Incorporating super-fine stainless wires to control thermal cracking of concrete structures caused by heat of hydration

Abstract

Super-fine stainless wires (SSWs) with micron diameter can form a widely distributed heat conduction network in reactive powder concrete (RPC) at low volume fraction, thus endowing RPC with high thermal conductivity and low specific heat. This shows great potential to reduce the thermal cracking risk of RPC structures caused by heat of hydration. Therefore, both experiments and finite element simulations were performed to investigate the effects of adding SSWs on the thermal and stress fields inside RPC specimens and structures, and then the thermal cracking risk of specimens and structures fabricated with SSW reinforced RPC were evaluated. The results show that incorporating only 0.5 vol% SSWs can effectively decrease the temperature rise in the center position and the temperature gradient between the core and surface positions inside RPC specimens and structures due to heat of hydration. When the content of SSWs is 1.5 vol%, the temperature gradients for pavement slab (with a size of 4.5 m × 5 m × 0.4 m) and pier cap (with a size of 3 m × 2 m × 1 m) are dropped by 6.9 ℃ and 10.7 ℃, and the maximum thermal stresses are reduced by 0.90 MPa and 1.43 MPa, respectively. As a result, the specimens and structures fabricated with SSW reinforced RPC have little or no thermal cracks at early ages. Therefore, adding SSWs into RPC is an effective way to inhibit the thermal cracking of structures caused by heat of hydration through improving temperature uniformity, reducing temperature gradient and decreasing thermal stress.