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Levent Selçuk,H. Süleyman Gökçe 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.6
The point load strength (Is(50)) is an alternative mechanical parameter to predict the compressive strength of concrete. The scope of this investigation is to develop an empirical equation relating the point load strength and compressive strength of concrete. In this context, crushed limestone aggregates at two different strength levels were used in concrete mixture. Point load strength and compressive strength tests on concrete specimens which had 6 different compressive strengths were performed for each limestone aggregate. A series of regression analyses was applied using any general statistical package to evaluate the ratio of point load strength test to cube compressive strength of concrete, (Is(50)/fcu). The accuracy and reliability of the equation in this investigation was assessed by means of the Mean Absolute Percent Error (MAPE). The relative error can be considered reasonably well for the empirical relationship. The ratio of Is(50)/fcu was also verified by a large database collected from previous studies. The proposed equation is quite compatible with the database. Furthermore, the ratio of Is(50)/fcu indicates significant material property of concrete and defines the material constant in strength criterions. It can be used to estimate the axial compressive strength of concrete under confining stress without performing triaxial tests, considered Hoek-Brown and Johnson empirical failure criterions.
H. S. Gökçe,N. Öksüzer,H. A. Kamiloğlu,M. Eyüboğlu,F. Yılmaz 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7
Foam concrete has recently become a key construction material in terms of meeting thespecial needs of modern engineering applications such as thermal insulation, absorption ofstatic and dynamic loads. In this study, the effect of polypropylene fiber content and variousuni- and tri-axial compression loads on the toughness response of polypropylene fiberreinforcedfoam concrete was investigated. Up to a certain strain level (0.1 mm/mm), theultimate compression stress of specimens under uni- and tri-axial loading increased fromabout 1 MPa to 16 MPa with the increased target densities of foam concrete. There was astrain-hardening capability of low-density foam concrete while the specimens failed by strainsofteningin the high-density series. The optimum fiber amounts were found to be 3.9%,4.6%, and 6.4% for low, medium, and high target densities of foam concrete, respectively. Atlow-density series, the bubbles were observed to be relatively bigger and mostly merged witheach other. A reduction in foam content (vice versa, increasing target density of mixture) andthe presence of fiber resulted in smaller pore size and a more homogenous distribution ofthem in the matrix. In conclusion, the desired pore structure and efficient bridging of fibers inthe matrix allowed the production of favorable foam concrete with higher toughness.