Development of self-stressing Engineered Cementitious Composites (ECC)

While high ductility Engineered Cementitious Composites (ECC) have demonstrated effectiveness for infrastructure repair, the microcracking induced by the high material shrinkage may decrease the structural durability of ECC in aggressive environments. The objective of this research is to develop a self-stressing ECC, the expansion of which against the restraint of the repaired structure automatically induces pressure onto the repair material. Super absorbent polymer (SAP), shrinkage reducing agent (SRA), and calcium sulphoaluminate cement/ expansive additive (CSA) were utilized together with Portland cement to tailor the composite expansion and expansive pressure. Free drying expansion/shrinkage, restrained expansive stress, and tensile performance were examined through standard shrinkage measurement, steel ring restrain test, and uniaxial tensile test, respectively. It was found that the 28 days drying shrinkage was decreased by 47% due to the use of SRA but was slightly increased when SAP was used. Substituting 42% of OPC with CSA (K42) increased ECC strength and ductility. The K42-ECC experienced a maximum expansion of 3756 mu epsilon at 3 days and retained 2026 mu epsilon expansion at 28 days. However, the expansion loss between 3 days and 28 days counteracted the expansive pressure. The deliberate combination of SRA and CSA provides a self-stressing effect tailoring the maximum expansion and expansion loss. The self-stressing performance along with a 7% ultra-high strain capacity and average crack width of 35-44 mu?m at 3% strain promotes the developed ECC as a more durable material for infrastructure repair.

Automated summary

The objective of this research is to develop a self-stressing ECC, which can automatically induce pressure onto the repair material, by utilizing a combination of super absorbent polymer (SAP), shrinkage reducing agent (SRA), and calcium sulphoaluminate cement/expansive additive (CSA). The deliberate combination of SRA and CSA tailors the maximum expansion and expansion loss, enhancing the durability of ECC for infrastructure repair in aggressive environments.