|Table of Contents|

Effect of Mixed Nano-SiO2 and Fly Ash on Properties of Recycled Aggregate Concrete(PDF)

《建筑科学与工程学报》[ISSN:1673-2049/CN:61-1442/TU]

Issue:
2020年01期
Page:
26-32
Research Field:
Publishing date:

Info

Title:
Effect of Mixed Nano-SiO2 and Fly Ash on Properties of Recycled Aggregate Concrete
Author(s):
XIAO Jian-zhuang;  CHEN Xiang-lei;  LI Biao;  XUE Song-tao;  DUAN Zhen-hua
(College of Civil Engineering, Tongji University, Shanghai 200092, China)
Keywords:
recycled aggregate concrete;  old mortar;  Nano-SiO2;  fly ash;  mass substitution method
PACS:
TU973.2
DOI:
10.19815/j.jace.2019.03027
Abstract:
The effects of fly ash and Nano-SiO2 on the workability, compressive strength(7, 28, 90 d), flexural strength(28 d)and splitting tensile strength(28 d)of recycled aggregate concrete(RAC)were studied by using mass substitution method. When casting the sample, a new two-stage mixing method was proposed based on the existing mixing method. The recycled coarse aggregate, Nano-SiO2 and additional water were stirred, so that some Nano-SiO2 particles could be absorbed by the recycled coarse aggregate to fill the pores and micro cracks of the old mortar. The results show that the slump of RAC decreases with the increase of Nano-SiO2 content, and the reduction of slump caused by Nano-SiO2 can be alleviated with the addition of fly ash. Under the condition of the same fly ash content, the compressive strength, flexural strength and splitting tensile strength of RAC grow up with the increased content of Nano-SiO2. With the combination of Nano-SiO2 and fly ash, not only the early strength reduction of RAC caused by fly ash can be compensated, but also the compressive strength of RAC at the age of 90 d is significantly higher than that of RAC adding the two materials respectively. When the mass fraction of Nano-SiO2 content is 1%, the compressive strength of recycled concrete at the age of 90 d increases by 3.0 MPa compared with RAC. The flexural strength and splitting tensile strength of RAC are significantly improved by adding both Nano-SiO2 and fly ash. The flexural strength of S2F30 is 24.17% higher than that of F30, and the splitting tensile strength of S2F30 is 12.68% higher than that of RAC mixed with Nano-SiO2 or fly ash alone.

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Last Update: 2020-01-13