Effects of Different Expansive Agents on the Properties of Expansive Cementitious Materials

Abstract Cracking happens in the case of restricted volumetric shrinking in cementitious materials which has a negative influence on the mechanical characteristics and longevity of concrete materials and hence, reduces the life of concrete structures. Many techniques have been developed to reduce the shrinkage cracking of concrete among which, usage of expansive agents (EA) has been utilised for decades. Different types of EA creates divergence due to its chemical characteristics. In this paper, three main categories (CaO, MgO & Sulphoaluminate based) EA have been reviewed based on four criteria of concrete structures, such as strength, expansibility, durability and flowability. The review clearly indicates that CaO-based EA boosts the strength but unable to control the temperature rise, which results in thermal cracking in the long run. While MgO-based EA is vastly used in China and Sulphoaluminate based EA have been industrially used worldwide for decades, both of these agents can successfully compensate thermal shrinkage while maintaining adequate mechanical strength and durability. Beside all this differences, all types of EA have been reported to decelerate the flowability of the concrete.

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Minimising the risk of thermally induced cracking in mass concrete structures through suitable materials selection and processing

MRS Advances ◽

10.1557/adv.2018.371 ◽

2018 ◽

Vol 3 (34-35) ◽

pp. 2051-2061

Author(s):

Yunus Ballim

Keyword(s):

Portland Cement ◽

Concrete Structures ◽

Cementitious Materials ◽

Heat Of Hydration ◽

Supplementary Cementitious Materials ◽

Mass Concrete ◽

Concrete Element ◽

Near Surface ◽

Temperature Development ◽

Different Types

ABSTRACTThe hydration of cement is an exothermic reaction which generates around 300 kJ/kg of cement hydrated. In mass concrete structures such as dams and large foundations, this heat of hydration causes a significant rise in temperature in the internal sections of the concrete. If thermal gradients between the internal sections and the near-surface zone of the concrete element are sufficiently large, the thermal stress can cause cracking of the concrete. This cracking may cause functional or structural problems in the operation of the structure. In order to minimise the potential for such cracking, it is necessary to minimise the rate and amount of heat that is evolved, particularly during the early period of the hydration process. This can be achieved by design engineers and concrete technologists through judicious selection and processing of concrete-making materials. This paper presents the observations and results obtained over a number of years from adiabatic testing of concretes, computational modelling of temperature development in large concrete structures and direct temperature measurements in actual structures, with a view to understanding the effects of concrete-making materials on temperature development in concrete. The paper considers the effects of different types of rock aggregates, different types of Portland cement, fineness of grinding of the cement, the addition of supplementary cementitious materials and variations in the concrete starting temperature on temperature development in a large concrete element over time. The results indicate that using a coarser ground cement, adding significant amounts of supplementary cementitious materials and cooling the concrete mixture before placing has a more significant effect in reducing the risk of cracking than varying the aggregate type of the Portland cement type.

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Influence of Alkalinity and Ambient Temperature on Long-Term Properties of GFRP Reinforcement

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.760.213 ◽

2018 ◽

Vol 760 ◽

pp. 213-218

Author(s):

František Girgle ◽

Lenka Bodnárová ◽

Ondřej Januš ◽

Vojtěch Kostiha

Keyword(s):

Tensile Strength ◽

Ambient Temperature ◽

Mechanical Characteristics ◽

Current Problem ◽

Concrete Structures ◽

Experimental Program ◽

Glass Fibres ◽

Metallic Reinforcement ◽

Gfrp Reinforcement

The article deals with the current problem of determining long-term reliability of non-metallic reinforcement in concrete structures. The alkaline environment of concrete with a pH higher than 12.0 affects the glass fibres degradative, whereas this degradation presents by reduction of their mechanical characteristics, resulting in a decrease in the tensile strength of the whole composite. The article summarizes the results of the ongoing experimental program so far, which aims to quantify this influence.

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Stability of On-Line Bin Packing with Random Arrivals and Long-Run-Average Constraints

Probability in the Engineering and Informational Sciences ◽

10.1017/s0269964800001753 ◽

1990 ◽

Vol 4 (4) ◽

pp. 447-460 ◽

Cited By ~ 7

Author(s):

Coastas Courcobetis ◽

Richard Weber

Keyword(s):

Bin Packing ◽

Random Processes ◽

Sufficient Condition ◽

Necessary And Sufficient Condition ◽

Expected Number ◽

Long Run ◽

Different Types ◽

On Line ◽

Necessary And Sufficient ◽

Uniformly Bounded

Items of various types arrive at a bin-packing facility according to random processes and are to be combined with other readily available items of different types and packed into bins using one of a number of possible packings. One might think of a manufacturing context in which randomly arriving subassemblies are to be combined with subassemblies from an existing inventory to assemble a variety of finished products. Packing must be done on-line; that is, as each item arrives, it must be allocated to a bin whose configuration of packing is fixed. Moreover, it is required that the packing be managed in such a way that the readily available items are consumed at predescribed rates, corresponding perhaps to optimal rates for manufacturing these items. At any moment, some number of bins will be partially full. In practice, it is important that the packing be managed so that the expected number of partially full bins remains uniformly bounded in time. We present a necessary and sufficient condition for this goal to be realized and describe an algorithm to achieve it.

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Determination of crystallinity of Chinese handmade papers by means of X-ray diffraction

Restaurator International Journal for the Preservation of Library and Archival Material ◽

10.1515/res-2019-0009 ◽

2020 ◽

Vol 41 (2) ◽

pp. 69-86

Author(s):

Peng Liu ◽

Hongbin Zhang ◽

Sinong Wang ◽

Hui Yu ◽

Bingjie Lu ◽

...

Keyword(s):

Negative Influence ◽

X Ray Diffraction ◽

Cross Sectional ◽

X Ray ◽

Eulaliopsis Binata ◽

Different Types ◽

Powder Samples ◽

Xrd Patterns ◽

Xrd Method

AbstractThe crystallinity indices (CrI) of Chinese handmade papers were investigated using the X-ray diffraction (XRD) method. Four Chinese handmade papers, Yingchun, Zhuma, Yuanshu and Longxucao papers were used as model substrates of mulberry bark, ramie, bamboo and Eulaliopsis binata papers, respectively. Two forms of the paper samples, paper sheets and their comminuted powders, were used in this study. The results showed that their XRD patterns belong to the cellulose-I type and Iβ dominates the cellulose microstructure of these paper samples. Moreover, it was found that the microstructures and CrIs of cellulose of these papers were changed by the grinding treatment. This work suggested that the sheet form of the handmade papers is suitable to determine CrI by XRD, despite the contribution of non-cellulosic components in the papers. The order of CrIs for these paper sheet samples was Yingchun, Zhuma, Longxucao and Yuanshu papers. Besides CrIs, differences in cross-sectional areas of the crystalline zone of cellulose can be used for comparing different types of handmade papers. It was also found that the CrIs and crystallite size of paper cellulose varied between the sheet samples and the powder samples, illustrating that the pulverisation has a negative influence on the microstructure of the handmade papers.

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Effect of High-Dispersible Graphene on the Strength and Durability of Cement Mortars

Materials ◽

10.3390/ma14040915 ◽

2021 ◽

Vol 14 (4) ◽

pp. 915

Author(s):

Xiaoqiang Qi ◽

Sulei Zhang ◽

Tengteng Wang ◽

Siyao Guo ◽

Rui Ren

Keyword(s):

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Cement Mortar ◽

Chloride Ion ◽

Cementitious Materials ◽

Chloride Ion Penetration ◽

Cement Mortars ◽

Strength And Durability ◽

Durability Performance

Graphene’s outstanding properties make it a potential material for reinforced cementitious composites. However, its shortcomings, such as easy agglomeration and poor dispersion, severely restrict its application in cementitious materials. In this paper, a highly dispersible graphene (TiO2-RGO) with better dispersibility compared with graphene oxide (GO) is obtained through improvement of the graphene preparation method. In this study, both GO and TiO2-RGO can improve the pore size distribution of cement mortars. According to the results of the mercury intrusion porosity (MIP) test, the porosity of cement mortar mixed with GO and TiO2-RGO was reduced by 26% and 40%, respectively, relative to ordinary cement mortar specimens. However, the TiO2-RGO cement mortars showed better pore size distribution and porosity than GO cement mortars. Comparative tests on the strength and durability of ordinary cement mortars, GO cement mortars, and TiO2-RGO cement mortars were conducted, and it was found that with the same amount of TiO2-RGO and GO, the TiO2-RGO cement mortars have nearly twice the strength of GO cement mortars. In addition, it has far higher durability, such as impermeability and chloride ion penetration resistance, than GO cement mortars. These results indicate that TiO2-RGO prepared by titanium dioxide (TiO2) intercalation can better improve the strength and durability performance of cement mortars compared to GO.

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Energy Prices, Real Estate Sales and Industrial Output in China

Energies ◽

10.3390/en11071847 ◽

2018 ◽

Vol 11 (7) ◽

pp. 1847 ◽

Cited By ~ 3

Author(s):

K. Chau ◽

Gaolu Zou

Keyword(s):

Real Estate ◽

Value Added ◽

Industrial Sector ◽

Data Series ◽

Energy Prices ◽

Industrial Output ◽

Energy Efficient Buildings ◽

Long Run ◽

Different Types ◽

Short Run

A majority of energy is consumed to control the indoor environment for human activities and industrial production. The demand for energies for these two uses are reflected in demand for different types of real estate and the volume of industrial outputs. The purpose of this study is to examine the long-run equilibrium and short-run dynamics between real energy prices and demand for different types of real estate and industrial output in China. Energy prices are measured in the real price of fuels and power. Demand for different types of real estate is measured in their sales volume in the first hand market, that is, floor areas of new real estate sold by developers. Industrial output is measured by the net output (value added) of the industrial sector. All data series were tested for stationarity (i.e., the existence of a unit root) before testing for a co-integration relationship. We found no long-term equilibrium relationship between energy prices and the demand for real estate and industrial output as predicted by theory, probably due to increased supply of energy efficient buildings. There is also no short-run relationship between energy prices and demand for housing due to the increase in vacancy rate resulting from speculative demand for housing. However, demand for commercial properties appeared to lead energy prices. Finally, there is strong evidence suggesting that an increase in energy prices will significantly reduce industrial output but not vice versa.

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Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations

Applied Sciences ◽

10.3390/app8101730 ◽

2018 ◽

Vol 8 (10) ◽

pp. 1730 ◽

Cited By ~ 19

Author(s):

Md. Safiuddin ◽

A. Kaish ◽

Chin-Ong Woon ◽

Sudharshan Raman

Keyword(s):

Service Life ◽

Concrete Structures ◽

Real Life ◽

Early Age ◽

Structural Elements ◽

Remedial Measures ◽

Curing Conditions ◽

Factors Affecting ◽

Different Types ◽

Service Conditions

Cracking is a common problem in concrete structures in real-life service conditions. In fact, crack-free concrete structures are very rare to find in real world. Concrete can undergo early-age cracking depending on the mix composition, exposure environment, hydration rate, and curing conditions. Understanding the causes and consequences of cracking thoroughly is essential for selecting proper measures to resolve the early-age cracking problem in concrete. This paper will help to identify the major causes and consequences of the early-age cracking in concrete. Also, this paper will be useful to adopt effective remedial measures for reducing or eliminating the early-age cracking problem in concrete. Different types of early-age crack, the factors affecting the initiation and growth of early-age cracks, the causes of early-age cracking, and the modeling of early-age cracking are discussed in this paper. A number of examples for various early-age cracking problems of concrete found in different structural elements are also shown. Above all, some recommendations are given for minimizing the early-age cracking in concrete. It is hoped that the information conveyed in this paper will be beneficial to improve the service life of concrete structures. Concrete researchers and practitioners may benefit from the contents of this paper.

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Durability of pulverised fuel ash (PFA) concrete exposed to acidic and alkali conditions

MATEC Web of Conferences ◽

10.1051/matecconf/201925805015 ◽

2019 ◽

Vol 258 ◽

pp. 05015 ◽

Cited By ~ 1

Author(s):

Saiful Baharin Duraman ◽

Md. Fadhil Hakim Haji Omar

Keyword(s):

Concrete Structures ◽

Pozzolanic Reaction ◽

Polluted Water ◽

Alkali Silica Reaction ◽

Acid Attack ◽

Fuel Ash ◽

Alkaline Environments ◽

High Alkalinity ◽

Acidic Conditions ◽

Strength And Durability

Pulverised Fuel Ash (PFA) is becoming an important component in concrete due to potentially improved properties such as workability, later age strength and durability. Concrete structures may be susceptible to acid attack due to exposure to acid rain, acidic soil or polluted water. Concrete structures exposed to high alkaline environments, in addition to the alkalinity level of the cement and aggregates, may promote alkali-silica reaction (ASR) leading to swelling and reduction in durability. This study looks into the durability properties of PFA incorporated concrete at various replacement levels when exposed to highly acidic and alkali conditions. Compressive strengths and water absorption tests were compared between concrete cured under normal conditions with concrete exposed to highly acidic and highly alkali conditions. All specimens exposed to acidic conditions showed significant decreases in mass and compressive strengths compared to specimens cured normally. Higher PFA replacement resulted in improved resistance to acid attack. All specimens exposed to alkali conditions showed minor increases in mass suggesting ASR occurring. Reductions in compressive strengths were found at lower replacement levels. At higher replacement levels, increases in compressive strengths were found, suggesting the possibility of increased pozzolanic reaction of the PFA due to the high alkalinity.

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MONETARY POLICY AND TELECOMMUNICATION OUTPUT IN NIGERIA

J-MACC : Journal of Management and Accounting ◽

10.52166/j-macc.v3i2.2070 ◽

2020 ◽

Vol 3 (2) ◽

pp. 62-73

Author(s):

John Abiodun Akinde ◽

Elijah Oludayo

Keyword(s):

Monetary Policy ◽

Money Supply ◽

Negative Relationship ◽

Negative Influence ◽

Favourable Effect ◽

Data Series ◽

Long Run ◽

Integration Test ◽

Short Run ◽

Positive Effect

Different policies impact on the growth of the telecommunication sector in Nigeria. One of these policies which influence the expansion or contraction of the telecommunication output is monetary policy. To this end, this research examined the effect of monetary policy on telecommunication output in Nigeria. For the purpose of analysis, time series secondary data were sourced from Central Bank of Nigeria (CBN) statistical bulletin covering the periods1986 to 2018. Autoregressive Distributed Lag (ARDL) technique was employed after examining the stationarity of the data series using Augmented Dickey-Fuller technique. The bound co-integration test revealed that there is long run equilibrium between the monetary policy variables employed and telecommunication output. The ARDL result revealed that money supply had significant and positive effect on telecommunication output in the short and long run; liquidity ratio produced an insignificant and negative relationship with telecommunication output in the short run and insignificant positive effect in the long run; exchange rate had insignificant negative effect in the short run and a significant positive effect on telecommunication output in the long run; consumer price index had significant negative influence on telecommunication outputboth in the short run and long run. The study concluded that monetary policy stimulates telecommunication output in Nigeria. Thus, it was recommended that the monetary authority should pursue an expansionary monetary policy to sustain the positive influence of money supply on telecommunication output in Nigeria while rolling out policy to reduce the liquidity ratio of banks in the short run but increase it in the long run so that the long term favourable effect of liquidity ratio can be felt on telecommunication output.

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The importance of knowledge for wellbeing of society in the contemporary world

Filozofija i drustvo ◽

10.2298/fid1704136m ◽

2017 ◽

Vol 28 (4) ◽

pp. 1136-1159

Author(s):

Dusan Markovic ◽

Mrdjan Mladjan

Keyword(s):

Developed Countries ◽

Contemporary World ◽

Types Of Knowledge ◽

National Competitiveness ◽

Long Run ◽

New Knowledge ◽

Physical Resources ◽

Potential Problems ◽

Different Types ◽

The Relationship

Following the recent wave of globalization, the possession of different types of knowledge became even more important for economic development than the possession of physical resources. The ability of a society to adopt existing and create new knowledge thus gained fundamental importance for its wellbeing. In this paper, we identify important aspects of the relationship between education, creation of knowledge, economic growth, as well as both material and immate?rial wellbeing of a society. We describe potential problems that prevent societies from maximizing the benefit from the effort its members invest in acquiring knowledge. The problems of failure of the national markets for education as well as the global migrations which lead to drain of knowledge towards economically highly developed countries are especially analyzed. In the long run, they lead to a decline in both national competitiveness and different aspects of the immate?rial wellbeing. As the basis for solving these problems we propose a combination of economic theory and the concept of solidarity between more and less devel?oped countries, individuals and societies of their origin, respecting the free will of individuals.

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