scholarly journals A Microstructure Based Strength Model for Slag Blended Concrete with Various Curing Temperatures

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
Li-Na Zhang ◽  
Wang Xiao-Yong ◽  
Kyung-Taek Koh
Keyword(s):  
Numerical Model ◽  
Carbon Dioxide Emissions ◽  
Cement Hydration ◽  
Elevated Temperatures ◽  
Strength Development ◽  
Granulated Blast Furnace Slag ◽  
Proposed Model ◽  
Hydration Model ◽  
Compressive Strength Development ◽  
Reduce Carbon Dioxide

Ground granulated blast furnace slag, which is a byproduct obtained during steel manufacture, has been widely used for concrete structures in order to reduce carbon dioxide emissions and improve durability. This paper presents a numerical model to evaluate compressive strength development of slag blended concrete at isothermal curing temperatures and time varying curing temperatures. First, the numerical model starts with a cement-slag blended hydration model which simulates both cement hydration and slag reaction. The accelerations of cement hydration and slag reaction at elevated temperatures are modeled by Arrhenius law. Second, the gel-space ratios of hardening concrete are calculated using reaction degrees of cement and slag. Using a modified Powers’ gel-space ratio strength theory, the strength of slag blended concrete is evaluated considering both strengthening factors and weakening factors involved in strength development process. The proposed model is verified using experimental results of strength development of slag blended concrete with different slag contents and different curing temperatures.

Modeling of hydration reactions to predict the properties of slag blended concrete

2014 ◽  
Vol 41 (5) ◽  
pp. 421-431
Author(s):  
Xiao-Yong Wang ◽  
Ki-Bong Park
Keyword(s):  
Portland Cement ◽  
Cement Hydration ◽  
Blended Cement ◽  
Numerical Procedure ◽  
Reaction Model ◽  
Heat Evolution ◽  
Mineral Admixture ◽  
Temperature History ◽  
Granulated Blast Furnace Slag ◽  
Hydration Model

The granulated blast furnace slag is commonly blended with Portland cement or clinker to produce slag blended cement after being ground to the fineness comparable to Portland cement. Hydration of slag-blended cement is much more complex than that of ordinary Portland cement because of the mutual interactions between the cement hydration and the slag reaction. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the reaction of slag, a numerical procedure is proposed to simulate the hydration of concrete containing slag. The numerical procedure includes two sub components, a cement hydration model and a slag reaction model. The heat evolution rate of slag concrete is determined from the contributions of the cement hydration and the slag reaction. Furthermore, the temperature history in hardening blended concrete is evaluated by combining the proposed numerical procedure with a finite element method. The proposed model is verified through experimental data on concrete with different water–cement ratios and mineral admixture substitution ratios.

Sustainable Development of Concrete Using GGBS: Effect of Curing Temperatures on the Strength Development of Concrete

2015 ◽  
Vol 776 ◽  
pp. 3-8
Author(s):  
Gidion Turu'allo
Keyword(s):  
Sustainable Development ◽  
Portland Cement ◽  
Elevated Temperatures ◽  
Curing Temperature ◽  
Strength Development ◽  
Environmental Preservation ◽  
Cement Production ◽  
Granulated Blast Furnace Slag ◽  
C 50 ◽  
Emission Of Greenhouse Gases

The World Earth Summits in Rio de Janeiro, Brazil and Kyoto, Japan in 1992 and 1997 respectively, have made it clear that uncontrolled increased emission of greenhouse gases to the atmosphere is no longer environmentally and socially acceptable for sustainable development. The increase of cement production will affect the environmental preservation, natural conservation and increase the CO2emission, which is one of the primarily gases that contribute to the global warming. The use of ground granulated blast furnace slag (ggbs) to replace a part of Portland cement in concrete can reduce the CO2emission. It also can provide significant benefits to concrete properties, such as increase the workability and durability of concrete. The early strength of ggbs concretes that had been cured at standard curing temperature (20°C) were slower than that of concretes with Portland cement only, cured at the same temperature. However, there are some indications show that curing the ggbs concrete at elevated temperatures will significantly enhanced the early age strength of the concrete. The objectives of this research are to find out the effect of curing temperatures and levels replacement of Portland cement by ggbs on the strength development of concretes. The levels of ggbs to replace Portland cement were 0, 20, 35, 50 and 70%, while the curing temperatures were 20°C, 50°C and adiabatic curing. The concrete cubes were tested at ages: 6 and 12 hours, 1, 2, 4, 8, 16, 32, 64, 128, 256 and 365 days. The results showed that curing the ggbs concrete at temperatures higher than standard curing temperature, increased the strength development of the concrete at early ages.

scholarly journals Property Analysis of Slag Composite Concrete Using a Kinetic–Thermodynamic Hydration Model

2021 ◽  
Vol 11 (16) ◽  
pp. 7191
Author(s):  
Ki-Bong Park ◽  
Yi-Sheng Wang ◽  
Xiao-Yong Wang
Keyword(s):  
Experimental Study ◽  
Thermodynamic Model ◽  
Experimental Studies ◽  
Hydration Heat ◽  
Strength Development ◽  
Phase Assemblage ◽  
Property Development ◽  
Hydration Model ◽  
Compressive Strength Development ◽  
Reaction Degree

Slag is increasingly unitized for the production of sustainable concrete. This paper presents a procedure with which to analyze the property development of slag composite concrete. Experimental studies of the hydration heat and compressive strength development and simulation studies using a kinetic hydration model and a thermodynamic model were performed. First, we performed an experimental study of the isothermal hydration heat of cement–slag blends. Based on the results of the experimental study on cumulative hydration heat, the reaction degree of slag was determined. We found that the reaction degree of slag decreased as the slag content increased. Second, the reaction degree of slag and cement were used as the input parameters for the Gibbs energy minimization (GEM) thermodynamic equilibrium model. Moreover, the phase assemblage of hydrating cement–slag was determined. The trends of calcium silicate hydrate (CSH) are similar to those of strength. Based on the CSH content, the strength of hardening cement–slag blends was determined. In addition, the calcium hydroxide (CH) content resulting from the thermodynamic model shows good agreement with the experimental results. In summary, the integrated kinetic–thermodynamic model is useful for analyzing the properties of cement–slag blends.

scholarly journals Evaluation of Workability and Mechanical Properties of Bottom Ash Aggregate Concrete

2020 ◽  
Vol 10 (22) ◽  
pp. 8016
Author(s):  
Yong-Hyok Kim ◽  
Hak-Young Kim ◽  
Keun-Hyeok Yang ◽  
Jung-Soo Ha
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Bottom Ash ◽  
Target Strength ◽  
Strength Development ◽  
Coarse Aggregates ◽  
Proposed Model ◽  
Reliable Model ◽  
Compressive Strength Development ◽  
Experimental Values

The purpose of this study is to evaluate the workability and mechanical properties of concrete containing bottom ash, which is an industrial byproduct, as an aggregate. Twelve concrete mixtures, including concrete containing bottom ash aggregate (CCBA), are classified into three groups of W/C 0.45, 0.375, and 0.3 according to the target strength. Each group includes four mixtures in which natural aggregate and bottom ash are applied as fine and coarse aggregates according to particular ratios. On the basis of the test results, a reliable model to predict the 28-day compressive strength of CCBA is proposed by applying regression analysis. The proposed model points out that when applying bottom ash as aggregate, the concrete density is lowered, and W/C should be reduced to offset the lowered compressive strength. As a result of comparing experimental values with the existing design code models, it is found that while the fib model accurately predicts compressive strength development and tensile resistance capacity in general, the ACI 318 code overestimates the elastic modulus at the oven-dried density (ρc) range of 1840 kg/m3 and above. Accurate prediction of the mechanical properties of CCBA requires the measurement of additional experimental data that consider W/C and ρc as important parameters.

Study on the Durability of Cementless Concrete Produced with Industrial By-Products

2015 ◽  
Vol 665 ◽  
pp. 189-192
Author(s):  
Jong Won Lee ◽  
Yong Il Jang ◽  
Byung Jae Lee ◽  
Wan Shin Park
Keyword(s):  
Carbon Dioxide Emissions ◽  
Chemical Resistance ◽  
Reduction Rate ◽  
Mass Reduction ◽  
Freezing And Thawing ◽  
Granulated Blast Furnace Slag ◽  
Binding Material ◽  
Reduce Carbon Dioxide ◽  
Furnace Slag ◽  
By Products

This study evaluated the durability of concrete produced with a cementless binding material and potassium hydroxide (KOH) based on ground granulated blast furnace slag and fly ash. These industrial byproducts are used to replace cement in order to reduce carbon dioxide emissions. The test conducted for the freezing and thawing resistance of concrete using cementless binding material revealed that the relative dynamic modulus was 83.4%. From the results of a chemical resistance test, the mass reduction rate stood at 12.3% for the 5% HCl solution and 12.7% for the 5% H2SO4 solution, showing better chemical resistance than concrete using cement. The depth of neutralization was observed to be 4.48mm, a similar level to that of cement-containing concrete.

scholarly journals Multi-Objective Production and Transportation Scheduling Considering Carbon Dioxide Emissions Reductions in Dynamic Supply Chains

2012 ◽  
Vol 6 (3) ◽  
pp. 322-330 ◽  
Author(s):  
Yoshitaka Tanimizu ◽  
◽  
Katuhumi Amano ◽  
Kana Harada ◽  
Chisato Ozawa ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supply Chains ◽  
Carbon Dioxide Emissions ◽  
Negotiation Process ◽  
Chain Model ◽  
Dynamic Configuration ◽  
Emissions Reductions ◽  
Delivery Times ◽  
Proposed Model ◽  
Reduce Carbon Dioxide

Previous studies have proposed a dynamic configuration method for two-layered supply chains consisting of a set of clients and suppliers. The proposed method provides suitable delivery times and prices of products through the modification process of production schedules of the suppliers and the negotiation process between the clients and the suppliers in consideration of transportation constraints. This research proposes a new supply chain model extended for carbon dioxide emissions reductions in the two-layered dynamic supply chains. The suppliers provide transportation plans to reduce carbon dioxide emissions in transportation processes without losing chances to enter into a large number contracts with the clients. The effectiveness of the proposed model is verified through computational experiments from the viewpoints of both the amount of carbon dioxide emitted in transportation processes and the profits of the suppliers.

scholarly journals A Semi-Empirical Model for Predicting Frost Properties

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 412
Author(s):  
Shao-Ming Li ◽  
Kai-Shing Yang ◽  
Chi-Chuan Wang
Keyword(s):  
Thermal Conductivity ◽  
Linear Programming ◽  
Numerical Model ◽  
Empirical Model ◽  
Quantitative Method ◽  
Predictive Ability ◽  
Dimensionless Temperature ◽  
Crystal Shape ◽  
Proposed Model ◽  
Semi Empirical

In this study, a quantitative method for classifying the frost geometry is first proposed to substantiate a numerical model in predicting frost properties like density, thickness, and thermal conductivity. This method can recognize the crystal shape via linear programming of the existing map for frost morphology. By using this method, the frost conditions can be taken into account in a model to obtain the corresponding frost properties like thermal conductivity, frost thickness, and density for specific frost crystal. It is found that the developed model can predict the frost properties more accurately than the existing correlations. Specifically, the proposed model can identify the corresponding frost shape by a dimensionless temperature and the surface temperature. Moreover, by adopting the frost identification into the numerical model, the frost thickness can also be predicted satisfactorily. The proposed calculation method not only shows better predictive ability with thermal conductivities, but also gives good predictions for density and is especially accurate when the frost density is lower than 125 kg/m3. Yet, the predictive ability for frost density is improved by 24% when compared to the most accurate correlation available.

scholarly journals Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid

2021 ◽  
Author(s):  
Jean Noël Yankwa Djobo ◽  
Dietmar Stephan
Keyword(s):  
Blast Furnace ◽  
Boric Acid ◽  
Blast Furnace Slag ◽  
Volcanic Ash ◽  
Strength Development ◽  
Main Process ◽  
Reaction Products ◽  
Setting Times ◽  
Granulated Blast Furnace Slag ◽  
Furnace Slag

AbstractThis work aimed to evaluate the role of the addition of blast furnace slag for the formation of reaction products and the strength development of volcanic ash-based phosphate geopolymer. Volcanic ash was replaced by 4 and 6 wt% of ground granulated blast furnace slag to accelerate the reaction kinetics. Then, the influence of boric acid for controlling the setting and kinetics reactions was also evaluated. The results demonstrated that the competition between the dissolution of boric acid and volcanic ash-slag particles is the main process controlling the setting and kinetics reaction. The addition of slag has significantly accelerated the initial and final setting times, whereas the addition of boric acid was beneficial for delaying the setting times. Consequently, it also enhanced the flowability of the paste. The compressive strength increased significantly with the addition of slag, and the optimum replaced rate was 4 wt% which resulted in 28 d strength of 27 MPa. Beyond that percentage, the strength was reduced because of the flash setting of the binder which does not allow a subsequent dissolution of the particles and their precipitation. The binders formed with the addition of slag and/or boric acid are beneficial for the improvement of the water stability of the volcanic ash-based phosphate geopolymer.

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