• Geomechanics and Engineering
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• v.28 no.6
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• pp.637-644
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• 2022

Loess soils are unsaturated and widely distributed in the northwest zone in China. Many steep slope of unsaturated are observed are observed to be naturally stable. However, a low factor of safety (FoS) for these slopes would be computed from the slope stability analysis following local code practices. It seems that the analyzed results following the local code practices do not agree with the real condition as observed in the field. It is commonly known that soil suction plays an important role in slope stability due to a higher shear strength of the unsaturated soil as compared with that of the saturated soil. In this paper, it is observed that the computed FoS can also be affected by unsaturated unit weight of the soil. However, the effect of unsaturated unit weight of the soil on the slope stability is commonly ignored in engineering practice. Therefore, both the effects of shear strength and unit weight of the unsaturated soil on the computed FoS of unsaturated soil slope are investigated in this study. It is observed that the unsaturated unit weight of soil on the computed FoS increases with increase in slope angle. It is also observed that the effects of the unsaturated shear strength and unsaturated unit weight on the computed FoS are more significant than the effect of 3D analyses compared to the 2D analyses on the FoS.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.19-27
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• 2017

This study investigated to predict the compressive strength of unsaturated polyester resin based polymer concrete using the maturity method. The test results show that the development of the compressive strength increased exponentially until an age of 24 hours. After 24 hours, the development of the compressive strength just increased gradually. This test result shows that the strength of unsaturated polyester resin based polymer concrete was developed mainly at the early age. Estimated datum temperature of unsaturated polyester resin based polymer concrete was $-20.67^{\circ}C$ which was much lower than of datum temperature ($-10^{\circ}C$) of Portland cement concrete. Also, this study result shows that the existing maturity index associated with Portland cement concrete was not applicable for polymer concrete because curing time of Portland cement concrete is different clearly with curing time of polymer concrete. The cause of different curing time was that there were different curing mechanisms between Portland cement concrete and polymer concrete. In order to best apply the experimental data to a model, CurveExpert Professional, the commercial software, was used to determine the predictive model regarding the compressive strength of unsaturated polyester resin based polymer concrete. As a result, Gompertz Relation or Weibull Model was an appropriate model as a predictive model. The proposed model can be used to predict the compressive strength, especially, it is more useful when the maturity is in the range between $40^{\circ}C{\cdot}h^{0.4}$ and $900^{\circ}C{\cdot}h^{0.4}$.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.371-376
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• 2001

The purpose of this study is to investigate toughening of unsaturated polyester resin by addition of polyuretane liquid rubber. In general, unsaturated polyester resin has strong brittleness in spite of its high strength Therefore; it is difficult to use unsaturated polyester mortar for the place where impact resistance is demanded. In this study, it was evaluated strength and Gf by using to polyurethane liquid rubber. As a result, the toughness of unsaturated polyester mortar was increased by polyuretane liquid rubber.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.909-915
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• 2006

To predict autogenous shrinkage of concrete, unsaturated pore compensation factor could be calculated by experiments of autogenous shrinkage of cement paste on the assumption that the differences between degree of hydration and strain rate of autogenous shrinkage are unsaturated pore formation rate. Applying unsaturated pore compensation factor on modified Pickket model considering contribution factor and non-contribution factor to autogenous shrinkage of concrete, experimental data and existing model were compared. From the results modified Pickket model was verified to present similar tendency between Tazawa model and experimental data, but CEB-FIP model might be corrected because this model uses ultimate autogenous shrinkage underestimated and the same autogenous time function of concrete material properties considering only compressive strength.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.6
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• pp.97-103
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• 2009

This study was performed to evaluate the strength and durability properties of recycled polymer concrete using unsaturated polyester resin and recycled aggregates. Unsaturated polyester resin, natural and recycled aggregates and fly ash were used. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate sizes (5-10 and 5-25 mm) and unit binder contents (10% and 12%). Tests for the compressive and flexural strength, freezing and thawing and durability for 20% sulfuric solution were performed. The compressive and flexural strength of recycled polymer concrete were in the range of 85~97 MPa and 17.9~20.8 MPa, respectively. The strengths of recycled polymer concrete using recycled aggregate have similar or slightly decreased compared to polymer concrete using natural aggregate. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of recycled polymer concrete were in the range of 0.13~1.42% and 94~99, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1115-1120
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• 2000

The purpose of this study is to investigate toughening of unsaturated polyester resin by addition of liquid rubber. In general, unsaturated polyester liquid has strong brittleness in spite of if high strength Therefore; it is difficult use polyurethane liquid rubber for the place where impact resistance is demanded. In this study, it was evaluated strength, impact resistance and fracture toughness by adding to polyurethane liquid rubber(0~25%). As a result, it was found that a tendency to be increase bearing impact and fracture toughness as polyurethane liquid rubber increased but strength was decreased.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.741-744
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• 2006

The study focuses on the mixture of materials for the development of porous concrete with unsaturated polyester resin. The materials used in the mixture include the coarse aggregates unsaturated polyester resin as binder, calcium carbonate and sand as a filler. An experimental procedure has been carried out to select the best combination of the materials that satisfy both the required permeability and compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.129-134
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• 2001

The purpose of this study is to investigate properties of unsaturated polyester mortar using the shale as find aggregates. To evaluate properties of unsaturated polyester mortar using crushed sand from Black shale, Red shale, Gray shale, we peformed the experiment according the F/B ratio of 25, 30, 35% and the volume of fine aggregate of 50, 53, 56%. The Result of this study is as follows. the strength of unsaturated polyester mortar is higher than those of river sand. The F/B ratio is higher and the volume of find aggregate is lower, the strength of unsaturated polyester mortar is higher

• Computers and Concrete
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• v.31 no.6
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• pp.485-499
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• 2023

Both damage and unsaturated conditions accelerate the transport of erosive media inside concrete. However, their combined effects have not been fully investigated. A multiscale mortar model using representative volume elements is developed, capturing the number and distribution in each phase. Afterwards, mortar damage microstructure evolution is simulated in the tensile process. Finally, the unsaturated mortar transport is predicted and analysed. The results indicate that damage significantly affects the diffusion process in the early stage, while the transport performance is weakened due to the obstruction of the nontransport phase in the later stage. The higher the saturation and the more connected pores, the faster the diffusion rate of chloride ions. Chloride ions spread around the cracks in a tree-like manner along. The model can very well predict the chloride ion transport performance of unsaturated and damaged mortar.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.2
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• pp.81-91
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• 1993

This study was performed to evalute effects of fillers on the mixing characteristics and mechanical properties of polymer concrete. Two types of unsaturated polyester polymer and two types of epoxy resin were used as binder material, and the portland cement, a fly ash and heavy calcium carbonate were used as filler. Following conclusions were drawn from the research results. 1. Working life of polymer concrete was not affected by filler types, but affected significantly by polymer types and quantities of hardener and catalysts. 2. Without concerning polymer types, use of heavy calcuim carbonate as filler was the best in improving workability.3. The highest strength was achieved by heavy calcium carbonate in using unsaturated polyester resin and by fly ash in using epoxy resin type.4. Elastic modulus was in the range of 2.05X 10-5~2.6X 10-5gf/cm$^2$, which was approximatly 60% of that of cement concrete. Heavy calcium carbonate with unsaturated polyester resin and fly ash with epoxy resin showed relatively higher elastic modulus.