Early ages shrinkage mechanisms of ultra-high-performance cement-based materials

Early age chemical and microstructural evolution of an ultra-high-performance cement-based material is analyzed by autogeneous shrinkage monitoring simultaneously with ultrasonic propagation measurements. The hydration progress is determined with a calorimetric equipment. The combined analysis with these complementary methods leads to the identification of five stages in this evolution: (1) a settling period with short-range reorganization without any cluster formation or shear resistance; (2) an aggregation period with unconnected clusters formation and growing leading to the percolation of solid particles; (3) a postpercolation bond development phase leading to a globally structured Framework; (4) a progressive reinforcement by multiplication of connections within the framework leading to a fully hyperstatic state; (5) a hyperstatic phase where all the particles are connected, with the consolidation by pores filling. (C) 2001 Elsevier Science Ltd. All rights reserved.