Panbacterial real-time PCR to evaluate bacterial burden in chronic wounds treated with Cutimed™ Sorbact™

The impact of polymicrobial bacterial infection on chronic wounds has been studied extensively, but standard bacteriological analysis is not always sensitive enough. Molecular approaches represent a promising alternative to the standard bacteriological analysis. This work aimed to assess the usefulness of a panbacterial quantitative real-time PCR reaction to quantitate the total bacterial load in chronic wounds treated with Cutimed™ Sorbact™, a novel therapeutic approach based on hydrophobic binding of bacteria to a membrane. The results obtained by panbacterial real-time PCR on conserved sequences of the bacterial 16S gene show that the bacterial burden significantly decreased in 10 out of 15 healing chronic wounds, and did not change in 5 out of 5 non-healing chronic wounds. On the contrary, classical culture for S. aureus and P. aeruginosa, and real-time PCR for Bacteroides and Fusobacterium did not show any correlation with the clinical outcome. Our study also shows that quantification of chronic wounds by panbacterial real-time PCR is to be performed on biopsies and not on swabs. These results show that panbacterial real-time PCR is a promising and quick method of determining the total bacterial load in chronic wounds, and suggest that it might be an important biomarker for the prognosis of chronic wounds under treatment

Effects of Freeze-Thaw and Wet-Dry Cycles on Tension Stiffening Behavior of Reinforced RAC Elements

In the last several decades, the growth of Construction and Demolition Waste (CDW) production and the increased consumption of natural resources have led to promoting the use of secondary raw materials for a more sustainable construction. Specifically, the use of Recycled Concrete Aggregate (RCA), derived from waste concrete, for the production of Recycled Aggregate Concrete (RAC) has attracted a significant interest both in industry and in academia. However, the use of RAC in field applications still finds some barriers. In this context, the present study investigates experimentally the effects of freeze-thaw and wet-dry cycles on the stress transfer mechanisms of reinforced RAC elements through tension stiffening tests. First of all, the paper presents a detailed analysis of the degradation due to the aging process of RAC with RCAs obtained from different sources. Particularly, the results of tension stiffening tests are analyzed in terms of crack formation and propagation, matrix tensile strength contribution and steel-to-concrete bond. The results highlight that the pre-cracking elastic modulus, the first crack strength as well as the maximum concrete strength are strongly influenced by the presence of the Attached Mortar (AM) in RCA, as the former affects the concrete's open porosity. Therefore, the amount of AM is identified as the key parameter for the evaluation of durability of reinforced RAC members: a degradation-law is also proposed which correlates the initial concrete open porosity with the damage observed in reinforced RAC elements

Water Absorption by Capillarity, Physical and Mechanical Properties of Concrete Containing Recycled Concrete Aggregate with Partial Cement Replacement by Metakaolin

An alternative way to mitigate the impact generated by the Construction and Demolition Waste (CDW) on the environment is recycling this material in order to utilize it as Recycled Concrete Aggregates (RCA) in concrete. Studies carried out demonstrated that while using a scientific mix-design, it is possible to have a Recycled Aggregate Concrete (RAC) with mechanical properties similar the ones in conventional concrete. However, the durability of the recycled concrete is still a matter that should be explored further. The use of Supplementary Cementitious Materials (SCMs), such as metakaolin, has been shown to be efficient when partially replacing cement. It has the ability to improve the packaging of concrete by decreasing the volume of the pores of the material and, consequently, reducing the water absorption capacity of RAC, since RCA presents greater water absorption compared to natural aggregates. Therefore, the aim of this study is to evaluate the durability and mechanical behavior of RAC with 60 MPa of compressive strength by totally replacing the natural coarse aggregate by RCA. Also, part of the cement was replaced by metakaolin. The coarse aggregate considered in this research has 19 mm as nominal maximum size. Total absorption, capillarity absorption, compressive strength test and tensile strength test were carried out for all mixtures. The research results showed that the use of metakaolin offset the increase in capillary absorption in recycled concrete caused by the use of RCA, reaching a value close to concrete with only natural aggregate and without metakaolin for this durability parameter