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Studying the Hydration of a Retarded Suspension of Ground Granulated Blast-Furnace Slag after Reactivation.

ABSTRACT: This article presents a combined use of a retarder (d-gluconic acid) and an alkaline activator (sodium hydroxide) in a binder system based on ground granulated blast-furnace slag. The properties of the retarder are extending the dormant hydration period and suppressing the generation of strength-giving phases. Different retarder concentrations between 0.25 and 1.00 wt.% regulate the intensity and the period of the retardation and also the characteristics of the strength development. The activator concentration of 30 and 50 wt.% regulates the overcoming of the dormant period and thereby the solution of the slag and hence the formation of the hydration products. The research objective is to produce a mineral binder system based on two separate liquid components. The highest concentration of retarder and activator generates the highest compressive strength and mass of hydration products-after 90 days of hydration a compressive strength of more than 50 N/mm². The main phases are calcium silicate hydrate and hydrotalcite. Generally, the combination of retarder and activator shows a high potential in the performance increase of the hydration process.

SUBMITTER: Schneider N

PROVIDER: S-EPMC5457240 | biostudies-other | 2016 Nov

REPOSITORIES: biostudies-other

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Reactivation of a Retarded Suspension of Ground Granulated Blast-Furnace Slag.

Project description:An effective retarded suspension of ground granulated blast-furnace slag (GGBFS) needs a strong activator to reactivate the hydration. In this research study, sodium hydroxide (NaOH) as an alkali activator in two different concentrations (30 and 50 wt.%) was used to overcome the retardation and give the hardened GGBFS the reasonable strength. The study was carried out with a mixture of GGBFS, a solution of 1.0 wt.% d-gluconic acid (C₆H12O₇) as a retarder in the mixing water and a methyl cellulose as a stabilizer. The reactivation was executed after seven different periods (up to 28 days) after the system was retarded. The following investigations were performed: slump test, measurement of ultrasonic (US) velocity, compressive strength and gross density, thermogravimetry (TG) and scanning electron microscopy (SEM). The analyses of the hardened samples were carried out seven, 28 and 90 days after the reactivation. The result of the study is an effective reactivation of a retarded suspension. In this case, the activator with 50 wt.% NaOH shows a very high performance. The setting time of the reactivated binders is much longer compared to the reference, but, in the longer term, the compressive strength and the progress of the hydration exceed the performance of the reference.

| S-EPMC5456691 | biostudies-other

Effect of the Formation of Amorphous Networks on the Structure and Hydration Characteristics of Granulated Blast Furnace Slag.

Project description:The slag obtained in the process of pig iron smelting has been widely used, but the variational hydration activity always is a significant factor affecting its quality. In this experiment, the laboratory simulated slag was prepared by adjusting the chemical composition and cooling method. The experiment primary characterized the structure and hydration process with different types of slag by using MAS NMR, XRD, compressive strength, ICP, SEM, and hydration heat, then obtained the influence of the composition of the network former S/A (the mass ratio of SiO2 and Al2O3 in chemical composition) and amorphous phase content on its structure and hydration activity. The result shows that lowering the S/A value can reduce the degree of vitreous polymerization in the slag; reducing the S/A value of the slag can make the slag hydration time advance, and consequently, the cumulative exotherm increases, the liquid phase Ca/Si and Al/Si ionic ratio increases, and the hydration product changes from C-S-H gel to C-A-S-H gel, which ultimately leads to an increase in compressive strength. In the high S/A value slag, the formation of the trace crystal phase of gehlenite is beneficial to reduce the degree of polymerization of the amorphous.

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Strength Development and Hydration Behavior of Self-Activation of Commercial Ground Granulated Blast-Furnace Slag Mixed with Purified Water.

Project description:In this study, ground granulated blast-furnace slag (GGBFS) samples from Singapore, Korea, and the United Arab Emirates were hydrated with purified water to estimate the cementing capabilities without activators. Raw GGBFS samples and hardened pastes were characterized to provide rational explanations for the strengths and hydration products. The slag characteristics that influenced the best strength of raw GGBFS were identified. Although it is widely recognized that GGBFS alone generally shows little cementing capability when hydrated with water, the GGBFSs examined in this study demonstrated various strength developments and hydration behaviors; one of the GGBFS samples even produced a high strength comparable to that of alkali- or Ca(OH)₂-activated GGBFS. In particular, as the GGBFS exhibited a greater number of favorable slag characteristics for hydraulic reactivity, it produced more C-S-H and ettringite. The results demonstrated a reasonable potential for commercial GGBFS with calcium sulfates to function as an independent cementitious binder without activators.

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Durability of Fibre-Reinforced Calcium Aluminate Cement (CAC)-Ground Granulated Blast Furnace Slag (GGBFS) Blended Mortar after Sulfuric Acid Attack.

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| S-EPMC7503559 | biostudies-literature

Predicting compressive strength of high-performance concrete with high volume ground granulated blast-furnace slag replacement using boosting machine learning algorithms.

Project description:Predicting the compressive strength of concrete is a complicated process due to the heterogeneous mixture of concrete and high variable materials. Researchers have predicted the compressive strength of concrete for various mixes using machine learning and deep learning models. In this research, compressive strength of high-performance concrete with high volume ground granulated blast-furnace slag replacement is predicted using boosting machine learning (BML) algorithms, namely, Light Gradient Boosting Machine, CatBoost Regressor, Gradient Boosting Regressor (GBR), Adaboost Regressor, and Extreme Gradient Boosting. In these studies, the BML model's performance is evaluated based on prediction accuracy and prediction error rates, i.e., R2, MSE, RMSE, MAE, RMSLE, and MAPE. Additionally, the BML models were further optimised with Random Search algorithms and compared to BML models with default hyperparameters. Comparing all 5 BML models, the GBR model shows the highest prediction accuracy with R2 of 0.96 and lowest model error with MAE and RMSE of 2.73 and 3.40, respectively for test dataset. In conclusion, the GBR model are the best performing BML for predicting the compressive strength of concrete with the highest prediction accuracy, and lowest modelling error.

| S-EPMC9184605 | biostudies-literature

Properties of Foamed Mortar Prepared with Granulated Blast-Furnace Slag.

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Effect of Na₃PO₄ on the Hydration Process of Alkali-Activated Blast Furnace Slag.

Project description:In recent years, the utilization of different non-traditional cements and composites has been increasing. Alkali-activated cementitious materials, especially those based on the alkali activation of blast furnace slag, have considerable potential for utilization in the building industry. However, alkali-slag cements exhibit very rapid setting times, which are too short in some circumstances, and these materials cannot be used for some applications. Therefore, it is necessary to find a suitable retarding admixture. It was shown that the sodium phosphate additive has a strong effect on the heat evolution during alkali activation and effectively retards the hydration reaction of alkali-activated blast furnace slag. The aim of the work is the suggestion of a reaction mechanism of retardation mainly based on Raman and X‑ray photoelectron spectroscopy.

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Using Experimental Statistical Models for Predicting Strength and Deformability of Self-Compacting Concrete with Ground Blast-Furnace Slag.

Project description:Ground blast-furnace slag is one of the waste products available in Ukraine and other countries. It is obtained at metallurgical enterprises in huge quantities and can be efficiently used for concrete production. The article is devoted to obtaining experimental-statistical models of the influence of technological factors that determine the composition of self-compacting concrete (SCC) based on ground blast-furnace slag and polycarboxylate superplasticizer on compressive strength, tensile strength, prismatic strength, elastic modulus and crack resistance. Analysis of the investigated factors' influence on the specified SCC properties is carried out and positive influence of blast-furnace slag and superplasticizer simultaneous action on durability and deformation characteristics is studied. A design method of SCC composition design using the obtained mathematical models is developed. It allows for the consideration of a set of necessary parameters simultaneously. A numerical example is given.

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Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag.

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Recovery of scandium and neodymium from blast furnace slag using acid baking-water leaching.

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| S-EPMC9056533 | biostudies-literature

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