Marijana Serdar

Shrinkage Behaviour of Fibre Reinforced Concrete with Recycled Tyre Polymer Fibres

Different types of fibres are often used in concrete to prevent microcracking due to shrinkage, and polypropylene fibres are among the most often used ones. If not prevented, microcracks can lead to the development of larger cracks as drying shrinkage occurs, enabling penetration of aggressive substances from the environment and reducing durability of concrete structures. The hypothesis of the present research is that polypropylene fibres, used in concrete for controlling formation of microcracks due to shrinkage, can be replaced with recycled polymer fibres obtained from end-of-life tyres. To test the hypothesis, concrete mixtures containing polypropylene fibres and recycled tyre polymer fibres were prepared and tested. Experimental programme focused on autogenous, free, and restrained shrinkage. It was shown that PP fibres can be substituted with higher amount of recycled tyre polymer fibres obtaining concrete with similar shrinkage behaviour. The results indicate promising possibilities of using recycled tyre polymer fibres in concrete products. At the same time, such applications would contribute to solving the problem of waste tyre disposal.

Use of sludge generated at WWTP in the production of cement mortar and concrete

U radu je opisana problematika vezana uz generiranje i zbrinjavanje mulja s UPOV-a (uređaja za prociscavanje otpadnih voda) u Hrvatskoj. Poseban osvrt je dan na mogucnost i opravdanost koristenja pepela dobivenog spaljivanjem mulja. Naglasak je stavljen na ugradnju pepela u betonskoj industriji, pri proizvodnji cementnog morta i betona. U radu su opisani rezultati do sada provedenih istraživanja u okviru svjetske prakse, s primarnim osvrtom na utjecaj ugradnje pepela na karakteristike cementnog morta i betona.

Shrinkage and Creep of Concrete Prepared with Quaternary Blended Cement

Environmental protection and energy saving are crucial problems set up against todays cement industry. The use of industrial by-products such as silica fume, slag, lime and fly ash in the concrete as cement substitution reduce cement production, and consequently lower the CO2 emission and save energy. This research work is inspired with the idea of replacing part of the cement with by-products of thermal power plants and metallurgical industry. Research already done in this area show that concrete prepared with blended cements has better permeability properties than the ordinary Portland cement concrete. In the present research emphasis was given on deformation properties of concrete and the effect of quaternary blended cements on total shrinkage, creep and mechanical properties of concrete. After performing shrinkage and creep tests and obtaining experimental results, shrinkage strain and creep coefficient were calculated according to European standard EN 1992-1 and Gardner/Lockman model, in order to compare the results and evaluate whether the values proposed by standards and model can be used during structural design of concrete prepared with quaternary blended cement.

Use of MID-MIX® treated sewage sludge in cement mortars and concrete

AbstractDeveloping beneficial applications for sewage sludge is a key challenge in many countries, given the amount of sludge generated and the disposal or recycling options currently available. Se...

High-Performance Concrete Incorporating Locally Available Industrial By-Products

AbstractThis paper presents the concept of industrial symbiosis in which four industries available locally (steel plant, thermal power plant, aluminum plant, and stone quarry) are connected with the concrete industry. By-products generated by these industries (slag, fly ash, red mud, and quarry dust) were activated with a small amount of clinker to form four concrete mixes. The heat of hydration and the autogenous shrinkage were monitored on the fresh concrete mixes. The chloride migration and electrical resistivity of the concrete were measured at different concrete ages over 91xa0days. Drying shrinkage was monitored for 56xa0days, and compressive strength was tested after 28 and 91xa0days. The concrete prepared with a high volume of fly ash, slag, red mud, and quarry dust had very low chloride migration coefficients and less drying shrinkage compared to concrete prepared with ordinary cement. The synergetic beneficial effect of these by-products is explained by their complementary chemistry and particle-size ...

Ocjena stanja betonskog obalnog zida izloženog djelovanju morske vode više od 30 godina

U radu su prikazane posljedice dugotrajnog izlaganja betonskih konstrukcija morskom okolisu, na primjeru betonskih blokova obalnog zida koji se nalaze u moru vise od 30 godina. Na blokovima je provedeno ispitivanje mehanickih (tlacna cvrstoca) i trajnosnih (plinopropusnost i kapilarno upijanje) svojstava, svojstava homogenosti (odskok sklerometrom i brzina prolaska ultrazvuka) te kemijska analiza (kolicina kloridnih i sulfatnih iona). Osim ispitivanja, provedeno je modeliranje ponasanja betona u morskoj vodi uz pomoc programskih paketa Stadium i Conclife.

Korištenje mulja s UPOV-a u proizvodnji cementnog morta i betona

U radu je opisana problematika vezana uz generiranje i zbrinjavanje mulja s UPOV-a (uređaja za prociscavanje otpadnih voda) u Hrvatskoj. Poseban osvrt je dan na mogucnost i opravdanost koristenja pepela dobivenog spaljivanjem mulja. Naglasak je stavljen na ugradnju pepela u betonskoj industriji, pri proizvodnji cementnog morta i betona. U radu su opisani rezultati do sada provedenih istraživanja u okviru svjetske prakse, s primarnim osvrtom na utjecaj ugradnje pepela na karakteristike cementnog morta i betona.

Condition assessment of concrete pier after three decades of exposure to sea water

U radu su prikazane posljedice dugotrajnog izlaganja betonskih konstrukcija morskom okolisu, na primjeru betonskih blokova obalnog zida koji se nalaze u moru vise od 30 godina. Na blokovima je provedeno ispitivanje mehanickih (tlacna cvrstoca) i trajnosnih (plinopropusnost i kapilarno upijanje) svojstava, svojstava homogenosti (odskok sklerometrom i brzina prolaska ultrazvuka) te kemijska analiza (kolicina kloridnih i sulfatnih iona). Osim ispitivanja, provedeno je modeliranje ponasanja betona u morskoj vodi uz pomoc programskih paketa Stadium i Conclife.

COST Action TU1404—Recent Advances of WG1: Testing of Cement-Based Materials

Work Group 1 (WG1) of COST Action TU1404 entitled “Testing of cement based materials” deals with determination of different properties of early age and hardened cement based materials with the following main objectives: (1) to recommend new advanced standard techniques which have been developed during the last years to become standard in the (near) future, (2) to test the ability of using different waste, recycled, and by-products as raw materials to design sustainable concrete mixture, and (3) to prepare a database of concrete mixtures which could serve designers and engineers to better predict lifespan, durability, and serviceability of concrete mixtures and structures. The paper describes organization and strategic view of WG1, presents its main objectives and gives important details about Round Robin Test, as a main tool that will be employed within WG1.

UTJECAJ OPLATA KONTROLIRANE PROPUSNOSTI NA MEHANIČKA I TRAJNOSNA SVOJSTVA ZAŠTITNOG SLOJA BETONA

Controlled permeability formworks (CPF) are made from fibrous membranes which absorbthe excess water and air from the surface layer of fresh concrete. By this mechanism, the surface layer of concrete with lower water-to-cement ratio, compared to the inner concrete, is created. The aim of the experimental research was to evaluate and compare the influence of two commercially available CPF materials on mechanical and durability properties of concrete. During preparation of concrete elements thickness of concrete cover was varied (3 and 5 cm). Also, once the set of samples was prepared, the same formwork was used again, to evaluate the possibility of multiple usage of the same material. Following mechanical and durability tests were performed: ultrasonic test, reboundnumber test, pull-off, gas permeability and capillary absorption test. Properties of concrete prepared with CPF were compared to the properties of concrete prepared in traditional wooden formworks.