Effect of chemical admixtures on the sulfate requirement of cement

1980 ◽  
Vol 7 (2) ◽  
pp. 256-263 ◽  
Author(s):  
M. A. Ward ◽  
S. M. Khalil ◽  
B. W. Langan
Keyword(s):  
Portland Cement ◽  
Initial Temperature ◽  
Precast Concrete ◽  
Steam Curing ◽  
Sulfate Content ◽  
Chemical Admixtures ◽  
Cost Of Energy ◽  
Hot Weather ◽  
The Cost ◽  
Ready Mixed Concrete

As the cost of energy and hence the cost of producing Portland cement increase, the question arises as to whether we are obtaining optimum performance from the admixtures we use. As an example, data are presented indicating that a significant improvement in strength and shrinkage can be achieved by optimizing the sulfate content of the cement for given cement–admixture combinations. It is shown that the optimum SO3 is clearly a function of the initial temperature of the concrete, particularly during the first 24 h after casting, a characteristic of considerable importance in hot weather concreting and steam curing of concrete products. It is recommended that more attention be directed towards optimizing the effectiveness of chemical admixtures in both the ready-mixed concrete and precast concrete industries.

scholarly journals ANALYSIS OF PROPERTIES OF CONCRETE USING POTASSIUM POWDER AS ADMIXTURE

2017 ◽  
Vol 5 (4RASM) ◽  
pp. 41-45
Author(s):  
Vishal Gadgihalli ◽  
Ramya ◽  
Abrar Khan ◽  
Raghavendra Prasad Dinakar
Keyword(s):  
Portland Cement ◽  
Chemical Reaction ◽  
Crucial Role ◽  
Paper Analysis ◽  
Hardened Concrete ◽  
Exothermal Reaction ◽  
Chemical Admixtures ◽  
Concrete Operations ◽  
The Cost

Chemical admixtures are the ingredients in concrete other than Portland cement, water and aggregate those are added to mix immediately before or during mixing. These admixtures are primarily used to reduce the cost of concrete construction, to modify the properties of hardened concrete, to ensure the quality of concrete during mixing, transportation, placing curing and to overcome certain emergences during concrete operations. In this paper analysis of properties of concrete using potassium power as admixture is studied and verified the strength of concrete and temperature emitted due to chemical reaction to normal Portland cement. Using potassium powder the temperature emitted due to exothermal reaction of concrete has reduced. Thus gives better results hence we can use this potassium powder as an admixture where the temperature and the emitting temperatures place a crucial role in construction and maintenance.

scholarly journals The chemical additives in the prefabricated reinforced concret technology

2015 ◽  
Vol 4 ◽  
pp. 7-14
Author(s):  
Usov B.A. ◽  
Okolnikova G.E.
Keyword(s):  
Portland Cement ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Heating Regime ◽  
Chemical Additives ◽  
Warm Up ◽  
Chemical Admixtures ◽  
Complex Agent ◽  
Curing Regimes

The article presents research data of concrete with chemical admixtures for precast concrete. To the additives are hardening accelerators, systems-based accelerators, plasticizers and air-entraining additives. The authors studied the effect of the addition of electrolytes (NаСl, Nа2SО4 СаСl2, Са(NO3)2), complex additives (on the basis of the electrolytes and plasticizers, air-entraining additives SPD and mikrokremnezema) on properties of concrete, strength of concrete steamed and some of its properties. By accelerating the effect of electrolyte additives studied were located in the sequence: СаСl2 > NаСl > Nа2SO4 > Са(NO3)2. It is noted that the increase of concrete strength with electrolytes increases with decreasing the duration of heating and the content of aluminates in Portland cement, which allows for 40...50% reduction in the warm-up of concrete or 5...15% of cement consumption. Complex agent (on their basis), irrespective of the Mineralogy of the cement is more efficient and reduce the cement consumption by 10...15%, superplasticizers up to 20%, but long-term modes and regardless of the type of Portland cement. The article contains a material with strength in different curing regimes, the indicators of reduction of consumption of cement and frost resistance of concrete with the introduction of air-entraining additives. Empirical formula to calculate the reduction of the duration of isothermal heating regime during heat treatment of concrete.

Optical properties of a thin layer of the Vanadium dioxide at the metal state

2015 ◽  
Vol 9 (1) ◽  
pp. 2303-2310
Author(s):  
Abderrahim Benchaib ◽  
Abdesselam Mdaa ◽  
Izeddine Zorkani ◽  
Anouar Jorio
Keyword(s):  
Optical Properties ◽  
Thin Layer ◽  
Vanadium Dioxide ◽  
Ultra Violet ◽  
Index Of Refraction ◽  
Cost Of Energy ◽  
Infra Red ◽  
Metal State ◽  
The Cost ◽  
Reversible Phase

The vanadium dioxide VO₂ currently became very motivating for the nanotechnologies’ researchers. It makes party of the intelligent materials because these optical properties abruptly change semiconductor state with metal at a critical  temperature θ = 68°C. This transition from reversible phase is carried out from a monoclinical structure characterizing its semiconductor state at low temperature towards the metal state of this material which becomes tétragonal rutile for  θ ˃ 68°C ; it is done during a few nanoseconds. Several studies were made on this material in a massive state and a thin layer. We will simulate by Maple the constant optics of a thin layer of VO₂ thickness z = 82 nm for the metal state according to the energy ω of the incidental photons in the energy interval: 0.001242 ≤ ω(ev) ≤ 6, from the infra-red (I.R) to the ultra-violet (U.V) so as to be able to control the various technological nano applications, like the detectors I.R or the U.V,  the intelligent windows to  increase  the energy efficiency in the buildings in order to save the cost of energy consumption by electric air-conditioning and the paintings containing nano crystals of this material. The constant optics, which we will simulate, is: the index of refraction, the reflectivity, the transmittivity, the coefficient of extinction, the dielectric functions ԑ₁ real part and  ԑ₂  imaginary part of the permittivity complexes ԑ of this material and the coefficient absorption. 

scholarly journals A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3467
Author(s):  
Ankit Kothari ◽  
Karin Habermehl-Cwirzen ◽  
Hans Hedlund ◽  
Andrzej Cwirzen
Keyword(s):  
Carbon Dioxide ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Supplementary Cementitious Materials ◽  
Short Exposure ◽  
Chemical Admixtures ◽  
Composite Cements ◽  
Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

scholarly journals Sustainable Retirement Living: What Matters?

2013 ◽  
Vol 1 (1) ◽  
pp. 56 ◽  
Author(s):  
Jake Barker ◽  
Bo Xia ◽  
George Zillante
Keyword(s):  
Sustainable Development ◽  
Questionnaire Survey ◽  
Energy Efficient ◽  
Energy Supply ◽  
Household Waste ◽  
Public Acceptance ◽  
Ageing Population ◽  
Cost Of Energy ◽  
The Cost ◽  
Survey Approach

There is a growing demand for sustainable retirement villages in Australia due to an increasing number of ageing population and public acceptance of sustainable development. This research aims to gain a better understanding of retirees’ understanding about sustainable retirement living and their attitudes towards sustainable developments via a questionnaire survey approach. The results showed that the current residents of retirement villages are generally very conscious of unsustainable resource consumption and would like their residences and community to be more environmentally friendly and energy efficient. The cost of energy supply is a concern to majority of respondents. However there is a certain level of concerns from residents too on the extra cost of going green in their residence. Education is required to residents about recycling household waste and how to use available facilities. A better understanding of retirees’ awareness and attitudes towards sustainability issues helps to improve the sustainable developments of retirement villages in the future.

Low Cement/High Fly Ash Concretes: Their Properties and Response to Chemical Admixtures

1987 ◽  
Vol 113 ◽  
Author(s):  
V. H. Dodson
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Calcium Hydroxide ◽  
Pozzolanic Reaction ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chemical Admixtures ◽  
Reaction With Water

ABSTRACTIn practice, the amount of fly ash added to portland cement concrete varies depending upon the desired end properties of the concrete. Generally, when a given portland cement concrete is redesigned to include fly ash, between 10 and 50% of the cement is replaced by a volume of fly ash equal to that of the cement. Sometimes as much as twice the volume of the cement replaced, although 45.4 kg (100 lbs) of cement will only produce enough calcium hydroxide during its reaction with water to react with about 9 kg (20 lbs) of a typical fly ash. The combination of large amounts of certain fly ashes with small amounts of portland cement in concrete has been found to produce surprisingly high compressive strengths, which cannot be accounted for by the conventional “pozzolanic reaction”. Ratios of cement to fly ash as high as 1:15 by weight can produce compressive strengths of 20.7 MPa (3,000 psi) at I day and over 41.4 MPa (6,000 psi) at 28 days. Methods of identifying these “hyperactive” fly ashes along with some of the startling results, with and without chemical admixtures are described.

scholarly journals Optimized Placement of Connecting the Distributed Generationswork Stand Alone to Improve the Distribution Systems Reliability

2013 ◽  
Vol 64 (2) ◽  
pp. 76-83
Author(s):  
Hamed Hashemi-Dezaki ◽  
Ali Agheli ◽  
Behrooz Vahidi ◽  
Hossein Askarian-Abyaneh
Keyword(s):  
Genetic Algorithm ◽  
Objective Function ◽  
System Reliability ◽  
Distribution Systems ◽  
Analytical Approach ◽  
Distributed Generations ◽  
Joint Point ◽  
Cost Of Energy ◽  
Optimum Solution ◽  
The Cost

The use of distributed generations (DGs) in distribution systems has been common in recent years. Some DGs work stand alone and it is possible to improve the system reliability by connecting these DGs to system. The joint point of DGs is an important parameter in the system designing. In this paper, a novel methodology is proposed to find the optimum solution in order to make a proper decision about DGs connection. In the proposed method, a novel objective function is introduced which includes the cost of connector lines between DGs and network and the cost of energy not supplied (CENS) savings. Furthermore, an analytical approach is used to calculate the CENS decrement. To solve the introduced nonlinear optimization programming, the genetic algorithm (GA) is used. The proposed method is applied to a realistic 183-bus system of Tehran Regional Electrical Company (TREC). The results illustrate the effectiveness of the method to improve the system reliability by connecting the DGs work stand alone in proper placements.

scholarly journals Techno-Economic Feasibility Study of Investigation of Renewable Energy System for Rural Electrification in South Algeria

2018 ◽  
Vol 8 (5) ◽  
pp. 3421-3426 ◽  
Author(s):  
F. Chermat ◽  
M. Khemliche ◽  
A. E. Badoud ◽  
S. Latreche
Keyword(s):  
Greenhouse Gas Emission ◽  
Electrical Energy ◽  
Energy System ◽  
Economic Feasibility ◽  
Maintenance Cost ◽  
Management Algorithm ◽  
Cost Of Energy ◽  
The Cost ◽  
Operation And Maintenance Cost ◽  
Different Sources

This work aims to consider the combination of different technologies regarding energy production and management with four possible configurations. We present an energy management algorithm to detect the best design and the best configuration from the combination of different sources. This combination allows us to produce the necessary electrical energy for supplying habitation without interruption. A comparative study is conducted among the different combinations on the basis of the cost of energy, diesel consumption, diesel price, capital cost, replacement cost, operation, and maintenance cost and greenhouse gas emission. Sensitivity analysis is also performed.

scholarly journals Techno-economical study of solar water pumping system: optimum design, evaluation, and comparison

2021 ◽  
Vol 6 ◽  
pp. 41
Author(s):  
Hussein A. Kazem ◽  
Anas Quteishat ◽  
Mahmoud A. Younis
Keyword(s):  
Optimum Design ◽  
Meteorological Data ◽  
Average Energy ◽  
Cost Evaluation ◽  
Successful Operation ◽  
Solar Water ◽  
Water Pumping ◽  
Cost Of Energy ◽  
Simulation Results ◽  
The Cost

Solar water pumping systems are fundamental entities for water transmission and storage purposes whether it is has been used in irrigation or residential applications. The use of photovoltaic (PV) panels to support the electrical requirements of these pumping systems has been executed globally for a long time. However, introducing optimization sizing techniques to such systems can benefit the end-user by saving money, energy, and time. This paper proposed solar water pumping systems optimum design for Oman. The design, and evaluation have been carried out through intuitive, and numerical methods. Based on hourly meteorological data, the simulation used both HOMER software and numerical method using MATLAB code to find the optimum design. The selected location ambient temperature variance from 12.8 °C to 44.5 °C over the year and maximum insolation is 7.45 kWh/m2/day, respectively. The simulation results found the average energy generated, annual yield factor, and a capacity factor of the proposed system is 2.9 kWh, 2016.66 kWh/kWp, and 22.97%, respectively, for a 0.81 kW water pump, which is encouraging compared with similar studied systems. The capital cost of the system is worth it, and the cost of energy has compared with other systems in the literature. The comparison shows the cost of energy to be in favor of the MATLAB simulation results with around 0.24 USD/kWh. The results show successful operation and performance parameters, along with cost evaluation, which proves that PV water pumping systems are promising in Oman.

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