Study on Permeability of Concrete Fortifications from WW2 Based on Mercury Intrusion Porosimetry

Quantification of water transport properties of concrete is crucial for prediction of the material degradation processes. In case of 80 years ́ old concrete of fortification structures of former Czechoslovakia, its permeability is the determining factor of the scale of degradation. Mercury intrusion porosimetry was used to characterize the porous system of seven existing bunkers from the defence line ”Pražská čára” and to calculate the permeability using model of Bágel and Živica. Results showed the altered structure of the old concrete, characterized by no notable peaks, which mark the critical pore radius most responsible for water intake. The majority of pores are small micropores, which does not contribute much in the water transport. However, calculated permeability is high enough to be the cause of several degradation processes. The performed program also confirmed high variability of permeability properties between individual structures.

Impact Resistance and Sodium Sulphate Attack Testing of Concrete Incorporating Mixed Types of Recycled Plastic Waste

Impact resistance, water transport properties and sodium sulphate attack are important criteria to determine the performance of concrete incorporating mixed types of recycled plastic waste. Nine mixes were designed with different combinations of the three plastic types; Polyethylene terephthalate (PET), High density polyethylene (HDPE) and Polypropylene (PP). The plastic partially substituted the coarse aggregate (by volume) at various replacement ratios; 10%, 15%, 20% and 30%. The impact resistance and water transport properties were evaluated for nine mixes while sodium sulphate attack test was performed for three mixes. The results showed that the addition of mixed recycled plastic in concrete improved the impact resistance. The highest impact resistance improvement was achieved by R8 (PET + HDPE + PP) at 30% replacement which was 4.5 times better than the control mix. Water absorption results indicated a slight increase in all plastic mixes while contradictory results were observed for sorptivity test. Analysis of sodium sulphate attack results showed that incorporating 30% mixed plastic reduced the sodium sulphate resistance slightly due to the collective effect of plastic entrapping of sulphate ions after 80 cycles. This study has shown some positive results relating to the impact performance of Mixed Recycled Plastic Concrete (MRPC) which enhances its use in a sustainable way.

Effectiveness and Compatibility of Nanoparticle Based Multifunctional Coatings on Natural and Man-Made Stones

The interaction of microorganisms with stone materials leads to biodeterioration processes, which may cause aesthetic damages and the loss of durability and strength of the substrates. Innovative solutions against this process are represented by nanotechnologies. In our previous works, 2-mercaptobenzothiazole was successfully encapsulated within two silica-based nanodevices: nanocapsules and mesoporous nanoparticles. Such loaded nanodevices have been dispersed in TEOS based coatings, characterized as far as their chemical–physical properties and in vitro biocide efficacy. Here, we adopt a multi-technic approach, to assess the coatings efficacy and compatibility with four types of stones of cultural heritage interest, namely, mortar, brick, travertine, and Carrara marble. In particular, we determine the protective function of the coatings, based on water transport properties (reduction up to a factor 10 of the water absorption for brick and mortar, without significantly influencing water vapor transmission rate), morphology of the surface (absence of coating cracks and color changes), and TiO2 photocatalytic activity. Consequently, these coatings can be considered suitable for application on stone artifacts, without interfering with their artistic appearance.

Physical Properties and Microstructure of Concrete with Waste Basalt Powder Addition

The natural aggregates are one of the main components in the production of concrete. Although deposits of natural aggregates lie on the earth’s surface or at low depths and belong to common deposits, the shortage of aggregate, especially natural sand, is presently observed in many countries. In such a situation, one is looking for other materials that can be used as a substitute for natural aggregates in mortars and concrete production. This paper presents the results of an experimental investigation carried out to evaluate the potential usage of waste basalt powder in concrete production. For this purpose, the waste basalt powder, which is a by-product of the production of mineral–asphalt mixtures, was substituted with 10%, 20%, and 30% sand replacement. In the experimental program, the workability, compressive strength, water transport properties, and microstructural performances were evaluated. The results showed that the production of concretes that feature a strong internal structure with decreased water transport behavior is possible with waste basalt usage. Furthermore, when waste basalt powder is used as a partial sand replacement, the compressive strength of concretes can be increased up to 25%. According to the microstructural analyses, the presence of basalt powder in concrete mixes is beneficial for cement hydration products, and basalt powder substituted concretes have lower porosity within the interfacial transition zone.

Polysulfone hemodialysis membrane incorporated with Fe2O3 for enhanced removal of middle molecular weight uremic toxin

Removing middle molecular weight uremic toxin remains as one of the most challenging tasks in hemodialysis. Hence, in this study a high performance polysulfone (PSf) hemodialysis membrane was developed by incorporating iron oxide (Fe2O3) nanoparticles. The PSf/Fe2O3 hemodialysis membrane and pristine PSf membrane were prepared via dry-wet spinning process. The membranes were characterized by scanning electron microscopy, water contact angle, average pore size, and porosity measurements. The biocompatibility profiles of the membranes were also evaluated in terms of protein adsorption and blood coagulation time. Next, the performance of the membranes was determined by measuring pure water permeability (PWP), bovine serum albumin rejection, and removal of various solutes such as urea and lysozyme. The incorporation of Fe2O3 resulted in significant increment of the PWP from 40.74 L/m2/h/bar to 58.6 L/m2/h/bar, mainly due to the improved water transport properties of the membrane. Moreover, the percent removal of urea and lysozyme was reported to be 75.1% and 35.6%, respectively. PSf/Fe2O3 hemodialysis membrane is proven to have a bright prospect for enhanced blood purification process.