Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: strength model

Sortuj według:

Ogranicz wyniki do:

The flexural behaviors and mechanism of wollastonite microfiber modified ultra-high performance concrete with steel fiber from micro to macro scale

Zeng Deming, Cao Mingli

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 1

art. no. e32, 2022

Wollastonite microfiber (WF) is a naturally occurring calcium silicate (CaSiO3) produced in fibrous form and often used in ceramic industry as a cheap and valuable mineral. It is tried to be applied in ultra-high performance concrete (UHPC) in this study with expectation to improve the flexural performance and compensate for the deficiencies of steel fiber in enhancing UHPC from micro scale. The effects of WF on the flexural behaviors of UHPC with or without steel fibers were explored. The bonding behaviors of steel fiber in WF-modified ultra-high performance concrete (WFMUHPC) under different curing conditions were researched combined with single fiber pull-out tests. The results showed that WFs could significantly resist and delay the formation of microcracks in UHPC. When WFs were added to UHPC with steel fiber, the flexural properties of concrete were significantly improved from micro to macro scale. Accelerated curing contributed to the flexural strengths but deteriorate the toughness of WFMUHPC with steel fiber. The presented load–deflection curves proved that WFs had a significant improvement of first crack load and there were post-peak curve gaps because of the reinforcing effect of WFs on the frictional sliding behavior of steel fiber. The results of X-ray diffraction and scanning electron microscope showed that WFs had the bridging and filling effect and improved the interfacial transition zone between WFs and matrix. Meanwhile, the combined effect between WFs and high temperature that WFs provided sites for hydration products from cement particles and active minerals including silica fume and fly ash further improved the flexural behaviors. Moreover, a flexural strength model established could accurately describe the reinforcing effect of WFs on this particular UHPC and was expected to provide guidance for practical engineering applications.

Failure characteristics and strength model of composite rock samples in contact zone under compression

Wang Qihu, Wang Jie, Ye Yicheng, Jiang Wei, Yao Nan

Archives of Mining Sciences

2020

Vol. 65, no. 2

347--361

Significant differences in the physical and mechanical properties exist between the rock masses on two sides of an ore-rock contact zone, which the production tunnels of an underground mine must pass through. Compared with a single rock mass, the mechanical behavior of the contact zone composite rock comprising two types of rock is more complex. In order to predict the overall strength of the composite rock with different contact angles, iron ore-marble composite rock sample uniaxial compression tests were conducted. The results showed that composite rock samples with different contact angles failed in two different modes under compression. The strengths of the composite rock samples were lower than those of both the pure iron ore samples and pure marble samples, and were also related to the contact angle. According to the stress-strain relationship of the contact surface in the composite rock sample, there were constraint stresses on the contact surface between the two types of rock medium in the composite rock samples. This stress state could reveal the effect of the constraint stress in the composite rock samples with different contact angles on their strengths. Based on the Mohr-Coulomb criterion, a strength model of the composite rock considering the constraint stress on the contact surface was constructed, which could provide a theoretical basis for stability researches and designs of contact zone tunnels.