Date of Graduation
5-2025
Document Type
Thesis
Degree Name
Master of Science in Civil Engineering (MSCE)
Degree Level
Graduate
Department
Civil Engineering
Advisor/Mentor
Bernhardt-Barry, Michelle L.
Committee Member
Coffman, Richard A.
Second Committee Member
Hale, W. Micah
Keywords
Additive Construction; Horizontal Construction; Materials Characterization
Abstract
Advantages of concrete additive construction (AC) include the ability to print an object at the point of need with less waste, the geometric flexibility for novel shapes, and the reduction in the amount of hard physical labor required by construction workers. To date, most AC structures are designed and built using select high-quality materials, however, the implementation of indigenous, locally sourced soils and aggregates has started to grow as a feasible alternative, especially in remote locations in which the acquisition of conventional or select materials is unattainable. The potential to use indigenous materials reduces the logistical burdens associated with most concrete construction, and it improves the sustainability aspects, making the technology even more attractive.
To evaluate the suitability of indigenous materials sourced on-site to create AC concrete mixes, a full suite of characterization tests was conducted on a variety of indigenous materials sourced from around the world. The properties of the materials were determined, and then concrete mixes were evaluated to better understand the influence of various properties on the printability and strength of the AC concrete. Printability in this study refers to the pumpability and buildability of a mix, meaning the fresh material could be pumped through a progressive cavity pump, and then extruded beads could be stacked consecutively without excessive slump or collapse. The selection of the appropriate set of tests for a future testing protocol was guided by the most influential soil characteristics for AC concrete mix performance: the fines content, plasticity, gradation, and specific gravity in conjunction with absorption. These properties provided the relevant information needed to assess the suitability of indigenous materials for AC concrete mixes and identify cases when further processing is required in the field.
The amount of fines present was shown to influence workability and the water demand, and higher fines contents tended to improve the pumpability and buildability of a mix. The plasticity of the indigenous soils also strongly influenced the fresh and hardened properties of AC concrete mixes. Increased plasticity enhanced the pumpability and buildability of mixes; however, these mixes tended to have higher shrinkage cracking and lower strength. The gradation of indigenous materials provided information regarding maximum particle size and the coarseness of an aggregate, delimiting AC equipment and printing parameters. Gradation also likely helps identify the potential for a mix to pack within the rotor-stator; however, more research is needed to confirm the observations in this study. Specific gravity and absorption are important properties in the mix design proportions and having these values can help precisely control total water demand to ensure pumpability, avoid segregation, and enhance adhesion between layers.
The Methylene Blue Value (MBV) test was proposed as a field-applicable test method to determine the clay content of soils. MBV presented challenges regarding the variation of results from each soil analyzed. MBV denoted a directly proportioned linear function with clay content values, however, each soil analyzed resulted in a unique range of MBV. Because of this, the MBV was not able to uniquely identify the clay content or plasticity of a given indigenous soil.
Citation
Serrano Espinoza, J. J. (2025). Indigenous Materials Characterization for Additive Construction Applications. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/5784
