Correction: Microenvironment-responsive multifunctional hydrogels with spatiotemporal sequential release of tailored recombinant human collagen type III for the rapid repair of infected chronic diabetic wounds

Correction for ‘Microenvironment-responsive multifunctional hydrogels with spatiotemporal sequential release of tailored recombinant human collagen type III for the rapid repair of infected chronic diabetic wounds’ by Cheng Hu et al., J. Mater. Chem. B, 2021, 9, 9684–9699, DOI: 10.1039/D1TB02170B.

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

With the vigorous development of infrastructure engineering, there are growing demands for high-performance rapid repair mortar, especially those using environmental-friendly and low-carbon cementitious materials. Hereupon, this work explored an innovative approach for rapid repair mortar preparation using solid waste-based calcium sulfoaluminate cement. The calcium sulfoaluminate cement was first prepared via synergetic–complementary use of industrial solid wastes and then adopted to prepare rapid repair mortar by proportionally mixing with standard sand and four additives (i.e., polycarboxylate superplasticizer, lithium carbonate, boric acid, and latex powder). The mechanistic analysis indicated that the four additives comprehensively optimized the mechanical strengths, fluidity, and setting time of rapid repair mortar by adjusting the hydration process of calcium sulfoaluminate cement. The test results showed that the 2-h compressive and flexural strength, and 1-day bonding strength of the prepared rapid repair mortar were 32.5, 9.2, and 2.01 MPa, respectively, indicating excellent early-age mechanical performance. In addition, the 28-day compressive and flexural strengths of the rapid repair mortar reached 71.8 and 17.7 MPa. Finally, a life cycle assessment and economic analysis indicated that this approach achieved environmental-friendly utilization of industrial solid wastes, and cost-effective and energy-saving natures, which supports current trends towards a circular economy and green sustainable development.

Evaluation of Rapid Repair of Concrete Pavements Using Precast Concrete Technology: A Sustainable and Cost-Effective Solution

Concrete and asphalt are the two competitive materials for a highway. In Sweden, the predominant material for the highway system is asphalt. But under certain conditions, concrete pavements are competitive alternatives. For example, concrete pavements are suitable for high-traffic volume roads, roads in tunnels, concentrated loads (e.g., bus stops and industrial pavement). Besides the load-carrying capacity, the concrete pavement has many advantages such as durability (wear resistance), resistance against frost heave, environment (pollution, recycling, and low rolling resistance leading to fuel savings), fire resistance, noise limitations, brightness, evenness and aesthetics. Concrete pavements are long-lasting but need final repair. Single slabs may crack in the jointed concrete pavement due to various structural and non-structural factors. Repair and maintenance operations are, therefore, necessary to increase the service life of the structures. To avoid extended lane closures, prevent traffic congestions, and expedite the pavement construction process, precast concrete technology is a recent innovative construction method that can meet the requirement of rapid construction and rehabilitation of the pavement. This paper evaluates rapid repair techniques of concrete pavement using precast concrete technology by analysing three case studies on jointed precast concrete pavements. The study showed that the required amount of time to re-open the pavement to traffic is dramatically reduced with jointed precast concrete panels.

Estimation of Seismic Economic Loss and Downtime of Precast Concrete Frames with “Dry” Connections

The seismic loss of buildings comes not only from the damaged structural components. Much more loss may be induced by non-structural components, the demolition loss and social impacts associated with excessive downtime. One of the main characteristics of a resilient city is that the buildings in the city should be able to recover to their pre-earthquake functionalities with minimized economic loss and downtime. For this purpose, a comparative study regarding seismic economic loss and downtime is conducted between the conventional cast-in-situ reinforced concrete frames (RCFs) and precast concrete frames (PCFs) with "dry" connections. The results show that the PCFs with prestressed tendons (PTs) can effectively reduce demolition loss given their extraordinary self-centering capacity provided by PTs. By adding web friction devices at the beam ends, the economic loss of structural components and drift-sensitive non-structural components can be effectively reduced. The downtime of PCFs is reduced at given hazard levels compared with RCF given their rapid repair speed and easy assemblage. In view of the rapid post-earthquake repair and lower earthquake loss, the PCFs are worth further investigation and application to develop resilient cities.

High-Fluidization, Early Strength Cement Grouting Material Enhanced by Nano-SiO2: Formula and Mechanisms

Cement grouting material is one of the most important materials in civil construction at present, for seepage prevention, rapid repair, and reinforcement. To achieve the ever-increasing functional requirements of civil infrastructures, cement grouting materials must have the specific performance of high fluidization, early strength, and low shrinkage. In recent years, nanomaterials have been widely used to improve the engineering performance of cement grouting materials. However, the mechanisms of nanomaterials in grouting materials are not clear. Hence, a high-fluidization, early strength cement grouting material, enhanced by nano-SiO2, is developed via the orthogonal experimental method in this study. The mechanisms of nano-SiO2 on the microstructure and hydration products of the HCGA, in the case of different curing ages and nano-SiO2 contents, are analyzed through scanning electron microscopy tests, X-ray diffraction tests, differential scanning calorimetry tests, and Fourier transform infrared spectroscopy tests.

Bivalves rapidly repair shells damaged by fatigue and bolster strength

ABSTRACT Hard external armors have to defend against a lifetime of threats yet are traditionally understood by their ability to withstand a single attack. Survival of bivalve mollusks thus can depend on the ability to repair shell damage between encounters. We studied the capacity for repair in the intertidal mussel Mytilus californianus by compressing live mussels for 15 cycles at ∼79% of their predicted strength (critically fracturing 46% of shells), then allowing the survivors 0, 1, 2 or 4 weeks to repair. Immediately after fatigue loading, mussel shells were 20% weaker than control shells that had not experienced repetitive loading. However, mussels restored full shell strength within 1 week, and after 4 weeks shells that had experienced greater fatiguing forces were stronger than those repetitively loaded at lower forces. Microscopy supported the hypothesis that crack propagation is a mechanism of fatigue-caused weakening. However, the mechanism of repair was only partially explained, as epifluorescence microscopy of calcein staining for shell deposition showed that only half of the mussels that experienced repetitive loading had initiated direct repair via shell growth around fractures. Our findings document repair weeks to months faster than demonstrated in other mollusks. This rapid repair may be important for the mussels’ success contending with predatory and environmental threats in the harsh environment of wave-swept rocky coasts, allowing them to address non-critical but weakening damage and to initiate plastic changes to shell strength. We highlight the significant insight gained by studying biological armors not as static structures but, instead, as dynamic systems that accumulate, repair and respond to damage.