tyre-road interaction phenomena and greatly affects road safety, vehicle's operational costs, and environmental sustainability. Surface texture and friction change over time with the action of the repeated passage of vehicle tires, especially those of heavy vehicles (long-term variations). Other factors related to asphalt mix composition, primarily the aggregates and their mineralogical composition, the binder and their combination, have a great effect on micro and macrotexture evolution. In particular, the extent to which a surface will polish depends on both the level of traffic and the ability of the aggregate to resist polishing. Moreover, an aggregate may provide different levels of skid resistance depending on where it is used because the polishing effect is also influenced by other stresses such as braking and cornering forces. In light of the above, this paper focused on a 4-year monitoring of a test site (both straight and curve sections) with four different dense graded friction courses designed and produced with aggregates of different petrographic nature: limestone, basalt, and expanded clay. Several devices and test methods (Skid Tester, Sand Patch Test, Laser Profilometer) were used in order to investigate skid resistance and macro-texture progression. Results showed that: (i) mixes have a different microtexture deterioration behavior in relation to aggregate type, especially during the pavement early life, confirming how limestone does not perform as well as basalt or expanded clay under traffic actions; (ii) macrotexture evolution trend is characterized by a consistent decrease after 4 years; the maximum value of macrotexture was registered 13 months after opening to traffic (when the migrated bitumen is completely removed by traffic). Results highlighted practical applications and perspectives for both practitioners and researchers.

Super Air Meter for Assessing Air-Void System of Fresh Concrete

Abstract: A key factor for freeze-thaw durability of concrete is the air void system; nevertheless, the current test methods for fresh concrete only allow for determination of total air content. There is a need for a fresh concrete test method capable of indicating that air void size and distribution are adequate. In an attempt to address this need, a new test method based on the super air meter (SAM) was developed by Ley and Tabb. This paper presented an investigation of the air void system of 64 mixtures, employing standard fresh and hardened concrete test methods, as well as the SAM test method. The study focused on mixtures with three different coarse aggregates, three air entraining admixtures, different total air contents levels, and slumps below 3 in. (75 mm), typical of paving concrete. Freeze-thaw tests were carried out on some of the mixtures with marginal air content. Data from this study at the Federal Highway Administration's Turner Fairbank Highway Research Center Laboratory showed that the SAM test of fresh concrete was able to provide an indication of air void adequacy in low-slump air entrained concrete; a SAM number of 0.20 psi (1.4 kPa) or above identified mixtures with poor spacing factor. However, a limit of 4.0 % fresh air content was also able to identify these mixtures as a good correlation between air content and spacing factor was found.

Performance of Fiber-Reinforced Concrete Made With Basalt-Bundled Fibers

Abstract: Fiber-reinforced concrete (FRC) has become a viable new material used in various flatwork construction projects, such as building pavements, large industrial floors, and runways. In this research, basalt chopped fibers in bundled form were used to make an FRC material called basalt fiber-reinforced concrete (BFRC) to study the possible improvement in the 28-day compressive strength and modulus of rupture, although the latter one is the more important factor in flatwork construction. The basalt fiber specimens were cast using basalt-bundled fibers of three different lengths and three different amounts. The results indicated that 36-mm-long chopped basalt-bundled fibers, and the fiber amount of 8 kg/m3 are the optimum fiber length and fiber quantity for achieving the best performance of both the compressive strength and modulus of rupture. This paper discusses the test matrix and test results obtained from various BFRC and plain concrete specimens.

Characterization of Sediments From the Sewage Disposal Lagoons for Sustainable Development

Abstract: The incessant growth in urbanization, and the population explosion associated with it, has resulted in an increased discharge in sewage disposal lagoons and has led to their overloading. This results in the improper functioning of these lagoons, which greatly affects the treatment of sludge and wastewater. The influents, which carry along with them a huge load of substance, referred to as socioeconomically generated sediments (SeGSs), substantially reduce the capacity of the lagoons and the retention time of the sewage water and sludge. This situation poses a major challenge to municipal engineers and town planners, and to overcome it, either periodic or once-per-lifetime desiltation of these lagoons is warranted. However, in present-day megacities, there are several concerns associated with the desiltation process, viz., selection of the most economical and efficient technique, the availability of dumping ground(s), and transportation of the SeGSs to these dumping grounds. This is where utilization of SeGSs as a manmade resource could be a good initiative towards sustainable development. However, this endeavor entails a holistic understanding of the SeGSs by conducting detailed investigations to characterize them based on their physical, chemical, morphological, and microbial attributes before postulating a strategy for their sustainable utilization. With this in view, extensive sampling of the SeGSs from sewage disposal lagoons located in the western part of India was conducted followed by their very comprehensive characterization. Details of the methodologies adopted for this exercise were presented in this manuscript, and recommendations were made to utilize SeGSs for sustainable development in the most efficient manner.

Assessment of Heavy Metals in Leachate of Concrete Made With E-Waste Plastic

Abstract: This experimental investigation employing leaching characteristics of concrete made with E-waste plastic [high-impact polystyrene (HIPS)] was carried out using the toxicity characteristic leaching procedure (TCLP). The heavy metals, such as Cd, Cu, Zn, and Pb, were analyzed from concrete with varying percentages of HIPS (0 %, 10 %, 20 %, 30 %, 40 %, and 50 %) at various ages, such as 28, 60, and 90 days. The concentrations of Cd in the TCLP extracts of all the samples were found to be lower than the regulatory level of 1 mg/l at 28, 60, and 90 days. The Cu, Zn leachate content decreased with curing, and all samples were found well below the prescribed level of 100 mg/L and 500 mg/L, respectively. The concentrations of Pb in the TCLP extracts of all the samples were found to be lower than the regulatory level of 5 mg/L at 28, 60, and 90 days. The results are also compared with Resource Conservation and Recovery Act (RCRA) prescribed limits for Cd, Cu, Zn, and Pb, which are 0.5 mg/L, 130 mg/L, 500 mg/L, and 1.5 mg/L, respectively, and which are within limits.

Improvement of Bending Fatigue Test for Asphalt Surfacing on Orthotropic Steel Bridge Deck

Abstract: In order to evaluate the fatigue performance for orthotropic steel bridge decks (OSBD) surfacing more scientifically and reasonably, one improved fatigue bending test for OSBD surfacing was developed based on the French “Laboratoire des Ponts et Chaussees” (LCPC) test. Besides, a better specimen preparation method was proposed based on the rolling compaction method. The loading force during testing was determined by building a three-dimensional finite element model of the entire bridge. In addition, a submodel technique was applied to enhance calculation accuracy. In order to verify the validation of this improved test, two types of deck surfacing mixtures: epoxy asphalt concrete (EAC) and high-strength asphalt concrete (HSAC) were tested, and the fatigue process of these two mixtures was recorded. During the fatigue test procedures, EAC surfacing can endure over 8 × 106 loading cycles and the fatigue life of HSAC surfacing was between 2 and 3 × 106 loading cycles. The EAC cracking process demonstrated brittle failure, while HSAC demonstrated ductile failure. These results reflected that the surfacing specimen fatigue performances during the laboratory test coincide with the practical OSBDs surfacing performance on an actual bridge. The improved bending fatigue test proved to be an effective way to reflect the OSBD surfacing mechanical response.

Criteria for Freeze-Thaw Resistant Concrete Mixtures

Abstract: Concrete, especially for improved durability, is typically specified with prescriptive provisions. More recently there has been increasing interest in evolving towards performance-based specifications, both within state highway agencies and industry (FHWA, 2014, “Guide to Developing Performance-Related Specifications, FHWA-RD-98-155, FHWA-RD-98-156, FHWA-RD-98-171, Vol. III, Appendix C,” http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/pccp/pavespec/ , last accessed July 28, 2014; ACI Committee 329, Report on Performance-Based Requirements for Concrete, American Concrete Institute, Farmington Hills, 2010; The P2P Initiative, 2014, “National Ready Mixed Concrete Association, Silver Spring,” http://www.nrmca.org/p2p/ , last accessed July 28, 2014). One of the challenges in successfully implementing performance-based specifications is the existence and use of reliable test methods and specification criteria that can measure the potential durability of concrete mixtures and provide the expected service life. A state pooled fund research project (TPF-5 (179), 2014, “Evaluation of Test Methods for Permeability (Transport) and Development of Performance Guidelines for Durability,” http://www.pooledfund.org/Details/Study/406 , last accessed July 28, 2014) was developed with an objective to propose performance criteria for concrete that will be resistant to penetration of chlorides, cycles of freezing and thawing, and sulfate attack. This paper summarized results pertaining to freeze-thaw resistance. Concrete freeze-thaw (F-T) performance was evaluated by ASTM C666/C666M-15 (AASHTO T161-08 (Standard Method of Test for Resistance of Concrete to Rapid Freezing and Thawing, Standard Specifications for Transportation Materials and Methods of Sampling and Testing, Part 2A: Tests, AASHTO, Washington DC, 2013)) and deicer salt scaling resistance was evaluated by ASTM C672/C672M-12. It was examined whether F-T performance of concrete correlated with results of rapid index tests for fluid transport characteristics of concrete. These tests included the rapid chloride permeability, absorption, and initial and secondary sorptivity. The impact of degree of saturation on the F-T resistance of concrete was also explored. Criteria for F-T resistant concrete mixtures depending on type of exposure were suggested.

Factors Affecting Direct Tension Pull-Off Test Results of Materials Bonded to Concrete

Abstract: The direct tension pull-off test (ASTM D7522/D7522M-15, ASTM D4541-09e1, ASTM C1583/C1583M-13 and others) is the only practical, in situ test to assess bond strength of materials bonded to a concrete substrate relatively. Although the method is prescribed, there are a number of variations anecdotally seen in practice which may affect the uniform interpretation of the test method results. In particular, it was hypothesized that both shear and normal stresses introduced by the drilling process damage the sample affecting results disproportionately with the depth of cut. This study systematically investigated this hypothesis with the aim of providing improved guidance associated with depth, and indeed method, of core drilling. Preformed, hand-drilled, and core-drilled specimens were tested, and the results were compared. Additionally, a system for applying a controlled torsional moment to the specimens was used to quantitatively investigate the effect of such force being applied during the specimen preparation. This study also investigated the effect of using square cuts. Hand-drilled and core-drilled specimens were observed to have reduced pull-off capacity—exhibiting a reduction of 0.03 MPa/mm depth and 0.04 MPa/mm depth, respectively—with increased core depth, although this was not attributed to the torsion that may be present during the drilling process. Square specimens exhibited marginally lower capacity than comparable round specimens and a similar increased reduction in capacity of 0.05 MPa/mm depth of cut. Finally, a discussion of the implications and interpretation of pull-off test results is presented.

Effects of Aggregate Properties on Rheology of Self-Consolidating Concrete

Abstract: Compared with conventionally vibrated concrete (CVC), the rheological properties of self-consolidating concrete (SCC) should be closely controlled in order to satisfy fresh property requirements. Rheology of concrete is normally described by Bingham model. To investigate the effects of various aggregate properties on rheology of SCC, 25 mixtures were studied. It was found that higher aggregate volume, higher fine aggregate to coarse aggregate ratio, smaller aggregate size, and lower aggregate packing density may increase yield stress of SCC mixture. Aggregate size has an insignificant effect on plastic viscosity. Mixtures with slump flow less than 580 mm exhibited anti-thixotropy manner, whereas mixtures with slump flow 630 mm or higher showed thixotropy manner. No clear correlation was observed between plastic viscosity and T50 and Tf in the slump-flow test.

Effect of Pozzolanic Admixtures on the Fresh Properties of Cement-Based Foam

Abstract: This experimental study was conducted to investigate the influence of pozzolanic admixtures on the fresh properties of cement-based foams. The cement-based foam mixes were tested at three different cast densities namely, 800, 600, and 400 kg/m3. Along with a reference mix, other series were prepared in which fly ash, silica fume, and metakaolin were added to the binder at up to 10 % and 20 % replacement by cement mass. The Marsh cone test and the flow cone test techniques were employed to measure the flowability and spreadability for 21 cement-based foam mixes. The results show that the addition of pozzolanic admixtures increases the flow time and the longest time recorded with metakaolin. A linear relationship of spread with the density of the mixes was found in this study. It was also found that with the addition of fly ash and silica fume, there was an increase in the demand for foam content. On the other hand, adding metakaolin reduced this demand. Based on the experimental results, an equation to predict the spreadability of the mixes with pozzolanic admixtures has been suggested.

Finite Element Modeling of Chloride Diffusion in Concrete Using Image Processing for Characterizing Real Shape and Distribution of Different Phases

Abstract: The objective of this work was to establish an approach to create a finite element based model using the actual image of the surface of the concrete. An image from the polished surface of a concrete specimen was prepared and used to develop the model. The model considered the actual shape of both fine and coarse aggregates and the interfacial transition zone (ITZ) around aggregates. To validate the model, concrete cylinders were exposed to chloride solution and the chloride penetration in concrete cylinders was measured at different times. Results showed that the model could precisely predict the chloride diffusion time, depth, and pattern through concrete. In addition, results indicated that it is imperative to consider all phases including the ITZ around both coarse and fine aggregate, when modeling concrete. The advantages and benefits of the image processing approach for model preparation, including incorporating all concrete phases with their real shapes, were discussed in this paper.

Investigation of Mott–Schottky Analysis Test Parameters to Study the Semiconductive Properties of Passive Films of Carbon Steel in Highly Alkaline Environments

Abstract: A testing methodology for using Mott–Schottky (M-S) analysis to study the semiconductive properties of passive films that form on carbon steel in simulated concrete pores solutions (pH > 12.5) is presented. The development of the methodology includes determining the proper M-S potential sweep range, rate, and frequency for the passive steel, which were found to be −0.5 to 0.5 V, 18 mV/s, and 1000 Hz, respectively. The methodology was then applied to steel rebar in a saturated calcium hydroxide passivating solution (pH 12.6) to simulate the highly alkaline environments seen in concrete. Potentiostatically formed passive film was different from the film formed under open-circuit conditions. The passive film on steel rebar was found to be n-type with two discrete donor species. A donor density on the order of 1021 cm−3, a flatband potential of −0.53 V, and a maximum space charge layer thickness of 0.4 nm at full passivation were reported.

Investigation of the Effectiveness of Surfactants with Different Partition Coefficients to Entrain Air in Cement Paste

Abstract: This paper outlines a modified version of ASTM C311/C311M-13 that was applied in the investigation of the effectiveness of different surfactants as air entraining agents (AEAs) in portland cement paste First, the architecture of surfactant molecules was investigated with respect to their effectiveness as air entraining agents The work was then generalized to the use of the partition coefficient (log P), a single numerical descriptor of the ratio of hydrophobicity and hydrophilicity of the molecule, to predict the ability to entrain air in concrete This prediction model showed agreement for all of the surfactants investigated Ranges of log P are given for satisfactory performance as well as the values that provide the highest volume of air per dosage of surfactant These findings can help research aimed at admixture development, allow admixture investigation in different cementitious systems, and can provide insights into admixture interactions

Factors Influencing the Long-Term Properties of Fly Ash-Based Geopolymer Mortar

Abstract: The primary goal of the paper was to study the effects of key factors on the long-term mechanical properties of fly ash-based geopolymer. The factors considered consisted of curing time, humidity, temperature, admixture, and water coefficient. In the study, the geopolymer paste and mortar specimens were prepared and cured at four different environmental conditions: (1) ∼24°C and approximately 45 % RH; (2) 95°C and 100 %R.H; (3) 80°C and 25 %RH; and (4) ∼24°C and 90 %R.H. The compressive and flexural strength tests were performed for the mortar specimens at the ages of 7, 28, 120, 360, 540, and 720 days. X-ray diffraction (XRD), X-ray fluorescence (XRF), and nuclear magnetic resonance spectroscopy (23Na, 27Al, 29Si, MAS NMR) tests were performed for the paste specimens at the ages of 7, 28, 120, 360, 540, and 720 days. Selected specimens were also examined under scanning electron microscope (SEM). The results indicated that water evaporation from specimens was a major cause of the strength development of the geopolymer. In addition to SiO4−4 anions in alkali activator, which accelerated the geopolymerization, the Na+, Ca2+, and Mg2+ ions in the system also played an important role in bridging -Si-O-Si-O-Al- chain, thus improving strength development of the geopolymer. The crystallization occurred only in the hydrothermal environment, and it had little influence on the strength development of the low calcium fly ash-based geopolymer mortar as a very small amount of crystalline phase was formed.

Laboratory and Economic Evaluations of Thin Lift Asphalt Overlay for Pavement Preservation

Abstract: The overall objective of this study was to assess the use of locally available materials in Nevada for the development of two durable fine-graded thin lift hot-mix asphalt overlay mixtures for pavement preservation. The investigation considered establishing two mix designs using typical local materials for the northern and southern part of the state. An optimal asphalt binder content was selected for each mixture based on the volumetric properties and following the Nevada Department of Transportation volumetric requirements. For each mixture, the optimal asphalt binder content was varied within the allowable tolerances to simulate the potential variation in asphalt binder content during plant production. The performance of the designed mixtures were evaluated at the various asphalt binder contents in terms of their resistance to moisture damage using indirect tensile strength, resistance to surface raveling and abrasion, dynamic modulus FOOPIPEE*FOOPIPE property, resistance to rutting using the flow number test, resistance to reflective cracking using the IPC overlay jig, workability, and the developed interlayer bond strength using the Louisiana interlayer shear strength tester (LISST). Overall, both designed fine-graded mixtures showed a very good performance and are expected to perform well when used as a thin lift hot-mix asphalt overlay. In particular, good stability, very good resistance to surface raveling and abrasion, and excellent resistance to reflective cracking were observed for both thin lift hot-mix asphalt overlay mixtures at all evaluated asphalt binder contents. A preliminary life cycle cost analysis was also conducted between the thin lift asphalt overlay and a typically used pavement surface treatment for Nevada: the chip seal. Based on the findings from this study, conclusions and recommendations were provided for implementing thin lift hot-mix asphalt overlay as a pavement preservation technique for the state of Nevada.

An Alternate Test Method for the Void Content of Pervious Concrete

Abstract: In recent years, pervious concrete has become an emerging material for healthier ground water recharge and superior control of high stormwater runoff. This is facilitated by the high void content of the material. The void content percentage is an important design variable, as it correlates permeability as well as the strength of the material. Therefore, an accurate quantification of the void content is needed. A recently developed ASTM standard (ASTM C1754/C1754M-12) presents a method for determining the density and void content of hardened pervious concrete; however, there are still some issues apparent with this standard. The main issue is that the standard does not consider the absorption of the aggregate or the paste, which could adversely affect the results. Other concerns include the buoyant force due to trapped air when submerging the specimens, the high drying temperature in drying method B, which causes cracking and renders the specimen unusable for other testing, and the lengthy time requirement. This study further articulated these issues and presented two alternative testing techniques, one novel technique (Torres method) and one modified ASTM C1754 test method that can be used to better determine the void content of pervious concrete. The Torres method developed in this study placed the pervious concrete specimen in saturated surface dry (SSD) condition prior to determining the void percentage, such that the absorbed water mass was removed from the calculation. Additionally, a modified ASTM C1754 was developed that also placed the specimens in an SSD condition while still using the water tank used in ASTM C1754. The results from both of the developed methods showed lower void percentages for the specimens tested than with the current ASTM C1754 (drying method A and B) standard. The results indicated that including the absorbed water mass into the calculation ultimately resulted in higher void percentages.

Using Fractal Geometry to Recover the 3D Air Void, Scale-Independent, Microstructure Information From 2D Sections of Mortars

Abstract: Advances in digital image analysis have allowed for rapid and detailed investigations of the microstructural topography of cementitious materials, and recent theoretical and analytical work have allowed for recovery of 3D information from 2D analyses. However, measurements of parameters such as the entrained air void size distribution and number density obtained from digital images of concrete are sensitive to the resolution of the image. To address this, an analytical model for recovering 3D information from 2D sections was applied to images of air-entrained mortar at different resolutions, and the results were interpreted in terms of fractal geometry. It is shown that there exists a “cutoff” resolution for scale independence, which is crucial for viewing stereological measurements in an absolute sense rather than relative to the resolution of the instrument used to acquire them. For the analysis of entrained air void structure, this cutoff resolution is around 3200 DPI; for such analyses, it is recommended that images be acquired at this resolution. Furthermore, the same analytical model was validated against full 3D X-ray microtomographic images.

Role of Rice Husk Ash and Water Extracted From Manioc in the Formation of Passive Film on Steel Reinforcement in Concrete

Abstract: Corrosive behavior in reinforced concrete specimens containing two agricultural byproducts, rice husk ash, and water extracted from manioc, called mandioca brava in Brazil, was investigated by accelerated corrosion tests in a modified immersion assay. The rice husk ash and mandioca brava were characterized by infrared analysis and X-ray diffraction technics. The carboxylate and silanol functional groups were detected in these agricultural byproducts and these functional groups were proposed here as a main cause of inhibition of the accelerated corrosion that occurred during a modified immersion assay. The mass loss from steel bars in concrete specimens after accelerated corrosion tests confirm the synergistic effect of rice husk ash and mandioca brava when used together in a concrete mixture against the corrosion. Anodic polarization measurements of CA-50 steel bars in simulated pore solutions indicated that the presence of these agricultural byproducts offered anticorrosive protection.

Evaluation of Modifications to the ASTM C672 Deicer Salt Scaling Test for Concrete Containing Slag Cement

Abstract: The standard ASTM C672/C672M-12 deicer salt scaling resistance test has been found to be overly aggressive to concretes containing slag cement or fly ash. It was compared to the recently adopted CSA A23.2-22A test method, based on the Quebec BNQ test, as well as several modifications, including use of an accelerated curing regime developed by Virginia (VADOT). Sixteen concrete mixtures were studied using high-alkali cement, low-alkali cement, grade 100 slag and grade 120 slag with slag contents of 0, 20, 35, and 50 %. Vinsol resin air-entraining admixture (AEA) was compared to a synthetic AEA. Modifications to the test method used in this study resulted in improved deicer scaling performance of concretes containing slag and many of these modifications have been incorporated into the CSA A23.2-22A test method. While it was found that increasing the level of slag replacement resulted in increased scaling, it was found that for slag mixtures, the synthetic AEA provided an improved air void spacing factor, higher hardened air content, and improved scaling resistance compared to Vinsol resin AEA.

Effect of Surface Preparation on the Deicing Salt-Scaling Resistance of Concrete With and Without SCM: Laboratory and Field Performance in the Presence of Sodium Chloride Deicing Salt

Abstract: Deicing salt scaling is a form of surface deterioration of concrete, which describes the progressive raveling of mortar, sometimes even coarse aggregate, from the surface. This paper presents findings from both laboratory and field studies on the deicing salt-scaling resistance of concrete incorporating various proportions of fly ash (25 % and 50 %) and slag (30 % and 60 %). In the laboratory study, concrete slabs finished with different methods as well as concrete with non-finished surfaces were tested for deicing salt-scaling resistance. For the field study, larger concrete slabs were cast and cured in the laboratory and then placed outdoors. Deicing salt solution was applied on the slabs following each snowfall during the winter seasons to maintain an ice-free condition on the surface of the slabs. The results from the laboratory study indicate that the reduced salt-scaling resistance of concrete incorporating supplementary cementing materials is not solely depended on the mechanical strength of the concrete itself. It is also shown that concrete containing high levels of fly ash and slag maybe more sensitive to finishing techniques.

A One Year Investigation of Self-Compacting Concrete With Recycled Asphalt Pavement

Abstract: This paper investigated the behavior of self-compacting concrete mixtures produced from high volume of supplementary cementitious materials incorporated with moderate and high percentages of recycled asphalt pavement as a partial replacement of coarse aggregate (CA). The mechanical properties and unrestrained shrinkage of 12 self-compacting concrete mixes through one-year timeframe are investigated. All mixes were proportioned to accomplish self-compacting concrete characteristics with constant water to cementitious materials ratio of 0.37. Three groups of mixtures were investigated while all groups consist of a control mixture without any cement replacement and three other mixtures made with various percentages of supplementary cementitious materials (SCMs), such as fly ash and ground granulated blast furnace slag. Mixtures in group I were made with 100 % natural coarse aggregate, whereas those in groups II and III, the coarse aggregates were partially replaced by 25 and 50 % recycled asphalt pavement, respectively. The fresh properties, the compressive and tensile strengths, and the unrestrained (free) shrinkage of all mixtures were investigated up to 365 days. The compressive strength was measured at 3, 14, 28, and 365 days, whereas the free shrinkage was periodically measured up to one year. Results show that self-compacting concrete (SCC) can be developed with up to 70 % of cement replaced by supplementary cementitious materials and up to 25 % of coarse aggregate replaced by recycled asphalt pavement, whereas up to the 25 % replacement, the proposed mixtures showed very comparable results to the conventional SCC mixtures. A linear regression analysis was also conducted to correlate the studied compressive strength to the mixture's ingredients and showed strong agreement with the experimental results.

A Critical Review of Methods for Measuring Mechanical Resistance to Aggregate Popouts

Abstract: Five variants of a test intended to characterize the mechanical resistance offered by either mortar or concrete to coarse-aggregate popouts were compared. Popout resistance increased with depth-of-cover to the source of internal pressure and was inversely proportional to the size of the expansion site. Composition of the paste, content of supplementary cementing materials, curing, and type of surface finish significantly influence popout resistance; for a given size and depth, popout resistance can vary by more than a factor of two due to these factors. In one comparison with two-year performance in the field, measurements of popout resistance at a depth of 7 mm correlated well with the incidence of aggregate popout failures, and correlated well with scaling in one laboratory study. Measurements of popout resistance at a depth of 11 mm did not correlate with scaling behavior.