Papers by Keyword: Durability

Abstract: It is crucial to utilize industrial waste and recycled bricks in concrete production, particularly in lightweight concrete, for the sake of sustainability. The objective of this investigation is to produce sustainable, durable, and structural lightweight concrete by replacing natural aggregates (dolomite and sand) with industrial waste (plastic waste) and recycled bricks (crushed lightweight bricks). Two groups of mixtures were conducted in which coarse plastic waste and coarse crushed lightweight bricks were used to partially and fully replace the coarse aggregate in the first group. In the second group, besides replacing the fine aggregate with fine crushed lightweight bricks, the coarse aggregate is also partially and completely replaced, respectively. This experimental work investigated how sustainable lightweight concrete performs in terms of dry density, compressive strength, resistance to chloride penetration, sorptivity, water permeability, and ecological impact. Based on experimental data, replacing aggregate reduced the density of lightweight concrete by up to 1400 kg/m³, lowered its compressive strength by up to 33.8 MPa upon complete replacement of the aggregate, and diminished carbon emissions by up to 2.05%. Compressive strength correlates directly with dry density and inversely with sorptivity and permeability. Investigations have concluded the potential for producing eco-friendly lightweight aggregate concrete suitable for sustainable structural applications.

Abstract: An experimental study was carried out to evaluate the feasibility of using concrete compositions containing waste wood for structural and non-structural building applications. First, the inert and wood aggregates used in the composite design were characterized. Five compositions containing a reference, 50% and 100% of wood particles were then produced and characterized in terms of physical and mechanical performance (e.g., apparent density, abrasion, compressive strength, and flexural strength). The selected specimens were used for additional experimental tests. These included water absorption and thermal tests. Increasing wood waste content considerably lower compressive and flexural strengths while improving the thermal insulation quality of wood waste-cement composite. The durability assessment of selected compositions further showed that the abrasion resistance of manufactured specimen decreased by adding wood waste in the cement matrix while there was an increase of the capillarity absorption coefficients. It appears that the incorporation of waste wood particles into mortars decrease their thermal conductivities to 0.3 W/mK. The use of wood waste treated by a lime solution improves the studied properties.

Abstract: Since the inception of self-compacting concrete, there has been a growing interest in integrating waste materials into its composition. This study explores the performance of self-compacting concrete and fibered self-compacting concrete, incorporating recycled aggregates sourced from the demolition and crushing of previously tested specimens. Additionally, it investigates the influence of steel fibers, both of commercial origin and those recycled from waste tires. The analysis spans both the fresh and hardened states, encompassing twelve concrete mixtures to assess workability (through measurements such as slump flow, T500, and L-BOX), segregation resistance, compressive strength, and flexural strength. Furthermore, the durability of these concrete mixtures is evaluated by examining mass loss and compressive strength after 56 days of exposure to acidic environments (HCl and H₂SO₄). The study is organized into three distinct series of concrete mixtures. The first series explores concrete without any fiber additives, focusing on replacing filler limestone with recycled concrete powder and/or substituting coarse aggregates with recycled concrete aggregates. In the second series, commercial fibers are introduced at a dosage of 30 kg/m³. The third series replaces the commercial fibers with recycled fibers with hooked ends. The assessment of the hardened state reveals enhanced mechanical properties in the case of fibered self-compacting concrete (compressive strength increased by more than 9%, and flexural strength increased by more than 8%). Notably, the results highlight that recycled aggregates exhibit improved resistance to HCl acid attack. Interestingly, the replacement of commercial fibers with recycled fibers does not substantially affect the concrete's resistance to acid exposure.

Abstract: The paper deals with evaluation and comparison of the effect of two substances on reduction of concrete absorbability and increasing the durability. In four tests the effect of hydrophobic impregnation of investigated substances on various properties of test specimens was examined. The penetration depth, the rate of water absorption and alkali resistance, drying ratio and weight loss after freeze-and-thaw cycles in sodium chloride solution were the followed parameters. The positive effect of both substances on the final durability of concrete was confirmed.

Abstract: The paper deals with the methods of software optimization of the concrete structure in terms of environmental issues, durability, and cost. It links to previously developed software tool that enables multi-criteria optimization of a 1 m² one-way slab. A feasibility study focused on the optimization of larger structural units, and it analyses and compares methods of concrete structures optimization in terms of environmental impacts, durability, and life-cycle cost.

Abstract: The service life of structural members is significantly impacted by the durability of the concrete and that they are made of. The embedded reinforcing steel in durable concrete is protected from corrosion, and the possibility of concrete spalling in the concrete as a result of chemical attack is reduced. This study investigates the effectiveness of geopolymer concretes prepared using fly ash or a mixture of fly ash and slag (SLG). The performance of OPC concrete is likewise evaluated for comparing the durability of geopolymer concretes. This is done in order to compare the two types of concrete. All of the prepared specimens were submerged in theee types of distinct solutions up to 9 months. Four different types of solutions are (i) sodium chloride with 5% concentration, (ii) sodium sulphate 5% concentration, (iii) combination of magnesium sulphate with sodium sulphate with 5% concentration both, and sulphuric acid 3% concentration. The variation in properties were evaluated throughout the duration of the exposure period. According to the findings, it has been demonstrated that Na₂SO₄ (sodium sulphate) has the most significant effect on the geopolymer concretes, whereas sulphuric acid has the greatest potential to break down OPC concrete. With the effect of sulfuric acid, the strength reduction was 26.57% for OPC concrete and where as for flyash & SLG concretes it is 10.87% & 7.26% respectively. According to the findings, the durability performance of geopolymer concrete is, in general, better to that of cement concrete.

Abstract: The purpose of this study is to detect the bridging effect formed at cracks after external forces act on various types of fiber-reinforced concrete reinforced with microfibers ranging in size from 10 μm up to 40 μm using a recurrent neural network (RNN). The bridge effect, which is an advantage of fiber-reinforced concrete(FRC) and a criterion for judging usability, can prevent cracks and brittle failure of concrete by forming a net with fibers from cracks formed in concrete to transmit stress. In this study, concrete surface image data taken from crack sections of various fiber-reinforced concrete were collected to create a crack and bridge effect exploration model based on RNN. Afterwards, the features of the part where the bridge effect appeared were directly labeled to enable high accuracy detection in the data added after model production. As a result of detecting surface cracks and bridge effects after modeling, the more sophisticated the labeling, the more accurate image data analysis was possible.

Abstract: This work focuses on the issue of corrosion and durability of mortar mixtures in aggressive environment. The intention was to find out and compare the impact of replacements on the durability of cement mortar exposed to an aggressive environment by comparison of various substitutes for cement, which are currently not widely used for this purpose with the commonly used ones.

Abstract: Wastes from various industrial processes are used in the construction industry in the production of cement composites, for example as a replacement for part of the cement. In addition to contributing to promoting circularity and reducing the carbon footprint, several waste materials have properties that promote improved durability of the resulting composites due to their pozzolanic properties. This paper deals with testing of the pozzolanic activity of selected wastes from local manufacturing processes such as slag, zeolite, microsilica and fly ash using the thermal analysis method (TG/DSC). The highest pozzolanic activity after 2 days was observed for blast furnace slag, however, after 56 days it was recorded for fly ash and ladle slag. Blas furnace slag and microsilica showed very similar pozzolanic activities evaluated by a comparable amount of unreacted calcium oxide of about 35%.

Abstract: The paper presents and discusses the durability parameters of concrete (total water absorption, capillary absorption, and compressive strength), which have been monitored over a long-term period of 3 years. The concretes were prepared with recycled brick aggregate of fraction 4/8, the latter being surface treated by different procedures before mixing the concrete. Surface treatments allow the RBA to achieve a lower water absorption capacity (45-82% decrease), thus gaining a potential to optimize the amount of mixing water, and thus improve the quality of the concrete. After 3 years of curing, all samples still show better property values than the initial values at 28 days, indicating good durability over this period.