Composition Of Concrete Mix Research Articles

Experimental study of mechanical properties of conventional concrete and geopolymer concrete with and without white soil

Abstract Concrete is an important material in the construction of buildings, but the use of cement produces CO2 gas emissions, so it is not considered environmentally friendly. One of the efforts to replace cement without reducing the quality of concrete involves utilising fly ash and a certain percentage of white soil as a substitute for fly ash. This study compares the compressive strength, elastic modulus, and Poisson’s ratio of conventional and geopolymer concrete with or without white soil substitution with 150 x 300 mm cylindrical specimens. The fly ash was F-grade from the Tanjung Jati B Jepara power plant, and the white soil was from Kupang, NTT. A conventional concrete mix composition used a ratio of cement to fine aggregate to coarse aggregate of 1: 1.831 : 2.434 with a cement water factor of 0.5. The geopolymer concrete maintains the same proportions, substituting cement with fly ash or white soil and incorporating an alkali activator composed of NaOH (12M) and Na2SiO3 Be52 in a 1:2.5 ratio. The concrete treatment is dry curing (room temperature). The results showed that conventional concrete has a higher compressive strength and elastic modulus but a lower Poisson’s ratio compared to geopolymer concrete.

ИСПОЛЬЗОВАНИЕ МЕТОДА ОПРЕДЕЛЕНИЯ ВОДООТДЕЛЕНИЯ ЦЕМЕНТА ПРИ ВХОДНОМ КОНТРОЛЕ КАЧЕСТВА В ПРОИЗВОДСТВЕ БЕТОНА

Fresh cement paste bleeding is one of the basic quality indicators, which, however, is not used for cements intended for the production of ordinary concrete mixtures. In some cases, during input inspection, it is necessary to obtain information on the quality of cement and its suitability for use in specific concrete mix compositions with minimal labor costs. Determining water separation allows to quickly obtain data on both the amount of bleeding water separation and its kinetics. The basic methodology is the standard method for determining the amount of water separation in GOST 310.6-2020, which additionally includes measurements of the height of the cement paste column, which allows plotting a water separation curve. In modified methods, measuring cylinders of various volumes were used. Statistical data on water separation of cement pastes from production batches of various plants are collected and presented. The relationship between water separation and normal consistency and setting time of cement is studied. The effect of a long (up to 5 months) shelf life of cements on the amount of water separation is studied. The geometric factors influencing the amount of water separation and the kinetics of the process are considered: the height of the cement paste column, the dimensions of the measuring cylinder. The influence of the initial water-cement ratio of the cement paste on the amount of water separation is studied. A three-stage process of water separation of cement is established with the prevalence of the channel type of water separation. A nonlinear decrease in water separation is noted with a decrease in the water-cement ratio. The obtained basic kinetic dependencies of water separation can be used to predict the water separation of concrete mixtures.

Research to evaluate the possibility of using sea sand to make roller compacted concrete as a surface layer for rural roads

In this period of very scarce river sand resources for construction activities, the use of sea sand and salt-contaminated sand to replace river sand in roller-compacted concrete is necessary and suitable to the needs of actual demand. This article presents some research results on the possibility of using the sea sand of "Can Gio" to produce roller-compacted concrete for rural road surface layers. The roller-compacted concrete mix composition is designed according to ACI 211.3R standards with a fly ash-to-cement ratio by volume of 0.3. The required compressive strength value of the roller-compacted concrete sample is 27 MPa at the age of 28 days. The technical requirements of roller-compacted concrete using sea sand have been evaluated including the hardness of the concrete mixture, compressive strength, and abrasion resistance of tested concrete, using the ratio of sea sand- aggregate by volume ranges from 0.41 to 0.50. The study also compared the physical properties of "Can Gio" sea sand according to the technical requirements of standard TCVN 13754:2023 to provide recommendations when using salt-contaminated sand and sea sand for roller compacted concrete mixture.

Low carbon concrete for prefabricated modular construction in circular economy: An integrated approach towards sustainability, durability, cost, and mechanical performances

The construction industry accounts for significant global resource consumption and carbon emissions through cement production, concrete mix design and building operation, which can be affected by the constituent composition, mechanical and thermal performance of concrete mix. Prefabrication and circular economy nowadays can be a game-changer for the construction industry. This study investigates the effects of concrete mix design on the sustainability, carbonation-induced durability, cost, and mechanical performances of a standard module of prefabricated modular construction throughout the whole life cycle in circular economy. Sixteen concrete mixes, including ordinary Portland cement (OPC) concrete blended with supplementary cementitious materials, ultra-lightweight cement composite (ULCC) with calcined clay and limestone replacement, and foam concrete, are examined. Comprehensive life cycle cost, mechanical, durability and sustainability assessments are conducted for the concrete mixes, considering expected service lives of 50, 100, and 150 years. Results indicate that prolonging service life from 50 years to 150 years in circular economy can improve the annual sustainability performances by up to 20 %. Utilizing lightweight concrete (ULCC and foam concrete) can reduce energy consumption for air-conditioning by 17 % and decrease transportation-related costs by from 30 % to 15 %. ULCC mix demonstrates superior overall performance due to its reduced weight, low thermal conductivity, and enhanced durability, showing improvements up to 25 % compared to OPC concrete.

FEATURES OF USING CRUSHED CONCRETE AS A COARSE AGGREGATE FOR CONCRETE

Problem statement. According to the results of a study by the Kyiv School of Economics as of June 2023 the total amount of direct documented damage to residential and non-residential infrastructure due to destruction and damage as a result of military actions exceeded $150.5 billion. During the post-war reconstruction Ukraine will face the problem of a large number of buildings and structures that will be subject to partial dismantling and demolition. This process will be accompanied by the generation of a significant amount of construction waste, which traditionally in Ukraine is taken to landfills without recycling. On the other hand, there will be a need for a large quantity of construction materials, the share of which in the construction cost may reach 50 %. To reduce the cost of objects, it is advisable to reuse materials from waste generated after dismantling. Such materials are called recycling. The most obvious option is the use of crushed concrete waste as a coarse aggregate for the production of new concrete. The purpose of the article. Identification of the features of recycled coarse aggregates from concrete waste and concrete with their use, determination of the influence of source concrete on the properties of recycled aggregates. Conclusions. The mesoscopic model of concrete with recycled coarse aggregate has been examined. The analysis of the current research results on both recycled concrete aggregates and concrete with their use showed that, in general, with correct calculations of concrete mix compositions that consider the actual physical and mechanical properties of recycled aggregates, the production of structural concrete is possible. At the same time, crushing methods and the grain composition of such aggregates have a significant influence. In order to standardize the approaches to the research of recycled aggregates, it is necessary to create an appropriate methodology or regulatory framework.

Increasing the Length of Concrete Pavement Slabs Using Shrinkage Reducing Admixture and Polypropylene Fiber

Pavement engineers frequently employ concrete pavements because of their benefits such as extended lifetime, superior performance and durability, and so on. However, there are some disadvantages of these pavements such as shrinkage which may lead to cracking, warping, and limiting the length of the concrete pavement slabs. Shrinkage reducing admixture (SRA) and polypropylene fibers can be employed to prevent or control shrinkage cracking. In this study, increasing the length of concrete pavement slabs using shrinkage reducing admixture and polypropylene fiber was investigated. For mix compositions, two water–cement ratios of 0.35 and 0.4 were employed, and the percentages of SRA and polypropylene fiber utilized in mixes were 2% and 1% by weight of cement, respectively. Slump, compressive strength, third point flexural strength, electrical resistance, free and restrained shrinkage tests were carried out as the experimental programming to investigate the effect of these materials on concrete behavior and evaluate the amount of concrete pavement design parameters. Statistical analysis and RSM were used to determine the significance of each parameter and their interactions on concrete properties. It was observed that the use of SRA had no influence on workability; however, polypropylene fibers reduced the slump flow of concrete. Also, the use of SRA resulted in a decrease in mechanical properties. In addition, the use of polypropylene fibers considerably enhanced the energy absorption of concrete. Furthermore, on concrete containing SRA and polypropylene fiber, the magnitude of free and restrained shrinkage and crack width were reduced. Finally, the length and thickness of concrete pavement slabs were evaluated using the experimental results on the Tehran-Shomal freeway as a case study. The slab length could be increased by about 20% without any significant change in the slab thickness using SRA and polypropylene fiber in concrete mix composition. This can lead to an increase in construction speed, improve the durability of pavement and generally increase the quality of the concrete pavement.

The Use of Recycled Polyethylene in Water‐Oil Emulsion for Lightweight Concrete

This study was to determine the suitability of recycled waste polyethylene (WPE) processed into water‐oil emulsion for lightweight concrete applications. The processed WPE in the form of polyethylene emulsion (PE‐e) is to promote physical interaction between the polymeric material and the cementitious matrix. The PE‐e used was also to partially replace concrete mix composition by PE‐e_1, PE‐e_2.5, PE‐e_5, and PE‐e_10 percents for reference concrete and to introduce plasticity into the mechanical behaviour of the concrete. The PE was processed into PE‐e to promote affinity for water, and this hydrophilicity was prominent in PE‐e_1 and PE‐e_2.5 percent concretes. Concretes with PE‐e_1 and PE‐e_2.5 percent formed good miscibility with the cementitious matrix. The density of the PE‐e concrete decreased to 13.68% with 10% PE‐e at 28 days. The replacement of mix constituents of PE‐e_1, PE‐e_2.5, and PE‐e_5 percent induced elastic to plastic behaviour in the concrete coupled with low water absorption. The FTIR data showed characteristic peaks of 3378 cm-1, 1740 cm-1, and 1148 cm-1 in the PE‐e. Using optical microscopy, it was shown that the PE particles were homogenously dispersed in the concrete matrix. The study shows the feasibility of using PE‐e_1 percent to produce structural lightweight concrete and up to PE‐e_10 percent for nonstructural applications mainly for light non‐load‐bearing partitions.

Concrete for Living Walls: Current Status and a New Design Recommendation

Concrete may be a promising material for application in living walls, broadening existing vertical greening systems and, most importantly, reducing installation costs. This study presents the concept of layered living concrete (LLC) wall panels that were developed and field-tested over the past 3 years. Simultaneously with long-term field observations, several laboratory studies on the selection of a rational concrete mix composition were carried out. Based on field data, the results of laboratory tests, and numerical simulations, a new LLC wall panel design was proposed. The new panel design retains the previous idea of a layered structure suitable for natural colonization by plants, but also adds improved material characteristics, rational dimensions, the economical use of water, and, potentially, the ability to hasten the greening of vertical surfaces.

Investigation of “elephant skin” on UHPC surface via a new test method: Influencing factors, formation mechanism and control measures

Shortly after the mixing of ultra-high performance concrete (UHPC), a viscoplastic layer forms on the surface, which is often colloquially called elephant skin. This layer can hinder the venting, through which air bubbles accumulate below the concrete surface, causing poor surface quality and aesthetics after finishing or resulting in an inferior composite in the case of multi-layer structural components. This paper aims to improve the surface performance of UHPC by reducing the effect of elephant skin. In the present work, the influence of various factors on the “elephant skin” formation on UHPC surface is firstly investigated using a newly developed test method that measures the development of the surface resistance of “elephant skin” on UHPC with time, based on the Vicat apparatus for testing the setting time of cement. Then, the formation mechanism of “elephant skin” on the surface of UHPC is discussed. Finally, some measures to minimize the effect of “elephant skin” on the UHPC surface are proposed. The results reveal that next to controlling the ambient relative humidity (RH) and temperature, an optimization of the concrete mix composition and manufacturing process, such as an increase of superplasticizer (SP) dosage, paste content and water-to-binder (W/B) ratio can help to slow down the “elephant skin” formation on UHPC surface, minimizing its negative effect while without significantly compromising the concrete compressive strength.

Experimental Investigation on Influence of Binder Constituents on Workability, Strength and Microstructure of SCGC

Abstract: The present study investigates the influence of bacteria on varying binder constituents to enhance the workability, strength, and microstructure properties of self-consolidating geopolymer concrete (SCGC). Geopolymer concrete is a sustainable alternative to conventional cement-based concrete, as it utilizes industrial by-products and reduces carbon emissions. The bacterial strains, known for their ability to promote mineral precipitation and improve concrete properties, are introduced in varying proportions to the geopolymer binder constituents. The goal of this experimental investigation is to better understand how Bacillus Cohnii bacteria affect the workability and strength of alkali-activated Self-consolidating Concrete (SCC) mix compositions. Three mix formulations with variable binder contents in the range of 400 kg/m3 and 450 kg/m3 were the subject of experimental research. This research work aims on investigating various binder constituents on Strength, Workability and Microstructure. Three different SCGC mixes were prepared by varying the percentage fly ash and Alcofine in range of 0%, 10%, 30% and 0%, 5%, 5% to the quantity of GGBFS respectively. Alcofine increases final setting time. For all mixes, ambient curing was done. As per EFNARC recommendations, the fresh qualities of SCGC were determined using the Slump test, T50 slump test, L-Box test, V- funnel test, and J-ring test. By conducting compression tests, split tensile tests, and flexure tests after 7, 14 and 28 days, the strength characteristics of SCGC were identified. The SCGC's microstructure and chemical composition were both determined by SEM and EDS analyses, respectively. According to test results, an alkaline solution sample with a 13M concentration and 450 kg/m3 of binder produced the highest compressive, flexural, and split tensile strengths after 28 days producing values of 58.32 MPa, 3.5 MPa, and 4.27 MPa, respectively.

A prediction of the printability of concrete through Artificial Neural Networks (ANN)

Digital Fabrication with Concrete (DFC) is acquiring potential because of the need of a technological advancement in the construction industry. The rheology of concrete finds evident meaning, because of the necessity of “handling” concrete in its early ages, when still fluid, and allowing it to immediately start developing its mechanical performance for the building process to advance. In order to make the material suitable for the printing process, it must comply with the printability requirements that are governed by parameters including yield stress and tensile and shear strength. Nowadays, the study behind the mix of a concrete material that fits all the printing requirements is still something that goes through an iterative trial and error process, due to the difficulty and the novelty that 3D Concrete Printing (3DCP) represents. For this reason, it can be helpful to develop a model, based on experience and the literature, that is able to predict if, for a given concrete mix design and printing process, all the requirements tied to 3DCP are satisfied. The employment of Artificial Intelligence (AI) can represent a solution to it. Applications of AI are very wide: referring to Civil Engineering, AI can be applied to concrete science and technology to handle several different topics including mix proportions, workability and overall mechanical performance, being instrumental to establish and assess multi-parameter correlations among the different involved material and process input parameters. AI tries to mimic the human brain, that is made up of many nerve cells driven by neurons which are in control of the external stimuli. The purpose of the paper is to analyse the printability through the implementation of AI techniques, designing a neural network between the parameters that control the mix composition and rheological properties of printable concrete mixes in the printability window.

Effect of Coarse Aggregate Grading on Mechanical Parameters and Fracture Toughness of Limestone Concrete

This work presents a discussion of the basic properties of broken mineral limestone aggregates with the specification of the properties affecting the fracture toughness of concretes made with these aggregates. To determine the influence of the grain-size distribution of coarse aggregates for each concrete series, two types of aggregate grain were used, with maximum grain sizes of 8 mm (series of concrete L1) and 16 mm (series of concrete L2). Fracture-toughness tests were carried out using mode I fractures in accordance with the RILEM Draft recommendations, TC-89 FMT. During the experiments the critical stress-intensity factor (KIcS) and crack-tip-opening displacements (CTODc) were determined. The main mechanical parameters, i.e., the compressive strength (fcm) and splitting tensile strength (fctm), were also assessed. Based on the obtained results, it was found that the grain-size distribution of the limestone aggregate influenced the concrete’s mechanical and fracture-mechanics parameters. The obtained results showed that the series-L2 concrete had higher strength and fracture-mechanics parameters, i.e.,: fcm—45.06 MPa, fctm—3.03 MPa, KIcS—1.22 MN/m3/2, and CTODc —12.87 m10−6. However, the concrete with a maximum grain size of 8 mm (series of concrete L1) presented lower values for all the analyzed parameters, i.e.,: fcm—39.17 MPa, fctm—2.57 MPa, KIcS—0.99 MN/m3/2, and CTODc —10.02 m10−6. The main reason for the lower fracture toughness of the concretes with smaller grain sizes was the weakness of the ITZ in this composite compared to the ITZ in the concrete with a maximum grain size of 16 mm. The obtained test results can help designers, concrete producers, and contractors working with concrete structures to ensure the more conscious composition of concrete mixes with limestone aggregates, as well as to produce precise forecasts for the operational properties of concrete composites containing fillers obtained from carbonate rocks.

THE POSSIBILITY OF USING SILICATE-CONTAINING WASTE IN THE PRODUCTION OF BUILDING MATERIALS

The solution to the problem of reducing the resource intensity of the construction industry is possible due to the involvement of large-tonnage waste in the production of building materials as a feedstock. Despite the fact that this task has been standing for a long time, the share of waste in raw materials for the production of building materials is still not large today. The article presents the results of research on the properties of concrete mixtures for self-leveling floors based on silicate-containing waste. In the course of experimental studies, the compositions of raw mixtures containing Portland cement, finely ground broken glass, concrete scrap, and liquid glass were optimized. The ratio of the composition of concrete mixes with the use of waste was revealed, at which the quality of the finished product is maintained. Keywords: cullet, concrete scrap, liquid glass, liquid glass, concrete mixtures.

Modification of Concrete Composition Doped by Sewage Sludge Fly Ash and Its Effect on Compressive Strength.

The sustainable development of construction materials is an essential aspect of current worldwide trends. Reusing post-production waste in the building industry has numerous positive effects on the environment. Since concrete is one of the materials that people manufacture and use the most, it will continue to be an integral element of the surrounding reality. In this study, the relationship between the individual components and parameters of concrete and its compressive strength properties was assessed. In the experimental works, concrete mixes with different contents of sand, gravel, Portland cement CEM II/B-S 42.5 N, water, superplasticizer, air-entraining admixture, and fly ash from the thermal conversion of municipal sewage sludge (SSFA) were designed. According to legal requirements in the European Union, SSFA waste from the sewage sludge incineration process in a fluidized bed furnace should not be stored in landfills but processed in various ways. Unfortunately, its generated amounts are too large, so new management technologies should be sought. During the experimental work, the compressive strength of concrete samples of various classes, namely, C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, and C35/45, were measured. The higher-class concrete samples that were used, the greater the compressive strength obtained, ranging from 13.7 to 55.2 MPa. A correlation analysis was carried out between the mechanical strength of waste-modified concretes and the composition of concrete mixes (the amount of sand and gravel, cement, and FA), as well as the water-to-cement ratio and the sand point. No negative effect of the addition of SSFA on the strength of concrete samples was demonstrated, which translates into economic and environmental benefits.

Multi-criteria comparison tools to evaluate cost- and eco-efficiency of ultra-high-performance concrete

This work was motivated by the increasing need for proper metrics and tools to demonstrate the effect of mechanical performance, as a function of concrete mix composition, in dictating the dimensions of structural elements and associated costs and embodied carbon dioxide (CO2) emissions. Mixture compositions associated with different concrete technologies were compared using multi-criteria comparison indices derived using structural design considerations and calculated using information on compressive strength, volumetric embodied CO2 and unit costs. In addition, predicted compressive strengths obtained with machine learning (ML) models are used to calculate these indices for a domain of mix proportions associated with ultra-high-performance concrete materials to generate multi-objective density diagrams (MODDs). The makeup of this tool facilitates the evaluation of rather complicated trends associated with mix proportions and multi-objective outcomes, allowing ML-based tools to be of easy interpretation by industry personnel with no expertise in artificial intelligence. MODDs could be used as aids in the decision-making process during mix design stages and serve as proof of mixture optimization that could be introduced in environmental product declarations. Results show that, in contrast to conventional wisdom, high-binder content and ultra-high strength concrete technologies are not necessarily detrimental to cost and/or eco efficiencies. For the applications evaluated herein, optimum solutions were mostly obtained with these types of concrete, suggesting that industry trends toward requiring minimization of embodied carbon footprint on a per volume of concrete basis are misguided and should not be used as a standalone metric to minimize the total carbon footprint of concrete structures.

Conventional and lightweight aggregate one-way reinforced concrete slabs subjected to fire and repeated loads: comparative experimental study

ABSTRACT This study presents experiments on nine one-way, reinforced concrete slabs with a slab weight reduction approach utilising lightweight expanded clay aggregate (LECA). All slabs’ sizes, steel reinforcing, and concrete mix composition were equal. They were subjected to the same repeated linear load and high-temperature conditions. The slabs were classified into three groups based on the presence of LECA. The main variables were the LECA ratio (0, 20, 40) % of coarse aggregate and the exposure temperatures (ambient, 400, 700) ℃. The repeated load was applied according to the ACI-19 code, 50% of the ultimate load for seven cycles. The results showed that the presence of LECA reduced flexural strength and fire resistance. The deflection of the slabs increased with the LECA. The most significant reduction in ultimate load capacity was approximately 35.1%, with a maximum increase in slab deflection of 37.2%. However, the stiffness decay was significant, about 50%.

Parameters of Concrete Modified with Micronized Chalcedonite.

The PN-EN 197-1:2012 standard allows the use of additives as the main component above 5.0% by mass, as well as as a secondary component in an amount less than 5.0% by mass of cement. Proper selection of additives positively affects the rheological characteristics and hardened concrete parameters during longer maturity periods. Additives have already become an integral component of concrete mixes. The aim of the research is to confirm the possibility of using the tested additive in the composition of concrete mixes in an amount of 15% relative to the amount of cement, which would solve the problem of storing and utilizing waste generated during the production of broken chalcedonite aggregates. The planned laboratory tests were carried out for concrete of three classes, C30/37, C35/45, C40/50, according to the PN-EN 206+A1:2016-2 standard, with the addition of chalcedonite dust in a constant amount of 15% relative to cement, and three series without additives as control series. The additive used for concrete mixes was chalcedonite dust with a diameter below 72 μm. It is waste from a broken aggregate mine. The research program included rheological tests of fresh concrete mix, i.e., air content, consistency, bulk density, as well as parameters of hardened concrete mix-compressive strength, absorbability, and capillary uptake. Compressive strength was tested after 7, 14, 28, 56, and 90 days. The laboratory tests aimed to verify whether the addition of 15% chalcedonite dust additive would not worsen the predicted hardened concrete parameters resulting from the designed concrete classes. All three tested series, C30/37, C35/45, and C40/50, with the addition of 15% chalcedonite dust relative to the amount of cement, achieved the assumed strength classes after 28 days of maturation. Concrete mix components were correctly designed. The addition of chalcedonite dust to the concrete mix did not cause a decrease in compressive strength to the extent that the analyzed series did not meet the normative requirements for concrete classes according to the PN-EN 206+A1:2014 standard. The results of absorbability testing indicate water absorption below 5%, while the increase in sample mass in the capillary uptake test gained similar values.

The oedometric EOS of equal strength and different mix compositions concrete specimens

The uniaxial compressive strength of concrete is commonly used to characterize concrete properties. The three-dimensional behavior of concrete structures is modelled by the hydrostatic and deviatoric relationships. These relationships are assigned to a given concrete according to its uniaxial compressive strength. Based on high velocity penetration test results at targets with identical concrete strength, that were prepared from different mix designs, the authors conjectured that the slab behavior is not governed by the uniaxial compressive strength but by the concrete composition.This paper presents an experimental investigation of concrete specimens of equal uniaxial compressive strength, that are made from different mix compositions, aiming at examining the equation of state (EOS) and its relationship to the uniaxial compressive strength and to several mix components, in attempt to validate the above conjecture.A set of specimens was prepared characterized by equal uniaxial compressive strength (fc = 56 MPa) measured on 100 mm sided cubes. Several specimen groups were tested, each of them made from a different composition. The mix variables were the weight of water (and the corresponding weight of cement), the aggregates weight and the maximum aggregate size. The specimens were tested in a special triaxial apparatus, to high load-levels (up to 5000 kN), at a quasi-static rate of ∼ 5 kN/sec. Test results show a wide scatter of the EOS curves, depending on the different mix parameters. These results refute the commonly assumed correlation between the uniaxial compression strength and the EOS and validates the conjecture that the EOS depends on the specific concrete mix composition.

Effect of Concrete Mix Composition on Greenhouse Gas Emissions over the Full Life Cycle of a Structure

As the need to determine and monitor carbon footprints (CFs) in the construction industry grows and given that concrete is a key construction material in this sector, the authors of the article conducted a carbon footprint analysis of 15 different concrete mixtures. The method for determining the carbon footprint of the entire life cycle of concrete was presented in detail. The authors conducted a comparative analysis of the CF for an example structure made of three significantly different concrete strength classes, in addition to determining the CF for 1 m3 of concrete mix. This analysis showed the need to consider the entire structure and the emissivity associated with the consumption of reinforcing steel when selecting the most favorable solution in terms of greenhouse gas (GHG) emissions. The study revealed that the composition of the concrete mix, primarily the type and amount of cement, has the greatest influence on the carbon footprint. Furthermore, the location and geometry of the structure, as well as the number of floors, should also be taken into account when selecting concrete. In the analyzed construction, the life-cycle phases related to the incorporation of the concrete mixture at the construction site (phases A4–A5) and those related to the demolition of the concrete at the end of its life cycle (phases C1–C4) constituted approximately 10% on average of the total value of CF emissions over the entire concrete life cycle.

Effect of coarse aggregate characteristics on the permeability properties of pervious concrete

This study analyses the effect of the geometric characteristics of coarse aggregate particles on the physical-mechanical properties and durability of hardened permeable concrete prepared by vibropressing compaction method. Four types of coarse aggregate were used to prepare the concrete mixture: gravel and crushed gravel stone of particle size fraction 4/16 and 8/16. The particle size and shape (rounded and rectangular) were considered. Four different concrete mix compositions were tested. The following properties of hardened permeable concrete were analysed in comparison: total porosity, water permeability, density, compressive strength, frost resistance, and abrasion resistance. The findings of this study showed that particle size and shape influence the physical-mechanical properties of permeable concrete. The total porosity and water permeability values were higher in the test specimens where crushed gravel stone of fraction 4/8 mm and 8/16 mm was used as coarse aggregate. The resistance of permeable concrete to volumetric freezing and thawing depends on the frost resistance of the coarse aggregate. It was also found that abrasion resistance of permeable concrete is affected by ravelling, i.e. disintegration of angular coarse aggregate particles from the concrete matrix.