Abstract
In this paper iron tailing sand (TS) are used as aggerate to develop ultra high-performance concrete (UHPC). The mix proportion of UHPC is designed and TS were added by 25%, 50%, 75% and 100% (wt.%, i.e., weight percentage) to replace natural river sand. Firstly, the influence of TS on the slurry behavior was carried out. The experimental result indicates that with the continuously increasing content of TS, the workability of slurry decreases, while the air content increases. Considering the workability, the optimal replacing dosage of TS should be less than 50%. Then, tests for the hardened specimens were taken. The compressive behavior and micro-porosity deteriorate with increasing content of TS, and the compressive strength had a positive linear relationship with the workability, which indicated that the decline the compressive behavior is mainly due to the loss of flowability. Finally, autogenous shrinkages of UHPC with different TS dosage were also tested. At the same time, the micro-structure of specimens was discussed, which was deteriorate with the increasing dosage of TS. Therefore, comprehensively considering the compressive behavior, micro-structure and shrinkage behavior, as much as 50% of the aggregate could be replaced by TS when developing UHPC.
Highlights
Published: 25 August 2021Ultra-high-performance concrete (UHPC) is a new type of cement-based material with high mechanical properties [1,2,3]
In the case of a fixed volume of cement paste, the decrease in packing density leads to a decrease in paste film thickness (PFT), which means that more cement paste is needed to achieve the river sand (RS) is similar (150–300 μm), the width of the particle size distribution of tailing sand (TS) is significantly narrow than that of RS, which is the main reason for the decrease in packing density [40]
In the case of a fixed volume of cement paste, the decrease in packing density leads to a decrease in PFT, which means that more cement paste is needed to achieve the same workability [38]; at the same time, according to the excess layer thickness theory [41], the highwater absorption of TS leads to an increase in the content of onset of flow water [42]
Summary
Ultra-high-performance concrete (UHPC) is a new type of cement-based material with high mechanical properties (compressive strength and flexural strength of over 120 MPa and 20 MPa, respectively) [1,2,3]. Considering that the larger particle size aggregate (such as gravel) is more likely to cause the heterogeneity of the mixture and pores between particles, only fine materials, including cementitious binder and fine silica sand, are usually used to improve the homogeneity and compactness, in order to get a great mechanical and durability properties [7,8,9,10]. The shape and angularity of IT show great effect on the flowability and mechanical behavior of concrete [32], so it is necessary to discuss the effect of iron tailings particle morphology on UHPC performance In this paper natural river sand (RS).
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