Search

Corrugated metal pipes (CMPs) deployed across North America are in various states of deteriorations with diminishing structural health that can cause road failure and pose serious threat to public safety. This paper presents an extensive experimental study conducted on deteriorated and retrofitted CMPs, and compares the results with available analytic approach — Modified Iowa equation. Simulated deterioration was performed on the new CMPs using mechanical approach and later, those CMP specimens were retrofitted using four different non-invasive methods. The specimens were tested under five different overburden pressures. Responses of the soil-pipe systems for deteriorated and rehabilitated specimens in terms of surrounding soil pressure and deformations at crown, spring-line, and invert were recorded and compared. It was found that the soil envelops and the CMPs experienced considerable change in pressure and deflections, respectively due to deterioration. However, rehabilitation using all the invasive approaches helped to regain soil pressures and deflections close to the original state, indicating their viability. The measured deflections from experimental studies were also compared with the predicted values obtained from the Modified Iowa equation. Such comparison is of immense importance to establish design guidelines for rehabilitated liner-CMP culvert systems.

There are many tools, models, and algorithms to aid in the selection of appropriate trenchless methods for pipeline installation or rehabilitation. However, one key concern is which method or technique provides optimum solution to the rehabilitation of multiple pipe segments rather than just a single pipe segment. Therefore, the searching criterion for an optimum decision support system is divided into two parts. First, the selection of the optimum method capable of solving the problem properly. Second, a simultaneous analysis of other parameters such as cost, time, and quality to improve the overall benefits of the project. It is observed that most of the real-world cases involves multiple segments in a single project. Therefore, an optimization of the solution must be made for those multiple pipe segments. Although use of different methods for each segment is a preferable solution, it may not be feasible in a wider consideration of project cost, quality, and time. Hence, one way to determine the optimal solution for multiple line segments is to minimize the number of methods and their anticipated total costs which include direct costs and social costs. This paper presents a mathematical approach to expedite the optimum solution by evaluating all of the trenchless technology methods capable of installing, replacing, or rehabilitating each pipe segment (a solution set) and minimizing the number of methods and their total costs.

Quasielastic neutron scattering (QENS) has been used to investigate the binding process of water molecules in pastes of calcium geopolymer prepared with low and high calcium fly ash contents, and at two different NaOH molarities, 10 and 14 M. The in situ measurements were carried at ambient and elevated curing temperatures (60 °C). By carefully monitoring the time evolution of the elastic peak intensity, we infer a gelation process, followed by polymerization and a hardening in the high calcium geopolymer paste at 60 °C, in agreement with previously proposed geopolymerization model. This behavior was neither observed at ambient temperature in both low and high calcium geopolymer cement paste, within the precision of the neutron instrument. Our study clearly shows that a minimal amount of heat is necessary to form gelation and polymerization during the activation process. The activation of geopolymer paste with high NaOH molarity involves more chemically bound water molecules than that at lower activator concentration. This work shows that the QENS technique can be effectively used to characterize the alkali-activation kinetics in certain geopolymer pastes, and that temperature and molarity of the activator play a vital role in controlling the gel mechanism.

Pipe rehabilitation and trenchless replacement technologies have seen a steadily increasing use and represent an increasing proportion of the annual expenditure on operations and maintenance of the water and wastewater infrastructure around the world. Despite the large public investment in use of these technologies, there has been little quantitative evaluation of how these technologies are performing. A retrospective study conducted by the U.S. Environmental Protection Agency collected 25 samples between 2009 and 2013 of in-service gravity sewer liners from 11 cities in North America. Testing of the various liners included thickness, annular gap, ovality, specific gravity, porosity, flexural strength, flexural modulus, tensile strength, tensile modulus, surface hardness, glass transition temperature, Raman spectroscopy, environmental stress crack resistance and pipe stiffness as appropriate to the liner type and condition. Cured-in-place pipe (CIPP) liners comprised 18 of the 25 samples. Other liners included were PVC fold-and-form, HDPE deform-reform and sliplining. The samples had seen from 5 years to 34 years in service. A number of areas where the QA/QC of liner installation should improve were noted in the studies but, overall, the liners were in excellent condition and the physical test results indicated that these liners are expected to last their 50-year design life and probably well beyond.

Future manned missions to the moon will require the ability to build structures using the moon’s natural resources. The geopolymer binder described in this paper (Lunamer) is a construction material that consists of up to 98% lunar regolith, drastically reducing the amount of material that must be carried from Earth in the event of lunar construction. This material could be used to fabricate structural panels and interlocking blocks that have radiation shielding and thermal insulation characteristics. These panels and blocks could be used to construct living quarters and storage facilities on the lunar surface, or as shielding panels to be installed on crafts launched from the moon surface to deep-space destinations. Lunamer specimens were manufactured in the laboratory and compressive strength results of up to 16 MPa when cast with conventional methods and 37 MPa when cast using uniaxial pressing were obtained. Simulation results have shown that the mechanical and chemical properties of Lunamer allow for adequate radiation shielding for a crew inside the lunar living quarters without additional requirements.

This paper provides new results gathered as part of a 6-year project funded by the U.S. Environmental Protection Agency (USEPA) to document the in-service performance of trenchless pipe rehabilitation techniques. The results from a pilot study focusing on cured-in-place pipe (CIPP) rehabilitation technologies were previously reported and the research program was extended to allow collection of additional CIPP samples and also to extend the study to other rehabilitation technologies (specifically included in this Phase 2 research were fold-and-form, deform–reform, and sliplining technologies). The establishment of a database to house performance evaluation data for rehabilitation technologies used in the water and wastewater sectors is also described. The additional retrospective data for CIPP and other rehabilitation technologies are reported and an overall assessment of CIPP life cycle performance is provided. The examination of CIPP liners with up to 34 years in service and other rehabilitation technologies with up to 19 years of service has shown that all of the rehabilitation technologies are showing little evidence of deterioration in service. The test results for 18 CIPP samples from nine cities across North America indicate that properly designed and installed CIPP liners should meet and likely exceed the typical 50-year expected design life. For the fold-and-form, deform–reform, and sliplining technologies, there are only two to three samples per rehabilitation technology and hence less can be said about overall performance. Nevertheless, all of the samples tested still met the material property requirements at installations after 14–19 years of service. In summary, the results provide an excellent prognosis for the rehabilitation technologies evaluated.

A key advantage of trenchless construction methods compared with traditional open-cut methods is their ability to install or rehabilitate underground utility systems with limited disruption to the surrounding built and natural environments. The equivalent monetary values of these disruptions are commonly called social costs. Social costs are often ignored by engineers or project managers during project planning and design phases, partially because they cannot be calculated using standard estimating methods. In recent years some approaches for estimating social costs were presented. Nevertheless, the cost data needed for validation of these estimating methods is lacking. Development of such social cost databases can be accomplished by compiling relevant information reported in various case histories. This paper identifies eight most important social cost categories, presents mathematical methods for calculating them, and summarizes the social cost impacts for two pipeline construction projects. The case histories are analyzed in order to identify trends for the various social cost categories. The effectiveness of the methods used to estimate these values is also discussed. These findings are valuable for pipeline infrastructure engineers making renewal technology selection decisions by providing a more accurate process for the assessment of social costs and impacts.

Geopolymer binders are aluminosilicate inorganic polymers with expanding applications as construction materials. For wider industrial use of these binders, limited controls of their rheological properties and short solidification time have to be improved. A surface modification of fly ash microcores allows for better control of the geo-concrete formation. Naturally occurring nanoclays, such as halloysite nanotubes and kaolin nanoplates are cheap and abundantly available materials allowing encapsulating alumosilicate microcores with simple and scalable layer-by-layer (LbL) nanocoating technique. An electrostatic attraction drives coating of anionic nanoclays onto fly ash particles providing a potential to controllably adjust properties of geopolymer composites. LbL technique was used to modify geopolymer through nanoarchitectural formation of composite shells on ash microcores. We describe mechanical and rheological enhancement of geopolymers produced from ash microparticles coated with tubule or platy nanoclays sandwiched with polycations, and its advantages for better concrete materials.

Reinforced geopolymer concretes prepared using three fly ashes of varying Ca content were subjected to accelerated carbonation for a period of 450 days. Changes induced in the concretes were determined after exposure to a 5% CO2 atmosphere, and electrochemical measurements were performed over the time of testing to evaluate the effects of carbonation on the corrosion process of the steel rebars. This study indicates that geopolymer concretes prepared with fly ashes having reduced calcium content are more suitable for the production of durable concrete for structural applications under exposure to carbonating environments, as the properties of these materials seem to mitigate the risk of carbonation-induced reinforcement corrosion in concrete.

Pipe rehabilitation and trenchless pipe replacement technologies have seen a steadily increasing use over the past 30–40 years. Despite the massive public investment in the rehabilitation of the US water and wastewater infrastructure, there has been little formal and quantitative evaluation of whether rehabilitation technologies are performing as expected and whether rehabilitation is indeed cost-effective compared to replacement. This paper describes the results of a pilot project for the retrospective evaluation of cured-in-place pipe (CIPP) liners. The pilot testing used CIPP samples from both large and small diameter sewers in two cities: Denver, CO and Columbus, OH. Testing on the liners included: thickness, annular gap, ovality, density, specific gravity, porosity, flexural strength, flexural modulus, tensile strength, tensile modulus, surface hardness, glass transition temperature, and Raman spectroscopy. In addition, environmental data was gathered as appropriate to each retrieval process including: external soil conditions and pH, and internal waste stream pH. Summaries of the test results and a discussion of their implications for CIPP performance are provided in this paper. All of the samples retrieved from the four locations involved in the pilot study testing were in excellent condition after being in use for 25 years, 23 years, 21 years and 5 years, respectively. Overall, it is concluded that there is no reason to anticipate that the liners evaluated in this pilot study will not last for their intended lifetime of 50 years and perhaps well beyond.

The durability of steel reinforced-concrete specimens made from three alkali-activated fly ash (FA) stockpiles and ordinary portland cement (OPC) in cyclic wet-dry chloride environment was evaluated over a period of 12 months. Testing methods included electrochemical methods, chloride diffusion and contents analysis, chemical and mechanical analyses, and visual examination. Geopolymer concrete (GPC) specimens made from Class F FA exhibited lower diffusion coefficients, chloride contents, and porosity compared with their GPC Class C FA and OPC counterparts. Overall, GPC specimens displayed limited signs of leaching and corrosion product formation, whereas OPC specimens exhibited the formation of multiple corrosion products along with significant leaching.

Geopolymers are an emerging class of cementitious binders formed by aluminum-silica rich activating materials. Experimental results indicate that geopolymer concrete is relatively stable at elevated temperatures, and could be possibly utilized in applications such as nozzles, aspirators and refractory linings. Geopolymer grouts with a Si:Al ratio of about 2:1 exhibited superior performance at elevated temperatures than lower geopolymer grouts, with lower Si:Al ratio. Sodium-alumino-silicate-hydrate and potassium-alumino-silicate-hydrate are primary products of geopolymer gels, and models of those systems were investigated using density functional theory, molecular mechanics and molecular dynamics in order to elucidate their behavior at different temperatures and varying Si:Al ratios.

This study reports the findings of an experimental investigation for alkali silica reaction (ASR) between reactive aggregates and the geopolymer matrix. Specimens were prepared using one Class C and two Class F fly ash stockpiles. Mechanical testing included potential reactivity of the aggregates via length change and compression test measurements, as per ASTM standards. Results suggest that the extent of ASR reaction due to the presence of reactive aggregates in fly ash-based geopolymer concretes is substantially lower than in the case of ordinary portland cement-based concrete, and well below the ASTM specified threshold. Furthermore, geopolymer concrete specimens appeared to undergo a densification process in the presence of alkali solutions, resulting in reduced permeability and increased mechanical strength. Utilizing ASR-vulnerable aggregates in the production of geopolymer concrete products could contribute to the economic appeal and sustainability of geopolymer binders in regions that suffer from insufficient local supply of high quality aggregates.

Geopolymers are novel cementitious binders that are finding new industrial applications every day. One of the most important aspects for the commercialization of these products is their behavior in plastic state. The workability of fresh geopolymer paste can be measured with several common tests used for Portland cement concrete, like flow and slump; however, a more in-depth characterization of their rheology is essential to understand its basic setting mechanisms. In this article, the rheological behavior of geopolymer paste prepared under different mix design formulations is studied. Special consideration is given to the rheological behavior of geopolymer paste under the action of a superplasticizer. The effect of the superplasticizers on the viscosity of fresh geopolymers was evaluated and recommendations about the use of these additives are provided.

Municipal solid waste (MSW) incineration is a common and effective practice to reduce the volume of solid waste in urban areas. However, the byproduct of this process is a fly ash (IFA), which contains large quantities of toxic contaminants. The purpose of this research study was to analyze the chemical, physical and mechanical behaviors resulting from the gradual introduction of IFA to an alkaline activated coal fly ash (CFA) matrix, as a mean of stabilizing the incinerator ash for use in industrial construction applications, where human exposure potential is limited. IFA and CFA were analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD) and Inductive coupled plasma (ICP) to obtain a full chemical analysis of the samples, its crystallographic characteristics and a detailed count of the eight heavy metals contemplated in US Title 40 of the Code of Federal Regulations (40 CFR). The particle size distribution of IFA and CFA was also recorded. EPA's Toxicity Characteristic Leaching Procedure (TCLP) was followed to monitor the leachability of the contaminants before and after the activation. Also images obtained via Scanning Electron Microscopy (SEM), before and after the activation, are presented. Concrete made from IFA, CFA and IFA-CFA mixes was subjected to a full mechanical characterization; tests include compressive strength, flexural strength, elastic modulus, Poisson's ratio and setting time. The leachable heavy metal contents (except for Se) were below the maximum allowable limits and in many cases even below the reporting limit. The leachable Chromium was reduced from 0.153 down to 0.0045 mg/L, Arsenic from 0.256 down to 0.132 mg/L, Selenium from 1.05 down to 0.29 mg/L, Silver from 0.011 down to .001 mg/L, Barium from 2.06 down to 0.314 mg/L and Mercury from 0.007 down to 0.001 mg/L. Although the leachable Cd exhibited an increase from 0.49 up to 0.805 mg/L and Pd from 0.002 up to 0.029 mg/L, these were well below the maximum limits of 1.00 and 5.00 mg/L, respectively.

Decisions related to the rehabilitation of wastewater and water infrastructure are increasingly more complicated as the number and complexity of technologies in the marketplace increases. Established methods, such as cured-in-place pipe (CIPP), are constantly evolving, and new techniques continue to be developed in North America and abroad. The need to assess the suitability of these constantly changing technologies creates the need for a resource capable of evaluation and selection of appropriate methods through a Web-based source that can be kept up to date. To meet that need, the Trenchless Technology Center (TTC), in collaboration with the National Utility Contractors Association (NUCA), Australasian Society of Trenchless Technology (ASTT), and National Association of Sewer Service Companies (NASSCO), through multiple research initiatives, has developed a comprehensive and interactive software for the evaluation of more than 70 technologies that can be employed in the installation, replacement...

Concrete pipes represent the backbone of the wastewater collection systems in many cities across North America. These pipes are in various stages of deterioration, generally due to microbiological induced corrosion and/or mechanical loading. A common method of rehabilitating these structures is the use of cementitious coatings. This paper describes the development and testing of three novel geopolymer mix designs prepared using metakaolin and fly ash (class C and F) precursors. Specimens prepared using Portland cement-silica fume blend were also tested for comparison purposes. The specimens were placed in several concentrations of sulphuric acid for a period of eight weeks. The corrosion resistance and remaining compressive strength of geopolymer mortar made from class F fly ash precursor were found to be substantially higher compared with the enhanced OPC formulation. The other geopolymer mix designs were found to perform equally or better compared with the OPC binary blend.

Horizontal Directional Drilling (HDD) is a commonly used construction method for the installation of underground pipelines, conduits and cables in urban areas and across obstacles such as rivers, railways and highways. A key concern in using the HDD method is the risk of hitting existing buried utilities during the pilot boring operation, which could potentially result in significant economic losses, disruption of services and injuries and/or loss of life. The Differential Impedance Obstacle Detection (DIOD) is a “look-ahead” sensory system, developed for the purpose of detecting metallic and thermoplastic pipes in the path of the boring head. The DIOD sensor was numerically simulated, and the model was validated by comparing its predictions with experimental measurements performed on a physical prototype in a controlled environment. Following validation of the model, a parametric study was undertaken to predict the performance of the DIOD under various scenarios that could be encountered in practice.

Health monitoring of concrete structures is performed by assessing the structure’s state of stress. One such method involves monitoring electrical resistance variations as an indirect measure of stress variations. Carbon fibers were added to fresh geopolymer mix to enhance its electrical conductivity. AC-impedance spectroscopy analyses were performed on sample specimens to obtain their electrical resistance. Geopolymer concrete specimens entrained with carbon fibers were dynamically loaded in bending and uniaxial compression to observe changes in electrical resistance with respect to variations in their stress state. For beam specimens electrical resistance was found to follow a descending trend with increasing bending stresses. A more complex relationship was noted for cylinder specimens that were loaded axially. Overall experimental results suggest that conductive geopolymer could serve as a smart material in health monitoring applications of concrete structures.

Geopolymer concrete is finding a growing number of niche applications in the field of civil engineering due to its high compressive strength and strength gain rate, retainage of structural properties in elevated temperature environments, chemical stability in highly acidic conditions and environmental benefits. Combining the above mentioned characteristics with induced electrical conductivity, could enable geopolymer cement to serve as a smart and sustainable cementitious material suitable for health monitoring of civil structures. Carbon fibers were added to fresh geopolymer and OPC (ordinary Portland cement) mixes to enhance their electrical conductivities. AC-impedance spectroscopy analysis was performed on the specimens with fiber fraction ranging from 0.008 to 0.8 with respect to the weight of cementitious binder, to measure their electrical resistivity values and to determine the maximum beneficial fiber content required to attain electrical percolation. Experimental observations suggest that CFR-geopolymer cement exhibits superior performance to CFR-OPC in terms of conducting electrical current.

A growing percentage of waste and storm water conveyance systems are approaching or exceeded their design life, suffering from accelerated deterioration and subsequently increased rates of failure. Discontinuities in the pipe wall may lead to the formation of voids in the soil embedment surrounding it via the transportation of fine soil particles by infiltrating ground water. This paper describes a method that utilizes ultra wideband (UWB) time domain principles to detect the presence and location of soil voids in early stages of formation, thus preventing a catastrophic collapse of the pipe and/or a structure above it (e.g., road surface). A three dimensional numerical model simulating the propagation of UWB pulses within a buried pipeline was developed. The results from the numerical model were validated using experimental measurements performed utilizing a full scale test bed. It is shown that a UWB based sensory system is capable of detecting even minor voids around non-ferrous buried pipes.

Microbiological induced corrosion (MIC) is a leading deterioration mechanism in concrete wastewater conveyance systems. The work reported herein focuses on breaking the MIC cycle by preventing colonization of the bacteria responsible for converting hydrogen sulfide to sulfuric acid. Electrokinetics was used to drive an antimicrobial agent (cuprous oxide) into the porous wall surface of a pre-cast concrete pipe. An electric potential difference, applied between the steel reinforcement embedded in the concrete and a copper electrode placed in the coating solution, provides the driving force to the copper ions. Atomic absorption tests performed on the coated specimens were used to determine the percentage of cuprous oxide that penetrated the porous surface and migrated into the hardened concrete matrix. A pilot study conducted on three mock pipe specimens demonstrated that the process is effective on partially corroded and non-corroded pipes. Test data also revealed that the amount of copper that migrated into the concrete matrix is time dependent. Based on preliminary test results a treatment procedure was designed and implemented on a 380 mm diameter commercial pre-cast concrete pipe. The data suggest that the method could be deployed to “immune” new and partially deteriorated steel reinforced concrete pipes against MIC.

The suitability of fly ash stock piles for geopolymer manufacturing was studied. The results of chemical analyses, X-ray diffraction (XRD) and particle size distribution (PSD) of five sources of fly ash obtained from coal-fired power generating plants in the US are presented. Geopolymer paste and concrete specimens were prepared from each stock pile. The specimens were subjected to an array of chemical and mechanical tests including XRD, RAMAN spectroscopy, setting time and compressive strength. A correlation study was undertaken comparing the fly ash precursor chemical and crystallographic compositions as well as particle size distribution, with the mechanical and chemical characteristics of the resulting geopolymer. Factors inherent to the fly ash stockpile such as particle size distribution, degree of vitrification and location of the glass diffraction maximum were found to play an important role in the fresh and hardened properties of the resulting geopolymer.

The bactericidal characteristics of nano-copper oxide or functionalized zeolite coated concrete pipes against Acidithiobacillus thiooxidans were studied by measuring the temporal variation of bacterial dry cell weight measurement, cellular Adenosine Triphosphate production, as well as oxygen uptake rate of the aforementioned bacterium. Uncorroded (UC), severely corroded (SC), and moderately corroded (MC) concrete pipes were electrochemically coated with a nano-copper oxide, while another uncorroded concrete pipe was used to apply functionalized zeolite coating (Z2). Specimens were characterized by field emission-scanning electron microscopy, and optical microscopy. Oxygen uptake rate of the bacterium was the highest in UC followed by the MC. Oxygen uptake rate and cellular Adenosine Triphosphate decreased progressively in Z2 and SC throughout the duration of the experiment due to decline in live bacterial cell. The maximum bacterial specific growth rate was 1.1 × 10 −2 day −1 for both UC and MC, with a decay rates varying from 1.4 × 10 −2 to 2.6 × 10 −2 day −1 . The minimum concentration limits for the inhibition of the bacterium in the nano-copper oxide coated concrete pipes ranged from 2.3 mg to 2.6 mg Cu per mg dry cell weight.

One of the first attempts to assess information regarding damage to underground pipelines and related infrastructure from hurricanes and flooding reveals a wide variety of direct and indirect damage mechanisms. Utilities with underground networks potentially in harm’s way would do well to learn from the experiences of their counterparts and take steps to prepare for — and possibly alleviate — future damage.

Heating of soil using microwaves has several applications in geosciences, including soil remediation, neutralization of land mines, and microwave-enhanced thermography. Numerical simulation of microwave-induced soil heating processes requires knowledge of the electrical properties of the soil as a function of temperature, moisture content, and frequency of the electromagnetic wave. This paper describes a semi-empirical model for calculating the dielectric properties of moist soils at various moisture contents, temperatures, and frequencies (within the band of 1–10 GHz). The proposed model is an extension of the generalized refractive mixing dielectric model (GRMDM) for moist soils. Predictions of the proposed model were found to be in good agreement with experimental data reported in the literature. Results of a parametric study suggest that the temperature dependency of the dielectric properties of moist sand is more pronounced for higher volumetric moisture contents.

An evaluation of the resistance of mortar specimens coated with silver bearing zeolite to biologically produced sulphate and their antimicrobial characteristics was carried out in this study using Acidothiobacillus thiooxidans. The evaluation was performed based on leaching Ca2+ and Si4+ from the cementitious matrix, rate of bacterial sulphur oxidation, increase in biomass concentration, and acid production. The cumulative concentration of Ca2+ leaching were 3.5-folds higher (28.5 mg Ca2+/g cement) and 2-folds higher (18 mg Ca2+/g cement) in the uncoated and epoxy coated mortar specimens compared to those of zeolite coated specimens (9 mg Ca2+/g cement and 8 mg Ca2+/g cement for type AC and AK respectively). The cumulative leaching Si4+ was also 2.6-folds higher in the control mortar specimens (0.65–1.8 mg Si4+/g cement). Biomass concentration in the control specimens reached 210 mg TSS/L, and that of the zeolites coated mortar specimens was 103 mg TSS/L. The bacterial sulphur oxidation was found to follow the same pattern of the bacterial concentration, 230–270 mg SO4/g S and 158–182 mg SO4/g S in the control and zeolite coated mortar specimens, respectively. The resistance of the zeolitic coating was further evidenced by the increase in pH of the control mortar specimens which demonstrated the leaching of Ca (OH)2 from the cement matrix. The stability of zeolite coated specimens was confirmed by the absence of corrosion products as was examined by FE-SEM and XRPD.

Hydrogen sulfide is a serious problem for many municipalities across North America and worldwide. Odor, safety, and corrosion are the major problems associated with the presence of hydrogen sulfide in sewerage systems. This paper investigates the effect on sulfide generation of using innovative coatings in concrete sewer pipes. A pilot-scale model, consisting of three concrete pipes (each 75 cm in length and 30 cm in internal diameter), was used to simulate the process of sulfide generation in a sewer system. Two of the pipes were internally coated with either cuprous oxide (C.O) or silver oxide (S.O), while the third one served as a control. Each of the oxides was mixed with a commercial epoxy, used for repairing concrete sewer pipes, prior to spraying on the internal surface of the concrete pipe specimens to form a coating film. Test data showed that the sulfide generation by sulfate-reducing bacteria (SRB) in the C.O and S.O coated pipes was reduced by 92% and 100%, respectively, compared with that of ...

A cast-iron water main rehabilitated with a thermoplastic structural liner can be viewed as a hybrid pipe. Depending on the degree of corrosion of the host pipe, stress levels carried by the liner may vary significantly. Several limit states can be developed for a liner-pipe structural system. One such state is related to the presence of a longitudinal fold in a cured-in-place-pipe (CIPP) liner that coincides with gaps in the host pipe’s wall. This paper reports the results of an experimental testing and numerical modeling study undertaken to evaluate the impact of a longitudinal fold on the ability of a CIPP liner to resist internal pressures when there are significant gaps present in the host pipe’s wall. Two 3-D numerical models were constructed and validated using physical testing and the analytical solutions provided in ASTM F 2207-02. The results of a parametric study performed to estimate the stress concentration in the fold as a function of the fold’s geometry and level of applied internal pressure are also reported. An empirical approach is proposed as a basis for a guideline regarding the maximum allowable oversizing of CIPP liners in pressure pipes.

Microbiologically induced corrosion is a leading cause of the deterioration of wastewater collection, transmission and treatment infrastructure around the world. This paper examines the feasibility of using artificial neural networks (ANNs) to predict the compressive strength of concrete and its degradation under exposure to sulphuric acid of various concentrations. A database incorporating 78 concrete mixtures performed by the authors was developed to train and test the ANN models. Data were arranged in a patterned format in such a manner that each pattern contains input variables (concrete mixture parameters) and the corresponding output vector (weight loss of concrete by H2SO4 attack and compressive strength at different ages). Results show that the ANN model I successfully predicted the weight loss of concrete specimens subjected to sulphuric acid attack, not only for mixtures used in the training process, but also for new mixtures unfamiliar to the ANN model designed within the practical range of the...

The degradation of concrete sewer pipes by sulphuric acid attack is a problem of global scope, resulting in substantial economic losses each year. In this study, five admixtures, which offer a range of potential improvement mechanisms, were used at various dosages to enhance the resistance of concrete made with Type 50E cement to chemical sulphuric acid attack. The resistance to sulphuric acid of concrete specimens incorporating these admixtures was measured and compared to that of control specimens. An attempt was made to determine whether there is a relationship between the effect of the various admixtures on mechanical strength and porosity and the resistance of concrete to H2SO4 attack. Results indicate that metakaolin reduced the mass loss of concrete specimens due to immersion for eight weeks in H2SO4 solutions having concentrations of 7% and 3% (by volume) by 38 and 25%, respectively, compared with that of the control specimens. Other admixtures (OCI, Caltite and Xypex) reduced the mass loss of concrete specimens in the range 12–20% for the 7% H2SO4 solution and in the range 9–16% for the 3% H2SO4 solution. Although silica fume effectively increased compressive strength and reduced the porosity of concrete, its contribution to the resistance of concrete to chemical sulphuric acid was minor. No clear relationship could be established between the mechanical and physical properties of concrete (compressive strength and porosity) and its resistance to sulphuric acid attack. It was also found that the decline in compressive strength of concrete specimens subjected to H2SO4 attack was directly proportional to their mass loss, following a linear relationship.

Corrosion of concrete sewer pipes by sulfuric acid attack is a problem of global scope, leading to multibillion dollar losses each year. However, research is still needed to better understand the mechanisms of sulfuric acid attack on concrete and the related effects of concrete mixture design parameters. In this paper, the combined effect of wetting-drying cycles and concrete mixture design parameters including cement content, water/cement (w/c) ratio, and coarse aggregate content on the resistance of concrete to sulfuric acid was investigated. Specimens from various concrete mixtures were soaked in sulfuric acid solutions with pH of 0.3, 0.6, 1.0, 1.5, 2.0, 2.5, and 3.0. The mass loss of concrete specimens due to immersion in sulfuric acid and wetting-drying cycles was used as a measure of concrete degradation. For specimens that experienced no mass loss due to low concentration of sulfuric acid, the thickness of the gypsum layer that formed on specimens' surface was measured on thin sections using transmitted light microscopy. The effect of exposure area/volume ratio of concrete specimens on their mass loss was also investigated. Results show that the mass loss of concrete specimens immersed in sulfuric acid solutions with pH

Advanced condition assessment technologies for buried municipal pipeline applications have been gaining significant attention in recent years. This paper presents a case study from the recently completed pipeline condition assessment project employing Ultra Wideband (UWB) radar system integrated with closed circuit television (CCTV) camera. Recently, a storm drain was rehabilitated using the trenchless slip lining technique. Following rehabilitation, a non-destructive testing (NDT) based quality assurance/quality control (QA/QC) analysis was performed to evaluate the quality of rehabilitation. Prior to the field test, laboratory based feasibility study was conducted using pipe specimen with artificially created defects. Results from both laboratory and field evaluations are presented in this paper. The results indicated the possibility of employing UWB radar as a tool for detecting quality control issues in the trenchless slip lining projects including grout blockage within the annular space, uniformity of grout thickness and proper alignment of liner pipe.

Predicting the borehole pressure during Horizontal Directional Drilling (HDD) is a significant part of HDD. Borehole stability means that pressure on the bore-face must be less than formation fracture pressure and more than the collapse pressure to avoid fluid losses or borehole breakouts. The proposed research is aimed at an analysis comparison between the mud pressure data collected in the real field and the ones the mathematical model predicted. Then the optimal model will be applied to predict the allowable maximum borehole pressure during HDD. Borehole stability during drilling consists of evaluating the drilling fluid weight to maintain the borehole wall integrity. The tensile failure (hydraulic fracturing) and dog-ear shape breakout are two main failure modes around boreholes during HDD. The cavity expansion model was used to calculate maximum and minimum allowable drilling fluid pressure in a bore. Both 2D and 3D finite element (FE) models of maximum borehole pressure were developed by the Drucker-Prager and Mohr-Coulomb theories using ANSYS Parametric Design Language (APDL) to support the customized parametric study. The result showed the maximum mud pressure closely matched the estimation obtained using the Delft equation in this field experiment for shallow layers within clay. The FE modeling procedure used was able to capture the volumetric compressive behavior of the soil around the borehole.

Many municipal water distribution systems across North America are reaching or have exceeded their design lives and, therefore, require extensive upgrading through rehabilitation and/or replacement. However, these needs far surpass the available resources, and decision makers must prioritize their replacement/rehabilitation needs. One such approach is the determination of the optimal replacement time based on the minimization of the total or annual average cost during a predetermined service period. This paper describes a simple approach for the optimization of replacement/rehabilitation activities for a network of buried pipes, which is based on the assumption that the occurrence of breaks in a pipeline segment follows a nonhomogeneous Poisson process. Equations for evaluating the optimal replacement time are derived by minimizing the expected annual average cost during the service period of the pipeline segment. Predictions are compared with those obtained by minimizing the expected total (accumulated) ...

The effect of geopolymer cement on the compressive strength and resistance to sulphuric acid of concrete made with type 10 and type 50E cements was studied. Hydration products and microstructure of various concrete mixtures incorporating geopolymer cement were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmitted light microscopy in order to identify the mechanisms underlying the effects of the geopolymer cement on concrete properties. Experimental results indicate that using geopolymer cement as partial replacement for ordinary Portland cement (OPC) effectively improved both the compressive strength and resistance to sulphuric acid. Replacement of 50% OPC by geopolymer cement increased the 28-day compressive strength by about 50% and reduced the mass loss of concrete specimens subjected to eight weeks of immersion in sulphuric acid solutions with pH of 0·3 and 0·6 by 42% and 30%, respectively. The effect of geopolymer cement on the compressive strength and sulphuric acid resistance of concrete made with type 50E cement was less significant than that for concrete made with type 10 cement. Results of XRD, SEM and light microscopy indicate that improvements in compressive strength and sulphuric acid resistance of the geopolymer modified concrete can be mainly attributed to the formation of new hydration products such as calcium–magnesium–aluminium-oxide silicates. A direct relationship between the ability of geopolymer modified concrete specimens to resist sulphuric acid and their normal 28-day compressive strength was found, but varied with the binder used.

An evaluation of the standard installation direct design (SIDD) prediction method has been undertaken by constructing and monitoring full-scale test beds installed according to SIDD Type IV specifications at four test sites across southern Ontario, Canada. Stresses around the test beds were monitored over a period of 20 months. The internal diameter of the test pipe segments varied from 600 mm to 900 mm; in situ soil conditions ranged from organic clay to sand, and burial depths varied from 1.5 to 3 times the diameter of the installed pipe. All test sections were subjected to frequent heavy traffic loads, representing a worse case loading scenario. Measurements from the 20 month monitoring period were compared with predictions from Ontario Provincial Standards and SIDD specifications. It was concluded that the SIDD method reasonably predicts the stress envelope around a buried rigid pipe installed using the cut-and-cover construction method. The indirect design method currently used by the Ontario Provincial Standards was found to provide an overly conservative prediction of soil stresses at the invert of the pipe. Field measurements also suggest that the value of the horizontal arching factor (HAF) currently recommended by SIDD for Type IV installations is overly conservative and can be increased while maintaining a conservative design approach.Key words: soil, pipe, interaction, rigid, SIDD, monitoring.

Emergency preparedness agencies are promoting community resiliency in the face of disasters through community involvement and planning. One aspect of such programs is the incorporation of disaster planning into the community normal operational activities. This paper presents a framework for a screening tool developed using the analytical hierarchy process and commonly used statistical tools to obtain a first-order estimate of the relative resilience of buried lifeline networks to earthquake loads. It is envisioned that the results will be incorporated into a municipality or utility prioritization scheme for the rehabilitation/replacement of its buried assets, as well as provide a basis for emergency response teams to prioritize their efforts following an earthquake event. A preliminary verification of the proposed model was conducted by comparing predictions with data collected during the aftermath of the Loma Prieta and Kobe earthquakes. It was shown that the proposed holistic approach is a viable method for tackling this complex, multivariable problem. The proposed model can be codified to run under standard geographical information system platforms, enabling access to existing electronic databases.

A literature review is presented that identifies a number of areas where procedures for the engineering design of bored installations in soil using horizontal directional drilling (HDD) can be improved through a more realistic consideration of drilling fluid drag effects and skin friction coefficients. The current HDD practice of calculating annular frictional pressure loss caused by drilling fluid drag based on the assumption of concentric annular flow of a Bingham plastic fluid is demonstrated to be overly conservative. Consequently, critical design parameters, such as depth of cover, which affects crossing length, and drilling equipment size, which is selected based on anticipated pulling load, cannot be optimized. This can result in overly conservative design and unnecessary construction costs. Parameter values currently employed in HDD pulling load prediction are challenged suggesting that the viscous shear of drilling fluid is significantly less than typically quoted and that the friction coefficients often employed are not representative of all skin friction effects in HDD. A new real-time monitoring cell for large-scale HDD is described that can be used to optimize installations and to assess and update current prediction models.

Communities that surround an operating construction site often find themselves subjected to negative impacts such as annoyances and economic losses. The latter often called “social costs”, refer to the monetary equivalent of consumed resources, loss of income and loss of enjoyment experienced by parties not engaged in the contractual agreement, solely due to a construction process. Social costs take many forms including loss of revenue, productivity and time, consumption of non-renewable resources and accelerated deterioration of secondary roads. Social costs, while widely acknowledged, are rarely considered in the design, planning or bid evaluation phases of construction projects in North America. This is attributed to the difficulty associated with quantifying social costs using standard estimating methods and the fact that these costs are borne by the community rather than the contractual parties. This paper outlines 22 sources of social costs associated with construction projects in urban environments. The concept of `social indicators' is introduced as a mean to link adverse impacts generated by construction activities and valuation methods. Thereafter, seven methodologies developed in the fields of economics and actuary are presented and their suitability for quantifying specific classes of social costs associated with construction projects are investigated. The capacity of current bid evaluation methods to account for social costs is also examined. It is concluded that a methodical approach for the incorporation of social costs in the bid evaluation process will be a key step towards a more sustainable-oriented construction industry. A generic framework for the development of such an approach is presented. Finally, the concept of developing a standard reference document to estimate social costs is examined and a sample format proposed.

Installation loads during 19 commercial horizontal directional drilling (HDD) installations were monitored using new in-hole monitoring cell technology. Fifteen of these installations were part of an 8.3 km section of 203 mm diameter by 4 mm wall thickness steel gas distribution line. The predominant soil type was silty clay, and similar construction practices were employed for all installations. The resistance to pipe advancement within the bore was found to increase in an approximately linear manner, varying from 0.20 to 0.31 kN/m, with a mean of 0.26 kN/m and standard deviation σx = 0.03 kN/m. Local peaks caused by borehole curvature or borehole anomalies were found to dissipate, usually within 10 m, before the underlying linear trend resumed. The remaining four installations were evaluated to determine the relationship between measured pull head load and borehole pressure. The correlation observed provides new insight into the factors that contribute to pulling forces during HDD installations. Based on the findings, a conceptual framework is proposed for an improved HDD design model. The framework outlines two development stages: stage 1, based on tabulated measurements of pulling force per length of pipe inserted; and stage 2, involving significant modifications to an existing prediction model to better represent field conditions.Key words: pipelines, tensile loads, mud pressure, directional drilling, load monitoring, pressure monitoring.

This paper describes the development and implementation of an automated real-time monitoring system for construction projects programmed in a Delphi environment. The system links time-lapse digital movies of construction activities, critical path method (CPM) and progress control techniques. It accepts digital images taken from multiple cameras, stores them in chronological order and links them to a database that contains schedule information. The digital pictures taken from up to four cameras are placed on a website from where a remote computer(s) can capture and store the pictures in the database. The system enables management staff at the contractor's and owner representatives' headquarters to follow developments at the construction site in real time. Additionally, time-lapse films of activities at the construction site taken by multiple cameras can be played back in synchrony with dynamic graphs showing planned versus actual schedules. PHOTO-NET II introduces a new concept in time-lapse photography that allows the user to manipulate the frame rate, enabling a reasonable playback time as well as the implementation of the technology for long-term construction projects using standard PCs.

As the complexity and size of the projects undertaken by horizontal directional drilling (HDD) contractors rapidly increase, there is a growing need for the development of dedicated software designed to meet the industry’s special needs and requirements. This paper presents the results of a survey of the HDD industry’s software needs as well as a summary of commercially available software specifically designed for this industry. In addition, the development of two computerized applications tailored for the HDD industry are described. The first of these applications is an integrated data management system that combines asset management, cost control, estimating, and project tracking capabilities, enabling decision makers to closely monitor field performance in terms of expenditure and productivity. The second application is a simulation model developed for optimizing the utilization of drilling rigs and hydro-vacuum trucks on large-scale urban projects. Both applications are designed to improve the planning, estimating, and productivity of directional drilling projects, ultimately reducing the cost of expanding underground infrastructure networks.

This paper presents an overview of quality management theory and its application in the area of trenchless technology in general, and horizontal directional drilling (HDD) in particular. Current practices that support quality management in the HDD industry are described and are classified using the relevant clauses of ISO 9000. The development of load cell technology aimed at enhancing the quality control/quality assurance (QC/QA) of HDD is then described. Based on load cell data collected during 20 commercial installations, electronic records of installation loads are demonstrated to be a powerful tool for implementing QC/QA programs. The records provide installation rates, the average pull load per unit length of pipe, the maximum load exerted on the pipe, as well as the entire load history of the installation. Radio transmitting capability provides real-time load cell data that can be used to adjust drilling practices to match the level of installation effort to the parameters of the given installation, thereby maximizing productivity. Load cell data are expected to benefit owners, contractors, and consulting engineers.

Naturally occurring nanoclays, such as halloysite nanotubes (HNTs) are relatively cheap and abundant materials with interesting applications in the construction industry. Recently, an electrostatic interaction was discovered between halloysite and fly ash particles, which has the potential to beneficially alter the properties of some hardened products of fly ash, such as geopolymer binders. Additionally, layer-by-layer deposition can be used to enhance even further the benefits of the fly ash-nanoclay interaction. This paper describes the nature of the interaction of the nanoclay particles with fly ash and the results of mechanical and rheological testing conducted on geopolymer produced from such nanocomposites, and the implications of this discovery for construction materials.