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Joseph Assaad
Rheology and stability of lightweight polymer-modified self-consolidating concrete

Appl. Rheol. 27:2 (2017) 25807 (11 pages)

Limited information exists in literature regarding the effect of styrene-butadiene rubber (SBR) latexes on rheology and stability of lightweight self-consolidating concrete (LWSCC) intended for repair and precast works. Four series of LWSCC mixtures prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project: The free water was adjusted to secure compressive strength of 40 ± 3.5 MPa. The slump flow remained fixed at 700 ± 25 mm, while unit weight varied from 1790 to 2280 kg/m3. Test results have shown that SBR additions lead to reduced concrete flow rate and passing ability. However, improved static stability such as bleeding, segregation, and floating of LWA. The rheological properties including yield stress and plastic viscosity increased for higher SBR additions, reflecting increased cohesiveness resulting from coalescence of water-soluble latexes and binding of cementitious matrix. Three categories of LWSCC classes specified in the European Guidelines were proposed with respect to rheological properties. A Ψ-factor was developed along with series of regression models to predict the combined effect of free water, viscosity-modifier, LWA, and SBR on rheology and stability of polymermodified LWSCC.

Cite this publication as follows:
Assaad J: Rheology and stability of lightweight polymer-modified self-consolidating concrete , Appl. Rheol. 27 (2017) 25807.

Joseph Assaad, Yehia Daou
Use of the equivalent mortar phase to assess thixotropy of fresh SCC - Prediction of interfacial bond strength between successive placement lifts

Appl. Rheol. 26:4 (2016) 42759 (10 pages)

Self-consolidating concrete (SCC) is very sensitive to delays or stoppages between successive lifts during casting, especially given that vibration is prohibited with this highly flowable type of concrete. The investigation reported in this paper seeks to quantify the effect of mixture proportioning on thixotropy along with the resulting effect on interfacial bond strength of hardened material that could result from successive lifts. The suitability of the equivalent mortar phase to simplify testing protocols and appropriately predict SCC properties was given particular attention; the concrete-equivalent-mortar (CEM) mixtures are derived from SCC by eliminating the coarse aggregate fraction and replacing it by an equivalent quantity of sand having equal surface area. Tests results have shown that SCC and CEM mixtures prepared with combinations of increased cement content, silica fume, and/or viscosity-modifier led to higher levels of thixotropy. Yet, the responses determined using SCC were higher by around 1.6 times than those of CEM, given the differences in unit weight and air content between both materials. Good correlations are established between thixotropy and interfacial bond strengths of SCC and CEM mixtures. Key words:

Cite this publication as follows:
Assaad J, Daou Y: Use of the equivalent mortar phase to assess thixotropy of fresh SCC - Prediction of interfacial bond strength between successive placement lifts, Appl. Rheol. 26 (2016) 42759.


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