Mingjiang Tao

Bio: Mingjiang Tao is an academic researcher from Worcester Polytechnic Institute. The author has contributed to research in topics: Geopolymer & Fly ash. The author has an hindex of 21, co-authored 59 publications receiving 1732 citations. Previous affiliations of Mingjiang Tao include Louisiana State University & University of Alaska Fairbanks.

Experimental feasibility study of geopolymer as the next-generation soil stabilizer

Abstract: In many civil engineering constructions, soft and weak soils are often stabilized with ordinary Portland cement (OPC) and lime. The production processes of traditional stabilizers are energy intensive and emit a large quantity of CO2. Geopolymer, with its high strength, low cost, low energy consumption and CO2 emissions during synthesis, offers a promising alternative to OPC. In this study, a lean clay was stabilized with metakaolin based geopolymer at different concentration (ranging from 3 to 15 wt.% of unstabilized soil at its optimum water content) to examine the feasibility of geopolymer in stabilizing soils. Geopolymer stabilized soil specimens were characterized with compressive strength testing, volume measurements during curing, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The testing results indicated that with geopolymer concentrations, compressive strength, failure strain and Young’s modulus of the stabilized soil specimens increased, and shrinkage strains during curing decreased. The microstructural analyses confirmed the formation of geopolymer gels in the stabilized soil, and showed the soil tended to form more homogeneous and compact microstructures after stabilization. This study illustrated that metakaolin based geopolymer can be an effective soil stabilizer for clayey soils. Further studies on the long-term performance of geopolymer stabilized soils, the use of geopolymers synthesized from industrial wastes, and the financial and environmental cost of applying geopolymer in soil stabilization are worth being conducted.

Review on solid-solid phase change materials for thermal energy storage: Molecular structure and thermal properties

Abstract: Solid-solid phase change materials (SS-PCMs) for thermal energy storage have received increasing interest because of their high energy-storage density and inherent advantages over solid-liquid counterparts (e.g., leakage free, no need for encapsulation, less phase segregation and smaller volume variation). Four main SS-PCMs for thermal energy storage are reviewed, with a focus on their thermal properties and the relationship between molecular structure, processes involved during phase transition, and thermal properties. This review aims to provide guidance for selecting appropriate SS-PCMs for various applications and tailoring the synthesis of SS-PCMs with desired thermal, physical and mechanical properties. Challenges and opportunities to use of SS-PCMs for thermal storage and other applications are also discussed.

Synthesis factors affecting mechanical properties, microstructure, and chemical composition of red mud–fly ash based geopolymers

Abstract: The influence of synthesis factors, including chemical composition of raw materials and curing conditions, on the microstructure and mechanical properties of geopolymers synthesized from red mud (RM) and class F fly ash (FFA) was investigated. Mechanical properties, microstructure, mineralogy, and chemical composition of the resulting geopolymers were characterized by unconfined compression testing, scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), respectively. Geopolymers were successfully synthesized at the ambient condition of 23 °C and 40–50% relative humidity (RH) with the 28-day unconfined compressive strength (UCS) ranging from 11.3 to 21.3 MPa. The formation of amorphous geopolymer gel was confirmed by XRD patterns, SEM images, and EDX spectra. This study suggests that a nominal Na/Al molar ratio in the range of 0.6–0.8 with a fixed nominal Si/Al molar ratio of 2 is a good starting point to synthesize geopolymer from RM and FFA. The ambient condition is also confirmed to be a practically feasible scheme for curing RM–FFA based geopolymers, and exceptional mechanical properties can be obtained at a curing time period of up to 180 days.

Effects of Warm-Mix Asphalt Additives on Workability and Mechanical Properties of Reclaimed Asphalt Pavement Material

Abstract: The soaring cost of liquid asphalt binder and anticipated stricter environmental regulations have driven highway agencies to maximize the amount of reclaimed asphalt pavement (RAP) used for pavement construction. However, because of already aged and stiffened asphalt binder in RAP, the use of high percentages of RAP in hot-mix asphalt (HMA) presents many challenges. Problems with workability and compactability during construction need to be resolved first. This study investigated the feasibility of using 100% RAP HMA as a base course with warm-mix asphalt (WMA) additives (Sasobit H8 or Advera zeolite) at a lower temperature (125°C). Mix samples (control set with 100% RAP; a set with 100% RAP plus Sasobit H8 at 1.5%, 2.0%, and 5.0%; and a set with 100% RAP plus Advera zeolite at 0.3%, 0.5%, and 0.7%) were compacted with 50 gyrations. Their workability, bulk specific gravity, indirect tensile strength at 0°C, and moduli at 0°C, 26.7°C, and 50°C were determined. The effects of different amounts of WMA additi...

Durability of red mud-fly ash based geopolymer and leaching behavior of heavy metals in sulfuric acid solutions and deionized water

Abstract: The durability and heavy metal leaching behavior of red mud-class F fly ash based geopolymers (RFFG) were investigated in this study. RFFG specimens were soaked in sulfuric acid solutions (pH = 3.0) and deionized water (pH = 7.0) for 1–120 days, and then their remaining mechanical properties and the change in the microstructures were characterized with unconfined compression tests, three-point bending tests, scanning electron microscopy, X-ray diffractometer and Fourier transform infrared spectroscopy, respectively. The leaching behavior of heavy metals in RFFG samples after soaking up to 14 days was also examined with atomic absorption spectroscopy. The RFFG samples’ resistance against sulfuric acid was comparable to the ordinary Portland cement (OPC), and their mechanical degradation was mainly attributed to the depolymerization and dealumination of geopolymer gels. The highest concentrations of the heavy metals leached by the sulfuric acid from the RFFG samples were much lower than the respective US EPA limits for soil contamination.

One-part alkali-activated materials : a review

Abstract: Alkali-activated materials (AAM) are recognized as potential alternatives to ordinary Portland cement (OPC) in order to limit CO2 emissions as well as beneficiate several wastes into useful products. However, the alkali activation process involves concentrated aqueous alkali solutions, which are corrosive, viscous, and, as such, difficult to handle and not user friendly. Consequently, the development of so-called one-part or “just add water” AAM may have greater potential than the conventional two-part AAM, especially in cast-in-situ applications. One-part AAM involves a dry mix that consists of a solid aluminosilicate precursor, a solid alkali source, and possible admixtures to which water is added, similar to the preparation of OPC. The dry mix can be prepared at elevated temperatures to facilitate the reactivity of certain raw materials. This review discusses current studies of one-part AAMs in terms of raw materials, activators, additives, mechanical and physical properties, curing mechanisms, hydration products, and environmental impacts.

Transplantation of chondrocytes utilizing a polymer-cell construct to produce tissue-engineered cartilage in the shape of a human ear

Abstract: &NA; This study evaluates the feasibility of growing tissue‐engineered cartilage in the shape of a human ear using chondrocytes seeded onto a synthetic biodegradable polymer fashioned in the shape of a 3‐year‐old child's auricle. A polymer template was formed in the shape of a human auricle using a nonwoven mesh of polyglycolic acid molded after being immersed in a 1% solution of polylactic acid. Each polyglycolic acid‐polylactic acid template was seeded with chondrocytes isolated from bovine articular cartilage and then implanted into subcutaneous pockets on the dorsa of 10 athymic mice. The three‐dimensional structure was well maintained after removal of an external stent that had been applied for 4 weeks. Specimens harvested 12 weeks after implantation and subjected to gross morphologic and histologic analysis demonstrated new cartilage formation. The overall geometry of the experimental specimens closely resembled the complex structure of the child's auricle. These findings demonstrate that polyglycolic acid‐polylactic acid constructs can be fabricated in a very intricate configuration and seeded with chondrocytes to generate new cartilage that would be useful in plastic and reconstructive surgery. (Plast. Reconstr. Surg. 100: 297, 1997.)

Fly ash-based geopolymer: clean production, properties and applications

Abstract: Fly ash is the fine solid particulate residue driven out of the boiler with the flue gases in coal-fired power plants. Now it can be used for making geopolymer which acts as a cement-like product. The geopolymer technology provides an alternative good solution to the utilization of fly ash with little negative impact on environment. This review summarizes and examines the scientific advances in the preparation, properties and applications of fly ash-based geopolymer. The production of fly ash-based geopolymer is mainly based on alkali activated geopolymerization which can occur under mild conditions and is considered as a cleaner process due to much lower CO 2 emission than that from the production of cement. The geopolymerization can trap and fix the trace toxic metal elements from fly ash or external sources. The Si/Al ratios, the type and the amount of the alkali solution, the temperature, the curing conditions, and the additives are critical factors in a geopolymerization process. The mechanical performances of the fly ash-based geopolymer, including compressive strength, flexural and splitting tensile strength, and durability such as the resistance to chloride, sulfate, acid, thermal, freeze-thaw and efflorescence, are the primary concerns. These properties of fly ash-based geopolymer are inherently dependent upon the chemical composition and chemical bonding and the porosity. The mechanical properties and durability can be improved by fine tuning Si/Al ratios, alkali solutions, curing conditions, and adding slag, fiber, rice husk-bark ash and red mud. Fly ash-based geopolymer is expected to be used as a kind of novel green cement. Fly ash-based geopolymer can be used as a class of materials to adsorb and immobilize toxic or radioactive metals. The factors affecting the performances of fly ash-based geopolymer concrete, in particular aggregate, are discussed. For future studies on fly ash-based geopolymer, further enhancing mechanical performance, scaling up production and exploring new applications are suggested.

On the Mechanistic Origins of Toughness in Bone

Abstract: One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.

Novel strategies and supporting materials applied to shape-stabilize organic phase change materials for thermal energy storage–A review

Abstract: Energy from renewable resources is a major concern nowadays and is being addressed by researchers over the globe to overcome the energy crises. Organic phase change materials are extensively utilized in thermal energy storage systems to integrate and manage the renewable energy. However, the tendency of organic phase change materials to leak out during the phase transition process, limits their practical applications in thermal energy storage. The shape-stabilization is an effective strategy to prevent the leakage and enhance the energy storage capacity of organic phase change materials. The shape stability can be achieved by entrapping the organic phase change materials in a shell through microencapsulation and by integrating into the supporting materials’ matrix or by developing phase change materials with the solid-solid phase change. This paper delivers a comprehensive detail on the diverse classes of novel shape stabilizing strategies containing organic, inorganic and polymeric materials with adequate critical analysis of thermophysical properties of phase change materials. Moreover, the versatile applications of shape-stable phase change materials in thermal management and energy storage systems have also been enlightened. Lastly, the critical issues in different shape-stabilization strategies and the possible rectifications are also discussed.