Change of Fatigue and Mechanical Fracture Properties of a Cement Composite due to Partial Replacement of Aggregate by Red Ceramic Waste

Fine-grained cement-based composites used in civil engineering and construction industry are usually made of cement-based matrix and natural aggregate (such as sand, gravel, crushed stone, etc.). Red ceramic waste aggregate is considered as a perspective replacement of a part of natural aggregate in modern environmentally oriented building materials. Fine-grained cement composite with natural aggregate partially replaced by ceramic waste aggregate usually show different mechanical fracture characteristics from ordinary fine-grained concrete. The specimens were tested at six different ages. This was the reason for conducting the research programme. Altogether, 6 fine-grained cement mixtures with various proportions of natural and red ceramic waste aggregate were prepared. The aim of this paper is to present and compare mechanical fracture properties obtained from static and fatigue tests. Bulk density, flexural and compressive cube strength, fracture toughness and fatigue properties (S−N − Wöhler curve) were of special interest. All of these tests are important for a practical application of concrete with ceramic aggregate for structures. All the results were statistically analysed and they showed that the fatigue and mechanical fracture properties were improved or at least kept up with the increasing levels of red ceramic waste aggregate. Environmental impact of application in construction industry of composites in question is discussed

UGIĘCIE DŁUGOTRWAŁE ELEMENTÓW FIBROBETONOWYCH WYTWORZONYCH NA BAZIE KRUSZYWA ODPADOWEGO

Zrównoważony Rozwój powinien dotyczyć każdej dziedziny gospodarki, również budownictwa, dlatego też podjęta w artykule tematyka jest szczególnie ważna dla obszarów północnej Polski. Artykuł prezentuje wyniki badań długotrwałych elementów wykonanych z betonu na bazie kruszywa odpadowego, zalegającego na hałdach kopalnianych, wzbogaconego dodatkiem w postaci minimalnej ilości włókien stalowych. Zakres prezentowanych badań towarzyszących obejmował wytrzymałość na ściskanie, moduł sprężystości oraz odkształcenia skurczowe i pełzania, wykonane na próbkach walcowych o średnicy 15 cm i wysokości 30 cm. Badania podstawowe przeprowadzono na specjalnie zaprojektowanych, skonstruowanych i skalibrowanych układach dźwigniowych, w których umieszczono 8 belek o wymiarach 0,15´0,20´3,3m. Belki i część walców obciążono po 28 dniach dojrzewania betonu i utrzymywano stałe obciążenie (6 kN×m dla belek i 1/3 wytrzymałości na ściskanie dla walców w próbie pełzania) przez okres 365 dni. Zakres prezentowanych w niniejszym artykule badań podstawowych ograniczono jedynie do ugięcia elementów belkowych, jednak ich analizę przeprowadzono w oparciu o normowe i autorskie metody obliczeń. W analizie wykorzystano aktualną metodę normową wg PN-EN-1992-1-1 i autorskie metody Tana wraz z różnymi zespołami oraz Bywalskiego. Na podstawie przeprowadzonych porównań i analiz stwierdzono, że wykorzystane metody szacowania wartości ugięcia długotrwałego są wrażliwe na stopień zbrojenia podłużnego belek. Część z nich wiernie odzwierciedla ugięcie dla belek o niskim stopniu zbrojenia (propozycja Bywalskiego), natomiast dla części lepszą zgodność uzyskano dla belek zbrojonych ekonomicznie - jedna z propozycji Tana z zespołem. Jednocześnie należy zauważyć, że metoda normowa wg PN-EN-1992-1-1 może być stosowana do określania ugięcia elementów belkowych wykonanych na bazie kruszywa odpadowego i włókien stalowych, jednak daje ona zawyżone wartości

Analysis of Rheological Properties of Cement Composites Based on Waste Materials

This report presents the results and analysis of long-term properties of fiber-reinforced cement composite based on waste aggregate. The long-term tests were carried out on the stand proposed by the authors for simultaneously testing three beams with dimensions of 100x200x2900 mm. A total of 8 mixtures of cement composites with aggregate from ceramic waste and waste sand were tested. Three beams were made for each mixture. One without dispersed reinforcement and two with 0.5% and 1.0% fiber reinforcement ratios. As dispersed reinforcement, steel cord and hooked steel fibers were used. The beams were subjected to a four-point bending test. The research was carried out for 1000 days. An optical system was used as an innovative solution in long-term research. Based on the measurements, the creep coefficient in the mid-span of the beams was determined, and the crackings of the beams were analysed. The results obtained using manual measuring devices and the optical system were compared. A good convergence of measurement methods was observed. During the analysis of the results, the coefficients modifying the method for calculating the crack width included in Eurocode 2 were determined

Numerical analysis of the reinforced concrete structure of a sports pool

W artykule przedstawiono analizę numeryczną istniejącego basenu. Analiza obejmowała trzy warianty obciążeniowe związane z jego modernizacją. Pierwszy przypadek obciążeń dotyczył rzeczywistej pracy basenu przed modernizacją. Natomiast dwa kolejne przypadki obciążeń obejmowały możliwe oddziaływania na basen po modernizacji. W wyniku przeprowadzonych analiz stwierdzono, że modernizacja basenu związana ze zmianą jego obciążenia, nie spowoduje przekroczenia jego stanów granicznych.The article presents the numerical analysis of the existing swimming pool. The analysis included three load variants related to the pool modernization. The first load case was related to the actual operation of the pool before its modernization. Next, two subsequent load cases included possible impacts on the swimming pool after its modernization. As a result of the conducted analyzes, it was found that the modernization of the swimming pool will not result in exceeding its limit states

Deflection of Steel Fiber Reinforced Concrete Beams Based on Waste Sand

The article describes the selected methods of calculating the deflection of steel fiber reinforced concrete beams. Additionally, the results of the study on the deflection of steel fiber reinforced concrete beams based on waste sand are presented. This paper compares deflections measured during the four point bending test of the steel fiber reinforced, waste sand fine aggregate concrete beam with values determined in accordance with Eurocode 2, the proposal of Tan, Paramasivam, and Tan, the modified method of Alsayed, Bywalski, and Kaminski, and Amin, Foster, and Kaufmann’s method. The analysis conducted shows that the best accordance with the study and calculation results was obtained by using the modified Alsayed method

Fracture Mechanical Properties of Cement Based Composites with Various Amount of Waste Aggregates

The importance of sustainability and recycling has become increasingly recognized and understood in academia and industry over the last several decades. Recycling of construction and debris waste is one of many avenues that provide a great opportunity to prevent waste material from entering landfills and reduce the construction industry reliance on decreasing natural resource supplies. The research program focused on fracture parameters of cement based composites with various amount of waste aggregate was conducted. There were prepared composites based on specifically composed aggregates (mixture of natural sand and red waste ceramic aggregate). There was utilized simplex experiment design. Altogether, 6 mixtures of aggregates were prepared. The aim of this contribution is to present and compared basic fracture parameter values. Flexural and compressive strength and fracture toughness were of special interest. All of these tests are important for a practical application of concrete with ceramic aggregates for structures

Modifying Water–Frost Resistance and Mechanical Properties of Lime Mortar Using Siliceous and Fluidised Bed Fly Combusted Ashes Activated with Cement

The research focuses on pozzolanic additives, which are compatible with traditional lime mortars, and enable the modification of the rheological, physical and mechanical properties of tested composites. It was noted that lime mortars with fluidised bed fly ash require sand without impurities to avoid possible ettringite crystallisation. The work presents siliceous fly ash and fluidised bed combustion fly ash to modify the frost resistance and mechanical properties of traditional lime mortars with and without the addition of cement. The results show better effects using fluidised bed ash. Traditional Portland cement CEM I 42.5R was used to activate ash and increase the results. The possibility of a significant improvement of properties is indicated with a hybrid addition to the lime binder of 15–30% ash (siliceous or fluidised bed ash) and 15–30% cement. Changing the class and type of cement provides an additional opportunity to alter the properties of the composites. For architectural reasons relating to colour, the suitability of lighter fluidised bed ash instead of darker siliceous ash and of white Portland cement instead of the traditional grey cement can be used. The proposed mortars can be the basis for future modifications with admixtures and additives, e.g., metakaolin, polymers, fibres, slag, glass powder and impregnating agents

Moment zginający belek żelbetowych z drobnego kruszywa odpadowego

This report presents the results of laboratory experiments of bending moment for fourteen concrete beams with steel bars. Twelve of the beams were made of waste fine aggregate concrete containing steel fibres: six with steel fibres 30/0.55 and six with steel fibres 50/0.80. The next two beams were made of plain concrete. The results of the experiments were compared with theoretical calculations based on a Eurocode 2 and also with the method suggested by Henager and Doherty.Artykuł przedstawia wyniki laboratoryjnych badań momentu zginającego czternastu belek żelbetowych. Dwanaście z nich wykonano na bazie piasku odpadowego wzbogaconego włóknami stalowymi tj.: sześć z włóknami 30/0.55 i sześć z włóknami 50/0.80. Pozostałe dwie belki wykonano z betonu zwykłego. Wyniki badań eksperymentalnych zostały porównane z obliczeniami przeprowadzonymi na podstawie Eurocode 2 i metody zaproponowanej przez Henager i Doherty

Laboratory Investigation and Numerical Modelling of Concrete Reinforced with Recycled Steel Fibers

In the last decades, fiber reinforced concrete have emerged as the possible key to revolutionize civil engineering. Among different types of fibers employed in concrete technology to date, the application of recycled steel fibers produced from end-of-life car tires appears to be a viable approach towards environmentally friendly construction. In this study, we demonstrate the laboratory research and numerical analysis of concrete reinforced with waste steel fibers recovered during the recycling process of end-of-life car tires. Concrete mixes with the following fiber contents: 0.5%, 0.75%, 1.0%, 1.25%, and 1.5% per volume were prepared and then tested in three-point bending conditions. The laboratory investigation revealed highly boosted properties of concrete under flexure. We further performed the finite element method (FEM) analysis of 2D models using Atena software in order to develop a material model allowing the numerical modelling of recycled steel fibers reinforced concrete (RSFRC) behavior. The parameters of RSFRC material model have been modified using the inverse analysis until matching the experimental performance of the material. The results, being in good agreement with the laboratory investigation, have indicated a high potential of RSFRC for real scale construction applications

Torsional Behavior of Waste Fiber-Reinforced Concrete

Factory made steel fiber and steel fiber derived from worn tires was used to develop cement concrete, which was subjected to torsional forces. A dedicated stand for torsion tests, allowing for the measurement of force, deflection, and torsion angle, was used. The test results showed that both the factory-made fiber and the waste steel fiber significantly improved torsional properties of the concrete matrix. The test results of specimens made with waste fiber were characterized by slightly worse results compared to factory-made fibers, but there was a significant improvement in torsional properties compared to samples without fibers. Taking into account the financial and environmental benefits, the application of waste steel fiber recovered from car tires could be an interesting alternative to using commercially sold steel fiber applied for the production of construction elements subjected to torsional forces