ABSTRACT
In this study, the effects of shrinkage reduction agent (SRA) content and filler type on the deformability characteristics of unsaturated polyester (UP) resin-based polymer concrete were experimentally investigated. Specifically, the setting shrinkage, thermal expansion, maximum compressive strain and the modulus of elasticity of UP polymer concrete were all analyzed. Setting shrinkage was found to be influenced by the UP resin, the SRA and filler. The thermal expansion, maximum compressive strain and modulus of elasticity were also affected by the aggregate. The effect of SRA content on deformability was found to be greater than that of the filler type. To put UP polymer concrete to efficient use, it is essential to secure proper deformability according to the intended purpose. At that time, it is desirable that the deformation characteristics resulting from the SRA content and filler type sufficiently reflect when the mix proportion is determined. The effects of filler type on the deformability of UP polymer concrete are such that: A uniform dispersion of filler particles impacts the setting shrinkage; the thermal expansion is influenced by the filler's various thermal expansion properties; the compressive strain is related to the nature of the small spherical particles that tend to fill porosity, producing better packing of the aggregate materials; and the modulus of elasticity is influenced by the density, which is related to the strength of the filler. However, additional in-depth studies are required on all of these elements.
ABSTRACT
The compressive and flexural strengths of mortars modified with ethylene-vinyl acetate (EVA) were experimentally investigated for use in three-dimensional (3D) additive construction (3DAC). EVA powder, which is available in a premix type, was employed as an admixture. The test results for the cast specimens showed that, at a curing age of 28 days, the compressive strengths ranged from 32.92 MPa to 43.50 MPa, and the flexural strengths ranged from 12.73 MPa to 14.49 MPa. The compressive and flexural strengths of the printed specimens were relatively lower: 23% to 26% and 3% to 7%, respectively. The compressive strength also decreased and the flexural strength increased when the EVA/cement ratio was increased. The results of the experiment reveal that the EVA-modified mortar had a high rate of strength development early on, making the material advantageous for use in 3DAC. It was determined that the appropriate EVA/cement ratio ranged between 5% and 15%. However, the printed specimens exhibited lower compressive and flexural strengths than did the cast specimens, and the compressive strength decreased as the EVA content was increased. This study provides the compressive and flexural strengths of common EVA-modified mortars, important data for 3DAC applications.
ABSTRACT
The primary purpose of this study was to investigate the feasibility of applying polymeric cementitious materials to three-dimensional additive construction (3DAC). Specifically, styrene-butadiene rubber (SBR) latex was employed as an admixture to produce SBR-modified cementitious mixtures, and their fresh properties were experimentally investigated to determine the feasibility of their use in the 3DAC process. The SBR/cement ratio was controlled based on four main materials (i.e., cement, sand, silica fume, and fly ash) in order to determine the optimal fresh properties. The test results revealed that the SBR-modified cementitious mixtures showed excellent flowability, extrudability, buildability, and open time, all of which are required for 3DAC materials. The optimal flow of the SBR-modified cementitious mixtures was 70% ± 1%, which is appropriate for 3DAC applications. According to the experiment results, the SBR-modified cementitious mixtures were sufficiently competitive to serve as a new class of materials for 3D additive construction.
ABSTRACT
In this study, the fresh properties of ethylene-vinyl acetate (EVA)-modified cementitious mixtures were experimentally investigated to evaluate the feasibility of this type of material being used in additive construction by extrusion (ACE). The EVA/cement ratio was a main variable to determine the properties, including flowability, extrudability, buildability, and open time. According to the flow test results, the optimized flow of the EVA-modified cementitious mixtures was found to be 65% for buildability. This excellent flowability could be achieved because the flow increased as the EVA/cement ratio increased; conversely, the extrudability was slightly reduced when the EVA/cement ratio increased. However, if the flow of the EVA-modified cementitious mixtures was maintained at 65%, ACE could be achieved without significant issues. In addition, the height of the additive concrete walls created was not substantially reduced after printing of these mixtures, even though different EVA/cement ratios were applied. Plus, ACE can be operated longer with such mixtures because the open time becomes longer as the EVA/cement ratio increases. In summary, the results clearly demonstrated that EVA-modified cementitious mixtures were feasible for use as ACE materials.
ABSTRACT
In the construction field, adhesives are frequently used to improve adhesion between two objects. Epoxy adhesives are applied as long-term solutions, improving the bond between repair materials and existing concrete structures. Experimental investigations of the relationship between the thickness of an adhesive layer and its shear strength have been conducted by a number of industries outside of the construction sector. However, that research used metal plates as adherends when determining the shear strengths of epoxy adhesives. Therefore, this study examines epoxy adhesives' shear strength development when applied to concrete adherends. The test results show that the thickness of the bond layer did affect shear strength development in the epoxy adhesives examined.
