Thermal stability of PVA fiber strain hardening cement-based composites

This paper reports the results of an investigation on the influence of pre-heating on the mechanical behavior of PVA strain hardening cement-based composites (PVA-SHCC) by using uniaxial tensile, bending and compression tests. Tests were conducted on specimens that were previously heated to temperatures ranging from 90 °C to 250 °C and unheated specimens. The temperatures were selected based on the results of thermal analyses tests carried out to investigate the thermal degradation of the PVA fiber. The results indicated that specimens preheated to 90 °C presented a strain hardening behavior with a pronounced multiple cracking pattern. This response is nearly the same as observed for the unheated specimens. After heating to 110 °C and 145 °C, although the composite still presented a strain hardening behavior the strain capacity was reduced. At 190 °C the strain capacity of the SHCC is even smaller and at 250 °C no further typical strain hardening behavior was observed; the reinforcing fiber failed suddenly after the cracking of the matrix. A similar behavior was observed for the samples submitted to bending loads, indicating that bending test was also efficient to indicate the composite degradation under thermal loads. Compressive strength of the composite has indicated an increase up to 190 °C due to a refinement of the matrix pore structure as indicated by the microstructural studies.