No abstract

In recent years, the construction industry has been faced with a decline in the availability of natural sand due to the growth of the industry. On the other hand, the metal casting industries are being forced to find ways to safely dispose of waste foundry sand (FS). With the aim of resolving both of these issues, an investigation was carried out on the reuse of waste FS as an alternative material to natural sand in concrete production, satisfied with relevant international standards. The physical and chemical properties of the FS were addressed. The influence of FS on the behaviour of concrete was evaluated through strength and durability properties. The test results revealed that compared to the concrete mixtures with a substitution rate of 30%, the control mixture had a strength value that was only 6.3% higher, and this enhancement is not particularly high. In a similar manner, the durability properties of the concrete mixtures containing FS up to 30% were relatively close to those of control mixture. From the test results, it is suggested that FS with a substitution rate of up to 30% can be effectively used in concrete production without affecting the strength and durability properties of the concrete.

Abstract:The development of cracking in concrete structures leads to significant permeability and to durability problems as a result. Approaches to controlling crack development and crack width in concrete structures have been widely debated. Recently, it was recognized that a high-performance fiber-reinforced cement composite (HPFRCC) provides a possible solution to this inherent problem of cracking by smearing one or several dominant cracks into many distributed microcracks under tensile loading conditions. However, the chloride permeability of HPFRCC under compressive loading conditions is not yet fully understood. Therefore, the goal of the present study is to explore the chloride diffusion characteristics of HPFRCC damaged by compressive loads. The chloride diffusivity of HPFRCC is measured after being subjected to various repeated loads. The results show that the residual axial strain, lateral strain and specific crack area of HPFRCC specimens increase with an increase in the damage induced by repeated loads. However, the chloride diffusion coefficient increases only up to 1.5-times, whereas the specific crack area increases up to 3-times with an increase in damage. Although HPFRCC shows smeared distributed cracks in tensile loads, a significant reduction in the diffusion coefficient of HPFRCC is not obtained compared to plain concrete when the cyclic compressive load is applied below 85% of the strength. OPEN ACCESSMaterials 2014, 7 5803

No abstract

In this study, the chloride resistant properties of concrete with MBC (marine blended cement) were evaluated by an accelerated corrosion test of reinforced concrete. The half-cell potential measurements indicated that the chloride resistance of MBC concrete is approximately 32% larger than that of TBC (ternary blended cement) concrete. As for the reinforcement corrosion area, while the TBC specimens exhibited 5.32-6.11% corrosion at the final 40th cycle, the MBC specimens did not show any sign of steel corrosion. The chloride penetration depth of the MBC specimens was approximately 41-79% smaller than that of the MBC specimens.

This paper presents the results of an experimental study on the effect of limestone powder on the compressive strength, tensile behavior, and micromechanical parameters of a highly ductile cement composite incorporating limestone powder. Four mixtures were determined according to the replacement ratio of cement with limestone powder. A series of experiments including compressive strength, uniaxial tension, single fiber pullout, and matrix toughness tests were performed. Test results showed that the strength (compressive, initial cracking, and tensile strength) decreased, and that the tensile strain capacity increased, with an increase of the replacement ratio of cement with limestone powder. Micromechanical tests and analysis supported the uniaxial tension test result.

No abstract

A basic study is performed on the application of highly ductile SHCC(Strain Hardening Cementitious Composites) to precast method. A special focus was placed on applying class C fly ash with a high CaO content to secure early-age strength of the steam cured SHCC. The flexural strength of the SHCC panels dependent on fly ash type and varied curing methods were evaluated. The results showed that class C fly ash could enhance the flexural strength of 1 day-old steam cured SHCC panels. Additionally, 1 day-old steam cured specimens produced with class C fly ash exhibited up to 58% of the flexural strength of 28 day-old wet cured specimens produced with class F fly ash.