Effects of increased aggregate size on the mechanical and rheological properties of RPC

Title: Effects of increased aggregate size on the mechanical and rheological properties of RPC
Author(s): A. Cwirzen, V. Penttala
Paper category : conference
Book title: 2nd International RILEM Symposium on Advances in Concrete through Science and Engineering
Editor(s): J. Marchand, B. Bissonnette, R. Gagné, M. Jolin and F. Paradis
Print-ISBN: 2-35158-003-6
e-ISBN: 2351580028
Publisher: RILEM Publications SARL
Publication year: 2006
Nb references: 12
Language: English

Abstract: The development of Reactive Powder Concrete (RPC) was based on the application of the theory of maximum packing density, low water to binder ratio, high dosage of silica fume and decrease of the maximum aggregates diameter to 600 µm. The obtained material is in principle a mortar characterized by ultra high strength and fluid-like consistency. This paper presents the results of the research on the incorporation of larger aggregates into RPC while sustaining its ultrahigh strength and very good rheological properties. The larger aggregates had diameters from 2 to 10 mm. The used aggregate mineral types were: basalt, granite, diabase, gabbro and bauxite. The concretes were produced with and without short steel fibres. The water to binder ratio varied from 0.17 to 0.2, the mixes contained 25% of amorphous silica and 20% of fine quartz filler of the portland cement by weight. The proportion by weight of the coarse aggregates to cement varied from 1/1 to 2/1. The curing procedure included water curing at 20°C and steam curing at 90°C. The results showed that it was feasible to obtain concretes having only slightly lower flowability and nearly the same mechanical properties compared to ordinary RPC. Furthermore, the RPC with larger aggregates needed shorter mixing times, had better distribution of the fillers, slightly lower air-content and smaller variations in the mechanical properties between samples produced from the same batch. The aggregates giving the best results were bauxite, basalt and diabase. The addition of steel fibres improved the strength properties. The highest compressive strength obtained by heat-treated concretes with steel fibres exceeded 200 MPa. In the case of non heat-treated concretes compressive strength values exceeded 160 MPa. The flexural strength reached a maximum value of 15 MPa in concretes with coarse aggregates and 36 MPa for regular RPC. Scanning electron microscope studies did not reveal any significant differences in the microstructure and microchemistry of RPC having larger aggregates in comparison with ordinary RPC. No visible interfacial transition zones were found between aggregate and cement paste or the steel fibers and binder matrix. The porosity tended to be finer in the case of heat-treated concretes and the presence of coarse aggregates or steel fibres did not appear to alter the microstructure of the matrix.

Online publication: 2006-08-02
Classification: 3.2 Theme 2: From Fresh to Hardened Concrete
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580028.049