Vidni natur beton: svojstva, primena i tehnička regulativa

Different aspects of exposed concrete application are discussed in this paper. Short historical review of exposed concrete application in Belgrade area and in Serbia is presented. Also, special attention is paid to the problems related to construction and exploitation of exposed concrete structures. The significance of formwork's type and quality is also underlined. The review of relevant technical regulation covering this area is given. Finally, conclusions related to possible application of exposed concrete in contemporary civil engineering are derived

Statistička analiza rezultata ispitivanja fizičko-mehaničkih svojstava kontrolnih betonskih kocki

Cilj ovog istraživanja je prikupljanje, obrada i statistička analiza rezultata ispitivanja uzoraka betonskih kocki koji su ispitani u Laboratoriji za materijale Građevinskog fakulteta u Beogradu prema standardu SRPS ISO 4012:2000 u periodu od 2012. do 2017. godine. Za potrebe analize, preuzeti su podaci iz Izveštaja o ispitivanju kontrolnih betonskih kocki, prepoznate su i klasifikovane osnovne karakteristike očvrslog betona. Izvršena je statistička analiza datuma betoniranja, starosti uzoraka, sastava betona, zapreminske mase, čvrstoće pri pritisku, zahtevane marke betona itd. Statistika je pokazala da su najčešće upotrebljavani cementi sledećih oznaka: CEM II A-M (V-L), CEM II A-M (S-L), CEM II A-S, a da najveće učešće imaju marke betona MB 30 sa 66,8% i MB 40 sa 14,3% udela

Applicability of Construction and Demolition Waste in Geopolymers – A Screening Test

In this study, the applicability of construction and demolition waste (C&DW) in geopolymerization technology was investigated. The C&DW components, concrete and solid bricks, were collected from demolition sites in Belgrade, Republic of Serbia. The concrete sample came from a demolished fifty-year-old construction road, while the remains of solid bricks originated from a 1930s building. Prior to mechanical testing, the C&DW components were characterized by XRD analysis for their mineralogical composition. The results showed that the concrete waste consisted mainly of quartz (SiO2) and calcite (CaCO3), while the brick waste sample contained anorthite from the feldspar group (CaAl2Si2O8), wollastonite (Ca0.957Fe0.043O3Si) and mullite (Al2.4O4.8SiO6). The mechanical properties were examined using the screening method on three geopolymer mixtures, one of each mixture of concrete and brick powders and a mixture of both C&DW components. According to the standard SRPS EN 12390-3:2010 for cubic samples, the geopolymer samples were prepared with alkaline activators for testing the compressive strength as the dominant parameter in the mortar and concrete evaluation. The compressive strength values increased in the range of 2.4 MPa for concrete, 10.2 MPa for brick, and 10.8 MPa for the mixed geopolymer sample. The low compressive strength result of the concrete sample was the consequence of the mineral composition, i.e., the absence of aluminosilicate. However, the brick and the sample with a combination of both types of waste showed moderately satisfactory compressive strength, which could be the starting point for further investigations

Vidni natur beton: svojstva, primena i tehnička regulativa

Different aspects of exposed concrete application are discussed in this paper. Short historical review of exposed concrete application in Belgrade area and in Serbia is presented. Also, special attention is paid to the problems related to construction and exploitation of exposed concrete structures. The significance of formwork's type and quality is also underlined. The review of relevant technical regulation covering this area is given. Finally, conclusions related to possible application of exposed concrete in contemporary civil engineering are derived

Investigation of cement based composites made with recycled rubber aggregate

The results of experimental investigations performed on cement based composites made with addition of recycled rubber as a partial replacement of natural river aggregate are presented in this paper. Different properties of cement based mortar were analyzed, both in fresh and in hardened state. Tested properties in the fresh state included: density, consistency and volume of entrained air. In the hardened state, the following properties were tested: density, mechanical properties (compressive and flexural strength), modulus of elasticity, adhesion to concrete substrate, water absorption, freeze-thaw resistance and ultrasonic pulse velocity. The obtained results indicate that recycled rubber can be successfully applied as a partial replacement of natural river aggregate in cement based composites, in accordance with the sustainable development concept. The investigation showed that physical-mechanical properties of cementituous composites depend to a great extent on the percentage of replacement of natural river aggregate with recycled rubber, especially when the density, strength, adhesion and freeze-thaw resistance are concerned. The best results were obtained in the freeze-thaw resistance of such composites