Concrete Units Research Articles

CO2 capture of concrete units for pavement through accelerated carbonation cure

CO2 capture of concrete units for pavement through accelerated carbonation cure

HOMOGENEOUS LOW-CRESTED STRUCTURES FOR BEACH PROTECTION IN CORAL REEF AREAS

In many countries, the health of the marine ecosystems and the sun-sand-sea tourism depend on the coral reefs, which have been retreating around the world during the last decades. Homogeneous Low-Crested Structures (HLCS), made of large rocks or pre-cast concrete units, can be placed to mimic the functions of beach protection and eventually serve as a refuge for species. HLCS is a type of multi-purpose green infrastructure which is functionally similar to conventional low-crested structures but have higher porosity and are more easily dismantled for re-use. Contrary to conventional low-crested structures, the functionality of HLCS protecting beaches depends on the selected placement grid; this paper describes physical and numerical placement tests on horizontal bottom used to characterize the layers coefficients of Cubipod HLCS. The Bullet Physic Engine (BPE) numerical model used in the gaming industry, which is based on the rigid body method, is calibrated using the physical placement tests. The layer coefficients of Cubipod HLCS measured in the physical placement tests were similar to those obtained with the BPE numerical model, which could be used to optimize placement grids of HLCS on specific sea bottom conditions. Finally, the influence of the placement grid of Cubipod HLCS on the structure height, crest freeboard and wave transmission is analyzed.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/5bi-jpuJYcQ

Influence of concrete properties on the initial biological colonisation of marine artificial structures

Artificial marine infrastructures now cover large stretches of the available natural shoreline in many parts of the world. This is having a substantial impact on the local marine ecosystems as biodiverse natural hard substrata are being replaced with man-made structures, which have been shown to support lower levels of biodiversity.The ecological value of artificial coastal structures could be enhanced through careful design of pre-fabricated ecologically engineered units. Material selection is a critical parameter in the design of these units. To maximise the potential of concrete units to support and increase biodiversity, this paper explores the impact of binder composition, aggregate type and plasticizer on surface chemistry and early biofilm formation which influence subsequent colonisation. Experiments in the current study have shown that the addition of ground granulated blast-furnace slag (GGBS) to the mix can increase the levels of biodiversity supported while maintaining engineering performance requirements in terms of strength, chloride resistance and alkalinity. Conversely the aggregate type and use of a plasticizer have a minor influence. In particular, the addition of GGBS was shown to increase the biomass of diatoms, cyanobacteria and green algae and barnacle abundance one month after immersion on both sheltered surfaces and those exposed to wave action. Results suggest that concrete composition can alter the surface chemistry of artificial structures and thereby can improve the ecological value of these structures as habitats for marine life.

Shear strength and cracking mechanism of precast bridge columns with grouted sleeve connections

Precast columns are widely adopted in Accelerated Bridge Construction (ABC) due to its fast construction speed, environment amity and little interference to existing traffic. The bending behavior of precast columns with grouted sleeve connections under seismic effect has been widely studied. However, studies on the shear behavior of this kind of columns (for example, short columns under seismic effect) are limited, which restricts the application of ABC in seismic regions. This study proposes an approach for evaluating the shear cracking mechanism of sleeve region and the shear strength of precast columns with grouted sleeve connection. In this approach, the sleeve units and concrete units in the sleeve region are established according to the different stiffness between sleeve and concrete, individually. The cracking angle of membrane element of units is solved based on the Modified Compression Field Theory (MCFT). Thus, the crack developing diagram is drawn in light of the cracking range of units. An improved model for computing the shear strength of precast columns with grouted sleeve connection is presented by the predicted cracking method in this paper. A skeleton curve prediction method based on the principal compressive strain in compression zone has also been proposed and verified. In general, the improved MCFT method given in the paper is effective for predicting shear failure of precast bridge columns with sleeve connection.

Effect of concrete unit weight on the mechanical properties of bottom ash aggregate concrete

The depletion of natural aggregates has already progressed significantly in some regions and countries, including South Korea, and it is critical to identify replacement materials to address this problem. In recent decades, researchers have focused on low-cost industrial residues or solid waste as potential solutions, and this study involves application of bottom ash (BA), a byproduct of coal-fired electrical power plants, as fine and coarse aggregates. The application of BA to the manufacture of concrete is noteworthy in terms of economic as well as ecological aspects for preserving natural resources. In the experiment, a total of 20 concrete containing bottom ash (CCBA) mixtures classified according to W/C and the bottom ash aggregate (BAA) mixing ratios were evaluated for their workability and various mechanical properties. The results of the experiment showed that the factor having the greatest effects on the mechanical properties of concrete was the usage of coarse BAA or lack thereof, and that the rates of decline in mechanical properties due to the replacement of fine BAA were within levels that could be controlled by other design factors, such as W/C. This study provides a comparison between the experimental results and the prediction results of several existing design codes, which will serve as basic data for proposing a reliable, predictive CCBA structural design model.

Viewpoint: Service products, development of service knowledge and our community’s target audience

PurposeThis paper aims to emphasize a research priority on the understanding of service products and how services can be productized. Furthermore, it provides perspectives on the contribution of service research to management practice and who should be the main target audience of service research.Design/methodology/approachThis paper is based on the personal reflections of an author of two leading services marketing textbooks.FindingsThis paper develops three propositions related to service research. First, it advances that academic service research has neglected the important topic of productizing services and that service products should be treated as concrete units of deliverables to customers rather than something fuzzy of unspecified quantity. That is, service products should be developed, designed, specified, configured, modularized, bundled, tiered, branded, priced sold and delivered to customers. More research is needed on how organizations can do this. Second, this paper argues that academics frequently underestimate the significant contributions service research has made to management practice and details important contributions that originated from the service research community. Third, it is proposed that the main target audience of service research should not be the marketing, sales and service departments. Rather, it should be decision makers (especially C-level executives) across all functions who should develop a service perspective and service mindset.Research limitations/implicationsThis paper urges service researchers to focus on what are service products and how firm can create, manage and deliver them. Furthermore, it suggests that service researchers should be more confident and proud of the significant progress and contributions they have made to management practice over the past few decades. Finally, service researchers should tailor their messages for decisions makers of all organizational functions and departments in service organizations.Originality/valueAs a writer of five editions of a services marketing textbook, the author has sifted through three decades of service research. The reflections in this paper originate from this unique perspective.

Analysis of potentials and attractions for the development of cultural tourism in the South-West Planning Region of the Republic of N. Macedonia

This paper is the result of the conducted research activities in the preparing of a Sub-strategy for Cultural Tourism in the Republic of N. Macedonia in 2019 in which the author was directly involved. The research involved determining the current state of cultural tourism through situation analysis and valorization of various cultural tourism potentials. This resulted in specifying concrete spatial units and values that have the most favorable opportunities for active inclusion in the current tourism offer. Two types of spatial units were defined - existing and new areas which were zoned and mapped. Existing areas have the aim to enrich the current tourism offer in order to make them more attractive. New areas have the purpose for creating new tourism products and services that will be competitive. This paper examines the South-west Planning Region as the most developed in the country with the aim to promote cultural tourism development.

ROLE OF ENGLISH AFFIXOIDS IN MODERN UKRAINIAN, RUSSIAN AND FRENCH

AbstractBackground. The article is devoted to the influence of borrowed affixoids on the wordbuildingsubsystems of the target languages.
 Purpose. The aim of the article is to reveal the peculiarities of the influence of borrowingsfrom English on the word-building subsystem of the target languages and namely to define the roleof affixoids in productive ways of modern word-building. The aim preconditions the performing ofthe following tasks: analysis of the nature of affixoids; revealing peculiarities of borrowed affixoidsfunctioning in target languages.
 Methods. In the article the following methods are used: 1) for detecting the volume andmeaning of the term affixoid the method of the review of the existing literature has been used; 2) forrevealing the constituent parts of the lexical units the method of distributive has been used; 3) fordescribing the peculiarities of quasi-composites and existing word-patterns the methods ofonomasiological and formal analysis have been used.
 Results. If one analyses the appearance of the affixoid. -gate, it is necessary to take intoconsideration, that it is formed due to the so-called “intercalated” or “telescopic” formation ofnew words, when one word is “inserted” into another, as a result of which an unusual, occasionalformation appears. In modern Ukrainian and Russian we can reveal the development of newmeaning which is absolutely different from the primary meaning. Some people are even sure that -gate is the synonym of the word scandal.
 Borrowing word-forming models is another character feature of language that causes theappearance of quasi-composites. In French, for example, it is possible to observe the interestingphenomenon of borrowing not structural parts, but word-building samples. The presence of “falseEnglishisms” in the French language proves once again that very often not only separate words areborrowed, but also word-forming material.
 Discussion. Processes of borrowing influence the target languages in many different ways.The most common of them is direct borrowing, assimilation of concrete lexical units. But recentlythe facts of influence of the source language have become more and more common, so processes ofborrowing have an impact not only on the lexical subsystem of the target language, but also on theword-building level by assimilating productive affixes and affixoids, as well as common wordbuildingpatterns and models. The field of affixoids still requires new linguistic research, especiallyin connection with the processes of borrowing and the tendency of the modern languages tosimplification. It is very important to observe new ways of enriching vocabulary where assimilationof foreign affixoids is becoming more and more productive. The independent functioning ofaffixoids in target languages is also worth describing and analyzing.

Evaluation of Heat Insulation and Surface Resistivity of Mineral Lightweight Aggregate Concrete(MLAC)

In this study, the fixed water/binder ratio is 0.40, four mineral admixtures: fly ash (FA), blast furnace slag (BFS), desulphurization slag (DLS), and glass LED powder (GLP), were added to lightweight aggregate concrete (LWAC), replacing 10% or 30% of the cement content, to study their heat insulation efficiency and engineering performance and to compare the economic impact of mineral admixtures on LWAC. In terms of heat insulation, the thermal conductivity (K value) of the controlled sample was 0.484 kcal/(m.h. °C) and the addition of mineral admixtures changed the concrete unit weight and water absorption ratio, thus reducing the K value by 0.41% to 25.71% and improving the heat insulation. As the mineral admixture hydration products and chemical contents differed, the heat insulation of the LWAC varied as well. The study indicated that the heat insulation is the greatest in concrete with the addition of 30% FA, followed by concrete with the addition of 10% GLP. The addition of mineral admixtures is 30%, the resistivity is 72–455% of the control group, and the resistivity of FA and GLP is higher than the control group. The study is indicated that the proper addition of mineral powder material has an apparent effect on increasing heat insulation efficiency.

IOT and context‐aware learning‐based optimal neural network model for real‐time health monitoring

AbstractRecently, numerous context‐aware approaches are established to provide physiological information regarding the wellness and healthcare of each individual. While monitoring the health condition of the patient there occur delays in transferring data to the cloud. So to overcome such types of delays, numerous IoT sensors are developed to monitor, track, and sense the activities of the elder persons. This paper proposes four‐module architecture comprises of IoT module (IoT‐M), data pre‐processing module (DP‐M), context‐aware module (CA‐M) as well as decision‐making module (DM‐M) for storing and processing numerous cumulative sensor data. Here, an IoT comprises a concrete or substantial hardware ecological unit, that is, sensors and actuators. On the other hand, the context‐aware computational approach comprises of insubstantial software ecological unit in understanding and processing the context directly into an accomplishment through various IoT devices. The initial module or the IoT‐M comprises of sensors whereas in the DP‐M phase includes data collection phase, data storage phase, and data redundancy phase. The third phase or the CA‐M comprises two different types of layers namely fog layer, cloud layer. In addition to this, a context‐aware learning phase is also enumerated. In the final phase or the DM‐P phase, the feature extraction and classification is done by Back‐Propagation Neural Network along with the Adaptive grasshopper optimization algorithm so as to obtain a best optimal solution. Thus, an alarm or a notification is sent to the medical practitioner regarding the health condition of the patient with very less response time, high accuracy, and a high scalability rate. The evaluation results and discussions are made by comparing our proposed approach with several other approaches and the evaluation results reveal that the proposed framework provides better results with high accuracy, scalability, network latency, and low response time.

Effect of Eggshell Waste Powder on Impact Resistance and Bond Charcteristics of Reinforced Concrete

This research studied the effect of eggshell powder as a partial replacement of cement on fresh and hardened properties of concrete. The cement was partially replaced with eggshell powder at these percentage 0%, 2.5 %, 5 %, 7.5% and 10%, (by weight of cement). The resulting concrete was compared for impact resistance, energy absorption, load-slip characteristics and ultimate bond strength. setting time (initial and final), slump, density and compressive strength also have been found. The obtaining results indicated the advantage of incorporation of eggshell powder in concrete. The concrete unit weight has not obviously affected by eggshell powder content. The 2.5% eggshell powder give the best results compared to reference mix.

Flexural capacity and ductility of lightweight concrete T‐beams

AbstractThe present study aims to estimate the flexural capacity and ductility of lightweight concrete T‐beams prepared using the expanded bottom ash and dredged soil granules (LWAC‐BS beams). Eight full‐scale beams were prepared under the main parameters including the unit weight and compressive strength of concrete and amount of longitudinal tensile reinforcement. The moment capacities and displacement ductility ratios measured for the present specimens were compared with those compiled from normal‐weight concrete (NWC) beams and lightweight concrete beams made using the expanded clay and fly ash granules (LWAC‐CF beams) with respect to the longitudinal reinforcement index (ωs). The coefficients for the equivalent rectangular stress block to assess the ultimate moment capacity of LWAC beams were formulated from the actual stress–strain curve of the concrete. The test results showed that the effect of the type of artificially expanded lightweight granules on the normalized cracking and ultimate moment capacities of LWAC beams was insignificant, whereas LWAC‐BS beams exhibited lower displacement ductility ratios than LWAC‐CF beams at the same ωs value. The maximum amount of longitudinal tensile reinforcement specified in ACI 318‐14 provision for preventing brittle failure of the beam needs to be lowered for LWAC beams. When determining the coefficients of the equivalent stress block for LWAC members, the concrete unit weight deserves consideration as a primary factor together with the compressive strength of the concrete.

Influences of earthquake input models on nonlinear seismic performances of minaret-foundation-soil interaction systems

Minarets, which are tall and slender structures, are important elements of mosques. Seismic performances of minarets can be strongly affected by the nonlinear dynamic soil-structure interaction and earthquake input mechanism models. The present paper investigates the influences of different earthquake input mechanism models on the nonlinear seismic performances of tall and slender minarets considering nonlinearity of both soil and structure behaviors. Three different minaret types constructed with concrete, masonry brick and stone materials are selected for the applications. Direct soil-structure interaction (SSI) approach is taken into account in the 3D finite element models of the minaret-foundation-soil interaction systems. Tie contact between the soil and foundation interfaces and infinite elements on the far sides of the soil domain are utilized in the 3D models. Nonlinear behaviors of masonry and concrete units, and homogenous soil domain are modeled using Concrete Damage Plasticity (CDP) and Mohr-Coulomb failure criteria. The standard rigid-base free, massless-foundation free, massed-foundation free and massed-foundation deconvolved earthquake input models are considered in the nonlinear seismic analyses. Three different earthquake records are selected for the nonlinear analyses and they are matched to the target response spectrum with return period of 475 years. The deconvolved ground motions at the rigid half-space bedrock are calculated from the matched records using the equivalent linear frequency domain analyses. Frequency and mode shapes, displacements, drift ratios, tensile strain and stress propagation patterns and damage ratios of brick, stone and concrete minaret models subjected to combined horizontal and vertical ground motions are determined for four earthquake input mechanism models and compared with each other.

IKTINOS a New Freight and Construction Standard to Evolve Concrete Beton Preparation from a Chaotic Contractor Site to a Container Box Mover International Industry

A local West Macedonia company sells a transportable beton concrete unit with a capacity of 60 tn every hour. The next step of this machine is to be fed with cement, aggregates, water and chemicals from standard containers. Our research focus on how to connect the various containers, topology layout, type of bus and cleaning. The results did not encourage us to continue our research temporary due to inability to attract research and development funds. We currently will be satisfied to sell a hand-full of “assembly line” contracts instead of a beton unit.

Behaviour of fresh and hardened concrete incorporating marble and granite sludge as cement replacement

The present article aims to study the effect of using marble and granite sludge, resulting from ornamental stone industry, as cement replacement on the properties of fresh and hardened concrete mixes. The chemical analysis, mineralogical composition, and physical properties of marble and granite sludge as well as OPC were measured using XRF, XRD, BET, and BT techniques. The experimental work has been conducted through two steps, the first step included preparation of nine mixes of blended cement pastes, and the second step included preparation of nine concrete mixes. The two steps were prepared using different proportions of marble and granite sludge substituting for cement binder by 10%, 20%, 30%, and 40% in addition to the control mixture with 0% sludge. The initial and final setting times of the blended cement pastes were determined using Vicat test. The workability of the fresh concrete mixes was determined using slump test. The physico-mechanical properties of all hardened concrete mixes such as water absorption, porosity, density, compressive, flexural, and splitting tensile strengths were measured at different curing ages starting with 7 days passing through 28 days and ending with 56 days. Regarding the durability performance of the hardened concrete mixes, various tests such as water penetration depth and chloride ion penetration were measured at 28 days of curing, and the acid attack test was determined at 7, 28, and 90 days of exposure after normal curing at 28 days.The results clearly revealed that there is an improvement towards the water penetration depth and sulphuric acid attack resistance at all replacement levels more than the control mixture. Regarding the other properties such as water absorption, density, strengths, and chloride penetration, there is insignificance decline up to 20% marble and granite sludge compared with the control mixes. It is recommended to utilize both marble and granite separately up to 20% as cement replacement in concrete making without adversely impact on its the mechanical or durability performance. The results of all hardened concrete mixes are in compatible with the requirements of concrete bricks and concrete paving units in terms of water absorption and compressive strength.

Monotonic behaviour of post-installed mechanical anchors installed in prestressed concrete hollow-core floor units

Post-installed anchors are used to connect structural and non-structural elements to the main concrete structure. Extensive research has been published on the behaviour of these anchor for various seismic loads and substrate conditions. However, the behaviour of post-installed anchors in prestressed concrete hollow-core floors is still largely unknown, despite several guidelines and acceptance criteria being published and manufacturers having qualified products available. The shallow concrete cover in the hollow regions compromises both the tensile and the shear behaviour of anchors installed in these regions, as acknowledge in international standard. The behaviour of anchors installed in the web regions can be assimilated to the behaviour of anchors installed in solid concrete, but the installation process can damage the prestressing strands. Additionally, it is not always possible for the installer to establish where the web regions or the hollow regions are. The behaviour of four types of anchors for non-structural applications was investigated, both in tension and shear loading conditions. The failure modes of the anchors were compared, in addition to the peak load, the displacement at peak load and the stiffness. The coefficient of variation was also included in the discussion. Anchors that were designed to be embedded deeper than the cover thickness in the hollow region exhibited a significant performance reduction (up to 35%). Anchors that were specifically designed to be installed in the hollow region performed poorly when installed in the web region. This behaviour was expected because the anchors were installed without complying with the instructions from the manufacturer, but justified as proper installation in the correct region cannot be guaranteed. Anchors that were embedded less than the thickness of the concrete cover in the hollow region did not experience any performance reduction. The recommendation was therefore to always use anchors assessed and approved for use in hollow core applications, considering that anchors that are shallower than the concrete cover in the hollow regions can help to mitigate the risks of improper installation.

Types of allography

AbstractVariation in writing is highly frequent at both the visual and the functional levels. However, as of yet, the associated notion of allography has not been systematically described. In this article, two major types of allography are proposed: graphetic allography, conceptually comparable to allophony, depends on visual similarity and captures how concrete units are associated with visual abstractions, i.e., how three graphs in <cabana> are instances of the basic shape |a|. Graphematic allography, conceptually closer to allomorphy, does not depend on visual similarity but groups together units that share the same function, i.e., represent the same linguistic unit (phoneme, syllable, morpheme, etc.) and are complementarily distributed, meaning there exist no contexts in which they contrast. An example is the positionally conditioned alternation between |σ| vs |ς| for the Greek grapheme <σ>. By means of a number of criteria, subtypes of graphetic and graphematic allography are proposed and examples are given from different writing systems. A special case that is discussed is the complex phenomenon of capitalization. Additionally, examples of variation phenomena that are not included in the concept of allography are given, and orthographic variation is addressed as a marginal case of variation dependent on the norm rather than the system.

On the coupled, flexural−flexural−torsional vibrations of an asymmetric concrete beam

This paper presents the analytical solution of an L-shaped cross-section asymmetric beam (concrete terrace unit) undergoing ‘triple coupling’, that is, flexural vibration in two mutually perpendicular planes (vertical and horizontal) plus torsional vibration about an axis passing through its shear centre, using the classical approach. Essentially, the procedure involved the development of three governing, coupled, partial differential equations based on Euler–Bernoulli theory for beams with isotropic material properties, from which the ‘exact’ solution was extracted. The warping effect was considered in the torsional equation. A comparison between the analytical solution and corresponding numerical and experimental results obtained earlier was attempted, and similarity and accuracy were discussed. It is reasonable to state that the analytical method in calculating the natural frequencies of a system is the most reliable, compared to experimental (needs, skills and experience) and numerical (calibration, updating, validation etc.). However, even the analytical solution may not be as accurate as expected, as it depends on several factors/parameters beyond the full control of the investigator. Some useful comments and conclusions are drawn.

Repair cost estimation techniques for reinforced concrete structures located at the seashore: Considering various probabilistic service life functions and actual mix proportions

RC (reinforced concrete) structures are durable and have a long service life. However, corrosion in embedded steel due to chloride ingress causes durability problems, and this poses a threat to structural performance degradation. The repair cost is very important for the maintenance of RC structures, through which the service life can be extended with reasonable performances. Unlike the conventional deterministic evaluation used to determine repair cost, the probabilistic method can provide a more reasonable result that considers various engineering uncertainties and continuous repair cost. In this paper, the repair cost for an apartment near the seashore was evaluated based on the actual concrete mix proportions and repair unit cost. Two patterns of PSLF (probabilistic service life function) using normal distribution and log distribution were considered for the repair cost evaluation. This was done after the derivation of service life was calculated based on two mix proportions. Within a given service life, various repair costs were evaluated and discussed that considered concrete mix proportions, the pattern of PSLF, and conventional techniques.

Characteristic compressive strength correlation of rubberized concrete interlocking masonry wall

The rapid growth in the construction industry has dictated the utilisation of the eco-friendly materials and recycling of wastes to produce sustainable products. In this study, rubberized concrete interlocking bricks have been developed by utilising crumb rubber (10%) and fly ash (56%) as partial replacements of sand and OPC, respectively. It is aimed to develop mean and characteristic compressive strength correlations of rubberized concrete interlocking hollow and grouted wall systems, corresponding to rubberized concrete interlocking brick and prism strengths. A systematic investigation of 20 rubberized concrete interlocking brick units, 10 hollow and grouted rubberized concrete interlocking prisms and 10 identical hollow and grouted rubberized concrete interlocking wall panels were cast, constructed and tested under compressive load. Results were statistically analysed and the design-charts for the mean and characteristic compressive strength of masonry were used. The results obtained for the strength of rubberized concrete interlocking brick, prism and wall revealed a normal distribution with 5% significant interval. Four types of regression models were proposed for statistical analysis and the best fit model was identified based on r2 (correlation coefficient). The power model for the mean and characteristic strength curves presented the best fit to the sorted data. The cracking pattern and modes of failure of the tested specimens were discussed. The relationships for characteristic strengths of rubberized concrete interlocking masonry hollow and grouted wall were derived in terms of rubberized concrete interlocking unit and prism strength and found to be fkw = 1.533fb0.290, fkw = 2.178fb0.337 and fkw = 1.119fp0.659, fkw = 1.023fp0.731, respectively.