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GARTNER Ellis：有替代硅酸盐水泥熟料的生产的选择吗？
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Vol. 40，No. 1 January，2012
JOURNAL OF THE CHINESE CERAMIC SOCIETY
碱激发水泥的类型与特点 史才军 1,2，何富强 2，A. FERNÁNDEZ-JIMÉNEZ3，V. Pavel KRIVENKO 4，Angel PALOMO 4 (1. 湖南大学土木工程学院，长沙 410082，中国；2. 厦门理工学院土木工程与建筑系，厦门 361024，中国；3. Eduardo Torroja Institute Consejo Superior de Investigaciones Científicas, c/Serrano Galvache s/n, 28033 Madrid, Spain；4. Kiev National University of Civil Engineering and Architecture, 31, Vozdukhoflotskii prospect, PO Box 161 Kiev 03037, Ukraine) 摘 要：基于所含胶凝组份的成分，可以将碱激发水泥分成 5 种类型：1)碱激发矿渣水泥；2)碱激发波特兰复合水泥；3)碱激发火山灰水泥；4)碱激 发石灰–火山灰/矿渣水泥；5)碱激发铝酸钙复合水泥，每种类型碱激发水泥包含几种胶凝体系。综述了这 5 种碱激发水泥的成分和特征。 关键词：碱激发水泥；特性；微结构；耐久性 中图分类号：TU502.4
文献标志码：A
文章编号：0454–5648(2012)01–0069–07
网络出版时间：2011–12–29 19:07:42
DOI：CNKI:11-2310/TQ.20111229.1907.011
网络出版地址：http://www.cnki.net/kcms/detail/11.2310.TQ.20111229.1907.011.html
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Classification and Characteristics of Alkali-Activated Cements
SHI Caijun1，HE Fuqiang2，A. FERNÁNDEZ-JIMÉNEZ3，V. Pavel KRIVENKO 4，Angel PALOMO4 (1. College of Civil Engineering, Hunan University, 410082 Changsha, China; 2.Department of Civil Engineering, Xiamen University of Technology, 361024, Xiamen China; 3. Eduardo Torroja Institute Consejo Superior de Investigaciones Científicas, c/Serrano Galvache s/n, 28033 Madrid, Spain; 4. Kiev National University of Civil Engineering and Architecture, 31, Vozdukhoflotskii Prospect, PO Box 161 Kiev 03037, Ukraine)
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Abstract: The alkali-activated cements can be classified into five categories based on the composition of the cementing component(s): 1) Alkali-activated slag-based cements; 2) Alkali-activated Portland blended cements; 3) Alkali-activated pozzolan cements; 4) Alkali-activated lime-pozzolan/slag cements; and 5) Alkali-activated calcium aluminate blended cement. Each category could include several cementing systems. The composition and characteristics of the five categories of alkali-activated cements are summarized.
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Key words: alkali-activated cements; property; microstructure; durability
1 Introduction
During the past decades, a variety of alkali-activated cements have been developed. Since the discovery of the principles for alkali-activated cementing materials by Glukhovsky in 1957, many researches have been conducted in this area, and they have been commercially produced and used for different purposes in a variety of construction projects in the former Soviet Union, China and some other countries. A variety of industrial by-products and recycled materials, such as blast furnace slag, steel slag, phosphorus slag, coal fly ash, waste glasses, or a combination or two or more of them can be 收稿日期：2011–08–26。
修订日期：2011–10–04。
基金项目：国家自然科学基金(50978093；51072050)；国家“973”计 划(2009CB6231001)资助项目。 第一作者：史才军(1963—)，男，博士，教授。 此文已在“2011 年可持续发展的水泥基材料与应用国际研讨会”上宣读。
used as the major ingredients of the cementing materials. Properly designed alkali-activated cements and concretes behave much better than Portland cements and concretes, especially in corrosive environments. The characteristics of the ingredients and activator dosage have a great effect on the hydration, microstructure and performance of alkali-activated cements. Shi et al.[1] summarized the progresses in this aspect. This paper reviewed the development and classification of alkali-activated cements into five categories based on the composition of their cementing component(s). The characteristics of each category of alkali-activated cements were also summarized. Received date: 2011–08–26.
Revised date: 2011–10–04.
First author: SHI Caijun (1963–), male, Ph.D., professor. E-mail:
[email protected]
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Classification of alkali-activated cements
Alkali-activated cements usually consist of two components, i.e., cementing component and alkaline activators. Usually, caustic alkalis or alkaline salts are used as alkaline activators of alkali-activated cements and concretes. In 1980, Glukhovsky, et al. classified them into six groups according to their chemical compositions: Caustic alkalies (MOH); Non-silicate weak acid salts (M2CO3, M2SO3, M3PO4, MF, etc.); Silicates(M2O·nSiO2); Aluminates (M2O·nAl2O3); Aluminosilicates (M2O·Al2O3·(2– 6)SiO2); Non-silicate strong acid salts (M2SO4). Of all these activators, NaOH, Na2CO3, Na2O·nSiO2 and Na2SO4 are the most widely available and economical chemicals. Some potassium compounds have been used in laboratory studies. However, their potential applications could be restricted due to their availability and costs. A variety of industrial by-products and wastes have been used as the cementing components in alkali-activated cements and concretes, which include granulated blast furnace slag, granulated phosphorus slag, steel slag, coal fly ash, volcanic glasses, zeolite, metakaolin, silica fume and non-ferrous slags. Based on the composition of the cementing component(s), the alkali-activated cements can be classified into five categories:[1–2] alkali-activated slag-based cements; alkali-activated portland blended cements; alkali-activated pozzolan cements; alkali-activated lime-pozzolan/slag cements; and alkali-activated calcium aluminate blended cement. 2.1 Alkali-activated slag based cements Alkali-activated slag based cements include the following cementing systems: alkali-activated blast furnace slag cement; alkali-activated phosphorus slag cement; alkali-activated blast furnace slag-fly ash system; alkaliactivated blast furnace slag-steel slag system; alkaliactivated blast furnace slag-MgO system; alkali-activated blast furnace slag based multiple component cement. Among these systems, alkali-activated blast furnace slag cement is the most widely investigated cement. Since many work have been conducted on this category of cements, the major features of alkali-activated blast furnace slag cement can be summarized as follows. The performance of alkali-activated slag cement and concrete is predominantly controlled by the nature of the slag and the nature/dosage of the activator(s) used. Properly designed alkali-activated slag cement and concrete can exhibit much higher strength and better other properties than conventional portland cement and concrete, as shown in Fig. 1. Alkali-activated slag cement paste and mortars may exhibit a more or less porous structure than Portland cement pastes and mortars based on the nature of the activator. The relationship between porosity and strength for
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Fig. 1
Strength development of alkali-activated slag and portland cement mortars[3]
alkali-activated slag cement is different from that for Portland cement, as shown in Fig. 2. In moist conditions, alkali-activated slag cements can exhibit a lower water and chloride permeability, and a better resistance to corrosive media such as acid, sulphate, chlorides than conventional cement and concrete. The acidic corrosion and sulphate attack resistance of alkaliactivated slag cements are shown in Fig. 3 and Table 1.
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Relationship between porosity and strength of alkaliactivated slagand portland cement mortars[4]
Under both saturated and moisture-controlled conditions, alkali-activated cements can be carbonated faster than conventional cement and concrete. When alkali-reactive aggregate is used, alkali-activated cement concrete may show high expansion. However, the expansion depends on the nature of the cementing components, the nature and dosage of activator and water-cement ratio. However, the alkali-aggregate reaction expansion may be eliminated by the introduction of pozzolan such as low calcium fly ash, silica fume and metakaolin. The addition of mineral admixtures and these commercial chemical admixtures for Portland cements have a limited or little effect on the workability and time of setting of alkali-activated slag cement pastes and mortars.
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Fig. 3 Corrosion of cement pastes in pH = 3 acetic acid solution[5] Table 1
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Air-entrainment agents for Portland cement concrete may not work with alkali-activated slag cement concrete. For given air void content and spacing, alkali-activated slag concrete exhibits as good as or even better resistance to freezing-thawing cycles than Portland cement concrete. Since hardened alkali-activated slag pastes and concrete contain no free Ca(OH)2, it shows a better fire resistance than Portland cement concrete. The main reaction products formed in all cases are C–S–H gels. However, the Ca/Si ratio and the Al content in the gels depend on the nature of the activator, chemical composition of cementing components and curing conditions (time and temperature). Secondary reaction products also depend on these variables. 2.2 Alkali-activated portland blended cement Supplementary cementing materials such as blast fur-
Flexural strength of the alkali-activated slag cement concrete specimens (10 mm × 10 mm × 60 mm) in different 6% (by mass) sulphate solutions[1] Flexural strength/MPa
Sulphate Alkaline activator Basic slag Mb = 1.18 3 month/6 month Na2SO4 ZnSO4 CuSO4
Na2CO3
11.23/11.44
Na2SiO3
16.23/17.58
Na2CO3
11.92/9.40
Na2SiO3
17.02/17.55
Na2CO3
2.04/2.81
Na2CO3 Na2SiO3
Al2(SO4)3
Na2CO3 Na2SiO3
(NH4)2SO4
Na2CO3
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Na2SiO3 MgSO4
Na2CO3
Na2SiO3 MnSO4
3 month/6 month 10.11/14.66 8 .07/13.33
17.14/2.01
8.63/4.67
6.80/0.00
14.85/15.41
9.66/ 9.17
0
7.82/6.65 0
2.10/0.00
4.76/2.27
0 0
Na2CO3
0
Na2SiO3
0
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9.32/13.54
3 month/6 month
3 month/6 month
12.01/13.14
8.76/ 7.67
6.34/3.71
9.43/13.20
6.88/1.34
10.58/11.92
7.23/2.16
9.01/11.11
6.50/1.16
8.21/7.39
0
8.98/6.92
0
18.25/19.87
19.84/20.39 10.76/5.22
16.55/16.74 8.26/6.46
17.38/12.40 6.19/9.38 7.82/6.65 0 0 0
nace slag, phosphorus slag, coal fly ash, and natural pozzolans are widely used for the production of blended cement or as a cement replacement in concrete. In general, the use of these materials usually increases the setting times and decreases the early strengths of the cement and concrete. Many researches have indicated that the addition of alkaline activators can activate the potential pozzolanic or cementitious properties of those supplementary materials and improve the properties of those cementing systems, especially at early ages. Many cementing systems, which have been investigated, include: 1) alkali-activated portland blast furnace slag cement; 2) alkali-activated portland phosphorus slag cement; 3) alkali-activated portland fly ash cement; 4) alkali-activated portland blast furnace slag-steel slag ce-
0 9.63/ 8.83
0 0
13.17/ 9.91
Portland cement
3 month/6 month
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2.73/2.50
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Acidic slag Mb = 0.75 Sulphate resistant portland cement
9.06/2.18
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Na2SiO3 NiSO4
Neutral slag Mb = 1.05
9.06/6.07
0
0
ment; 5) alkali-activated portland blast furnace slag-fly ash cement; 6) alkali-activated multiple components blended cements; 7) the activation and main features of alkali-activated Portland blended cements. The activation and main features of alkali-activated Portland blended cements can be summarized as follows: 1) Alkali sulphates are efficient and cost-effective activators when portland cement or cement clinker content is >20%, depending on the characteristics of the supplementary cementing materials; 2) The strength of alkali sulphate-activated cements is only slightly higher or even lower than that of the pure Portland cement, but significantly higher than that of the cement in the absence of alkali sulphate; 3) Waterglass is usually rather effective when Portland cement or cement clinker content is (7–8) mole the zeolite “precursor” prevailed in the resultant paste, whereas the alkaline concentration was lower, C–S–H gel was the main reaction product. Figure 7 shows the strength development of limenatural pozzolan cement pastes without any activator at different temperatures. An increase in curing temperature accelerates the early age strength development greatly. The pastes do not show the measurable strength until about 4 d at 23 ℃, but have the strength of 2.5 MPa after 1 d at 65 ℃. The strength levels off to a shallow slope (plateau) at 75 d at 23 ℃, 20 d at 35 ℃, 15 d at 50 ℃ and 10 d at 65 ℃. The rate of initial strength development increases with increasing the curing temperature.
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Fig. 8
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Effect of curing temperature on strength development of lime-natural pozzolan pastes with 4% Na2SO4[4]
2.5
Alkali-activated calcium aluminate blended cement Theoretically, all aluminosilicate materials can be potentially activated by alkalis. However, they have to meet certain criteria, including: 1) The solubility of the material in basic media should be higher; 2) The availability of Al2O3 and SiO2 in the environment should also be higher. As a general rule, materials with a high reactive silica content are in more plentiful supply than those with reactive alumina. In light of that fact, recent studies explored the possibility of using calcium aluminate cement (CAC) as a source of reactive alumina in the alkali activation of aluminosilicates.[2,30] Three combinations were investgated: Alkali-activated Metakaolin/CAC; Alkaliactivated pozzolan/CAC; Alkali-activated fly ash/CAC. The main features of alkali-activated CAC blends cement are summarized as follows: 1) The CAC of < 30% may be used as a source of reactive Al in the alkali activation of materials with low reactive alumina but high reactive silica contents; 2) Under these conditions, the CAC does not undergo normal hydration. While it appears to form a metastable intermediate compound, no cubic or hexagonal hydrates, or Al(OH)3 were detected in any of the materials studied; 3) Under the synthesis conditions, the Al and Ca from the CAC are taken up into the N–A–S–H gels formed as the primary product obtained from alkali-activated aluminosilicates materials. As a function of blends materials and reaction conditions two aluminium-rich gels are obtained: a majority of N–A– S–H gel and a minority of C–A–S–H product. Aluminium plays a primary role in the formation of a hydrated sodium aluminosilicate gel (N–A–S–H), particularly in the early phases of the reaction, for as the link between the silicon tetrahedra it initiates the condensation reactions. Although little definitive studies on how to enhance or reduce aluminium availability during the synthesis of these alkaline mineral polymers have been forthcoming, the strength development in the final prod-
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Effect of curing temperature on strength development of lime-natural pozzolan pastes[4]
The addition of Na2SO4 does not change the trends just noted (see Fig. 8), but the pastes with 4% Na2SO4 show higher strength than the control of pastes at a given curing temperature and age. The characteristics of the strength plateau are also similar to those of control of pastes at the same curing temperature, but the chemically activated cement pastes exhibit much higher strength than the control pastes.
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uct has been shown to depend on the presence of a certain minimum quantity of reactive aluminium in the original system.[2,30] In these alkali-activated CAC blends cements, the calcium aluminate can supply tetrahedral aluminium to these systems and give some extra reactivity to the solid mixtures; The CAC can even contribute to some mechanical strength.
[11] KRIVENKO P V. Alkaline cements: terminology, classification, aspects
3 Summary
[14]
of durability [C]//Proceedings of the 10th International Congress on the Chemistry of Cements, Goeteborg, Sweden, 4iv046–4iv050, 1997. [12] DAVIDOVITS J. Properties of geopolymer cements [C]//Proceedings of 1st International Conference on Alkaline Cements and Concretes, VIPOL Stock Company, Kiev, Ukraine, 131–149, 1994. [13] BAKHAREV T. Resistance of geopolymer materials to acid attack [J]. Cem Concr Res, 2005, 35: 658–670. FERNANDEZ-JIMENEZ A, GARCIA-LODEIRO I, PALOMO A. Durability of alkali-activated fly ash cementitious materials [J]. J Ma-
Since the discovery of the principles for alkali-activated cements and concrete in the later 1950s, a variety of alkali-activated cements and concrete have been developed and investigated. Many industrial by-products and recycled materials, such as blast furnace slag, phosphorus slag, steel slag, coal fly ash, can be used as their major cementing components. The characteristics of the cementing component, and the nature/dosage of activators have a great effect on the hydration, microstructure and performance of alkali-activated cements and concretes. The properly alkali-activated cements and concretes can exhibit better performances than conventional Portland cement and concrete. However, high drying shrinkage, potential alkali-aggregate reaction expansions, consistency of raw materials and quality control and quality assurance of alkali-activated cements and concretes are the main concerns for the use of alkali-activated cements and concretes.
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