Gamma and X radiation absorption characteristics of specially selected types of concrete

Medical institutions with linear accelerators, cyclotrons as installations for particles acceleration, nuclear facilities as nuclear power stations and nuclear research reactors using concrete in building construction. In cost-benefit analysis the question is what are the radiation characteristics of different types of concrete, which could be used to protect against gamma and X rays. In this paper, computer code XCOM was used for the calculation of the total mass attenuation coefficients, which is an important factor for determination of the photon attenuation, as well as during research and testing of radiation protection properties for concrete with components of different type materials. Thereby, the basic absorption radiation characteristics of ordinary and barite concretes, as well as specially selected type of concrete with magnetite and steel and concrete UHPC with barite and nanosilica as specific material composition, were considered. The results of this research point to the conclusion that before the concrete production of certain mechanical properties is approached, it is reasonable to apply the appropriate methodology with the numerical calculation of the basic absorption characteristic of the concrete for protection against gamma and X radiation.SynerCrete’18 International Conference on Interdisciplinary Approaches for Cement-based Materials and Structural Concrete; October 24-26, r 2018, Funchal, Madeira Island, Portuga

Physical-Mechanical Properties of Cement Stabilized RAP/Crushed Stone Aggregate Mixtures

The paper presents and analyzes the results of testing the properties of cement stabilized mixtures of reclaimed asphalt pavement (RAP) and crushed stone aggregate (CSA). Tests were carried out on reclaimed asphalt pavement and crushed stone aggregate mixtures with varying RAP content (0%, 20%, 40%, 60% and 80%), as well as with a varying addition of cement (3%, 5% and 7%). The purpose of these tests was to determine the optimal proportion of recycled asphalt pavement in a mixture with crushed stone aggregate, and the optimal addition of cement as a hydraulic binder. Furthermore, the aim was to determine physical-mechanical parameters: the indirect tensile strength (Rt) and the dynamic modulus of elasticity (E), which are applied in pavement design during the process of cold recycling. On the basis of the obtained values, categorization of the stabilized mixture was carried out according to the standard EN 14227-10: 2006, which continues to be applied in the design of pavements. The maximum proportion of recycled asphalt in the stabilized mixture was determined as being up to 60%; the stabilized mixture was categorized into the "T1" and "T2" categories - gravelly soils

Some properties of concrete with recycled brick as aggregate

U radu je prikazana mogućnost upotrebe reciklirane opeke kao agregata za beton. Eksperimentalni rad je uključio vise vrsta betona spravljenih sa 350 kg/m3 cementa i sa ili bez dodatka polimera. Kao agregat je korišćena kombinacija rečnog peska i reciklirane opeke. Izloženi su rezultati komparativne analize betona na bazi reciklirane opeke na sledeća svojstva betona: čvrstoću pri pritisku, statički i dinamički modul elastičnosti zavisnost napona i deformacija i dilatacije skupljanja.Possibility of using recycled brick as a component (aggregate) of concrete is shown in this paper. Experimental work included few kinds of concrete, made with the same cement content (350 kg/m3) and with or without polymer admixture. Combination of river sand and recycled brick were using as aggregate. The results of comparative analyze of concrete based on recycled brick are shown. Investigations included follow properties: compressive strength, statical and dynamical module of elasticity, stress-strain dependent and shrinkage dilatation

Resistance of CEM III/B based materials to acid attack

Cementni materijali u poljoprivrednim i drugim industrijskim objektima izloženi su dejstvu kiselina. Zbog toga vek konstrukcija zavisi od trajnosti maltera ili betonskih elemenata u agresivnoj sredini. U radu je predstavljena otpornost na koroziju koja je uzrokovana sulfatnom, nitratnom, ureom, mlečnom i sirćetnom kiselinom. Skenirajuća elektronska mikroskopija (SEM) korišćena je da se ispita efekat agresivnih rastvora na mikrostrukturu i mehaničke osobine maltera. Hemijska otpornost prizmi od maltera i dve vrste betona testirana je prema metodi Koch-Steinegger. Kako je uslov za otpornost na agresivne rastvore taj da zatezna čvrstoća maltera nije manja od 70% u odnosu na referentne prizme negovane u vodi, može se zaključiti da su malter i beton, napravljeni sa CEM III/B, u ovom istraživanju otporni na sve kiseline kojima su tretirani. .Cement based materials in the agricultural and other industrial structures are exposed to acid attack. That is the reason why the service life of structure depends on the durability of mortar or concrete elements in aggressive environment. Resistance to corrosion caused by sulphate, nitrate, carbamide, lactic acid and acetic acid was presented. Optical and scanning electron microscopy (SEM) was used to examine the effect of aggressive solutions on the microstructure and mechanical properties of mortar. The chemical resistance of mortar prisms and two types of concrete were tested according to the Koch-Steinegger method. As the condition for resistance in aggressive solution is that flexural strength of mortar prisms is no less than 70 % compared to referent prisms cured in water it can be concluded that mortar and concrete made with CEM III/B in this investigation are resistant to all treated acids

Variable Scales of Architecture – from Object to the Territory: Notes for the Manifest

For the future development of the cities in the light of climate change it is necessary to have clear guidelines (some kind of manifest) that would include principles of resilience on different scales. These principles must vary in size, from micro to macro scale. In order to achieve the resilience of the city in its various scales (micro and macro), it is necessary to provide the possible approaches for the operation within the variable scales of architecture – from micro to macro scale, from object to the territory. This is precisely in accordance with the aim of this research paper – to give Notes for the future manifest for the formation of these principles. The manifesto is viewed differently from the strategy – it should serve like a guideline, but not the instruction. Therefore, the principles that maintain openness, flexibility, and capacity for adapting to different conditions (which is one of the basic characteristics of resilience) are examined. For purpose of this research, the territory of Belgrade was selected as an experimental field of activity, or even more precise, zones of dominant naturalness, such are Zvezdara Forest, Košutnjak and/or Park Ušće

Transport and storage of heavy metals in the Sava river basin in Serbia

Selected heavy metals (Cu, Zn, Pb and Cd) in Sava River water and sediment in Serbia were investigated on three locations in the vicinity of industrial and urban settlements (Šabac, Obrenovac, Beograd) during the period spring 2007-autumn 2011. The fluxes of heavy metals from river water to sediment due to sedimentation and heavy metal re-suspension fluxes due to sediment re-suspension at a high flow were determined, by applying the model for assessment of the transport the pollutants through rivers. Those fluxes were attributed mainly to natural processes. [Projekat Ministarstva nauke Republike Srbije, br. 43009

Investigation of the mortar and concrete resistance in aggressive solutions

U radu je prikazan utjecaj dva agresivna rastvora – sulfata i nitrata na žbuku i beton. U eksperimentalnom radu ispitivane su prizme od žbuke s 5 % specijalnog dodatka. Četiri vrste betona su također izložene agresivnim rastvorima. Kemijska otpornost ispitivana je prema metodi Koch-Steinegger. Kako je uvjet za otpornost kod agresivnih rastvora da zatezna čvrstoća žbuke nije niža od 70 % u odnosu na referentne prizme njegovane u vodi, može se zaključiti da žbuka i beton izrađeni s kombinacijom cementa i dodataka, prikazani u ovom istraživanju, nisu otporni na rastvor amonijak nitrata ali jesu na sulfatnu koroziju.Testing the influence of two aggressive solutions - sulphate and nitrate on mortar and concrete was presented in this paper. Experimental work included testing of mortar prisms with 5 % special admixture. Also, four types of concrete were exposed to aggressive solutions. The chemical resistance was tested according to the Koch-Steinegger method. As a condition for resistance in aggressive solution means that flexural strength of mortar prisms is no less than 70 % of referent prisms cured in water it can be concluded that mortar and concrete made with combination of cement and admixture presented in this investigation are not resistant to ammonium nitrate solution, but are resistant to sulphate corrosion

Concrete mix design for reconstruction of northwest breakwater in the Tripoli harbour - Libya

Reconstruction of Northwest breakwater in the Tripoli Harbour - Libya (about 4500 m long) required manufacture of various concrete elements (cubes and accropodes) in total amount of 550 000 m(3). Volumes of cubes were 6,3 m(3), 8,5 m(3) and 12,7 m(3), volumes of accropodes were 6,3 m(3) and 9,0 m(3). After preliminary trials and trial production, an optimum mix proportion was chosen, in compliance with technical specification requirements. One of the main causes for concrete blocks cracking is the temperature difference between core and external surface of the blocks, so new blocks with new mix proportions were made (three variations in cement content). Temperature was measured at three characteristic points: in the middle of the cube, in the middle of vertical outer surface and in the middle of horizontal upper edge. Finally, optimal proportions of the constituent materials were adopted

The estimation of compressive strength of normal and recycled aggregate concrete

Procena čvrstoće pri pritisku se postavlja kao važan zadatak proizvođačima betona, naročito pri projektovanju betonskih mešavina i obezbeđenju zahtevanog kvaliteta proizvedenog betona. U radu je prikazano poređenje eksperimentalnih rezultata čvrstoće pri pritisku betona sa prirodnim i recikliranim agregatom sa rezultatima dobijenim na osnovu jednačina prikazanih u tehničkoj regulativi. Prikazan je koeficijent determinacije eksperimentalnih podataka i rezultata dobijenih na osnovu preračuna prema jednačinama datim u EN 1992-1-1, ACI 209 i tabeli za preračun datoj u SRPS U.M1.048. Prikaz zavisnosti čvrstoće pri pritisku betona na osnovu jednačina datih u radu se odnosi na određivanje zavisnosti u odnosu na vrstu upotrebljenog cementa i starosti betona negovanog na konstantnoj temperaturi.Estimation of concrete strength is an important issue in ready-mixed concrete industry, especially, in proportioning new mixtures and for the quality assurance of the concrete produced. In this article, on the basis of the existing experimental data of compressive strength of normal and recycled aggregate concrete and equation for compressive strength calculating given in Technical regulation are compared. The accuracies of prediction by experimental data obtained in laboratory as well as by EN 1992-1-1, ACI 209 and SRPS U.M1.048 are compared on the basis of the coefficient of determination. The determination of the compressive strengths by the equation described here relies on determination of type of cement and age of concrete with the constant curing temperature

Frost resistance of concrete with crushed brick as aggregate

Predmet istraživanja su betoni spravljeni sa recikliranom opekom kao agregatom. Eksperimentalni rad je obuhvatio više vrsta betona spravljenih sa istom količinom cementa (385 kg/m3) i istom konzistencijom (sleganje oko 1 cm). Kao agregat je korišćena reciklirana opeka i kombinacija reciklirane opeke i prirodnog rečnog agregata. Posmatran je uticaj upotrebljenih frakcija drobljene opeke i njihovog procentualnog učešća na čvrstoću pri pritisku, upijanje vode i otpornost prema dejstvu mraza. Na osnovu rezultata eksperimentalnih istraživanja može se zaključiti da se primenom reciklirane opeke kao agregata dobija novi kompozitni materijal sa zadovoljavajućim fizičko - mehaničkim karakteristikama.The investigation included concrete made by using recycled brick as aggregate. Experimental work included several types of concrete made with the same cement content (385 kg/m3), and same consistency (slump about 1 cm). Recycled brick and combination of natural river aggregate and recycled brick were used as aggregates. The influence of percentage and grain size of crushed brick aggregate on concrete compressive strength, water absorption and frost resistance were observed. On the basis of the results obtained during experimental research, a general conclusion can be drawn that the application of recycled concrete as aggregate can lead to new composites with satisfactory physical-mechanical properties