• Geomechanics and Engineering
• /
• v.16 no.4
• /
• pp.375-384
• /
• 2018

Unconfined compressive strength (UCS) of high plasticity clayey soil mixed with 5 and 10 % of Portland cement and four chemical agents such as sodium hexametaphosphate, aluminum sulfate, sodium carbonate, and sodium silicate with 0, 5, 10, and 20% concentrations was comparatively evaluated. The individual and combined effects of the cement and chemical agents on the UCS of the soil mixture were investigated. The strength of the soil-cement mixture generally increases with increasing the cement content. However, if the chemical agent is added to the mixture, the strength of the cement-chemical agent-soil mixture tends to vary depending on the type and the amount of the chemical agent. At low concentrations of 5% of aluminum sulfate and 5% and 10% of sodium carbonate, the average UCS of the cement-chemical agent-soil mixture slightly increased compared to pure clay due to increasing the flocculation of the clay in the mixture. However, at high concentrations (20%) of all chemical agents, the UCS significantly decreased compared to the pure clay and clay-cement mixtures. In the case of high cement content, the rate of UCS reduction is the highest among all cement-chemical agent-soil mixtures, which is more than three times higher in comparison to the soil-chemical agent mixtures without cement. Therefore, in the mixture with high cement (> 10%), the reduction of the USC is very sensitive when the chemical agent is added.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.401-404
• /
• 2008

This study exploited the design of mixture proportion for the high strength concrete to establish the method of the quality control and high strength ready-mixed concrete for the application to the construction filed systematically how to output the estimated formula which could forecast mixture proportion for the high strength concrete classed 40${\sim}$60MPa through a experiment. It might contribute for systematic establishment of the method of the quality control and high strength ready-mixed concrete because it was possessed of the function of common data though a server, preservation and output of data, and estimation for the design of mixture proportion for the high strength concrete due to the experimental result, and Visual Basic, MS-SQL were used. Simply, it was produced corresponding to the condition of a laboratory, so it could be fundamental data for the design of mixture proportion for the high strength concrete. If upgrade is enforced with mixture proportion data of the each factory after then, it may contribute to the stability on quality and manufacture of high strength ready-mixed concrete to agree with the properties of each factory.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.166-171
• /
• 1999

Porous concrete contains about 20% voids after compaction so that it has high permeability which secures underground water resources. It is introduced in domestic since 1980' but has problems such as lack of optimized mixture, low strength and durability, efflorescence and other defects, etc. In this study, several mixture were designed based upon site works, and test specimens for compressive strength, tensile strength, flexual strength and permeability, were prepared in a laboratory. After 28days of curing, every performance was tested to find optimum mixture. The mixture was proposed as 380kg/㎥ of unit cement weight, 32% of W/C 10∼13mm of aggregate.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.583-586
• /
• 2005

Strength of concrete is very important factor in design and quality management and may represent overall quality of concrete. Such strength of concrete may differ depending on amount of cement mixed, water and fine aggregate ratio. Classic concrete products have been produced mainly with ordinary portland cement(hereinafter 'cement'), water and fine aggregate as shown above, but various additives and mixture materials have been used for concrete manufacturing, along with development of high functional concrete and diversification of structures. Various kinds of chemical mixtures agents and mixture materials have been used as it requires concretes with other features which cannot be solved with existing materials only, such as high strength, high flexibility and no-separation in the water. Such addition of various mixture agents may cause change in cement hydrate, affecting strength. Hydration of cement is the process of producing potassium hydroxide, C-S-H, C-A-H and Ettringite, while causing heat generation reaction after it is mixed with water, and generation amounts of such hydrates play lots of roles in condensation and hardening. This study aims to analyze its strength and features with hydrates by making specimen according to curing temperature, types of mixture agent, mixing ratio and ages and by analyzing such hydrates in order to analyze role of cement hydrate on early strength of concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.11a
• /
• pp.55-56
• /
• 2014

In this research, the effect of types of aggregate and SP on fundamental properties of ultra-high performance concrete of 80 MPa of compressive strength was evaluated to provide solution for high cost of ultra-high performance concrete. As the results of a series of tests, the mixture using limestone and silica aggregates showed improved workability rather than the mixture using granite aggregate. For compressive strength of UHPC, the UHPC mixtures using limestone and silica aggregates showed higher compressive strength than the UHPC mixture using granite aggregate while all mixtures satisfied target compressive range.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2015.11a
• /
• pp.19-20
• /
• 2015

In this research, by examining the influence that high quality fine aggregate and low quality fine aggregate have on the strength of concrete through tests, the manifest strength of concrete according to high quality fine aggregate was reviewed. The results showed that compared to low quality fine aggregate usage mixture, the unit volume to achieve the same liquidity decreased and accordingly the W/B also decreased therefore increasing the strength of concrete, and as high quality fine aggregate was used, it is determined that there can be improvements to the economically feasibility of usage mixture and improvement in durability etc.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.11a
• /
• pp.127-128
• /
• 2014

The aim of this research is selecting an economical aggregate type for ultra-high strength concrete with 80 to 120 MPa of compressive strength. As the tests, the effect of water-to-binder ratios and types of aggregate on autogenous shrinkage of ultra-high strength concrete were evaluated. as the results of a series of tests performed, the slump flow was satisfied the target range of 600 ± 100 mm, and the concrete mixture with RLA showed higher elastic modulus than the other cases. For the autogenous shrinkage preventing performance, in the case of water-to-binder ratio of 15, and 20 %, the mixture with BA showed slightly improved autogenous shrinkage reducing effect than the mixture with RLA while the mixture with RLA showed better performance at 25 % of water-to-binder ratio. Therefore, based on the tests results of slump flow, elastic modulus, and autogenous shrinkage, the RLA is considered as a better aggregate type for this purpose.

• Advances in concrete construction
• /
• v.11 no.2
• /
• pp.99-109
• /
• 2021

Slag blended concrete is widely used as a mineral admixture in the modern concrete industry. This study shows an optimization process that determines the optimal mixture of air-entrained slag blended concrete considering carbonation durability, frost durability, CO2 emission, and materials cost. First, the aim of optimization is set as total cost, which equals material cost plus CO2 emission cost. The constraints of optimization consist of strength, workability, carbonation durability with climate change, frost durability, range of components and component ratio, and absolute volume. A genetic algorithm is used to determine optimal mixtures considering aim function and various constraints. Second, mixture design examples are shown considering four different cases, namely, mixtures without considering carbonation (Case 1), mixtures considering carbonation (Case 2), mixtures considering carbonation coupled with climate change (Case 3), and mixtures of high strength concrete (Case 4). The results show that the carbonization is the controlling factor of the mixture design of the concrete with ordinary strength (the designed strength is 30MPa). To meet the challenge of climate change, stronger concrete must be used. For high-strength slag blended concrete (design strength is 55MPa), strength is the control factor of mixture design.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.11
• /
• pp.2374-2382
• /
• 2002

Aluminum alloy/aramid fiber reinforced plastic(Al/AFRP) laminates consists of high strength metal(A15052) and laminated aramid fiber with structural adhesive bond. The mixture ratio effect of epoxy resin curing agent accelerator on the tensile strength and T-peel strength characteristic in Al AFRP laminates were investigated in this study. The epoxy. diglycidylether of bisphenol A(DCEBA), It'as cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test , five kinds of Al/AFRP laminates were named as Al/AFRP(1) and three others of Al/AFRP laminates were named as Al/AFRP(2). The comparison of tensile strength and T-peel strength with variation of resin mixture ratio were studied. Respectively. Al/AFRP(1) and Al/AFRP(2) indicated approximately 6.0 times and 7.0 times more improved maximum tensile strength in comparison with those of monolithic A15052. Al/AFRP(2) indicated approximately 1.5 times more impoved maximum T-peel strengths in comparison with those of Al/AFRP(1). As results. Al/AFRP(2) turned out to have more effective characteristics on the tensile strength and T-peel strength than those of Al/AFRP(1).

• Structural Engineering and Mechanics
• /
• v.85 no.1
• /
• pp.29-53
• /
• 2023

High-strength shielding concrete against gamma radiation is a priority for many medical and industrial facilities. This paper aimed to investigate the gamma-ray shielding properties of high-strength hematite concrete mixed with silica fume (SF) with nanoparticles of lead dioxide (PbO₂), tungsten oxide (WO₃), and bismuth oxide (Bi₂O₃). The effect of mixing steel fibres with the aforementioned binders was also investigated. The reference mixture was prepared for high-strength concrete (HSCC) containing 100% hematite coarse and fine aggregate. Thirteen mixtures containing 5% SF and nanoparticles of PbO₂, WO₃, and Bi₂O₃ (2%, 5%, and 7% of the cement mass, respectively) were prepared. Steel fibres were added at a volume ratio of 0.28% of the volume of concrete with 5% of nanoparticles. The slump test was conducted to workability of fresh concrete Unit weight water permeability, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity tests were conducted to assess concrete's engineering properties at 28 days. Gamma-ray radiation of 137Cs emits photons with an energy of 662 keV, and that of 60Co emits two photons with energies of 1173 and 1332 keV were applied on concrete specimens to assess radiation shielding properties. Nanoparticles partially replacing cement reduced slump in workability of fresh concrete. The compressive strength of mixtures, including nanoparticles was shown to be greater, achieving 94.5 MPa for the mixture consisting of 7.5 PbO2. In contrast, the mixture (5PbO₂-F) containing steel fibres achieved the highest values for splitting tensile, flexural strength, and modulus of elasticity (11.71, 15.97, and 42,840 MPa, respectively). High-strength shielded concrete (7.5PbO2) showed the best radiation protection. It also showed the minimum concrete thickness required to prevent the transmission of radiation.