Incorporation of liquid phase into solid particle packing model for precise design of low water/binder cement-based composites (LW/B-CC): Modelling and experiments

Abstract

This paper addresses a novel method for the precise mixture design of low water/binder cement-based composites (LW/B-CC) by incorporating the liquid phase into a solid particle packing model. To achieve this goal, a typical LW/B-CC material, ultra-high performance concrete (UHPC), is used to clarify and verify this design method. More exactly, an optimized mixture of UHPC can be obtained by the following steps: Firstly, the water film thickness (WFT) is implanted into the modified Anderson and Andreasen model to obtain the optimized solid constituents proportions; then, a WFT predicted model based on D-optimal design approach is built; finally, proportions of liquid constituents (superplasticizer (SP) and water) are determined by the solution of simultaneous equations. To demonstrate the superior performance of the newly designed UHPC, its micro-meso-macro properties are evaluated in detail. The experimental results reveal that except water, the addition of SP can also significantly increase the WFT in UHPC. Moreover, the newly designed UHPC has advanced pore structure in all micro, meso and macro scales, where the total porosity is 7.07%, thereby contributing to excellent compressive strength (134.2 MPa). Additionally, some new insights are proposed to understand the development of LW/B-CC microstructure and strength by combining centroplasm effect, water film theory and particle packing theory. Overall, this research highlights the feasibility on optimized design of LW/B-CC incorporating the liquid constituents, which could further perfect the fundamental design theory of LW/B-CC materials.