Performance of rapid-repair concrete in an aggressive marine environment

Development and Performance Evaluation of Fibrous Pseudoplastic Quaternary Cement Systems for Aerial Additive Manufacturing

“…The second consideration is the status and reputation of CAC systems due to the historically misunderstood conversion reaction [39,40] leading to the potential reduction in strength to a stable long-term level when material experiences temperatures higher than those experienced during formation [32]. In CAC at low and intermediate temperatures, metastable hydrates CAH 10 and C 2 AH 8 form, whereas at higher temperatures stable hydrates C 3 AH 6 and AH 3 (alumina gel) are formed.…”

“…Instead, poorly detailed design or lowquality aggregates were determined as primary causes of collapse [32]. However, CAC has remained an important material for ground anchoring [43] and rapid repair work [31,36], particularly in marine and tidal environments [40], roads and airfield runways [44]. In OPCrich blended cement systems such as OPC/CAC/CS, the smaller amount of CAC typically used does not lead to the formation of the metastable hydrates, and thus conversion would not occur [31].…”

“…This study investigates the feasibility of adding calcium aluminate cement (CAC) and calcium sulphate (CS) to OPC and PFA for AAM through the development of a novel fibrous quaternary OPC/PFA/CAC/CS binder system augmented with rheologymodifying admixtures (RMA) to promote ease of extrusion and rapid curing following extrusion. CAC acts as an accelerator [45], promoting early strength [40] and hardening of material, which would be an asset once material has passed through the deposition system to prevent deformation prior to hardening [46] due to either self-weight, trajectory imperfection or subsequently deposited layers. Fibres were required to add ductility to cured material and mitigate crack propagation, and pseudoplastic properties were desired to promote liquid-like properties in fresh material mixes while under stress within the miniature deposition system and solid-like properties with a significant increase in viscosity once deposited.…”

Synergetic–Complementary Use of Industrial Solid Wastes to Prepare High-Performance Rapid Repair Mortar

“…However, the concrete structures can be damaged due to natural disasters, climate change, or continuous load, which affect the safety and normal of the facilities (Han et al, 2015;Song et al, 2018;Feng et al, 2019). Therefore, the maintenance and repair industries of concrete structures and facilities are likely to develop rapidly, and there will be massive demands for rapid repair mortars (RRMs) with properties of fast hardening, high fluidity, and early compressive strength (i.e., ≥ 20 MPa in 2-4 h) (Moffatt and Thomas, 2017). For decades, ordinary Portland cement (OPC) has been commonly used as a cementing material for RRM preparation (Feng et al, 2019;Phoo-ngernkham et al, 2019).…”

“…Researchers have found that CSA cement is very suitable as the cementing material for RRM preparation (Zhang J. et al, 2018;Long et al, 2019;Yeung et al, 2019). Moffatt and Thomas (2017) prepared RRM by blending 30% CSA cement with 70% OPC as the cementing material, and achieved a compressive strength of 22 MPa at 3 h. Shi et al (2021) also prepared RRM using CSA cement, and the flexural and compressive strengths at 1 day reached ∼7 and ∼36 MPa. Furthermore, CSA cement is regarded as a green cement category because of its low calcination temperature (∼1,250 °C) and low carbon dioxide emissions (Benhelal et al, 2013;Ren et al, 2017a).…”