Efficient use of pultruded carbon fiber–reinforced plastic profiles (CFRP tendons) to prestress high-performance concrete (HPC) highly depends on the performance of the anchorage system and on material choice. For current applications, a prestressing degree of approximately 40% of the CFRP material strength is utilized in pretensioned concrete elements. A higher prestress implicates lower costs of fully prestressed concrete elements. The present project aimed to optimize the design of a removable and reusable pretensioning anchorage system for sand-coated CFRP rods. The optimized design was achieved by means of finite-element calculations in which parametric studies were complemented with extensive experimental work for validation. Analytical results demonstrated a reduction up to 25% for the relevant stress peaks in the tendons. The static rupture load under laboratory conditions increased by 25%, and the pretensioning level on-site could be increased by 50%. This improvement in production efficiency can...

More sustainable precast concrete structural elements are emerging from the research community utilizing high-strength, self-consolidating fiber-reinforced concrete (HPSCC) reinforced with noncorroding prestressed carbon-fiber-reinforced polymer (CFRP). An example of this is a new type of precast CFRP pretensioned HPSCC panel intended as load-bearing beams or columns for use in building envelopes. Such elements have recently been applied to architectural façade elements in Europe. A key issue in the implementation of these elements as load-carrying members in buildings is demonstrating satisfactory performance in fire. It is well known that the bond between FRP reinforcing bars and concrete deteriorates at elevated temperatures. It is also known that high-strength concrete is susceptible to explosive spalling when subjected to fire. Reductions in FRP reinforcement tensile and bond strength during fire, effects on the load-bearing capacity of prestressed concrete structures, and the explosive spall...

Nano-sized, functionalized organo-silicate fillers dispersed in the epoxy matrix are one approach that is investigated for improving the delamination resistance of fiber-reinforced composites. The variety of nano-silicate fillers available on the market, of processing conditions and the related characterization effort make it desirable to have a simple, easily analyzed screening method for both, nano-modified resins and laminates. An impact test using hail simulation equipment and visual assessment on glass-fiber laminates with nano-modified epoxy matrix yields rough indications of the effect of nano-modification on the fracture behavior of the specimens that correlate with more sophisticated macroscopic and microscopic characterization.

The objective of this project is evaluating the potential of microbes (fungi and bacteria) for the depolymerization of epoxy, aiming at the development of a circular management of natural resources for epoxy in a long-term prospective. For depolymerization, epoxy samples were incubated for 1, 3, 6 and 9 months in soil microcosms inoculated with Ganoderma adspersum. Contact angle data revealed a reduction in the hydrophobicity induced by the fungus. Environmental scanning electron microscopy on epoxy samples incubated for more than 3 years in microbiological water revealed abundant microbiota. This comprised microbes of different sizes and shapes. The fungi Trichoderma harzianum and Aspergillus calidoustus, as well as the bacteria Variovorax sp. and Methyloversatilis discipulorum, were isolated from this environment. Altogether, these results suggest that microbes are able to colonize epoxy surfaces and, most probably, also partially depolymerize them. This could open promising opportunities for the study of new metabolisms potentially able depolymerize epoxy materials.