EXPERIMENTAL STUDY ON THE SULFURIC ACID RESISTANCE OF LOW CARBON CONCRETE

In recent years, deterioration of concrete structures of sewerage facilities due to sulfuric acid attacks has been progressing. Therefore, it can be concluded that the demand for sulfur-acid resistant concrete is extremely high. In addition, concerning recent global warming countermeasures, research and development is underway on low-carbon concrete that reduced cement, which emits a large amount of carbon dioxide during the manufacturing process. The purpose of this study is to develop low carbon concrete with high sulfur-acid resistance by replacing cement with large amounts of blast furnace slag and various admixtures. As a result, it was found that the sulfur-acid resistance was improved when using blast furnace slag fine powder and fly-ash. In particular, when cement content was 20% of binder by mass, it was confirmed that the sulfur-acid resistance was excellent. What is more, there was no loss in compressive strength. It was considered that almost Ca(OH) produced by hydration reaction of cement reacted with blast furnace slag and fly-ash, so the reaction of sulfur-acid and calcium hydroxide was suppressed.

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Effect of Fly Ash and Ground Granulated Blast-Furnace Slag on Sulfuric Acid Resistance of Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.1860 ◽

2011 ◽

Vol 243-249 ◽

pp. 1860-1865

Author(s):

Bei Xing Li ◽

Kai Yang ◽

Jiang Liu ◽

Ming Kai Zhou

Keyword(s):

Blast Furnace ◽

Sulfuric Acid ◽

Fly Ash ◽

Cement Paste ◽

Blast Furnace Slag ◽

Acid Resistance ◽

Basic Reason ◽

Granulated Blast Furnace Slag ◽

Furnace Slag

The effect of Fly ash (FA) and ground granulated blast-furnace slag (GGBS) on sulfuric acid resistance of concrete has been investigated in this study. Cement was replaced by FA with the incorporation amount from 20% to 50% or by GGBS from 35% to 65%. Results indicate that with an increase in fly ash replacement amount, the sulfuric acid resistance of concrete was improved. Sulfuric acid resistance of concrete with GGBS was improved only when the replacement amount of GGBS exceeds 50%. The basic reason for deterioration of concrete in sulfuric acid is the degradation of C-S-H gel in matrix. Increasing the content of SiO2 in cement paste can improve the acid resistance of concrete.

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Modeling of Alteration Behavior on Blended Cementitious Materials

ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management, Parts A and B ◽

10.1115/icem2011-59096 ◽

2011 ◽

Author(s):

Hitoshi Owada ◽

Tomoko Ishii ◽

Mayumi Takazawa ◽

Hiroyasu Kato ◽

Hiroyuki Sakamoto ◽

...

Keyword(s):

Blast Furnace ◽

Fly Ash ◽

Chemical Composition ◽

Mineral Composition ◽

Blast Furnace Slag ◽

Fine Powder ◽

Cementitious Materials ◽

Leaching Tests ◽

Measured Concentration ◽

Furnace Slag

A “realistic alteration model” is needed for various cementitious materials. Hypothetical settings of mineral composition calculated based on the chemical composition of cement, such as Atkins’s model, have been used to estimate the alteration of cementitious material. However, model estimates for the concentration of certain elements such as Al and S in leachate have been different from experimental values. In a previous study, we created settings for a mineralogical alteration model by taking the initial chemical composition of cementitious materials from analysis results in experiments and applying their ratios to certain hydrated cement minerals, then added settings for secondary generated minerals in order to account for Ca leaching. This study of alteration estimates for ordinary portland cement (OPC) in groundwater showed that the change in Al and S concentrations in simulated leachate approached values for actual leachate[1]. In the present study, we develop an appropriate mineral alteration model for blended cementitious materials and conduct batch-type leaching experiments that use crushed samples of blast furnace slag cement (BFSC), silica cement (SC), and fly ash cement (FAC). The cement blends in these experiments used OPC blended with blast furnace slag of 70 wt.%, silica cement consisting of an amorphous silica fine powder of 20 wt.%, and fly ash of 30 wt.%. De-ionized water was used as the leaching solution. The solid-liquid ratios in the leaching tests were varied in order to simulate the alteration process of cement hydrates. The compositions of leachate and minerals obtained from leaching tests were compared with those obtained from models using hypothetical settings of mineral composition. We also consider an alteration model that corresponds to the diversity of these materials. As a result of applying the conventional OPC model to blended cementitious materials, the estimated Al concentration in the aqueous solution was significantly different from the measured concentration. We therefore propose an improved model that takes better account of Al behavior by using a more reliable initial mineral model for Al concentration in the solution.

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