ANALIZA EKOLOŠKOG UTJECAJA SADRŽAJA TEŠKIH METALA U OTPADNIM MATERIJALIMA PRIMIJENJENIM U CESTOGRADNJI

Use of solid waste in place of conventional materials in civil engineering structures preserves natural resources and energy and avoids expensive and/or potentially harmful waste disposal. Many studies are investigating the application of waste materials in civil engineering structures. However, in an effort to find out new areas of waste materials utilization, the environmental impact of the installation of such materials in building structures often remains neglected. This study focused on the environmental aspect of the application of currently investigated waste materials in Croatia with an emphasis on heavy metal content. Heavy metal concentration in steel slag, river sediment, and biomass ash was measured, and the possibility of their use in road construction in accordance with currently valid legislation was assessed.Uporaba krutog otpada umjesto konvencionalnih materijala u građevinarstvu pridonosi očuvanju prirodnih izvora i energije, čime je ujedno izbjegnuto skupo te potencijalno opasno odlaganje takvog otpada. Mnogo je istraživanja na temu primjene otpadnih materijala u graditeljstvu. Međutim, u nastojanju da se pronađu nova područja primjene otpadnih materijala, utjecaj ugradnje takvih materijala u građevinske konstrukcije na okoliš često puta ostaje zanemaren. Ovaj rad bavi se ekološkim aspektom primjene trenutačno istraživanih otpadnih materijala u Hrvatskoj, s naglaskom na sadržaj teških metala. Određeni su sadržaji teških metala u čeličanskoj zguri, talogu iz riječnog nanosa i pepelu biomase te procijenjena mogućnost njihove primjene u cestogradnji s obzirom na trenutačno važeće zakonodavstvo

State and perspectives of sustainable production of traditional silicate ceramics

The traditional ceramics industry uses large amounts of primary mineral raw materials. Improvements in the production of building materials based on non-metallic minerals can contribute to sustainable development in many ways, such as saving natural resources, using waste materials, reducing energy consumption, decreasing emissions hazardous to the health and the environment, particularly carbon dioxide, and reclamation of mines after exploitation of raw materials, etc. This paper describes the state of application of mineral raw materials and waste in the traditional ceramics industry with a perspective on future challenges. Intensified research is needed to complement the laboratory data and re-scale to the industrial-sized products while improving communication between both sectors

Möglichkeit der Verwendung von Bioasche beim Straßenbau

Biopepeli su neizbježan proizvod ispunjavanja zahtjeva za sve većom primjenom obnovljivih izvora u proizvodnji energije. Ekološki i ekonomski problemi zbrinjavanja biopepela, zbog prikladnih kemijskih i fizikalnih svojstava, mogu se smanjiti njegovom primjenom kao sirovine u građevinarstvu. U radu se daje pregled istraživanja mogućnosti primjene biopepela pri gradnji cesta, uzimajući u obzir velik raspon svojstava koja ga karakteriziraju ovisno o porijeklu biomase i uvjetima izgaranja. U radu je također dan pregled istraživanja biopepela nastalog kao proizvod izgaranja biomase u termoelektranama na području Republike Hrvatske.Bioashes are inevitable product of meeting the demands to satisfy the increased use of renewable resources in energy production. Ecological and economic problems of bioash disposal, due to its appropriate chemical and physical properties, can be reduced by its application in the construction industry as raw materials. The paper therefore provides an research overview on various aspects of the bioash application in road construction, in compliance with a range of properties depending on the type of biomass and the conditions of combustion. Also shown is current state of research of bioash generated in the domestic thermal power plants.Bioasche ist aufgrund der Erfüllung der Forderungen nach immer größerer Verwendung von erneuerbaren Quellen bei der Energieerzeugung ein unvermeidliches Produkt. Die ökologischen und wirtschaftlichen Probleme bei der Entsorgung von Bioasche können wegen der angemessenen chemischen und physikalischen Eigenschaften durch dessen Verwendung als Rohstoff im Bauwesen verringert werden. Die Abhandlung gibt eine Übersicht über die Untersuchungen der Möglichkeiten der Verwendung von Bioasche beim Straßenbau, unter Berücksichtigung der großen Bandbreite an Eigenschaften, die sie abhängig von der Herkunft der Bioasche und den Verbrennungsbedingungen charakterisieren. Die Abhandlung gibt auch eine Übersicht über die Untersuchungen der Bioasche, die als Produkt der Verbrennung von Biomasse in Wärmekraftwerken auf dem Gebiet der Republik Kroatien entstanden ist

Influence of Clogging and Unbound Base Layer Properties on Pervious Concrete Drainage Characteristics

This paper aims to assess the influence of clogging on paving material (pervious concrete) drainage characteristics as well as the influence of the properties of an unbound base layer on drainage characteristics of the whole paving system. The clogging influence has been studied measuring the drainage characteristics on pervious concrete flags before and after their clogging, according to ASTM C1701-09. Additionally, the drainage characteristics of uncontaminated pervious concrete as a paving material was assessed using the falling head method. To assess the influence of properties of an unbound base course (UBC) on drainage characteristics of the whole paving system, the unbound base layer was compacted in two different levels of compaction and the drainage characteristics were measured (according to ASTM C1701-09). It is concluded that pervious concrete prepared with a smaller aggregate fraction is more prone to clogging. Regarding the influence of UBC, it is important to find a balance between pervious concrete infiltration and UBC exfiltration rate, particularly in a case of pervious concrete flags made of coarse aggregate

Feasibility of Agricultural Biomass Fly Ash Usage for Soil Stabilisation of Road Works

Agricultural biomass ash is a waste material produced by incineration of residue from fields after harvesting crops. The use of agricultural biomass in industry produces large quantities of ash that represent an ecological problem. Another ecological problem is the dependency of road building on natural materials, which has been traditionally used for all pavement layers. Today, roads are built on less accessible and suitable terrains, increasing the need for improving the mechanical characteristics of locally available materials by various means of stabilisation. Within this research, three agricultural biomass fly ashes are used as lime substitutes for hydraulically stabilised soil. The purpose of this research is evaluation of potential use of agricultural biomass fly ash for the soil stabilisation of road works, i.e., for embankment and subgrade purposes. The results indicate that there is a potential of using barley, sunflower seed shells and wheat fly ash as lime substitutes in the soil stabilisation of road works. The strength characteristics of stabilised soil incorporating biomass fly ash are highly dependent on its chemical composition. Using a three-dimensional digital image correlation technique, it is concluded that the elastic properties of stabilised soil correlate to a fracture mechanism that can be efficiently defined by this modern research tool

Influence of Freeze/Thaw Cycles on Mechanical and Thermal Properties of Masonry Wall and Masonry Wall Materials

In this study, the influence of freeze/thaw cycles on the mechanical and thermal properties of bricks and mortar as building parts of masonry walls, as well as the influence on the masonry wall itself is investigated. At the material level, the influence of freeze and thaw cycles on the mechanical and thermal properties of masonry components (bricks and mortar) was investigated; at the construction level, the influence of freeze and thaw cycles on the mechanical and thermal properties of a masonry wall was studied. To study the influence of freezing on the energy demand characteristics of masonry buildings, in terms of energy conservation and greenhouse gas emission, a case study was investigated on a typical structure of a historical building located in Croatia, that had undergone a process of energy certification. The applied freeze/thaw regime negatively influenced the compressive strength and the thermal properties of bricks and mortar, as well as the mechanical and thermal properties of the wall. Considering the thermal properties of the material before and after its exposure to freeze/thaw cycles, we concluded that the annual energy consumption, the heating costs, and the CO2 emission of a family house could increase up to 3.7% after frost action in the studied case

The effect of crystalline waterproofing a dmixtures on the self-healing and permeability of concrete

This paper investigates the effectiveness of a specific crystalline waterproofing admixture (CWA) in concrete as a function of a water–binder ratio. Four concrete mixes with and without CWA were preparedtwo of them with a water–binder ratio of 0.45 and two of them with a water– binder ratio of 0.55. Water permeability and compressive strength were tested on hardened concrete specimens and self-healing of cracks over time was observed. Cement paste and CWA paste were prepared to clarify the results obtained on the concrete specimens. SEM and EDS and XRD and FTIR were performed on the hardened pastes to explain the mechanism of CWA working. The results show that the addition of CWA had no significant effect on the compressive strength of the concrete, but reduced the water penetration depth in the concrete, and the reduction was more effective for mixes with lower water–binder ratio. Regarding the self-healing effect, it can be concluded that the addition of CWA improves the crack healing in concrete, but the efficiency of self-healing is highly dependent on the initial crack width. The mechanisms involved in the reduction of water penetration depth and crack healing in concrete can be explained by different mechanismsone is creation of the CSH gel from unreacted clinker grains, then formation carbonate, and additional mechanism is gel formation (highly expansive Mg-rich hydro-carbonate) from magnesium based additives. The presence of sodium silicate, which would transform into carbonate/bicarbonate, also cannot be excluded

Recycling waste rubber tyres in road construction

Road construction relies on natural material exploitation and it is necessary to find new ways of reducing its negative environmental impact. Simultaneously, number of tyres placed on Croatian (and world) market is constantly growing and the need for waste tyres management will begin to increase due to the wear and tear of tyres in use at the moment. This paper presents a review of latest international and domestic researches on waste rubber application in road construction with special emphasize on Croatian researches within this topic. Preliminary results of ongoing research on waste rubber application in cement bound mixtures are also presented

Influence of the size and type of pores on brick resistance to freeze-thaw cycles

This paper estimates the frost resistance of bricks using the ratio of compressive strength before freezing to compressive strength after freezing to describe the damage degree of bricks being exposed to freeze-thaw cycles. In an effort to find the ratio that clearly distinguishes resistant bricks from non-resistant bricks, the authors attempted to establish the correlation between the ratio and Maage factor as a recognized model for assessing brick resistance. To clarify the degree of damage of individual bricks, the pore size distribution has been investigated by means of mercury porosimetry. Additionally, micro computed X-ray tomography (micro-CT) has been employed to define the influence of the type of pores (open or closed) and their connectivity on the frost resistance of bricks. According to the results, it can be concluded that there is a good correlation between the Maage factor and the ratio of pre- to post-freeze-thaw cycle compressive strengths, and that the latter ratio strongly correlates with the percentage of large pores (≥3 mm) in the brick. If such a correlation could be confirmed in a larger sample, then the ratio of pre- to post-freeze-thaw cycle compressive strengths could be used as a new method for assessing brick resistance to freeze-thaw cycles and it would be possible to determine the minimum percentage of large pores required to ensure the overall resistance of brick to freeze-thaw conditions. The complexity of the problem is, however, evidenced by the fact that no clear connection between the type (open versus closed) or connectivity of pores and the frost resistance of bricks could be revealed by micro-CT

Field and Laboratory Assessment of Different Concrete Paving Materials Thermal Behavior

Impervious pavement surfaces within urban areas present serious environmental problems due to waterlogging, flooding and in particular, the urban heat island (UHI) phenomenon. Another issue that has recently been highlighted is user comfort in pedestrian and cycling areas. Materials that have potential for overcoming these issues include pervious concrete (PC), a new type of construction material with improved drainage properties and thermal properties. In this study, the thermal properties and behavior of commonly used concrete paving materials in urban areas (dense concrete (DC) and concrete pavers (P)) and pervious concrete (PC) paving flags were investigated and compared in terms of their thermal properties. Material behavior under different temperature conditions was investigated within laboratory research measuring thermal conductivity (λ) and the capacity for heating and cooling using infrared lamp. Complementary to laboratory tests, field research was conducted analyzing the surrounding conditions on pavement wearing course behavior under real weather conditions. Dense concrete paving material had the highest thermal conductivity coefficient and heat absorption capacity, and slowest heating and cooling speed, compared with the other paving materials. The results also highlighted the similar thermal properties of PC and P but with potentially improved user comfort for PC due to its draining properties. The base layer and surrounding characteristics had a significant influence on the thermal behavior of pavements, and future research should consider these parameters when addressing the UHI effect for different paving materials