Mechanical properties of EVA-modified cement for underground gas storage

Kim²,

et al. 2019

Materials

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.

Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

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Compressive and Flexural Strengths of EVA-Modified Mortars for 3D Additive Construction

Kim²,

et al. 2019

Materials

“…Polymer-modified cement mortar (PCM) is superior to ordinary cement mortar in terms of strength, durability, chemical resistance, and workability and is widely used for repairing and strengthening reinforced concrete (RC) structures [1][2][3][4]. In earlier studies, PCM has shown different physical and mechanical properties than those of ordinary inorganic cement mortar and concrete because PCM is a mixture of polymeric organic material and cement mortar [5][6][7]. Considering the maintenance of RC buildings and the use period of the structures, the change in the physical properties of the PCM when exposed to high-temperature environments, such as fires, should be evaluated [8,9].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Degradation and Thermal Decomposition of Ethylene-Vinyl Acetate (EVA) Polymer-Modified Cement Mortar (PCM) Exposed to High-Temperature

et al. 2019

A polymer-modified cement mortar (PCM) is widely used as a repair material for reinforced concrete (RC) structures owing to its excellent strength and durability. However, considering the maintenance of the RC structures and the use period of the structures, the change in the physical properties of the PCM should be evaluated when exposed to various high-temperature environments, such as fires. In this study, the degradation of the mechanical properties (compressive strength and modulus of elasticity), thermal decomposition of the PCM in various high-temperature environments, and the change in the pore structure of the PCM after exposure to high temperatures were quantitatively investigated. A mechanical property evaluation of PCM was performed under three heating conditions: (i) heating in a compression tester, (ii) heating the specimen in an oven to a predetermined temperature and then moving it to a compression tester preheated to the same temperature, and (iii) cooling to room temperature after heating. In the experiment, a PCM specimen was prepared by changing the polymer–cement ratio (polymer content) of ethylene-vinyl acetate (EVA), the most commonly used polymer, to perform a high-temperature sectional test from 200 to 800 °C. In addition, to investigate the change in the PCM mechanical properties in the high-temperature region, in terms of the pyrolysis of EVA, the porosity change and mass change were examined using thermal analysis and mercury intrusion porosimetry. Before heating, the compressive strength of the PCM increased with the EVA content up to 10 % of the polymer–cement ratio. Under the cooling conditions after heating up to 200 °C, the mechanical performance of the PCM was restored, whereas the degradation of the mechanical properties of the PCM without cooling was more pronounced. Furthermore, the mass loss, heat flow, and the total porosity of the PCM increased as the EVA content increased, which is correlated with the degradation of the mechanical properties of the PCM.

“…Cement stone with residual emulsifiers swell and soften after encountering water, and the strength is greatly weakened, which substantially impacts the sealing effect and corrosion resistance of the cement sheath. 13 , 14 Soap-free latex polymerization uses only a trace amount of emulsifier or no emulsifier during the reaction process. Compared to the properties of conventional latex, soap-free latex has the advantages of a high solid content, good stability, and clean latex particles, which has aroused the interest of many researchers.…”

Section: Introductionmentioning

confidence: 99%

Study on the Preparation and Anti-CO₂ Corrosion Performance of Soap-Free Latex for Oil Well Cement

et al. 2020

To improve the resistance to CO 2 corrosion of oil well cement, soap-free emulsion polymerization was used to prepare a soap-free latex (PSAC) with sodium styrene sulfonate (SSS) and nano-SiO 2 (SSS/SiO 2 ) as the ionic copolymer emulsifier. The effects of SSS/SiO 2 on the performance, thermal stability, and latex particle morphology of the PSAC were investigated through zeta potential, TGA, and TEM measurements, respectively. The carbonation resistance properties of cement with PSAC were evaluated, and the anticorrosion mechanism of the PSAC cement was determined by SEM, EDS, XRD, and 29 Si NMR analyses. The results showed that the PSAC particle size was uniform, the particles were monodispersed, and they had a typical core–shell structure and good heat resistance. The carbonation resistance test results showed that after 60 days of corrosion, the corrosion depth of the cement with 12.0% PSAC content was only 2.16 mm, the permeability was 0.0018 mD, and the decrease in the compressive strength was 6.65%. The porosity in the cement was reduced significantly, and the pore volume (>50 nm) of the cement was reduced by 0.24 times. The PSAC film formation decreased the contact between hydration products and CO 2 . In addition, the nano-SiO 2 in the PSAC reacted with Ca(OH) 2 to reduce the free Ca(OH) 2 content in the cement and generate C–S–H gel with a low Ca/Si ratio and high polymerization, which did not react as readily with CO 2 .