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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 28 Abstracts search results
Document:
22-288
Date:
April 1, 2024
Author(s):
Christian Negron-McFarlane, Eric Kreiger, Lynette Barna, Peter Stynoski, and Megan Kreiger
Publication:
Materials Journal
Volume:
121
Issue:
2
Abstract:
An experimental investigation was carried out using the volumetric proportioning approach to achieve printable portland cement concrete mixtures. The types of aggregates investigated were rounded pea gravel and coarse and fine sand. The test matrix of potential concrete mixtures was prepared based on watercement ratios (w/c) of 0.46 to 0.48, sand-to-stone ratios (sa/st) of 1.18 to 1.91, and paste-aggregate ratios (p/a) of 0.74 to 0.81. The workability and early-age strength of fresh concrete were characterized by field-friendly flow-table and unconfined compressive strength (UCS) tests. Test results indicated that the w/c, sa/st, and p/a all significantly affect fresh concrete pumpability and early-age strength. The overall research results revealed that pumpability and buildability can be evaluated with these two tests. The results of these two tests together are used to define a printable region.
DOI:
10.14359/51740265
22-217
Amin K. Akhnoukh and Mathew Campbell
The U.S. National Ocean Service estimates 95,741 miles (154,080 km) of shoreline in the United States, where 163 miles per year are hardened by bulkheads and riprap. These shoreline protection techniques are costly and require frequent maintenance. Different agencies are examining “nature-based” solutions that combine vegetation with traditional concrete. Digital construction, advanced manufacturing, and innovative cementitious composites have also been proposed as potential means to lower material use, cost, and environmental impact. This paper presents a novel advanced manufacturing technique using a reactive-diffusion morphological process, called “dry-forming,” to three-dimensionally (3-D) printed concrete structures of various shapes, sizes, and complexities with standard concrete mixtures. This technology has reduced 60% of material use, enhanced local habitats, and increased the resiliency of the shoreline to sea level rise. The widespread use of this technology would increase the resiliency of coastal communities, protect aquatic life, and protect waterfront public and private real estate investments.
10.14359/51740264
22-076
Kavya Vallurupalli, Nicolas Ali Libre, and Kamal H. Khayat
Successful implementation of extrusion-based three-dimensional (3-D) printing requires the development of print materials with adapted rheology. In this study, filtration characteristics coupled with rheological properties of mortar mixtures are investigated to characterize the extrudability of print materials and establish a “printability window” (that is, the acceptable range of material properties for successful extrusion and shape stability). The extrudability was measured as the maximum force needed for the ram extrusion of the material. The fluid filtration rate was assessed in terms of desorptivity of the fresh mixture under pressure. The yield stress, plastic viscosity, and desorptivity were varied by changing the water-cement ratio (w/c), high-range water-reducing admixture (HRWRA) dosage, and welan gum (WG) content. Regression analysis indicated that during extrusion-based printing, the yield stress and desorptivity values can exhibit a more significant effect on extrudability than plastic viscosity.
10.14359/51740301
22-286
K. Sriram Kompella, Andrea Marcucci, Francesco Lo Monte, Marinella Levi, and Liberato Ferrara
The early-age material parameters of three-dimensional (3-D)-printable concrete defined under the umbrella of printability, namely, pumpability, extrudability, buildability, and the “printability window/open time,” are subjective measures. The need to correlate and successively substitute these subjective measures with objective and accepted material properties, such as tensile strength, shear strength, and compressive strength, is paramount. This study validates new testing methodologies to quantify the tensile and shear strengths of printable fiber-reinforced concretes still in their fresh state. A tailored mixture with high sulfoaluminate cement and nonstructural basalt fibers has been assumed as a reference. The relation between the previously mentioned parameters and rheological parameters, such as yield strength obtained through International Center for Aggregates Research (ICAR) rheometer tests, is also explored. Furthermore, in an attempt to pave the way and contribute toward a better understanding of the mechanical properties of 3-D-printed concrete, to be further transferred into design procedures, a comparative study analyzing the work of fracture per unit crack width in three-point bending has been performed on printed and companion nominally identical monolithically cast specimens, investigating the effects of printing directions, position in the printed circuit, and specimen slenderness (length to depth) ratio.
10.14359/51740302
22-164
Avinaya Tripathi, Sooraj A. O. Nair, Harshitsinh Chauhan, and Narayanan Neithalath
Conventional approaches to concrete three-dimensional (3-D) printing relies on printing concrete in a straight (linear) print path, with layers overlaid on top of each other. This results in interlayer and interfilament joints being potential weak spots that compromise the mechanical performance. This paper evaluates simple alterations to the print geometry to mitigate some of these effects. A printable mixture with 30% of limestone powder replacing cement (by mass), with a 28-day compressive strength of approximately 70 MPa in the strongest direction is used. S- and 3-shaped print paths are evaluated as alternatives to the linear print path. Staggering of the layers ensures that the interfilament joints do not lie on the same plane along the depth. Flexural strength enhancement is observed when print geometries are changed and/or layers are staggered. The study shows that print geometry modifications mitigate mechanical property reductions attributed to interfilament defects in 3-D concrete printing.
10.14359/51740262
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