Concrete Specification Research Articles

순환굵은골재를 포함하는 콘크리트의 역학적 특성 및 강도 예측

KS기준 및 콘크리트표준시방서에는 순환골재를 사용한 콘크리트의 압축강도를 27 MPa 이하로 제한하고 있으며, 이에 따라 27 MPa를 초과하는 순환골재 콘크리트에 대한 역학적 특성에 대한 연구결과는 부족한 상황이다. 따라서, 이 연구에서는 순환굵은골재 사용의 확대를 위해 압축강도 30~60 MPa 범주의 굵은순환골재를 사용한 콘크리트의 압축강도를 포함한 역학적 특성을 연구하였다. 실험변수로써 물-시멘트 비와 굵은순환골재의 치환율을 고려하였다. 고려된 물-시멘트 비는 0.36, 0.46 및 0.53 이고, 순환굵은골재의 치환율은 30, 50, 70 및 100%이다. 실험변수에 따른 순환골재 콘크리트의 7일 및 28일 압축강도, 탄성계수, 인장강도 및 파괴계수 특성을 분석하였다. 물-시멘트 비가 0.36일 때의 탄성계수에 비해 0.53일 때의 탄성계수는 10% 이상 감소하였다. 탄성계수 실험결과와 기존설계코드에 의한 탄성계수 예측결과를 비교하였으며, 설계코드에 의한 탄성계수 예측결과는 실험결과를 과다평가하고 있다. 반면에 설계코드에 의한 파괴계수 예측결과는 압축강도 40 MPa 이상의 콘크리트의 파괴계수 실험결과를 과소평가하고 있다. According to KS and Standard Specifications for Concrete, the compressive strength of concrete containing recycled aggregate is limited to 27 MPa and thereafter there are little research on concrete containing recycled aggregate of its compressive strength of greater than 27 MPa. Therefore, to expand the applicability of concrete recycled coarse aggregate(RCA), this paper concerns the mechanical properties of concrete containing RCA with compressive strength ranging from 30 to 60 MPa. The experimental parameters were water-cement ratio and replacement ratio of RCA. Water-cement ratio(w/c) was 0.36, 0.46 and 0.53, and replacement ratio of RCA was 30, 50, 70 and 100%. The experimental results were discussed about compressive strength, elastic modulus, split tensile strength and modulus of rupture. Test results of elastic modulus were compared to the design code predictions. Experimental elastic modulus for concrete with w/c=0.53 decreased by greater than 10% compared with that for concrete with w/c=0.36. The design code predictions for elastic modulus overestimated the experimental results. Whereas, the design code predictions for modulus of rupture underestimated the measured values.

Temperature Reduction of Concrete Pavement Using Glass Bead Materials

In this study, different proportions of glass beads used for road marking were added into the concrete samples to reduce the temperature gradient through the concrete pavement thickness. It is well known that decreasing the temperature gradient reduces the risk of thermal cracking and increases the service life of concrete pavement. The extent of alkali–silica reaction (ASR) produced with partial replacement of fine aggregate by glass bead was investigated and compressive strength of concrete samples with different proportion of glass bead in their mix designs were measured in this study. Ideal results were obtained with less than 0.850 mm diameter size glass beads were used (19 % by total weight of aggregate) for C30/37 class concrete. Top and bottom surface temperatures of two different C30/37 strength class concrete slabs with and without glass beads were measured. It was identified that, using glass bead in concrete mix design, reduces the temperature differences between top and bottom surfaces of concrete pavement. The study presented herein provides important results on the necessity of regulating concrete road mix design specifications according to regions and climates to reduce the temperature gradient values which are very important in concrete road design.

Mechanical Properties of Self-Compacted Concrete

In this research, trial mixes were conducted according to Self-Compacted Concrete (SCC) specifications, a mix that gave a higher compressive strength to the age of seven days has been selected. Then after selecting the appropriate mix, concrete samples had poured and were distributed into five groups; each group consists of six cubes, six cylinders, and six prisms. The samples of each group are testing for compressive, tensile splitting, and flexure strengths respectively for the ages of 7, 14, 28, 60, and 90 days respectively. Before of conduction of destructive tests, the samples were tested using ultrasonic waves to determine the relationship between the concrete strength and pulse velocity and in the same way for all ages in above. Experimental results showed that, all concrete mechanical properties have improved, and the maximum improve was in flexural strength followed by compressive strength and tensile splitting strength. The cube compressive strength increased according to (G1 at 7 days curing) from 34.3% to 71.8%, the percentage of increase of tensile strength according to (G1 at 7 days curing) from 16.8% to 64.3% , modulus of rupture increased according to (G1 at 7 days curing) from 34.6% to 98.7% for ages (14, 28, 60, 90 days) respectively. Pulls velocity increased according to (G1 at 7 days curing): For cube from 5.1% to 23.9%, for cylinder from 21.4% to 40.3%, for prisms from 7.1% to 29.2%.

Evaluation of Surface Resistivity for Concrete Quality Assurance in Missouri

This research evaluated a series of Missouri Department of Transportation (DOT) concrete mixtures to verify existing relationships between surface resistivity (SR), rapid chloride penetrability (RCP), and the AASHTO penetrability classes. Eleven mixtures that represented a range of currently allowable mixtures and several mixtures with potential use were produced in the laboratory. The classes of concrete mixtures included those used for paving, bridge deck, structural, and repair. The results showed an excellent correlation between SR and RCP that matched existing relationships provided by AASHTO and other state DOTs. The structural mixture containing 50% Class F fly ash had the best performance with very low chloride ion penetrability at 90 days. A ternary paving mixture with 20% Class C fly ash and 30% slag replacement for cement also demonstrated low penetrability as well as high compressive strength, with an average compressive strength value of over 9,000 pounds per square inch at 90 days. The two repair mixtures showed moderate to low penetrability readings and high early strength, consistent with their desired purpose. The extensive amount of SR testing (>4,500 tests) of 14 concrete mixtures at ages ranging from 3 h to 90 days by multiple laboratories, types of equipment, operators, and curing conditions verified the RCP. SR testing presents an opportunity to improve Missouri DOT concrete mixtures and specifications to increase durability without significant additional testing costs.

SELF COMPACTING CONCRETE (SCC) AS GREEN CONCRETE WITH RECYCLED CONCRETE AGGREGATES (RCA) – AN EXPERIMENTAL STUDY

The construction industry has become one of the main sources of environmental pollution due to the emission of carbon monoxide and other pollutants during the production of construction materials and operation of construction equipment. Self-compacting concrete (SCC) provides a healthier working environment by avoiding noise pollution, emission of smoke and vibrations during construction. Also, the depleting sources of natural aggregate (NA) and disposal problem of demolished waste have prompted the researchers to take up studies& investigations on the use of Recycled Concrete Aggregate (RCA) in structural concrete. Thus, SCC with RCA has more significant environmental related advantages in comparison to the vibrated concrete. This paper presents experimental results of investigations carried out on SCC of grade M20 with RCA designed on the basis of modified NAN-SU mix design and the workability tests performed in this research were as per The European (EFNARC) Guidelines for Self Compacting Concrete (SCC) Specification to arrive at the SCC mix proportions. Workability and hardened state properties of Self-compacting concrete (SCC) with various percentages of RCA as partial replacement of natural aggregates (NA) (0%, 25%, 50% 75% & 100%) were studied. The results have indicated that the natural aggregate can be replaced completely with the RCA for low strength concrete with more or less 10% deviation in strength which can be compensated by proper designing of mix.

Briefing: Abrasion performance of concrete in coastal structures

Abrasive wear of concrete in coastal structures can be a significant issue in areas where coarse or gravel sediments abound. In such environments, abrasion may be the governing factor for concrete specification in new construction. In the case of hard defences, concrete will constitute a major project cost, thus necessitating optimisation of mix design. This briefing paper explores some of the background to the problem and existing approaches in design codes. A case study of a major coast protection scheme in the UK is discussed, focussing on the approach to concrete specification through abrasion testing.

Concrete Mix Design, Quality Control and Specification, 4th edn

Concrete Mix Design, Quality Control and Specification, 4th edn

Effect of Aggregate Gradation on the Stiffness of Asphalt Mixtures

Abstract Aggregate gradation plays an important role in the behaviour of asphalt mixtures. Packing of aggregate is a very important factor that will be affected by changing the aggregate gradation. Many researchers have investigated different ways of describing packing both theoretically and practically. Bailey ratios have recently been used to understand the volumetric properties of mixtures. In this paper, the Bailey ratios have been used, and two further ratios have also been introduced to allow the asphalt mixture gradation to be fully understood. Thirteen different aggregate gradations have been chosen within the 14 mm asphalt concrete specification to investigate the effect of particle size distribution on the stiffness of the mixture. It was found that variation in aggregate gradation has a significant effect on asphalt stiffness, even within specification limits, and a reasonable correlation between the set of ratios investigated and the Indirect Tensile Stiffness.

Concrete Mix Design, Quality Control and Specification, fourth edition

Concrete Mix Design, Quality Control and Specification, fourth edition

잔골재 표준입도를 고려하여 조파쇄 바텀애시를 혼입한 일반강도 모르타르의 성능

Properties of normal-strength mortar containing coarsely-crushed coal bottom ash considering standard particle size distribution of fine aggregate were investigated. Mortar containing raw bottom ash was applied as a reference. By crushing the bottom ash with a particle size larger than fine binder but smaller than fine aggregates, i.e., coarse-crushing, water absorption and specific gravity of the particles could be controlled as similar levels to those of natural fine aggregates. Workability and strength of the mortar were not changed and even increased when the coarsely-crushed bottom ash was added considering standard particle size distribution in Standard Specification for Concrete, while those were decreased when raw bottom ash was added without any treatment. When a replacement ratio of coarsely-crushed bottom ash was less than 30 vol.%, there were no significant decrease in dynamic modulus of elasticity and dry shrinkage of the mortar.

Challenges of using systems engineering for design decisions in large infrastructure tenders

Decision-making in the tender phase of large, multidisciplinary, integral infrastructural projects is a complex task for contractors. They have to make decisions in design, construction, maintenance and regularly financing that will have long-term effects based on complex client requirements. The constrained environment of a tender, such as limitations of time and budget, and the unique context of every tender add more complexity. Therefore, no standard models are available for structuring the decision-making process in public tender procedures. Introducing systems engineering (SE) in the construction industry has led to more structured, process-based working methods. Dealing with uncertainty in design information due to the low level of concrete specifications is for the contractors’ decision-making process still a significant challenge. As a result, contractors struggle with designing a solution that will not only persuade the client, but will also deliver the optimum value and reduce the risks associat...

Effects of recycled paperboard mill wastes on the properties of non-load-bearing concrete

Population growth and increasing demand for industrial enterprises such as pulp and paper production lead to environmental problems such as over-exploitation of resources and pollution of soil, air and water. Thus, for the importance of reducing the negative effects of incineration and landfilling of wastes for the protection of environment, two kinds of recycled paperboard mill wastes were used as partial replacement of sand (volume percentage), to produce non-load-bearing lightweight concrete. Waste type 1 consists of paperboard chips mixed with small amount of sand, and waste type 2 consists of paperboard chips mixed with expanded polystyrene and nylon. This study was carried out in laboratory scale to achieve acceptable strength and minimum density by using maximum amount of waste, in accordance with ASTM-C129 for non-load-bearing lightweight concrete construction. Therefore, three types of concrete, including concrete containing waste type 1 (replacing 0, 60, 70 and 80 % of waste and sand), concrete containing waste type 2 (replacing 0, 55, 75 and 95 % of waste and sand) and concrete containing both waste types, were constructed. Different tests on the fresh and hardened concrete, including slump, pH, oven-dry density, compressive and tensile strengths, flexural strength, flexural toughness and water absorption, were carried out. The results indicate that the use of waste type 1 is more reliable than waste type 2 in terms of concrete specifications and standard-conforming viewpoints. Results revealed that use of these wastes in concrete can save the paperboard industry disposal costs and produce ‘greener concrete’ for construction.

Concrete Mix Design, Quality Control and Specification, fourth edition

Concrete Mix Design, Quality Control and Specification, fourth edition

UHPC From Research to Standardization: European Approaches

Abstract In Europe, different approaches to standardize ultra-high-performance concrete (UHPC) materials, and the design of structures made from it, are pursued based on different philosophies and market situations. The first standard available was published in France. It primarily deals with material models and design procedures for steel-fiber-reinforced UHPC. Material-related aspects are not considered. This is because, as a rule, industrially prefabricated dry premixed concretes with consistent material properties are used. Thus, the European Standard for concrete materials, EN 206 [EN 206, 2012-03, 2012, “Concrete—Specification, Performance, Production and Conformity,” German Version, German Standardization Body, Beuth Verlag, Berlin], is of minor relevance. The philosophy in other countries, like in Germany, is to make UHPC a commonly available material based on individual, application-oriented compositions, as far as possible being manufactured in precast or ready-mix plants from appropriate regionally available raw materials. Thus, the application of UHPC will be favorably supported by considering UHPC to be part of the harmonized European concrete materials and design standards, EN 206, covering the material aspects, and EN 1992-1-1 [EN 1992-1-1: 2011-01, 2011, “Eurocode 2:2 Design of Concrete Structures. Part 1-1: General Rules and Rules for Buildings,” German Version, German Standardization Body, Beuth Verlag, Berlin] (Eurocode 2) covering the design. This approach requires advice on how to evaluate the appropriate raw materials, to prepare adequate mixtures, and to define technically based rules and requirements covering both mechanical, as well as durability aspects, e.g., by defining strength- and durability-related classes, as for ordinary and high-performance concrete. The requirements have to be related to reliable testing procedures. It has been proven by several research projects in Germany that European standard testing procedures may principally be adopted but have to be modified in some points, e.g., with respect to the specific fresh concrete properties, the specimen preparation, tests to evaluate the fiber efficiency, etc. These topics are under discussion in a UHPC-related committee of the German Standardization Body (DIN) drafting a standard-like technical guideline covering all three aspects, namely, materials, design, and testing. Another technical guideline on UHPC is elaborated by Fédération Internationale du Béton (FIB). The approach is “in between,” meaning that some material aspects are covered as far as their relevance for the structural design. The focus lies on the design covering different design procedures for fiber, as well as for conventionally reinforced structural elements.

On the verification of architectural reconfigurations

In a reconfigurable system, the response to contextual or internal change may trigger reconfiguration events which, on their turn, activate scripts that change the system׳s architecture at runtime. To be safe, however, such reconfigurations are expected to obey the fundamental principles originally specified by its architect. This paper introduces an approach to ensure that such principles are observed along reconfigurations by verifying them against concrete specifications in a suitable logic. Architectures, reconfiguration scripts, and principles are specified in Archery, an architectural description language with formal semantics. Principles are encoded as constraints, which become formulas of a two-layer graded hybrid logic, where the upper layer restricts reconfigurations, and the lower layer constrains the resulting configurations. Constraints are verified by translating them into logic formulas, which are interpreted over models derived from Archery specifications of architectures and reconfigurations. Suitable notions of bisimulation and refinement, to which the architect may resort to compare configurations, are given, and their relationship with modal validity is discussed.

Concrete Thinking for Sculpture

This article proposes to explore the variegated plays of concrete as a travelling concept through four specific examples, viewed from the locality of the Yorkshire Sculpture Triangle in 2015. It will be argued that ‘concrete’ makes possible a triangulated reading practice in, of and for sculpture. The first example looks to the use of concrete, as a material, in some of the ‘technical’ experiments of Henry Moore, from the 1920s-1930s. The second example is the only public concrete sculpture by Barbara Hepworth on record, entitled Turning Forms. This is a kinetic work which was commissioned for the Festival of Britain in 1951. The psychic registrations of form-in-concrete will be explored through the aesthetic reception and understanding of these works. The third example examines the interplay between abstraction and concretion in a work of structural engineering: the Arqiva transmission tower on Emley Moor. This structure is a working utilitarian model of the telecommunications industry which took hold in the 1960s and 1970s. It is also a sculptural monument in a landscape of other design ‘types’. The fourth example considers the recent display of Lygia Clark’s Bichos at the Henry Moore Institute, Leeds, in 2014-2015. Bicho Passaro do Espaco (‘Creature Passing through Space’) (1960) reveals a particular translation between concrete thinking and concrete experience. These examples call upon the semantics of the concrete as a thought process and will track a journey into a region marked by three interconnected points: the concrete specificity in the material works selected, the broader field of concrete forms within which the sculptural may sit and the philosophical/aesthetic language of concrete for sculpture.

Investigation of Mix Design Method in Concrete Mixed with SSPCM Based on Mechanical Behaviors

As energy consumption of building and the reduction of carbon dioxide emissions have been emphasized, phase change materials(PCM) have been introduced as building materials due to its high heat storage performance. Using shape-stabilizing technique, octadecane/xGnP shape-stabilized PCM(SSPCM) can prevent leakage and improve heat storage performance. The objectives of this study are to propose mix design method of concrete mixed with SSPCM and to evaluate mechanical behaviors of the concrete mixed with SSPCM manufactured according to the proposed mix design. Based on the previously reported material test result, the existing mix design of plain concrete(Concrete standard specification, 2009) is modified to consider reduction of strength in concrete due to the addition of SSPCM. To verify the proposed mix design, specimens are fabricated according to the proposed mix design and axial strength tests and three-point loading tests are performed. Test results show that compressive strengths of the tested specimens reach the designed strength even when two different mix ratios of SSPCM are used. From three-point loading tests, flexural stresses decrease as mix ratio of SSPCM increases.

Stepwise refinement of sequence diagrams with soft real-time constraints

UML sequence diagrams and similar notations are much used to specify and analyze computer systems and their requirements. Probabilities are often essential, in particular for capturing soft real-time constraints. It is also important to be able to specify systems at different levels of abstraction. Refinement is a means to relate abstract specifications to more concrete specifications in such a way that constraints and analysis results are preserved through the transition. In order to allow soft real-time constraints to be included as an integral part of sequence diagram specifications, this paper presents an approach to extend UML 2.x sequence diagrams to capture probabilistic choice in general and soft real-time constraints in particular. The approach is supported by formal semantics and pragmatic refinement relations with mathematical properties that allow stepwise and modular development of specifications. An example focusing on communication is provided to demonstrate the language and refinement relations.

Voice as Action: Towards a Model for Analyzing the Dynamic Construction of Racialized Voice

Shirley Verrett once asked an interviewer: When you hear my sound, would you think it's a black The interviewer replied without hesitation: No. Verrett responds, That's it. And people told me this a long time ago. So, it mixes me up a little bit. (Schmidt--Garre 2000) Vocal timbre is commonly believed to be an unmanipulable attribute, akin to a sonic fingerprint. (1) Because the arises from inside the body, quotidian discourse tends to refer to someone's vocal sounds as inborn, natural, and true expressions of the person. What, then, are we to make of the common notion that a person's race is audible in her voice? While it has been conclusively demonstrated that many of the physiognomic aspects historically employed as evidence of a person's race--including skin color, hair texture, and dialect or accent (2)--actually evidence nothing more than the construction of race according to the ideological values of beholders, vocal timbre continues to elude such deconstruction. (3) Recent critical thought on the intermingling of the physical senses, including the so-called sensory turn in anthropology, new materialist philosophies, and recent advances in science, technology, sound studies, and media studies, underscores the need for scholarship that recognizes the and vocal categories as culturally conditioned material entities. (4) Trends such as the metaphorical notion of having voice (5) have to some degree obscured the material and multisensory aspects of voice. Conceived within the specific context of musicology and the general context of the humanities, this article seeks to demonstrate how the re-framing of implied by sensory and material inquiries redraws the topology of voice. I believe that this exercise may offer a deepened understanding of racial dynamics as they play out in our interactions with voice. Firstly, I oppose the common metaphor that equates with unified subjectivity--an association that assum[es] myths of constancy, coherence, and universality (6Ira Sadoff, quoted in Wheeler, 2008:37)--and instead examine the in its concrete specificity, as an unfolding event articulated through a particular sensing and sensed body. Secondly, I take issue with musical research that has traditionally construed as sound (or even conflated it with notations in a score), and instead suggest that because is always already materially grounded across all points of contact, we might understand it as corporeally enacted throughout all acts of voicing, transduction, and reception. (7) In short, I wish to offer vocal research that centers on the material, sonorous, and sensory as it is produced and imagined. Encouraged by the critical discourse enabled by the aforementioned sensory turn in anthropology, history, and philosophy, I submit four contentions about the ways in which vocal timbre is racially framed, and offer two interventions in the form of analytical models. The first two contentions address distinct, but nonetheless intermingling and reinforcing, perceptions of vocal timbre as an indicator of race, bearing in mind the fact that vocal sounds are never experienced in a purely sonorous realm, divorced from contextual information. Rather, non-sonic aspects, including preconceptions of race, tend to influence how sound is perceived. My third and fourth contentions deal with the definition and subsequent analysis of voice. Both claims account for the fact that each vocal sound uttered is materially produced and through that process imprinted onto the vocalizer's body and therefore, in time, becomes part of the vocalizer's vocal sound; and both recognize the complexity that this adds to any attempt at thinking through and race. I hence propose, drawing on concepts from dance and choreography, a theoretical and analytical framework that can address as the product of both societal shaping and individual articulation and materiality. …

The Unified Calculation Model for Shear Capacity of RC Slabs

Based on the experimental data of reinforced concrete (RC) slabs subjected to concentrated loads, the influence of breadth span ratio on the failure characteristics and shear capacity is analyzed. It can be concluded that with the increment of breadth span ratio, the failure patterns of RC slabs will gradually convert from beam shear failure to punching shear failure and then punching failure. Furthermore, a formula derived from a range of experimental data for the shear capacity calculation of RC slabs is put forward. Then a comparison between the calculated values and test results is carried out which demonstrates a high degree of consistency. The suggested formula has fairly good practical value in engineering application and provides a beneficial reference to the concrete specification revision in the future.