Cement-based bearing pads for precast concrete connections

This paper reports some new results for cement-based bearing pads for precast concrete connections. The pads were composed of Portland cement mortar, incorporating heat-expanded vermiculite, latex and short fibres. These ingredients were used to obtain a cement-based material of greater deformability and higher toughness in comparison with ordinary cement mortar, to transfer compressive stresses in an appropriate manner. The paper presents a means of obtaining the range of material admixtures based on the mechanical characteristics of the material and the concentrated load tests on bearing pad strips. Uniform compression load tests on bearing pads, with monotonic and cyclic load, and uniform compression load tests on two concrete blocks connected by bearing pads were performed. Based on the experimental results, the main conclusions are: (a) the vermiculite amount should be around 10%; (b) after 1200 cycles, bearing pads do not exhibit appreciable plastic deformation or rigidity deterioration, showing resilient capacity for cyclic loads; (c) from the test of bearing pads in precast connection, it can be concluded that the proposed cement-based bearing pads can improve the connection strength by 20 to 35%, with respect to a connection without bearing pads.