Chan-Gi Park

Performance Evaluation of Porous Hwang-toh Concrete Using Blast Furnace Slag Cement

This study aims to evaluate a porous concrete using hwang-toh, blast furnace slag and blast furnace slag (BFS) cement instead of type I cement. The tests that were carried out to analysis the properties of porous hwang-toh BFS cement concrete included compressive strength, continuous void ratio, absorption rate, and pH value, repeated freezing and thawing test were conducted. Test results indicated that the performance in porous hwang-toh concrete are effective on the kaoline based binder materials. The pH value were shown in about 9.5 ~ 8.5. The compressive strength was increased and void ratio was decreased with increasing the kaoline based binder materials, respectively. The void ratio and compressive strength were in the range of about 21 ~ 30 %, 8 ~ 13 MPa, respectively. The increased in void ratio of more than 25 % is showed to reduce the resistance of repeated freezing and thawing. Also, the resistance of repeated freezing of thawing and the compressive strength of porous hwang-toh BFS cement concrete are independent with hwang-toh content and BFS cement amount. But, the void ratio was decreased with increasing the high volume hwang-toh contents (more than 15 %).

Effect of Blast Furnace Slag, Hwang-toh and Reinforcing Fibers on The Physical and Mechanical Properties of Porous Concrete Using Blast Furnace Slag Coarse Aggregate

The effects of blast furnace slag, hwang-toh, and reinforcing fiber on the physical and mechanical properties of porous concrete using blast furnace slag coarse aggregates have been evaluated in this study. The effect of the depending on replacement ratio of blast furnace slag to cement was investigated such that the replacement ratio was varied to 0 %, 25 % and 50 %. Also, the replacement ratios of hwang-toh were 0, 20 and 30 %. The polyvinyl alcohol fiber was used for the reinforcing fiber. A series of pH, unit mass, and void ratio tests have been performed to study the physical properties of the porous concrete using blast furnace slag coarse aggregates with the polyvinyl alcohol fiber and the replacement ratios of blast furnace slag, hwang-toh, while a series of compressive tests have been performed to evaluate the strength property depending on polyvinyl alcohol fiber and the replacement ratios of blast furnace slag, hwang-toh. The test results indicated that the physical and mechanical properties of porous concrete using blast furnace slag coarse aggregates is affected by the replacement ratio of blast furnace slag, and the fiber contents. According to the tests with polyvinyl alcohol fiber contents, the void ratio was decreased and the compressive strength was upgraded.

Effects on the Physical and Mechanical Properties of Porous Concrete for Plant Growth of Blast Furnace Slag, Natural Jute Fiber, and Styrene Butadiene Latex Using a Dry Mixing Manufacturing Process

To evaluate the effects of industrial by-products materials on the performance of porous concrete for plant growth, this study investigated the physical, strength, and freeze/thaw resistances of porous concrete for plant growth, prepared by replacing cement with blast furnace slag powder at 60% by weight, and replacing natural stone aggregates with coarse blast furnace slag aggregates at rates of 0%, 20%, 40%, 60% and 100% by weight. In addition, the effects of adding natural jute fiber and styrene butadiene (SB) latex to these concrete mixtures were evaluated. The void ratio, compressive strength, and freeze/thaw resistance of the samples were measured. With increasing replacement rate of blast furnace aggregates, addition of latex, and mixing of natural jute fiber the void ratio of the concrete was increased. Compressive strength decreased as the replacement rate of blast-furnace slag aggregates increased. The compressive strength decreased after 100 freeze/thaw cycles, regardless of the replacement rate of blast furnace slag aggregates or of the addition of natural jute fiber and latex. The addition of natural jute fiber and latex decreased the compressive strength after 100 freeze/thaw cycles. The test results indicate that the control mixture satisfied the target compressive strength of 10 MPa and the target void ratio of 25% at replacement rates of 0% and 20% for blast furnace aggregates, and that the mixtures containing latex satisfied the criteria up to an aggregate replacement rate of 60%. However, the mixtures containing natural jute fiber did not satisfy these criteria. The relationship between void ratio and residual compressive strength after 100 freeze/thaw cycles indicates that the control mixture and the mixtures containing jute fiber at aggregate replacement rates of 20% and 40% satisfied the target void ratio of 25% and the target residual compressive strength of over 80% after 100 freeze/thaw cycles. The mixtures containing latex and aggregate replacement rates up to 60% satisfied the target void ratio and compressive strength.

Effect of Mineral Admixture on Bond between Structural Synthetic Fiber and Latex Modified Cement Mortar under Sulfate Environments

It has been well known that concrete structures exposed to acid and sulfate environments such as sewer etc. show significant decrease in their durability due to chemical attack. Such deleterious acid and sulfate attacks lead to expansion and cracking in concrete, and thus, eventually result in damage to cement mortar by forming expansive hydration products due to the reaction between cement hydration products and acid and sulfate ions. In this study, the effect of fly ash and blast furnace slag on the bond performances of structural synthetic fiber in latex modified cement mortar under sulfate environments. Fly ash and blast furnace slag contents ranging from 0 % to 20 % are used in the mix proportions. The latex modified cement mortar specimens were immersed in fresh water, 8 % sodium sulfate () solutions for 28 and 50 days, respectively. Pullout tests are conducted to measure the bond performance of structural synthetic fiber from latex modified cement mortar after sulfate environments exposure. Test results are found that the incorporation of fly ash and blast furnace slag can effectively enhance the PVA fiber-latex modified cement mortar interfacial bond properties (bond behavior, bond strength and interface toughness) after sulfate environments exposure. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results under sulfate environments.

Durability of Low-Heat, Ultra Rapid-Hardening, Latex-Modified Polymer Concrete

To address the shortfalls of existing varieties of ultra rapid-hardening cement, which is becoming more popular for resurfacing bridge deck overlays, we evaluated the effects of adding metakaoline and a latex polymer to such concrete. The modified cement showed excellent durability, based on its permeability characteristics and resistance to abrasion, repeated freezing and thawing, and scaling, and may prove an effective long-term solution for resurfacing bridge deck overlays.

Evaluation of Crack Control and Permeability of Hydrophilic PVA fiber Reinforced Cement Composite

Plastic shrinkage crack occurs at the exposed surfaces of freshly placed concrete due to consolidation of the concrete mass and rapid evaporation of water from the surface. This so-called shrinkage crack is a major concern for concrete, especially for flat structures such as pavements, slabs for industrial factories and retaining walls. This study has been performed to obtain the plastic shrinkage and the permeability of hydrophilic poly vinyl alcohol(PVA) fiber reinforced mortar and concrete. Test results indicated that PVA fiber reinforced cement composite showed an ability to reduce the total crack area and the maximum crack width (as compared to plain and polypropylene fiber reinforced concrete). Also, according to the permeability test result, it was found that PVA fiber reinforced cement composite was more reducing than polypropylene fiber reinforced cement composite.

Effect of Polyvinyl Alcohol Fiber Volume Fraction on Pullout Behavior of Structural Synthetic Fiber in Hybrid Fiber Reinforced Cement Composites

In this study, the effect of polyvinyl alcohol (PVA) fiber volume fraction on the pullout behavior of structural synthetic fiber in hybrid structural synthetic fiber and PVA fiber cement composites are presented. Pullout behavior of the hybrid fiber cement composites and structural synthetic fiber were determined by dog-bone bond tests. Test results found that the addition of PVA fiber can effectively enhance the structural synthetic fiber cement based composites pullout behavior, especially in fiber interface toughness. Pullout test results of the structural synthetic fiber showed the interface toughness between structural synthetic fiber and PVA fiber reinforced cement composites increases with the volume fraction of PVA fiber. The microstructural observation confirms the incorporation of PVA fiber can effectively enhance the interface toughness mechanism of structural synthetic fiber and PVA fiber reinforced cement composites.

Mechanical Properties and Durability of Latex-Modified Fiber-Reinforced Concrete: A Tunnel Liner Application

This study assessed the mechanical properties and durability of latex-modified fiber-reinforced segment concrete (polyolefin-based macrosynthetic fibers and hybrid fiber-macrosynthetic fiber and polypropylene fiber) for a tunnel liner application. The tested macrosynthetic fiber-reinforced concrete has a better strength than steel fiber-reinforced concrete. The tested concrete with blast furnace slag has a higher chloride ion penetration resistance (less permeable), but its compressive and flexural strengths can be reduced with blast furnace slag content increase. Also, the hybrid fiber-reinforced concrete has higher compressive strength, flexural strength, chloride ion water permeability resistance, impact resistance, and abrasion resistance than the macrosynthetic fiber-reinforced concrete. The modified fiber improved the performance of concrete, and the hybrid fiber was found to control the formation of micro- and macrocracks more effectively. Therefore, overall performance of the hybrid fiber-reinforced concrete was found superior to the other fiber-reinforced concrete mixes tested for this study. The test results also indicated that macrosynthetic fiber could replace the steel fiber as a concrete reinforcement.

Bonding Characteristics of Macro Polypropylene (Pp) Fibre in Pva/Macro Pp Blended Fibre-Reinforced Styrene Butadiene Latex-Modified Cement-Based Composites

The bonding properties of macro polypropylene (PP) fibres in blended fibre-reinforced polymer-modified cement-based composites (BFRPMCCs) containing styrene butadiene (SB) latex were evaluated. A blend of polyvinyl alcohol (PVA) and macro PP fibres was used in the study. The pullout behaviour was investigated using dog-bone test specimens compliant with JCI SF-8. The macro PP fibre was added at 0.45 kg/m3 and the PVA fibre was added at 12.6 kg/m3 to fabricate the BFRPMCCs, and SB latex was added at 0–25 wt% of the cement. The addition of SB latex improved the dispersion of the PVA fibres, increased the pullout resistance of the macro PP fibre embedded in the BFRPMCC, and induced strain hardening in the debonded zone. The maximum bond strength occurred at an SB latex content of 10%, and the maximum interface toughness occurred at an SB latex content of 15%. Microstructural analysis of the macro PP fibre surfaces was carried out following pullout of the fibres embedded in the SB-latex-containing BFRPMCC. The amount of scratches increased with increasing SB latex content until 15%, but then decreased at SB latex contents above 20%, indicating that the bonding of the composite was optimum at a latex content of 15%.

Bond Properties of Glass Fibre-Reinforced Polymer Dowel Bars in Jointed Concrete

Dowel bars installed at the transverse joints of concrete slabs reduce the deflection and stress at the joint edges while transferring the traffic load from one slab to the next. We used draw-out and push-back tests to simulate the movement of a glass fibre-reinforced polymer (GFRP) dowel bar installed in a horizontal linear section of a concrete pavement undergoing repeated shrinkage and expansion movements. The tests were carried out on three different sizes and shapes of dowel bar. The pull-out strength was lower in GFRP dowel bars with an elliptical cross section, which would be a better fit as a load transfer device in concrete pavement. Since they do not restrict shrinkage and expansion of concrete pavement and allows free movement, they would prevent destruction of a concrete slab by curling.