High-early-strength ductile cementitious composites with characteristics of low early-age shrinkage for repair of infrastructures

Abstract

Reduced performance in concrete infrastructures is mainly caused by the formation of cracks, which may arise due to deteriorating mechanisms during service life. In most cases, reduced performance calls for urgent repairs to the degraded section. Therefore, it is highly desirable to develop dimensionally stable, ductile repair materials that can attain adequately high strength in a limited amount of time, compensate for significant deformation due to mechanical and environmental loadings, and prevent early-age shrinkage cracks. In this paper, the performance of such a material (high-early-strength engineered cementitious composites, HES-ECC, with very low early-age shrinkage capacity) was investigated by studying mechanical properties and dimensional stability. Composites were produced with different water to cementitious materials and slag to Portland cement ratios. In order to enhance composite properties in terms of ductility and early-age shrinkage characteristics, saturated lightweight aggregates replaced sand in the mixtures. The experimental results show that the majority of HES-ECC mixtures developed in this study attained compressive strength values of more than 20.0 MPa and minimum flexural strength of 6.0 MPa within 6 h. Moreover, the HES-ECC mixtures exhibited strain-hardening behavior with strain capacities comparable to normal strength ECC, as well as substantially reduced autogenous shrinkage strain, both of which are unlikely to trigger the formation of cracks in tension at early ages. The integration of these conflicting parameters suggests that HES-ECC can easily meet the need for fast and durable repairs.

Nano-modification to improve the ductility of cementitious composites

“…The major effect of CaCO 3 in HVFA has been reported as higher early strength values [11,13,14], which is also one of the main setbacks reported for ECC [23]. Additionally, the literature indicates that strength enhancement in HVFA mixtures is improved when CaCO 3 particle size is reduced [12]-especially nano-sized CaCO 3 -which significantly improves the micro-hardness and modulus of elasticity values of HVFA [14].…”

External treatments for the preventive repair of existing constructions: A review

“…Sufficient bond strength must be guaranteed in order to withstand the interface stresses induced by environmental and/or mechanical actions. As a matter of fact, the interface is usually a weak zone in repair systems, due to the differences in physical, chemical and electrochemical properties between the two materials [4][5]. Morgan [6] has schematized the requirements that patch repair mortars must meet to ensure structural compatibility with the concrete substrate ( Figure 1).…”

Dimensional stability of deflection‐hardening hybrid fiber reinforced concretes with coarse aggregate: Suppressing restrained shrinkage cracking

“…It needs to be stated that higher FA/PC ratios were not that effective in lowering the MOR results as evident as in the case of compressive strength results (Figure b). This may be due to that flexural strength of HPFRC mixtures are affected by complex parameters such as tensile first cracking strength, ultimate tensile strength, and tensile strain capacity to a greater extent than compressive strength, especially when the material is characterized with strain/deflection‐hardening response . When similar FA/PC ratios and fiber type/amount were selected, increasing the A/B ratios increased the MOR results (Table ).…”