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Category: Publications: Geotechnical and Structures Laboratory (GSL)
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  • Graphene in Cementitious Materials

    Abstract: This project aims to determine the influence of laboratory-generated graphene (LGG) and commercial-grade graphene (CGG) on the chemical structure and compressive strength of graphene-cement mixtures. Determining the graphene-cement structure/processing/property relationships provides the most useful information for attaining the highest compressive strength. Graphene dose and particle size, speed of mixing, and dispersant agent were found to have important roles in graphene dispersion by affecting the adhesion forces between calcium silicate hydrate (CSH) gels and graphene surfaces that result in the enhanced strength of cement-graphene mixtures. X-ray diffraction (XRD), Raman, and scanning electron microscope (SEM) analyses were used to determine chemical microstructure, and compression testing for mechanical properties characterization, respectively. Based on observed results both LGG and CGG graphene cement mixtures showed an increase in the compressive strength over 7-, 14-, and 28-day age curing periods. Preliminary dispersion studies were performed to determine the most effective surfactant for graphene dispersion. Future studies will continue to research graphene—cement mortar and graphene—concrete composites using the most feasible graphene materials. These studies will prove invaluable for military programs, warfighter support, climate change, and civil works.
  • Evaluation of Venturi Pump Blower Attachment Prototype

    Purpose: The US Air Force Civil Engineer Center (AFCEC) tasked the US Army Engineer Research and Development Center (ERDC) with (1) developing a prototype venturi pump blower attachment for removing standing water from open excavations and (2) comparing its performance to that of traditional pumps. This technical note summarizes testing conducted as a part of the development of the prototype and provides analysis and conclusions based on the results.
  • Development and Characterization of Ultra-High-Performance Concrete for the Rehabilitation of Navigation Lock Structures

    Abstract: This report details the history of vertical lock wall repairs and the development and laboratory characterization of an ultra-high-performance concrete (UHPC) using locally sourced materials for improved durability of lock walls subjected to impact and abrasion from navigational vessels. This UHPC, referred to as Lock-Tuf, has been designed for use in a precast environment with ambient curing methods and serves as a material proof-of-concept for future lock wall rehabilitations. Mechanical properties such as unconfined compressive strength, flexural response, tensile capacity, impact resistance, and abrasion resistance have been quantified experimentally.
  • Dynamic Material Properties of Grade 50 Steel: Effects of High Strain Rates on ASTM A992 and A572 Grade 50 Steels

    Abstract: Uniaxial tensile tests were conducted on American Society for Testing Materials International (ASTM) A992 and A572 Grade 50 steels at increasing strain rates to determine the material strength properties of structural members subjected to dynamic loadings. The increase in dynamic yield strength and ultimate tensile strength was determined to update design criteria within UFC 3-340-02, which are currently limited to ASTM A36 and A514 steels. The proposed updates will provide the necessary information required to design blast-resistant structures utilizing modern-day structural steels. The dynamic material properties determined by high-rate tensile tests were compared to static values obtained from ASTM E8 standard tensile tests. The comparisons were used to calculate dynamic increase factors (DIFs) for each steel at strain rates from 2E-3 to 2E0 inch/inch/second. The experiments revealed that the A992 steel exhibited an increase in yield strength up to 45% and ultimate tensile strength up to 20% as strain rate increased over the range tested. The A572-50 steel exhibited a similar increase in yield strength up to 35% and ultimate tensile strength up to 20%. The DIF design curves developed during this research will allow engineers to more efficiently design structural steel components of hardened structures for the protection of our nation’s critical infrastructure.
  • Low-Logistic Erosion Control Methodologies

    Purpose: This paper provides an in-depth review of certain slope stability practices discussed in ERDC/GSL TR-19-44, a technical report titled Erosion Control of Earth Covered Magazines to Maintain Minimum Cover Requirements. At the request of the sponsor, US Army Engineering and Support Center, this document specifically focuses on cost-efficient, low-logistic methods of erosion control such as shotcrete and spray-applied stabilizers.
  • Advanced Cementitious Materials for Blast Protection

    Abstract: Advanced cementitious materials, commonly referred to as ultra-high performance concretes (UHPCs), are developing rapidly and show promise for civil infrastructure and protective construction applications. Structures exposed to blasts experience strain rates on the order of 102 s-1 or more. While a great deal of research has been published on the durability and the static properties of UHPC, there is less information on its dynamic properties. The purpose of this report is to (1) compile existing dynamic property data—including compressive strength, tensile strength, elastic modulus, and energy absorption—for six proprietary and research UHPCs and (2) implement a single-degree-of-freedom (SDOF) model for axisymmetric UHPC panels under blast loading as a means of comparing the UHPCs. Although simplified, the model allows identification of key material properties and promising materials for physical testing. Model results indicate that tensile strength has the greatest effect on panel deflection, with unit weight and elastic modulus having a moderate effect. CEMTECmultiscale® deflected least in the simulation. Lafarge Ductal®, a commonly available UHPC in North America, performed in the middle of the five UHPCs considered.
  • Naval Expeditionary Runway Construction Criteria: P-8 Poseidon Pavement Requirements

    Abstract: A full-scale airfield pavement test section was constructed and trafficked by the US Army Engineer Research and Development Center to determine minimum rigid and flexible pavement thickness requirements to support contingency operations of the P-8 Poseidon aircraft. Additionally, airfield damage repair solutions were tested to evaluate the compatibility of those solutions with the P-8 Poseidon. The test items consisted of various material thickness and strengths to yield a range of operations to failure allowing development of performance predictions at a relatively lower number of design operations than are considered in traditional sustainment pavement design scenarios. Test items were trafficked with a dual-wheel P-8 test gear on a heavy-vehicle simulator. Flexible pavement rutting, rigid pavement cracking and spalling, instrumentation response, and falling-weight deflectometer data were monitored at select traffic intervals. The results of the trafficking tests indicated that existing design predictions were generally overconservative. Thus, minimum pavement layer thickness recommendations were made to support a minimum level of contingency operations. The results of full-scale flexible pavement experiment were utilized to support an analytical modeling effort to extend flexible pavement thickness recommendations beyond those evaluated.
  • Exploration of Two Polymer Nanocomposite Structure-Property Relationships Facilitated by Molecular Dynamics Simulation and Multiscale Modeling

    Abstract: Polyamide 6 (PA6) is a semi-crystalline thermoplastic used in many engineering applications due to good strength, stiffness, mechanical damping, wear/abrasion resistance, and excellent performance-to-cost ratio. In this report, two structure-property relationships were explored. First, carbon nanotubes (CNT) and graphene (G) were used as reinforcement molecules in simulated and experimentally prepared PA6 matrices to improve the overall mechanical properties. Molecular dynamics (MD) simulations with INTERFACE and reactive INTERFACE force fields (IFF and IFF-R) were used to predict bulk and Young's moduli of amorphous PA6-CNT/G nanocomposites as a function of CNT/G loading. The predicted values of Young's modulus agree moderately well with the experimental values. Second, the effect of crystallinity and crystal form (α/γ) on mechanical properties of semi-crystalline PA6 was investigated via a multiscale simulation approach. The National Aeronautics and Space Administration, Glenn Research Center's micromechanics software was used to facilitate the multiscale modeling. The inputs to the multiscale model were the elastic moduli of amorphous PA6 as predicted via MD and calculated stiffness matrices from the literature of the PA6 α and γ crystal forms. The predicted Young's and shear moduli compared well with experiment.
  • Waste Management and Landfill Facilities Assessment Using Unmanned Aircraft Systems

    Abstract: Finite and decreasing landfill space on Army installations is a significant concern. Efficient waste management is essential for achieving resiliency and extending the lifespan of remaining landfills. The purpose of this demonstration was to conduct independent performance tests of small unmanned aircraft systems (sUAS) and their utility for providing landfill assessments in remote areas where physical presence is either dangerous or inefficient. An active, near capacity construction and demolition (C&D) landfill at Fort Gordon, Georgia, was identified for the demonstration. The flights, data requirements, and outputs generated by the sUAS flyovers were analyzed for efficacy in detecting cell capacity and subsidence. Each flight took 1–2 hours for mobilization, ground marker placement, flight, and postflight analysis. Volumetric and topographic surveys were analyzed in less time than is typical for traditional surveying methods. After initial setup of ground markers and rectification, sUAS flights save a significant amount of time. However, skilled individuals are required for flights and for processing and maintaining data. The technology is widely relevant to the Army, is commercially available, and offers an average of 30% cost savings in terms of manpower, repeatability, and equipment. The use of sUAS technology is recommended for monitoring and surveying Army landfills.
  • Characterization of Pigmented Microbial Isolates for Use in Material Applications

    Abstract: Organisms (i.e., plants and microorganisms) contain pigments that allow them to adapt and thrive under stressful conditions, such as elevated ultraviolet radiation. The pigments elicit characteristic spectral responses when measured by active and passive sensors. This research study focused on characterizing the spectral response of three organisms and how they compared to background spectral signatures of a complex environment. Specifically, spectra were collected from a fungus, a plant, and two pigmented bacteria, one of which is an extremophile bacterium. The samples were measured using Fourier transform infrared spectroscopy and discriminated using chemometric means. A top-down examination of the spectral data revealed that organisms could be discriminated from one another through principal component analysis (PCA). Furthermore, there was a strong distinction between the plant and the pigmented microorganisms. Spectral differences resulting in samples with the highest variance from the natural background were identified using PCA loading plots. The outcome of this work is a spectral library of pigmented biological candidates for coatings applications.