scholarly journals The Application of Berkovich nanoindenter to the study of interfacial transition zone in concretes containing fly-ash

2014 ◽  
Vol 13 (2) ◽  
pp. 085-092
Author(s):  
Grzegorz Golewski
Keyword(s):  
Fly Ash ◽  
Grain Boundary ◽  
Transition Zone ◽  
Interfacial Transition Zone ◽  
Berkovich Indenter ◽  
Fly Ashes ◽  
Transition Zones ◽  
Coarse Aggregates ◽  
Percent Increase ◽  
Technique Analysis

The paper presents the results of nanohardness (HB) in the Interfacial Transition Zones (ITZ) of concretes with the addition of 0, 20 and 30% siliceous fly ashes (FA). A compact platform CSM Instruments was used in the testing. An area in the ITZ of coarse aggregates with paste was analysed in the five measurement points during the experiments, i.e. at the distance of: 5, 25, 50, 100 and 150 µm from the grain boundary. The indents in concrete were create by Berkovich indenter using DSI technique. Analysis of the results revealed that the 20% additive of FA causes a few percent increase in nanohardness, while 30% FA additive leads to between ten and twenty percent drop of HB. On the basis of nanohardness distributions in particular concretes, it was found that the most heterogeneous one is the ITZ zone within the distance of 25µm from the aggregate grain.

scholarly journals Experimental study on the compressive strength, damping and interfacial transition zone properties of modified recycled aggregate concrete

2019 ◽  
Vol 6 (12) ◽  
pp. 190813
Author(s):  
Bin Lei ◽  
Huajian Liu ◽  
Zhimin Yao ◽  
Zhuo Tang
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Transition Zone ◽  
Loss Factor ◽  
Steel Fibre ◽  
Interfacial Transition Zone ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Damping Properties ◽  
Aggregate Concrete

At present, many modification methods have been proposed to improve the performance of recycled aggregate concrete (RAC). In this study, tests on the compressive strength and damping properties of modified RAC with the addition of different proportions of recycled coarse aggregate (RCA) (0, 50, 100%), rubber powder (10, 15, 20%), steel fibre (5, 7.5, 10%) and fly ash (15, 20, 5%) are carried out. To elucidate the effect of the modification method on the interfacial transition zone (ITZ) performance of RAC, model ITZ specimens are used for push-out tests. The results show that when the replacement rate of RCA reaches 100%, the loss factor of the RAC is 6.0% higher than that of natural aggregate concrete; however, the compressive strength of the RAC decreases by 22.6%. With the addition of 20% rubber powder, the damping capacity of the modified RAC increases by 213.7%, while the compressive strength of the modified RAC decreases by 47.5%. However, with the addition of steel fibre and fly ash, both the compressive strength and loss factor of the RAC specimens increase. With a steel fibre content of 10 wt%, the compressive strength and loss factor of the RAC increase by 21.9% and 15.2%, respectively. With a fly ash content of 25 wt%, the compressive strength and loss factor of the RAC increase by 8.6% and 6.9%, respectively. This demonstrates that steel fibre and fly ash are effective in improving both the damping properties and compressive strength of RAC, and steel fibre is more effective than fly ash. Two methods were used for modification of the RAC: reinforcing the RCA through impregnation with a 0.5% polyvinyl alcohol (PVA) emulsion and nano-SiO 2 solution, and strengthening the RAC integrally through the addition of fly ash as an admixture. Both of these techniques can improve the ITZ bond strength between the RAC and new mortar. Replacing 10% of the cement with fly ash in the new mortar is shown to be the best method to improve the ITZ strength.

Increase of bond strength at interfacial transition zone by the use of fly ash

2000 ◽  
Vol 30 (2) ◽  
pp. 253-258 ◽  
Author(s):  
Masao Kuroda ◽  
Tomohide Watanabe ◽  
Nariaki Terashi
Keyword(s):  
Fly Ash ◽  
Bond Strength ◽  
Transition Zone ◽  
Interfacial Transition Zone

Strengthening Effect of Graphene Oxide on Mechanical Properties of Interface Transition Zone of Recycled Concrete

2020 ◽  
Vol 852 ◽  
pp. 49-58
Author(s):  
Kai Guo ◽  
Jing Hai Zhou ◽  
Ming Liu ◽  
Lin Liu
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
Elastic Modulus ◽  
Transition Zone ◽  
Structural Characteristics ◽  
Interfacial Transition Zone ◽  
Recycled Concrete ◽  
Strengthening Effect ◽  
Transition Zones ◽  
The Mean

The micro-mechanical properties and micro-structural characteristics of the interfacial transition zones of recycled concrete with graphene oxide were studied by using nanoindentor. The results showed that the average elastic modulus and width of the interfacial transition zone of recycled concrete with graphene oxide between new paste matrix and natural aggregate were about 20GPa and 30-35μm, respectively; The mean elastic modulus and transition zone width of the interfacial transition zone between new paste matrix and old paste matrix was about 35GPa and 25-30μm, respectively. By analyzing and calculating the probability distribution of hydration products, it was found that the graphene oxide template increased the proportion of calcium silicate hydrate in the hydrate and enhanced the content of calcium hydroxide crystal group. Compared with ordinary recycled concrete, the elastic modulus distribution in the interfacial transition zone was more uniform and the microstructure was more stable. It can be concluded that graphene oxide can enhance the mechanical properties and microstructure of the interfacial transition zone of recycled concrete so as to improve the macroscopic mechanical properties of recycled concrete.

Interfacial Zone Percolation in Concrete: Effects of Interfacial Zone Thickness and Aggregate Shape

1994 ◽  
Vol 370 ◽  
Author(s):  
D.P. Bentz ◽  
J.T.G. Hwang ◽  
C. Hagwood ◽  
E.J. Garboczi ◽  
K.A. Snyder ◽  
...  
Keyword(s):  
Transition Zone ◽  
High Performance ◽  
Dynamic Range ◽  
Hard Core ◽  
Concrete Specimen ◽  
Interfacial Transition Zone ◽  
Interfacial Zone ◽  
Transition Zones ◽  
Soft Shell ◽  
Aggregate Shape

AbstractPreviously, a hard core/soft shell computer model was developed to simulate the overlap and percolation of the interfacial transition zones surrounding each aggregate in a mortar or concrete. The aggregate particles were modelled as spheres with a size distribution representative of a real mortar or concrete specimen. Here, the model has been extended to investigate the effects of aggregate shape on interfacial transition zone percolation, by modelling the aggregates as hard ellipsoids, which gives a dynamic range of shapes from plates to spheres, to fibers. For high performance concretes, the interfacial transition zone thickness will generally be reduced, which will also affect their percolation properties. This paper presents results from a study of the effects of interfacial transition zone thickness and aggregate shape on these percolation characteristics.

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