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    Effect of carbonic anhydrase enzymes on strength of soil cement
    (2026-06-01)
    Kingnoi, Namthip
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    Ayawanna, Jiratchaya
    ;
    Mase, Lindung Zalbuin
    ;
    Omar, Rohayu Che
    ;
    Chaiyaput, Salisa
    This research proposes the originality of using carbonic anhydrase (CA) biocatalyst enzyme with soil cement material for strength development. The soft Bangkok clay with cement up to 30 wt% of dried soil was prepared with the addition of CA at an amount of 100 µl and a concentration of 100 µM. The suitable preparation and curing method of soil cement containing CA was also investigated using different mixing methods (dry mixing and wet mixing) and curing conditions (air curing and plastic wrap curing) for up to 28 days. The improvement of soil cement strength was achieved by increasing cement content and curing time. The compressive strength of soil cement is highly improved with the addition of CA, particularly in the air-curing condition. The formation of CaCO<inf>3</inf> was observed with a tightened microstructure. In addition, the wet mixing method is favorable for improving strength with biocatalyst enzymes due to the dispersion of hydrated cement particles. Mixing small amounts of CA in soil cement not only enhances strength but also contributes to environmental sustainability, making it a viable option for sustainable future construction applications and adaptable ground improvement techniques.
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    Microstructure investigation of soft clay after a vacuum PVD second improvement: a case study in Bangkok area Thailand
    (2023-10-01)
    Chaiyaput, Salisa
    ;
    Kotkhangphlu, Pornsuda
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    Chao, Kuo Chieh
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    Chanin, Chatchai
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    Ayawanna, Jiratchaya
    This study first demonstrates the microstructural changes of soft Bangkok clay at a real construction site following vacuum PVD modification of soft clay at a − 9-m elevation obtained from Thailand’s Suvarnabhumi Airport. In contrast to the undisturbed soil and the first-improvement soil, the second vacuum PVD improvement transformed the face-to-face orientation of the soil structure into edge-to-face flocculated particles. This approach also greatly affected the inorganic NaCl salts leaching from the pore water, resulting in stronger bonding with less soil permeability and an improved consolidation of soil structure. The repulsive interactions between the soil particles lowered the average liquid limit and plastic limit values, which contributed to the edge-to-face flocculation of the soil particles and greatly increased the shear strength. Vacuum PVD with a second improvement is a highly effective solution for raising the settlement rate and minimizing the settlement time to improve soft clay with low strength and high compressibility.
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    Utilization of ladle furnace slag from a steelwork for stabilization of soil cement
    (2022-10-25)
    Ayawanna, Jiratchaya
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    Kingnoi, Namthip
    ;
    Sukchaisit, Ochakkraphat
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    Chaiyaput, Salisa
    Ladle furnace (LF) slag, waste from the steel-making process, was incorporated to improve the compressive strength of soil cement. LF slag was mixed to replace the cement in the soil-cement samples with wt% ratio 20:0, 15:5, and 10:10 of cement and slag, respectively. LF slag in the range of 5, 10, and 20 wt% was also separately added to the 20-wt% cement-treated soil samples. The soil-cement mixed LF slag samples were incubated in a plastic wrapping for 7, 14, and 28 days. The strength of soil cement was highly developed to be higher than the standard acceptable value (0.6 MPa) after incorporating slag into soil cement. The mixing of LF slag resulted in more hydration products for bonding soil particles, and hence improved the strength of soil cement. With the LF slag mixing either a replacement or additive materials in soil cement, the LF slag to cement ratio is considered to be less than 1, while the cement content should be more than 10 wt%. This is to promote a predominant effect of cement hydration by preventing the partially absorbed water on slag particles and keeping sufficient water content for the cement hydration in soil cement.
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    Effect of curing conditions on the strength of soil cement
    (2022-06-01)
    Chaiyaput, Salisa
    ;
    Arwaedo, Nakib
    ;
    Kingnoi, Namthip
    ;
    Nghia-Nguyen, Trong
    ;
    Ayawanna, Jiratchaya
    An experimental program was directed to the evaluation of the strength of soil (ball clay)-cement, and soil (soft clay)-cement samples with different curing conditions; tap water, lime-saturated water, plastic wrapping, and open ambient air at 28 days. The compression, and the scanning electron microscopy results were used to describe the effect of curing conditions on the compressive strength of soil-cement samples. The compressive strength of soil-cement samples was ~ 50% that of the plain cement sample. The compressive strength of the soft clay-cement samples was slightly higher than the ball clay-cement samples because of the coarse particles of soft clay containing a high amount of quartz, allowing the water to react with cement powder and increased the strength of soil-cement samples. The tendency of compressive strength development in the soil-cement samples was similar to that of the cement sample. The highest compressive strength was obtained for the lime-saturated water cured samples, suggesting a higher rate of hydration process by the protection of CaCO<inf>3</inf> leaching from cement in the lime water. Thus, the compressive strength in soil-cement samples was enhanced by the binding of cement hydration products between the adjacent soil particles.
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    Electrical resistivity survey for evaluating the undrained shear strength of soft Bangkok clay at some of the canal-side road investigation sites
    (2022-01-01)
    Chaiyaput, Salisa
    ;
    Sutti, Nut
    ;
    Suksawat, Taweephong
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    Ayawanna, Jiratchaya
    A resistivity-undrained shear strength equation was proposed in this work to investigate the relationship between the undrained shear strength and electrical resistivity of soft Bangkok clay. The field vane shear and screw driving sounding tests were used to evaluate the undrained shear strength of the soft Bangkok clay from 10 field investigations of the canal-side roads. Meanwhile, the electrical resistivity was collected by the low-cost nondestructive resistivity survey method. The relationship between the measured resistivity corresponding to the undrained shear strength was expressed as a linear equation of S<inf>u</inf> = 7.061ρ with a high statistical correlation (96.20%) between the undrained shear strength and resistivity. The validation between the predicted undrained shear strength from the equation and the measured undrained shear strength from the field sites confirmed the statistically significant relation of data and the reliability of the proposed equation. By using this equation, it successfully predicted the undrained shear strength of the soft Bangkok clay at a depth of 4.00–10.00 m below the ground surface of canal-side roads (zones C, D, and E in the zonation map). The proposed new equation from the resistivity survey in this work, therefore, serves as an alternative tool to fast estimate the shear strength of soft soil in the large area for the preliminary evaluation of road construction.