scholarly journals Screening of predominant microorganisms occurring on the concrete structures from selected locations

2021 ◽  
Vol 900 (1) ◽  
pp. 012010
Author(s):  
M Holosova ◽  
A Estokova
Keyword(s):  
Cement Paste ◽  
Microbial Growth ◽  
Raw Materials ◽  
Concrete Structures ◽  
Cementitious Materials ◽  
Cementitious Composites ◽  
Materials Research ◽  
Cultivation Process ◽  
Basal Media ◽  
The City

Abstract The aim of the present work is to provide an overview of the predominant microorganisms that effects structures of cementitious composites, which lead to biocorrosion, subsequently to the degradation of cementitious materials. Research is done by sampling of specimens taken from selected parts of the city of Košice. The sampling was mainly focused on insulated apartment panel buildings, part of the specimens was taken from uninsulated concrete and masonry plastered surfaces. Specimens were taken with sterile lab tubes, scalpels, and swabs by using dry, semi-dry and wet methods. The specimens were preserved in the cold place until their performance for the cultivation process. For cultivation purposes were important to prepare basal media for specimens of microorganisms and proceed isolation of cultures and their cultivation on appropriate media, identification of individual cultures. Data obtained after cultivation confirmed presence of predominant fungi genus such as Aspergillus, Botrytis, Cladosporium, Eutypella, Penicillium, Rhodotorula, Mucor, which create the ground for further research focused on the durability of cement paste based on secondary raw materials and their resistance against the predominant groups of microorganisms occurring in the objective location also by using extracts of several herbals as a prevention of microbial growth.

Evaluation and Application of Recipe for Binding Materials in Self-Compacting Concrete

2014 ◽  
Vol 629-630 ◽  
pp. 405-416
Author(s):  
Wei Chung Yeih ◽  
Jiang Jhy Chang ◽  
Mao Chieh Chi ◽  
Cheng Chin Chang ◽  
Ran Huang
Keyword(s):  
Raw Materials ◽  
Setting Time ◽  
Cementitious Materials ◽  
Heat Of Hydration ◽  
Test Results ◽  
New Era ◽  
Materials Research ◽  
Hardened Properties ◽  
The Stability

Concrete consists of many kinds of raw materials, the safety and quality of construction are greatly influenced by the stability of concrete. Thus, how to improve the performance of concrete and construction method, i.e. avoid the bleeding, segregation and honeycomb, etc, becomes a very important issue and imminent mission. This study discusses the different mixing designs of SCC with the amounts of cementitious materials ( OPC, GGBFS, and FA) ranged from 400 - 500 kg/m3. Meanwhile, the fresh and hardened properties of SCC, such as the slump flow, setting time, heat of hydration, and compressive strength were also determined. Test results indicate SCC binding materials can be classified by its compacting ratio. For instance, to pass the boxing test of R1/R2 within and without hindrance, the minimum binding materials should be 500kg/m3, 450kg/m3 and 400kg/m3. The optimum binding materials research shows if use cement, GGBFS and FA at the same time , it can increase the initial and final setting time and decrease the heat of hydration. The SCC binding materials’ concept will meet the requirement of " Safety, Durability, Workability and Ecology " for the new era. Thus, the amount of cement was at least 250kg/m3 or more for SCC mix design and the adding of GGBFS and FA was recommended to maintain 20 - 40 % of all cementitious materials based on the test results.

scholarly journals The Assessment of Strength of Cementitious Materials Impregnated Using Hydrophobic Agents Based on Near-Surface Hardness Measurements

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4583
Author(s):  
Martyna Nieświec ◽  
Łukasz Sadowski
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Concrete Structures ◽  
Surface Hardness ◽  
Cementitious Materials ◽  
Schmidt Hammer ◽  
Near Surface ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
The Impact

Recently, the surfaces of concrete structures are impregnated to protect them against the environment in order to increase their durability. It is still not known how the use of these agents affects the near-surface hardness of concrete. This is especially important for experts who use the near-surface hardness of concrete for estimating its compressive strength. The impregnation agents are colorless and, thus, without knowledge of their use, mistakes can be made when testing the surface hardness of concrete. This paper presents the results of investigations concerning the impact of impregnation on the subsurface hardness concrete measured using a Schmidt hammer. For this research, samples of cement paste with a water–cement ratio of 0.4 and 0.5 were used. The samples were impregnated with one, two, and three layers of two different agents. The first agent has been made based on silanes and siloxanes and the second agent has been made based on based on polymers. The obtained research results allow for the conclusion that impregnation affects the near-surface hardness of concrete. This research highlights the fact that a lack of knowledge about the applied impregnation of concrete when testing its near-surface hardness, which is then translated into its compressive strength, can lead to serious mistakes.

scholarly journals An Overview on the Rheology, Mechanical Properties, Durability, 3D Printing, and Microstructural Performance of Nanomaterials in Cementitious Composites

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2950
Author(s):  
Hongwei Song ◽  
Xinle Li
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Three Dimensional ◽  
Cementitious Materials ◽  
Research Area ◽  
Cementitious Composites ◽  
Split Tensile Strength ◽  
Contour Crafting ◽  
Wide Range ◽  
Active Research

The most active research area is nanotechnology in cementitious composites, which has a wide range of applications and has achieved popularity over the last three decades. Nanoparticles (NPs) have emerged as possible materials to be used in the field of civil engineering. Previous research has concentrated on evaluating the effect of different NPs in cementitious materials to alter material characteristics. In order to provide a broad understanding of how nanomaterials (NMs) can be used, this paper critically evaluates previous research on the influence of rheology, mechanical properties, durability, 3D printing, and microstructural performance on cementitious materials. The flow properties of fresh cementitious composites can be measured using rheology and slump. Mechanical properties such as compressive, flexural, and split tensile strength reveal hardened properties. The necessary tests for determining a NM’s durability in concrete are shrinkage, pore structure and porosity, and permeability. The advent of modern 3D printing technologies is suitable for structural printing, such as contour crafting and binder jetting. Three-dimensional (3D) printing has opened up new avenues for the building and construction industry to become more digital. Regardless of the material science, a range of problems must be tackled, including developing smart cementitious composites suitable for 3D structural printing. According to the scanning electron microscopy results, the addition of NMs to cementitious materials results in a denser and improved microstructure with more hydration products. This paper provides valuable information and details about the rheology, mechanical properties, durability, 3D printing, and microstructural performance of cementitious materials with NMs and encourages further research.

scholarly journals Stabilizing effect of methylcellulose on the dispersion of multi-walled carbon nanotubes in cementitious composites

2020 ◽  
Vol 9 (1) ◽  
pp. 93-104
Author(s):  
Mingrui Du ◽  
Yuan Gao ◽  
Guansheng Han ◽  
Luan Li ◽  
Hongwen Jing
Keyword(s):  
Carbon Nanotubes ◽  
Pore Solution ◽  
Cementitious Materials ◽  
High Ionic Strength ◽  
Cementitious Composites ◽  
Uniform Distributions ◽  
Stabilizing Effect ◽  
Multi Walled Carbon Nanotubes ◽  
The Stability ◽  
Walled Carbon Nanotubes

AbstractMulti-walled carbon nanotubes (MWCNTs) have been added in the plain cementitious materials to manufacture composites with the higher mechanical properties and smart behavior. The uniform distributions of MWCNTs is critical to obtain the desired enhancing effect, which, however, is challenged by the high ionic strength of the cement pore solution. Here, the effects of methylcellulose (MC) on stabilizing the dispersion of MWCNTs in the simulated cement pore solution and the viscosity of MWCNT suspensions werestudied. Further observations on the distributions of MWCNTs in the ternary cementitious composites were conducted. The results showed that MC forms a membranous envelope surrounding MWCNTs, which inhibits the adsorption of cations and maintains the steric repulsion between MWCNTs; thus, the stability of MWCNT dispersion in cement-based composites is improved. MC can also work as a viscosity adjuster that retards the Brownian mobility of MWCNTs, reducing their re-agglomerate within a period. MC with an addition ratio of 0.018 wt.% is suggested to achieve the optimum dispersion stabilizing effect. The findings here provide a way for stabilizing the other dispersed nano-additives in the cementitious composites.

Using of Untreated Carbon Nanotubes in Cement Compositions

2016 ◽  
Vol 865 ◽  
pp. 6-11 ◽  
Author(s):  
Kateryna Pushkarova ◽  
Maryna Sukhanevych ◽  
Artur Martsikh
Keyword(s):  
Carbon Nanotubes ◽  
Cement Paste ◽  
Cementitious Materials ◽  
Positive Influence ◽  
Mechanical Tests ◽  
Strength Characteristics ◽  
Concrete Durability ◽  
Cement Mortars ◽  
Optimum Decision ◽  
Cement System

One of the most important problem of concrete durability is increasing of waterproofing. Researches are devoted studying of cement mortars modified by carbon nanotubes, dispersed in plasticizers solutions. Were investigated physico-mechanical properties of cement paste, cement-sand mortar into which structure entered untreated carbon nanotubes (production of plant TM "Spetsmash" Kyiv, Ukraine) in various quantity. Were used as plasticizers in cement compositions additives substances of the various chemical nature – naphtaleneformaldehyde, melamineformaldehyde and polycarboxylate. Quantity of untreated nanotubes varied from 0,5%; 1,0% and to 1,5%. Concentration of additives was accepted taking into account recommendations of producers and made about 1% from the weight of cement. Were studied some technological processes of introduction untreated carbon nanotubes in cement system and is shown that the way of introduction of nanomodifiers has essential impact on strength characteristics of cementitious materials. Optimum decision introduction of untreated carbon nanotubes is using its in dispersion plasticizer of the working concentration prepared in an ultrasonic dispergator is established. Results of physico-mechanical tests of cement paste and cement-sand mortar showed positive influence at introduction of untreated carbon nanotubes as cement modifiers on strength characteristics of samples. Resalts is shown that the nanomodifier, used quantity about 1% in solution of lignosulfonate with polycarboxylate and melamineformaldehyde plasticizer has great impact on strength characteristics.

scholarly journals Determinants of Ready-to-eat Products Purchase Intentions: An Empirical Study among the Italian Consumers

HortScience ◽  
2018 ◽  
Vol 53 (5) ◽  
pp. 656-660 ◽  
Author(s):  
Filippo Sgroi ◽  
Fabrizio Piraino ◽  
Enrica Donia
Keyword(s):  
Food Consumption ◽  
Consumer Choice ◽  
Recent Literature ◽  
Nuclear Family ◽  
Raw Materials ◽  
Purchase Intentions ◽  
Classical Literature ◽  
Time Saving ◽  
Consumer Decisions ◽  
The City

The considerable diffusion of ready-to-eat products has focused attention on the reasons for their increasingly prominent success in the market. Although their prices are much higher than the prices of simple raw materials, their consumption has increased rapidly and with no end in sight, a situation that has challenged the conclusions of the classical literature on the importance of price and/or income in consumer decisions. In fact, more recent literature has broadened the classical vision by introducing potential additional variables that could influence consumer choice of certain foods. These variables, however, are not always easy and clear to identify because they reflect the cultural characteristics of a society. For this reason, the French scholar Malassis has introduced the concept of a model of food consumption, which, in fact, stems from a concept of food consumption as driven by factors that are not the same for all the societies that might be studied. Among these variables, regarding the consumption of ready-to-eat products, a factor that certainly acts as a driving force in an increasingly frenetic and dynamic society is the time saving that they are able to provide. Thus, it was considered essential to analyze this in a concrete way, through the variance analysis of a sample of 77 subjects resident in the city of Palermo, noting their characteristics in terms of age, education level, and number of nuclear family members. The results obtained indicate that subjects who consumed ready-to-eat products at a higher frequency belonged to a higher age group, had a higher level of education, and belonged to a family that was not particularly numerous. With these results, it can be stated that the consumption of ready-to-eat products is influenced by people’s need to optimize their available time, considered as a real, scarce resource.

Effect of Kaolin on the Properties of Flue Gas Desulphurization Gypsum-Steel Slag Cementitious Materials

2011 ◽  
Vol 306-307 ◽  
pp. 1553-1556
Author(s):  
Lei Zhang ◽  
Zhi Wang ◽  
Li Ying Fan ◽  
Guo Pu Shi
Keyword(s):  
Flue Gas ◽  
Setting Time ◽  
Steel Slag ◽  
Cementitious Materials ◽  
Cementitious Composites ◽  
Excitation Mechanism ◽  
Final Setting Time ◽  
Micro Morphology ◽  
Scanning Electron ◽  
Flue Gas Desulphurization

The effects of kaolin on the properties of flue gas desulphurization gypsum-based steel slag composites were analyzed in this article and the influence rules of setting time, final setting time on the flexural strength and compressive strength of cementitious composites were also discussed. The micro-morphology of the composite was observed by scanning electron microscope. At the same time, the excitation mechanism of kaolin on gas desulphurization gypsum-based steel slag was put forward. It was demonstrated that kaolin with content of 3% in the composites can better stimulate the activity of steel slag and improve the mechanical properties of cementitious composites.

Selective Use of High Performance Cementitious Composites in Concrete Structures

2008 ◽  
Vol 400-402 ◽  
pp. 27-36
Author(s):  
Christopher K.Y. Leung
Keyword(s):  
High Performance ◽  
Concrete Structures ◽  
Cementitious Composites ◽  
Conventional Concrete ◽  
Practical Applications ◽  
Concrete Members ◽  
High Performance Fiber ◽  
Cast Concrete ◽  
Good Potential ◽  
Concrete Science

Recent advancements in concrete science and technology have made possible the development of high performance fiber reinforced cementitious composites (HPFRCC) with excellent mechanical properties and long-term durability. However, the costs of these materials are many times that of conventional concrete and the construction of complete structures with them is hard to justify. The strategic application of high performance materials, in selected parts of concrete structures, can bring along higher performance/cost and wider acceptance of the material in practice. This paper will investigate several examples of selective HPFRCC application, including the fabrication of permanent formwork for durability enhancement, the replacement of steel reinforcements at the anchorage zone of post-tensioned members to relieve the steel congestion problem as well as the development of simple and narrow joints for pre-cast concrete members. Based on the experimental results obtained so far, the selected use of HPFRCC in concrete structures appears to have good potential for practical applications.

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