Nanocarbon black-based ultra-high-performance concrete (UHPC) with self-strain sensing capability

• A nCB-UHPC composite with self-compressive strain sensing capability. • Quantum tunneling enabled inside cementitious matrix by chain-structured nCB. • Low percolation zone of 0.50–1.50% nCB. • High strain sensitivity (gauge factor: >130) and responsiveness to dynamic loading. • Ultra-high 28-day compressive strength of >140 MPa. Ultra-high-performance concrete (UHPC) exhibits exceptional mechanical properties and durability. While the dense microstructure contributes significantly to the superior performance of UHPC, it limits the mobility of potential piezoresistive additives. Therefore, it is generally considered challenging for UHPC to achieve the compressive strain-sensing capability. This paper presents the development of a new type of UHPC with strain-sensing capability by incorporating chain-structured nanocarbon black (nCB-UHPC). nCB is a highly conductive and low-cost material; when used as a filler material in a concrete mix, it makes the cementitious matrix conductive through the quantum tunnelling mechanism due to its chain structure. The present study involves comprehensive experimental investigations into various properties of the nCB-UHPC, including its mechanical and piezoresistive properties as well as its microstructure. The nCB content was taken as the key variable in the tests. The test results show that by incorporating nCB of a proper content (e.g., 1.0–1.5 %), the resulting nCB-UHPC can have an ultra-high 28-day compressive strength (>140 MPa), sufficiently good workability (slump spread ≥ 170 mm) and excellent strain-sensing capability (gauge factor > 130) at the same time.