scholarly journals The effect of fine aggregates produced from anthropogenic waste and low-modulus fiber on the workability of self-compacting concrete (SCC)

Author(s):  
D. A. Akhmetov ◽  
◽  
Yu. V. Pukharenko ◽  
Ye. N. Root ◽  
S. B. Akhazhanov ◽  
...  

This article gives information about the research of the new promising material in construction industry of the Republic of Kazakhstan, namely, self-compacting concrete (SCC). We have studied such important physical and technical properties as workability, durability, gain in strength in the early stages of concrete hardening. The data obtained are presented in summary tables, a mathematical model is given, generalizing conclusions are made.

2019 ◽  
Vol 8 (3) ◽  
pp. 2844-2848

The economy of a developing country depends to a great extent on the construction industry. Developing countries like India are investing heavily in infrastructure development. The excessive exploitation of natural resources for construction threatens the sustainability of aggregates and poses a number of serious problems. At the same time, the disposal of fly ash and stone residues in landfills cause several environmental crises and pollute the environment. This article deals with a study on the structural behavior of the partial replacement of fine natural aggregates by 0 -40% crystal stones in order to obtain the flow properties of fly-ash-based self-compacting concrete (SCC) by using super plasticizers. Many tests have been done to test the feasibility of using crystal stones in M30 grade SCC. On the basis of the results obtained, the optimum percentage of fine aggregates with crystal stone was calculated at 30% and it was concluded that the increasing percentage of crystal stone replacement by fine aggregates did not affect its workability. The structural performance of simply supported RCC beams of size 150 × 200 × 1500 mm made from SCC with crystalline stone was tested


2018 ◽  
Vol 146 ◽  
pp. 03011 ◽  
Author(s):  
Petra Nováková

Current requirements for building insulation are constantly increasing, not only in terms of the technical properties of the material used but also in terms of the environmental burden. This article focuses on the use of technical hemp in the building industry, describes individual products, its properties and uses. Part of the article is also the experience of realization and use of the building along with photographs.


2021 ◽  
Vol 1 (3) ◽  
pp. 76-86
Author(s):  
R.O. Maksimov ◽  
◽  
I.V. Chichekin ◽  

To determine the maximum loads acting in the rear air suspension of a truck at the early stages of design there was used computer modeling based on solving equations of dynamics of solids and implemented in the Recurdyn software. The components of the developed virtual test bench, includ-ing hinges, power connections, drive axles, a wheel-hub assembly with a wheel and a support plat-form, are considered in detail. The test bench is controlled using a mathematical model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The test bench is controlled using a mathemati-cal model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The use of such a test bench makes it possible to determine the loads in the hinges and power connections of the suspen-sion, to determine the mutual positions of the links for each load mode, to increase the accuracy of the calculation of loads in comparison with the flat kinematic and force calculation. The mathemati-cal model of the virtual test bench allows to carry out numerous parametric studies of the suspension without the involvement of expensive full-scale prototypes. This makes it possible at the early stages of design to determine all hazardous modes, select rational parameters of the elements, and reduce design costs. The paper shows the results of modeling the operation of a virtual test bench with an air suspen-sion in the most typical loading modes, identifying the most dangerous modes. The efficiency and adequacy of the mathematical model of the suspension was proved. Examples of determining the force in all the joints of the structure, the choice of maximum loads for design calculations when designing the air suspension of vehicle were shown.


2021 ◽  
Vol 79 (2) ◽  
pp. 110-121
Author(s):  
Alexandru LUCINESCU

Currently, the definition of security that was put forward in 1952 by Arnold Wolfers in his article “National Security as an Ambiguous Symbol” is widely cited within the field of security studies while the definition of this concept that have been advanced by Walter Lippmann in his book from 1943, “US foreign policy: Shield of the Republic” is largely absent, a situation which hinders the turning into a research topic of the connections between these definitions. However, there are authors who cite both the definition of security advanced by Wolfers and the definition of it put forward by Lippmann, but they either do not mention the existence of connections between these definitions or take notice of them but do not investigate them, with the consequence that a thoughtful consideration of this problem is lacking. In order to fill this gap in the study of the early stages of the development of security studies, this article provides an in-depth investigation of the links between the two definitions of security which reveals that Wolfers’ reflection on security was meant to explain implicit aspects of Lippmann’s definition of this concept but that eventually and somehow unintentional Wolfers advanced a different perspective on security.


2020 ◽  
Vol 17 ◽  
pp. 00250
Author(s):  
Rogat Minikayev ◽  
Lilia Gaffarova

Experimental samples of biological products based on endophytic microorganism strains were tested on sugar beet root plants. The studies were carried out at ZAI Agrofirm LLC, Zay District, the Republic of Tatarstan. The most effective preparations applied at the early stages (3–4 leaf phase) were RECB – 31 B (1.5 l/ha), RECB – 74 B (1.5 l/ha), RECB – 74 B (1.5 l/ha), RECB – 44 B (2.0 l/ha), RECB – 50 B (2.0 l/ha), and RECB – 74 B (2.0 l/ha). Biological preparations applied in the row closing leaf phase have an advantage over chemical preparations when applying RECB – 14 B (1.5 l/ha), RECB – 31 B (1.5 l/ha), RECB – 74 B (1.5 l/ha), RECB – 74 B (2.0 l/ha). At the late vegetation stages, experimental preparations increased the yield. A significant increase was observed when applying RECB – 95 B (1.5 l/ha).


2012 ◽  
Vol 18 (5) ◽  
pp. 724-734 ◽  
Author(s):  
Romuald Rwamamara ◽  
Peter Simonsson

Many of those working on construction sites are exposed to demanding work loads; construction workers lift and carry heavy materials and work in awkward postures. Occupational injuries and accidents due to poor ergonomics are more common in the construction industry and many times lead to human tragedies, disrupt construction processes and adversely affect the cost, productivity, and the reputation of the construction industry. In Sweden, it is reported that concrete workers have the highest relative work-related musculoskeletal injury frequency. Therefore, the use of ergonomic production methods to prevent this can have a significant human, social and financial impact. Research introduced here presents a case study of comparative analyses of ergonomic situations for concrete workers performing concrete casting processes. Three different ergonomic risk assessment methods were used to assess the physical strain, hand-arm vibration and noise affects risks involved in concrete casting work tasks. The combination of technical and managerial factors results in a system where workers are as efficient and safe as possible during their work tasks, and thus, makes the construction work environment sustainable. The aim of our research is to find practical methods to evaluate and compare two different concrete casting methods from an ergonomic perspective. The focus is on the production of cast-in-place concrete bridge constructions where the traditional concrete casting method is compared with the SCC (Self-Compacting concrete) casting method. To be able to identify work-related musculoskeletal injury risks due to concrete casting work tasks, QEC (Quick Exposure Check for musculoskeletal risks), PLIBEL (Checklist for identification for Ergonomics Hazards) and ErgoSAM (Ergonomic production technology method) methods were used. Ergonomic risks analysis methods QEC, PLIBEL and ErgoSAM have all shown capabilities to evaluate construction work activities and thus determine whether a construction work activity constitutes a musculoskeletal risk to the worker or not before any ergonomic intervention is introduced. As a result the present ergonomic risks emanating from work methods used in the traditional concrete placing can be significantly reduced with the use of self-compacting concrete (SCC) that eliminates awkward work postures, noise and hand arm vibration, thereby reducing if not eliminating musculoskeletal injuries among concrete workers during their concrete casting work tasks.


2018 ◽  
Vol 877 ◽  
pp. 248-253
Author(s):  
Thete Swapnil Tanajirao ◽  
D. Arpitha ◽  
Suman Saha ◽  
C. Rajasekaran

Large quantity of the quarry dust gets produced annually in the quarries during the extraction of the crushed coarse aggregate. As a result, disposal problems of this material gain significant momentum as these disturb environmental systems also. Now-a-days many of the countries like India is facing problems of ban on the extraction of sand and lacunae in procuring of fine aggregate, which is important constituent of the concrete. To overcome this problem, present study is focused on the suitability to utilize the quarry dust in Self Compacting Concrete (SCC) partially as fine aggregate with the natural fine aggregates. In this work, quarry dust is used as replacement of sand in a different level (0%, 15%, 30%, 45% and 60%) for producing the SCC. Fresh properties such as slump flow and V-funnel time have been measured for all mixes and hardened properties as compressive strength, splitting tensile strength and flexural strength of the concrete have been checked for all the mixes and it has been found that optimum utilization of quarry dust up to 30% can been done to produce SCC without compromising with its properties.


2015 ◽  
Vol 1125 ◽  
pp. 370-376
Author(s):  
Ahmad Farhan Hamzah ◽  
Mohd Haziman Wan Ibrahim ◽  
Norwati Jamaluddin ◽  
Ramadhansyah Putra Jaya ◽  
Norul Ernida Zainal Abidin

The influence of coal bottom ash on fresh properties of self-compacting concrete (SCC) were presented in this paper. Self-compacting concrete mixtures were produced by 0.40 water/powder ratio and coal bottom ash as a replacement of fine aggregates in varying percentages of 0%, 10%, 15%, 20%, 25% and 30%. The fresh concretes were tested for the key workability belongings of self-compacting concrete such as passing and filling abilities and segregation resistance. The fresh properties were investigated by slump flow; T500 spread time, sieve segregation and L-box test. It was found that the slump flow decreased whereas the T500 spread time increased with higher coal bottom ash content. The L-box blocking ratios changed from 0.92 to 0.65 and were mostly showed satisfactory blocking ratio. The presence of coal bottom ash improved the stability of SCC mixture and the segregation index obtained from sieve test reduced with greater bottom ash content. It can be concluding that the filling and passing ability of SCC decreased when the amount of coal bottom ash content increased. In addition, the segregation resistance index decreased with higher coal bottom ash content.


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