Effective low-energy mixing procedure to develop high-fluidity cementitious pastes

Abstract

Preparing a high fluidity paste is a major step in ultra-high performance concrete (UHPC) development with respect to its self-compacting ability as well as its ultra-high strength. In this regard, some experiments have been carried out in order to study various superplasticizer (SP) addition methods and times. Among these procedures, stepwise and delayed methods seem to be more efficient compared to direct addition of SP with or immediately after water addition. However, few studies regarding water addition time and method have been conducted since now. In this research work, the effects of water and SP addition methods on the fluidity of paste were investigated. The results demonstrated that stepwise and delayed water beside delayed SP addition remarkably reduce the flow time. This maximum fluidity was achieved after totally 15 minutes of mixing including 3 minutes after 70% of water addition to powder, as first-part water, 6 minutes after SP addition and finally an extra 6 minutes after second-part water which is 30% of the total water. Based on this procedure, the opportunity for developing self-compacting and durable UHPC could be accessible. Furthermore, using higher content of aggregates and supplementary cementitious materials would be possible due to higher fluidity of the paste which finally results in an eco-efficient UHPC.

Sustainable construction through eco-efficient ultra-high performance concrete

“…It should be followed by adding the optimum dosage of SP and mixing for at least 4 minutes, 6 minutes seems preferable based on visual assessment, and finally adding the remaining 30% of water and blending for an extra 6 minutes to reach a steadystate consistency. The fibers are usually added at the end of this stage with continuing the mixing for another one minute (Ferdosian & Camões, 2016).…”

Development and Characterization of Eco-Efficient Ultra-High Durability Concrete

“…The last two approaches are related to the formulation of concrete. Several scientific works have been developed [11][12][13][14][15][16][17][18][19] with the goal of optimizing the proportion of UHPC constituents, which falls under the second approach. Regarding the third approach, the use of supplementary cementitious materials of micrometric and nanometric size has also been widely studied to partially replace the cement Portland in the production of UHPC, citing as examples the studies carried out by Chan and Chu [20], Droll [21], Tuan et al [22], Ghafari et al [4], Zhao and Sun [23], Yu et al [10], Ferdosian et al [24], etc.…”