Influence of Silica Fume on Mechanical Properties and Microhardness of Interfacial Transition Zone of Different Recycled Aggregate Concretes

2021 ◽  
Vol 10 (1) ◽  
pp. 20210011
Author(s):  
Suhas Vijay Patil ◽  
K. Balakrishna Rao ◽  
Gopinatha Nayak
Keyword(s):  
Mechanical Properties ◽  
Transition Zone ◽  
Silica Fume ◽  
Interfacial Transition Zone ◽  
Recycled Aggregate

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.

The Influence on High-Temperature Mechanical Properties of Hybrid-Fiber-Reinforced High-Performance Concrete and Microscopic Analysis

2012 ◽  
Vol 226-228 ◽  
pp. 1709-1713
Author(s):  
Lan Yan ◽  
Y.M. Xing ◽  
Ji Jun Li
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Transition Zone ◽  
High Performance ◽  
Room Temperature ◽  
Steel Fiber ◽  
High Performance Concrete ◽  
Interfacial Transition Zone ◽  
Hybrid Fiber ◽  
High Temperature Mechanical Properties

This paper investigated the high temperature mechanical properties of the hybrid fiber reinforced high performance concrete (HFHPC) and normal concrete (NC) .After being subjected to different elevated heating temperatures, two kinds of concretes have been tested for the compressive strength, splitting tensile strength and flexural strength of test specimen at room temperature and 200 °C,400 °C,600 °C,800 °C.Microstructure changes of concrete were also observed by using Scanning Electron Microscopy (SEM) after high temperature. The results show that the hybrid fiber can significantly increase mechanical properties of the concrete at room temperature and high temperature. SEM and XRD analysis shows that there is a permeable diffusion layer in the steel fiber surface because of solid state reaction in the Interfacial Transition Zone of steel fiber and concrete. This permeable diffusion layer is white, bright, serrated and mainly consist of FeSi2 and the complex hydrated calcium silicate. The compounds of this layer change the Interfacial Transition Zone structure, enhance bonding capacity of the steel fiber and matrix, and increase the high temperature mechanical properties of concrete.

scholarly journals Effect propylene glycol as a quality improvers for Portland and Portland-limestone cements

2019 ◽  
Vol 4 (1) ◽  
pp. 1-7
Author(s):  
Hashem FS ◽  
Eisa E Hekal ◽  
Abdel M Wahab
Keyword(s):  
Mechanical Properties ◽  
Propylene Glycol ◽  
Transition Zone ◽  
Cement Paste ◽  
Cement Hydration ◽  
Interfacial Transition Zone ◽  
Setting Times ◽  
Sand Particles

The performance of propylene glycol (PG) on the grindability, setting and hardening of Portland (OPC) and Portland-Limestone cements (PLC) was studied. Propylene glycol was added to OPC clinker with percentage ratios; 0, 0.03, 0.04 and 0.05 wt.% of the OPC clinker. PLC was made by replacing 5 and 10 wt. % of OPC with limestone. PG offers better grinding aid performance with higher Blaine areas. Besides, presence of PG shows higher water of consistency and lower initial and final setting times. The mechanical properties of mortar specimens made from OPC and PLC admixed with PG were improved especially in the first 7 days. This explained due to increase in the cement fineness which leads to an increase in the degree of cement hydration, as well as to improvement in the interfacial transition zone between the cement paste and sand particles, thus resulting in an enhancement in the strength. DTA and SEM results confirmed the improved properties achieved due to admixing OPC or PLC with PG.

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