波特兰石灰石水泥和混凝土的性能分析--材料科学与工程毕业论文外文资料翻译.doc

xx大学毕业论文外文资料翻译

毕业论文外文资料翻译

题 目 波特兰石灰石水泥和混凝土的
性能分析
学 院 材料科学与工程
专 业 材料科学与工程
班 级 XXXXXX
学 生 xx
学 号 xxXXXXXX
指导教师 XXXX

二零一三年四月二十日
Cement & Concrete Composites 24 (2002) 371–378
An analysis of the properties of Portland limestone
cements and concrete

S. Tsivilisa,*, E. Chaniotakis b, G. Kakali a, G. Batis a
a Chemical Engineering Department, National Technical University of Athens, 9 Heroon Polytechniou St., 15773 Athens, Greece
b Department of Research and Development, Titan Cement Company S.A., Kamari Plant Viotias, P.O. Box 18, 19200 Elefsis, Greece

Abstract
In this paper the main factors afecting the properties of Portland limestone cements are discussed while the hydration behavior of limestone cements is examined. In addition, the intergrinding process, concerning the production of the limestone cements, is studied. Finally the properties and the behavior of limestone cement concrete as well as the corrosion behavior of limestone cement mortar are investigated. It is concluded that the fineness of clinker and limestone is strongly connected with the limestone content and the fineness of the cement. The limestone cements indicate satisfactory strength and generally demand less water than the relative pure cements. The limestone addition improves the clinker reactivity and the exploitation of its hydraulic potential. The Portland limestone cements indicate competitive concrete properties and improve the corrosion performance of the concrete. 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Portland limestone cement; Intergrinding; Cement properties; Hydration; Concrete properties; Corrosion

1. Introduction
The use of Portland limestone cements seems to have many benefits, both technical and econmic al [1-3]. In addition, the European Standard EN 197-1 identifies two types of Portland limestone cement containing 6- 20% limestone (type II/A-L) and 21-35% limestone (type II/B-L), respectively [4]. It is expected that the future world production of Portland limestone cement will be continuously increased. The wide use of limestone cement requires a thorough knowledge of the cement and concrete properties.
As far as the cement is concerned, the research work is focused on three areas. The first one is the efect of limestone on the cement performance [3,5-8]. The second one deals with the participation of limestone in the hydration reactions of clinker [9-19], while the third one with the production process and specifically the intergrinding of clinker and limestone [5,20-22]. Although there is a disagreement in many partial topics, the knowledge level is satisfactory and continuously extended.
As far as the limestone cement concrete is concerned, the few available references are focused on two areas. The first one is the efect of limestone on the concrete properties and behavior [23-29]. The second one deals with the ''thaumasite problem'', correlated with the use of limestone cement concrete and calcareous aggregates. Recent research work shows that Portland limestone cement pastes are susceptible to the thaumasite forma- tion, due to sulfate attack at 5 ℃, after only a few months exposure to sulfate solutions [30-35].
In this paper the main factors afecting the properties of Portland limestone cements are evaluated, while the hydration behavior of the limestone cements is examined. In addition, the intergrinding process, concerning the production of the limestone cements, is studied. Finally the properties and the behavior of limestone cement concrete as well as the corrosion behavior of limestone cement mortar are investigated. This work is a part of a project, developed in our laboratories, concerning the properties of limestone cement and concrete.
2. Intergrinding of clinker and limestone
Ordinary Portland clinker of industrial origin and limestone of high calcite content (CaCO 3: 95.3%) were used (Tables 1 and 2). Four clinker/limestone mixtures, containing 10%, 20%, 30% and 40% limestone, respectively, were ground to four diferent fineness each one in a pro-pilot plant ball mill (16 samples CLi-j of Table 3).

Table 1 Chemical and mineralogical composition of clinker

Table 2 Chemical composition (%) of limestone

Table 3 Particle size distribution (passing %) of clinker, limestone and mixture

aCLi-j: C: clinker, L: limestone, i: limestone content (%), j: grinding time (A¼35 min, B¼50 min, C¼65 min,D¼85 min).
bCEM: mixture (cement).
cS: specific surface (Blaine), n: uniformity factor of RR distribution.

In order to determine the particle size distribution of clinker and limestone after their intergrinding, a sedimentation method (Andreasen apparatus) was used. A sample of each mixture was well dispersed in absolute ethyl alcohol. At predefined time intervals samples were withdrawn using a pipet. The selected time intervals correspond to particle sizes less than 32, 16, 8 and 4 lm. The alcohol was removed by drying and the limestone content was determined by measuring the loss of ignition (LOI) at 1000℃. Finally, the particle size distribution of clinker and limestone was computed.
The Rosin-Rammler distribution was used for de-scribing the particle size distribution of the interground samples. The values of the uniformity factor ðnÞ have been computed (Table 3). It is seen that the increase of the limestone content, as well as the increase of the ce-ment fineness, leads to wider particle size distribution. The particle size distribution of the clinker is significantly diferent than that of the mixture. The limestone is concentrated in the fine fractions (<8 lm), while the clinker is concentrated in the coarser fractions. Fig. 1 presents limestone and clinker contents of the diferent size fractions. It is seen that the limestone content in the fraction with size less than 4 lm is 24.8% and the clinker content is 75.2%. It must be noticed that the initial sample contains 20% limestone and 80% clinker. However, the size fraction greater than 56 lm contains only 12% limestone.
According to data given in Table 3, the increase of the mixture fineness influences the clinker fineness but not to a significant degree. In addition, a limestone content over 30% obstructs the grinding of both clinker and reduced clinker and limestone finenesses, compared with those containing 30%.
All the above results show that the particle size distribution of the Portland limestone cements, as well as the finenesses of clinker and limestone, is strongly con- nected with the limestone content and the fineness of the mixture. In order to produce a Portland limestone cement of desired properties, the grinding to higher fine- ness (compared with the pure cements) is the easy way, but the proper one is to define the optimum fineness level, taking into account the limestone content and the grinding properties of the components.
3. Properties of Portland limestone cements
Portland limestone cements were produced by inter- grinding of clinker (Table 1), limestone (Table 2) and gypsum in a pro-pilot plant ball mill of 5 kg capacity. The composition and the properties of the cements tes- ted are given in Table 4.
Fig. 2 shows the influence of limestone content on the strength development of CL-c-45. It is observed that the addition of 10% limestone does not significantly alter the compressive strength at any age of samples having fineness up to 3800 cm 2=g. Further increase of the cement fineness leads to the production of limestone cements having compressive strength lower than the pure ones. In general, the influence of the fineness on the compressive strength is stronger for limestone addition up to 10%.
Table 4 also presents the cement paste water demand, the setting time and the expansion of the tested samples. The limestone cements, despite their higher fineness, generally demand less water than the relative pure cements. In limestone cements containing 10% limestone, there is a reduction of water demand from 26% to 25%. The increase of the limestone content to 20% and 35% causes a decrease of the water demand to 23.5- 22.8%. The efect of limestone on the paste water demand of cements can be attributed to the diferent particle size distributions of the samples. Limestone cements despite their higher fineness have wider particle size distributions - lower value of uniformity factor (n) of the Rosin- Rammler distribution-compared with Portland cements (Table 4). This is due to the intergrinding of an easy-ground material such as limestone with the clinker.
The initial and final setting times of limestone cements (Table 4) are similar to those of the Portland cements. The soundness of the limestone cements (Table 4) is satisfactory. The expansion measured according to the Le Chatelier process varies from 0.5 to 1.5 mm while the limit according to EN 197-1 is 10 mm.

Fig. 1. Limestone (L) and clinker (C) content in different size fractions after their intergrinding (mixture fineness: 3890 cm2/g, limestone content: 20%).

4. Hydration of Portland limestone cements
Limestone cements containing 0%, 10%, 20% and 35% w/w limestone were examined (samples C-45, CL10-45, CL-20-45 and CL-35-45 of Table 4). The properties of the studied cements are given in Table 4.
Pastes were prepared by mixing solid and carbon dioxide-free distilled water in polyethylene vials subjectedto rotation from time to time. The water-to-cement ratio used is 0.3. After periods of 1, 2, 7 and 28 days, the samples were dried in vacuum for 24 h and subjected to X-ray difraction. Thermogravimetric analysis (TGA) was used for the determination of non-evaporable water and calcium hydroxide content in dried cement pastes, using a TA Instruments Thermal Analyst 3000. The samples (_50 mg) were heated over the range 20-900 ℃ at a constant rate of 15 ℃/min in an atmosphere of carbon dioxide- free nitrogen, flowing in 90 cm 3/min.
Table 5 shows the hydration products in the C-45 and CL-35-45 pastes. In C-45 pastes, ettringite is gradually transformed into monosulfate. In CL-35-45 pastes, the formation of ettringite is delayed and monocarboalu- minate is preferably formed instead of monosulfate. Calcium aluminate hydrates (3CaO·Al2O3·Ca(OH)·18H2O and Ca2Al2O5·8H2O) are detected in C-45 pastes but not in limestone pastes, probably because of the dilution of the samples by limestone.

Table 4 Composition and properties of Portland limestone cements

aLimestone cement: CL-c-t, C: clinker, L: limestone, c: limestone (%), t: grinding time (min).
bn: Uniformity factor of RR distribution.

Fig. 2. Influence of limestone content on cement strength development (grinding time: 45 min).

Concerning the CH and non-evaporable water de- terminations (Table 6), the higher content of bound water, in the pastes made from limestone cements, in- dicates that limestone improves the clinker reactivity and the exploitation of its hydraulic potential. This ef- fect may be related to the structure modification of the hydration products as well as to the nucleating action of the finely ground limestone. The increase of Ca(OH )2 content in pastes of limestone cement indicates an acceleration of calcium silicates hydration, especially in cement containing 10% limestone.
5. Properties of limestone cement concrete
The composition and properties of the tested cements are given in Table 7. Portland limestone cements were produced by intergrinding of clinker, limestone and gypsum in a pro-pilot plant ball mill of 5 kg capacity. The cements LC1-LC4 contain 0%, 10%, 15% and 20% limestone, respectively, and have the same 28d com- 2 pressive strength (48-51 N/mm , strength class 42.5R of EN 197-1). The cement LC5 contains 35% limestone (32.5R of EN 197-1).
The concrete production was carried out in a mixer of 50 l capacity. The mix proportions and the aggregate grading are given in Table 8.
The concrete properties of the tested cements are given in Table 9. The mixes with limestone cement,although their higher fineness, indicate a satisfactory workability. The slump of the mixes was in the range 110-130 mm (class S3 of EN 206). A plasticizer (Poz- zolith 390N) was used in concrete containing cement with 35% limestone (LC5). Concerning the compressive strength, all the mixes belong to the class C20/25 of EN 206.

Table 5 Hydration products in samples C-45 and CL-35-45

Table 6 Non-evaporable water and Ca(OH )2 content in limestone cement pastes

Table 7 Characteristics of the tested cements

Table 8 Concrete mix proportions and aggregate grading

aPlasticizer (Pozzolith 390N).

Table 9 Concrete properties

6. Corrosion behavior of limestone cement mortar
The cements of Table 7 have been used for the rela- tive tests. The W =C ratio was 0.50 and the calcareous sand:cement ratio was 3:1. Prismatic specimens (80 _80 _ 100 mm 3) were constructed and four cylindrical steel bars (12 ×100 mm 2) were embedded in each one. Each bar has a properly attached copper wire. Both, the top surface of all specimens and the part of steel bars which protrudes over the concrete, are covered with an epoxy glue to protect the bars from atmospheric corrosion.
The specimens were partially immersed in a 3 wt% NaCl solution, up to a height of 25 mm, in order to accelerate the corrosion process. After immersing all specimens in the corrosive solution, the following measurements were carried out: (a) gravimetric mass loss of the rebars after 9 and 12 months exposure, (b) mean carbonation depth, after 9 and 12 months, using phe- nolphthalein indicator, anointed across a vertical section of the specimen and (c) porosity of the specimens, after 9 months exposure, using a Carlo Erba 2000 Hg porosi- meter. It must be noted that the advanced investigation of steel rebars corrosion with strain gauges is the subject of a future study [36]. Fig. 3 presents the mass loss of rebars (average value of four specimens), expressed as mg=cm 2 of surface of the rebars. There is an explicit decrease of corrosion in specimens with limestone. The mass loss of rebars decreases as the limestone content increases up to 20%. It must be noticed that the corrosion rate of LC4 is three times lower than LC1 (0.030 mg/cm 2 month against 0.093 mg/cm 2 month). The mass loss of specimens with
20% and 35% limestone is the same, in the frame of statistical analysis.
Concerning the carbonation depth, all types of Portland limestone cements used did not show any carbonation after exposure times of 9 and 12 months. The Portland cement specimen had a carbonation depth of 3- 5 mm. In addition, the specimens with limestone had lower porosities compared with those of the Portland cement specimen (LC1: 15.3%, LC