The Effect of Minor Elements on Clinker Minerals … 太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第172号(2017)：曽我他 effects on clinker minerals and cement

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太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第172号(2017)：曽我他 ―――――――――――――――――――――――――――――――――――――――――――――――――――――――

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*中央研究所第１研究部セメント化学チーム Cement Chemistry Team, Central Research Laboratory **中央研究所第１研究部セメント化学チームリーダー

Manager, Cement Chemistry Team, Central Research Laboratory

◇論文◇

The Effect of Minor Elements on Clinker Minerals and Cement Hydration

少量成分がクリンカー鉱物

およびセメント水和に及ぼす影響

SOGA, Ryota*; MERKO, Paige*; HAYASHI, Kensuke*;

HOSOKAWA, Yoshifumi*; UCHIDA, Shunichiro**

曽我亮太*, Paige MERKO*, 林建佑*，

細川佳史*, 内田俊一郎**

要旨

セメント業界は原燃料を副産や廃棄物に置き換え，環境への貢献を進めているが，これらの

代替原燃料中の少量成分は，クリンカー鉱物やセメントの特性に影響する．代替原燃料の活用

を推進するため，本研究ではクリンカー鉱物や水和に及ぼす少量成分の影響を評価し，MgO，NiO，

CuO，ZnO，TiO2および P2O5の限界値を決定した．

少量成分は，クリンカー鉱物に与える影響を基に３グループに分けることができた．(1)MgO

や NiOは，f.MgOや f.MgOに似た結晶を形成した．(2)CuOや ZnOは，シリケート相への影響は

わずかであり，多量添加するとセメントの水和を遅延させる酸化物を形成した．(3)TiO2や P2O5は，C3S量を低下させた．セメント水和や強さへの影響から少量成分の限界値は，CuOは 0.48%，

ZnOは 0.97%，MgOは 2.00%，NiOは 1.95%，TiO2は 0.50%まで，P2O5は 0.91%までとなった.

キーワード：副産物，廃棄物，少量成分，鉱物組成，結晶多形，水和発熱速度，圧縮強さ

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ABSTRACT

Cement manufacturers are in the process of replacing conventional raw materials and fuels with by-products and wastes as a means to contribute to the environment. Alternative raw materials and secondary fuels contain minor elements which can influence burnability as well as properties of clinker minerals and cement. Burnability influences the amount of free lime in clinker, which results in variations in mineral composition and cement hydration. In order to optimize the use of alternative resources, this study evaluated the effects of minor elements on clinker minerals and cement hydration under a constant free lime effect and determined the limits of MgO, NiO, CuO, ZnO, TiO2 and P2O5.

Minor elements were classified into three groups based on similarity in the effect on clinker minerals. Group I including MgO and NiO was distinguished by the presence of periclase and periclase-like crystals. Group II including ZnO and CuO was characterized by negligible changes to the silicate phase along with, at high content, the formation of excess oxides which acted as a retarder in cement hydration. Group III including TiO2 and P2O5 was defined by a decrease in C3S. This study led to the following recommended limits for minor elements based on cement hydration and strength are as follows: MgO ≤ 2.00% for negligible effect, NiO ≤ 1.95% for negligible effect; CuO ≤ 0.48% for negligible effects; ZnO ≤ 0.97% for beneficial strength gain; TiO2 ≤ 0.50% for negligible effects; and P2O5 ≤ 0.91% for negligible effects. Keywords：By-products, Wastes, Minor element, Mineral composition,

Crystal olymorph, Heat generation rate, Compressive strength 1. INTRODUCTION

Cement manufacturers are moving towards more sustainable manufacturing by replacing conventional materials and fuels with alternative resources, such as waste and by-products. Use of various alternative materials and secondary fuels reduces the environmental impact, which inevitably introduces significant amounts and various types of minor elements into clinker. Minor elements can have influence on clinker and cement properties which may be either beneficial or detrimental to cement performance. Assessments of minor elements are needed in order to safely and effectively incorporate alternative materials and fuels into cement manufacturing.

Although many studies have examined the effects of various minor elements in clinker and cement 1)-6), their results among studies are often contradictory and insufficient for determining

the limits of minor elements in clinker. Contradictions arise from differences in materials used (analytical grade chemicals or plant raw meal), burning conditions (time and temperature), free lime (f.CaO) content 7) 8), and/or specific surface area of the cement. Studies using fixed amount of minor elements added to the clinker material neglect the variations in the effects that can occur with changes in minor element additions rate. In order to properly utilize materials containing minor elements, limits of minor elements that maintain or improve cement performance need to be defined. It is specifically necessary to determine the effects of minor elements at varied addition rates under fixed conditions in terms of burning time and temperature, f.CaO content and specific surface area of cement.

This paper determined the limits of six minor elements by evaluating and analyzing their

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effects on clinker minerals and cement hydration. The minor elements evaluated in this study were: magnesium, nickel, copper, zinc, titanium and phosphorus. 2. MATERIALS AND METHODS Clinker raw meal was prepared using ordinary portland cement plant feed with analytical grade chemicals for adjustments. Magnesium, nickel, copper, zinc and titanium were added in their respective oxide forms: MgO, NiO, CuO, ZnO, and TiO2, while phosphorus was added as calcium phosphate, Ca3(PO4)2, for P2O5. Minor elements were added at varied rates to achieve a final calculated content in the sintered clinker between 0.375% and 4.0%. Analytical chemicals (SiO2 - quartz form, Al2O3, and Fe2O3) were used to adjust the hydraulic, silica, and iron modulus to be consistent with OPC clinker (see Table 1). Clinker material of 130 g in total was ground in a dish and puck mill for 90 seconds to adequate homogeneity and fineness. The resulting powder was mixed with ethanol and pressed into seven cylindrical pellets weighing approximately 20 g. Pellets were stored in a drying oven at 40°C to evaporate ethanol and allowed to stand still there until the time of clinkering. The clinkering process was as follows: Pellets were placed in a box furnace pre-heated to 1000°C. Temperature temporarily dropped during that operation but quickly regained 1000°C. Pellets were burned for 30 minutes at 1000°C, after which the temperature was gradually raised to 1500°C in 30 minutes and held that temperature for four hours to minimize f.CaO. Pellets were then quickly removed and allowed to cool in ambient air.

Chemical composition of the clinker was determined using X-ray fluorescence (XRF).

Mineral composition was determined using X-ray diffraction (XRD) and Rietveld refinement (Rv). Intensity patterns at 2θ = 51 - 52° were used to identify C3S polymorphs. The silicate phase was dissolved by salicylic acid-methanol extraction to identify C3A polymorphs and minor phase using XRD. The ethylene glycol method (JCAS I-01: 1997) was used to determine f.CaO. The distributions of added minor elements within clinker phases were examined using a scanning electron microscope (SEM) with an energy dispersive X-ray spectrometer (EDS). Cement samples were produced by grinding clinkers with desulfogypsum and Ca(OH)2 to achieve a SO3 and f.CaO contents of 2% and 0.5%, respectively. Samples were milled until their Blaine specific surface area was within 3200 – 3450 cm2/g.

Heat of hydration was observed using a conduction calorimeter. Cement weighing 10 g was mixed with 5 g of water for 3 minutes. Compressive strength was determined using modified tests 9) for small mortar samples. Mini- mortars consisting of 45 g cement, 135 g JIS sand and 22.5 g tap water were manually and mechanically mixed using a solder paste mixer. Six specimens (2×2×3 cm) were molded from the mortars and stored in a humidity box. Molds were removed the following day, and specimens were submerged in 20°C water until the time of testing. Compressive strengths were tested at 3, 7 and 28 days. The average compressive strength between each two samples was taken. 3. RESULTS AND DISCUSSION 3.1 Clinker

(1) Mineral composition Mineral composition of clinkers can greatly influence cement hydration and strength

Table 1 Modulus and Mineral composition calculated by Bogue formula

Modulus Mineral composition (Bogue, %)

HM SM IM C3S C2S C3A C4AF

2.10 2.41 1.77 55.3 21.7 9.9 10.1

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development. Fig.1, 2 shows the clinker mineral compositions plotted against the minor element weight percentage detected by XRF. The ratios of f.CaO in the P2O5 1.70%, P2O5 2.58% and CuO 1.71% clinker were 0.06%, 2.58% and 0.46%, respectively, as determined by the ethylene glycol method (JCAS I - 01). No f.CaO was detected in other clinkers. Data from XRD distinguished three different groups of minor elements.

Group Ⅰ, comprised of MgO and NiO, was characterized by an increase in periclase (f.MgO) or periclase-like crystals. The formation of f.MgO increased as more MgO was added to the clinker. Addition of MgO also increased in C3S and C4AF

Fig. 1 Mineral composition of clinker containing a minor element

Fig. 2 Amount of f.MgO in clinker

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which reached a maximum at 3.03% and 2.00%, respectively. C2S and C3A were oppositely affected. XRD also indicated an increase in f.MgO in the NiO clinkers; however, phase diagrams proposed the possibility that the crystal structure detected was a continuous solid solution of NiO-MgO. SEM was used to verify the presence and composition of this solid solution, later. Effects of NiO were negligible on the silicate phases. However, the interstitial phases were observed to have a decrease in C3A and an increase in C4AF until 1.95%, after which the tendencies reversed like MgO at high addition rates.

Group Ⅱ , comprised of CuO and ZnO, was characterized by negligible changes to the silicate phases. CuO at 1.71% caused a small amount of C3S to decompose and form C2S and f.CaO. ZnO did not change the composition of the silicate phases but showed effects on the interstitial phases as an increase in C4AF and a decrease in C3A.

Group Ⅲ , comprised of TiO2 and P2O5, was characterized by a decrease in C3S. TiO2 showed a decrease in C3S and an increase in C3A at all additional rates. But, C2S and C4AF were not affected. P2O5 showed greater declines in C3S than those found in the TiO2 clinkers; however, unlike in the TiO2 clinkers, effects also appeared in C2S.

(2) Crystal Polymorph and Minor Mineral Changes in polymorphs were likely to influence

the hydration reactivity of minerals. Intensity patterns used for the polymorph identification of C3S are shown in Fig.3. The M1 polymorph is identified by the presence of a single peak at 51-52.5°. Two distinct peaks indicate M3 while one distinct peak coupled with a soft peak indicates a combination of M1 and M310). C3S was present as M1 in the blank, P2O5 and TiO2 clinkers, and at low minor element addition rate. Greater addition rate of CuO, ZnO, MgO and NiO resulted in a more pronounced peak indicating an increase in the M3 polymorph.

XRD patterns of clinkers after salicylic acid methanol extraction to identify C3A polymorphs are shown in Fig.4. The C3A in the blank, MgO, NiO, CuO, TiO2 and P2O5 clinkers was in the cubic phase. However, the C3A in the ZnO clinker was found to be in orthorhombic phase. Na2O is known to alter the C3A phase to the orthorhombic type thus causing enhanced hydration reactivity11)12). The hydration reactivity of the C3A was evaluated by the heat generation rate and discussed later.

XRD patterns of the clinkers treated with salicylic acid methanol extraction are shown in Fig.5. Minor phases were detected in the simple oxide form in the MgO, NiO and ZnO clinkers, respectively.

Fig. 3 XRD patterns of clinker at 51-52.5°

51 52.5

CuO 2/°

0.36%

0.48%

0.93%

1.71%

0.01%

51 52.5

ZnO 2/°

0.50%

0.73%

0.97%

1.91%

0.03%

51 52.5

MgO 2/°

1.23%

2.00%

3.03%

4.04%

0.86%

51 52.5P2O52/°

0.49%

0.91%

1.70%

2.58%

0.30%

51 52.5NiO 2/°

0.49%

0.97%

1.95%

2.92%

0.02%

51 52.5

TiO2 2/°

3.02%

2.02%

1.00%

0.50%

0.26%

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(3) Element Map SEM with EDS was used to visualize the distribution of minor elements within clinker minerals and verify the composition of new phases in clinkers at the highest minor element addition rate. Backscattered electron (BSE) images of clinkers coupled with X-ray imaging of each added minor element are shown in Figs 6, 7. X-ray color maps of the clinker area －bottom right of each BSE image－ are used to visualize the distribution of the added minor element throughout the clinker. The image obtained indicated that the minor elements influenced the clinker microstructure, integrating existing minerals and/or forming new minerals.

In group Ⅰ, MgO and NiO exhibited additional structures in the clinker. In the MgO clinker, f.MgO was identified as the black regions which corresponded to the areas with high in MgO. The NiO clinkers showed no presence of f.MgO. Instead, the clinker contained white high regions indicative of a high NiO presence. Point analysis verified that these white regions consisted primarily of NiO and MgO, confirming the presence of the NiO-MgO solid solution.

In group Ⅱ , addition of CuO and ZnO was found to cause formation of excess CuO or ZnO which appeared as white spots, throughout the interstitial phases. This was verified using point analysis.

In group Ⅲ, TiO2 and P2O5 was distributed throughout the clinker minerals. TiO2 was preferentially distributed throughout C4AF followed by C3A. Small amounts of TiO2 also entered the C2S phase. Conversely, P2O5 was distributed primarily in C2S, with very little entering C3S and none detected in the interstitial. Simple oxide of TiO2 or P2O5 was not observed.

(4) Element Distribution To discuss the effects on mineral composition,

the elements distribution of clinker minerals was quantified. The distribution was determined using grid analysis with SEM-EDS. A grid was composed of 32-by-32 points 13), and the grid spacing was 30 μm. The analyzed points of the blank clinker are shown in Fig.8. The obtained data was sieved considering the total chemical composition. Data points that had a total

Fig. 4 XRD patterns of clinker after salicylic acid/methanol extraction at 20.0-22.5°

Fig. 5 XRD patterns of clinker after salicylic acid/methanol extraction at 35-45°

50m

Fig. 6 BSE image of blank clinker

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chemical composition between 90% and 110% were regarded as clinker. Other data points were seemed as void or resin and excluded. Each data point was classified a major clinker mineral by the threshold values shown in Fig.9.

The threshold value between C3S and C2S was determined to separate their clusters shown in Fig.10, 11 shows the relationship between Al2O3 and Fe2O3. Because the C3A and C4AF phases were not separated into two clusters by Al2O3/Fe2O3, the threshold value between C3A and C4AF was determined so that the mineral composition of blank clinker quantified by grid analysis matched the one obtained by Riedvelt analysis. Fig.11 shows

The minor element distributions are shown in Fig.12. The relationship between TiO2 and Al2O3 of the C4AF phase is presented in Fig.13. The addition of TiO2 led a loss in Al2O3 in the C4AF phase. This Al2O3 from C4AF could participate in the forming of additional C3A. An increase in C3A was observed when adding TiO2 (see Fig.1). The CaO leading to form C3S might be reduced by the additional C3A formation, and TiO2 also replaced SiO2 of C2S as presented in Fig.14, thus causing the C3S reduction observed in Fig.1.

Fig. 8 BSE image of blank clinker (each dots shows an analyzed grid point)

Fig. 7 BSE images and elemental maps of clinker containing a minor element

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Fig. 9 Decision flowchart to differentiate the clinker minerals based on chemical composition

Total oxide >90 (EDS, %)

Void or resin

Al2O3+Fe2O3

> 24 (EDS, %)CaO+SiO2

> 80 (EDS, %)

Al2O3/Fe2O3

> 1.75 (EDS, %/%)CaO/SiO2

> 2.57 (EDS, %/%)

C3A

C4AF

C3S

C2S

Ambiguous point

true

false

false false

falsefalse

true

true true

true

Fig. 12 Minor element distributions

Fig.11 Al2O3 vs Fe2O3 of blank clinker Fig.10 CaO vs SiO2 of blank clinker

Minor Element of Bulk Clinker (XRF,%) Minor Element of Bulk Clinker (XRF,%) Minor Element of Bulk Clinker (XRF,%)

Min

or e

lem

ent

of m

iner

al(E

DS

,%)

Min

or e

lem

ent

of m

iner

al(E

DS

,%)

Min

or e

lem

ent

of m

iner

al(E

DS

,%)

24


Fig. 13 Relationship between Al2O3 and TiO2 of the C4AF phase

Fig. 14 Dependence of SiO2 on Minor element of the silicate phase

Fig. 15 Heat generation rate of cement containing minor element for the first 0.6h

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3.2 Cement (1) Heat of hydration

Heat of hydration, which is influenced by quantity and quality of clinker minerals, impacts the workability, setting and strength development of cements. Fig.15 shows the first heat generation rate of all cement samples including samples those exceeding the maximum specific surface area, i.e., NiO 1.95% and ZnO 0.97%. It is known that first hydration heat peak is related to C3A hydration which influences workability. First hydration peak height correlated to the amount of minor element is shown in Fig.16. The decrease in C3A due to additions of MgO led to less hydration heat. First hydration heat peak per C3A vs amount of minor element is shown in Fig.17. Assuming that hydration heat peak per C3A depend on hydration reactivity of C3A, ZnO could enhance C3A reactivity. The C3A polymorphs in the ZnO clinker were orthorhombic type according to XRD analysis (see Fig.4). Orthorhombic C3A is believed to have superior reactivity to the cubic phase, and the orthorhombic C3A by ZnO addition could also lead to higher hydration heat. ZnO reduced the amount of C3A but appeared to enhance hydration reactivity. For both effects, no constant tendency might be observed in the relationship between the chemical composition and hydration heat.

Heat generation rate at 0-72h related to C3S hydration is shown in Fig.18.

In group Ⅰ, MgO and NiO exhibited negligible effects to the hydration despite the formation of periclase and NiO-MgO solid solution in the respective clinkers. It is proposed that the solubility of these crystals is very slow or nonexistent, contributing little to the cement hydration. Analysis of the pore solution is needed before confirmation can be made.

In group Ⅱ, there were significant detrimental effects to the hydration in the cements with the addition of CuO; however, small amounts of ZnO promoted the hydration of C3S. Cements with CuO at 0.93% or greater experienced delays in the acceleration period and reduced heat generation rates. CuO at 1.71% recorded the longest induction period and no second hydration peak was observed until 72h. The calorimetry carried out up to 168h revealed that induction period of CuO at 1.71% lasted 84h, with the acceleration period peaking at 100 h. Observations showed that ZnO at 1.91% caused similar delays to the CuO samples with a prolonged induction period. However, the hydration rate was comparable to the reference cement. Conversely, ZnO at less than 1.91% demonstrated positive accelerating capabilities by shortening the induction period and increasing

Fig. 16 Relationship between first peak height and minor element concentration

Fig. 17 Relationship between first peak height per C3A and minor element concentration

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the hydration rate. ZnO is known as a retarder14) 15), and f.ZnO has been detected in the clinker by SEM observation and XRD analysis. To clarify the effect of f.ZnO in clinker on cement hydration, the hydration heat of commercial cement mixed with ZnO powder was measured. Heat generation rate of the cement with ZnO powder is presented in Fig.19. ZnO powder mixed with cement exhibited the retarding effect, with acceleration period extended to 144h by a 0.5% addition. F.ZnO in the clinker would have acted as retarder, thus resulting in the retarded hydration of the ZnO 1.91% cement.

In group Ⅲ, P2O5 and TiO2 exhibited delayed and reduced hydration rates which corresponded to their loss in C3S. The effect was amplified in P2O5 cements due to the larger loss in C3S. Water soluble P2O5 is also known as a retarder; however, P2O5 was not observed in its simple oxide forms such as CuO and ZnO.

Fig. 18 Heat generation rate of cement containing minor element for the first 72h

0.0

1.5

3.0

4.5

6.0

7.5

0 24 48 72 96 120 144 168

Hea

t gen

erat

ion

rate

(J/h・

g)

Time (h)Blank ZnO 0.025%ZnO 0.05% ZnO 0.1%ZnO 0.5%

Fig. 19 Heat generation rate of cement mixed with ZnO powder

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The C3S polymorph containing divalent cations (Mg2+, Ni2+, Zn2+ and Cu2+) was M3 type, and the blank, TiO2 and P2O5 were M1 type. Crystal polymorphs were considered to alter hydration reactivity. ZnO enhanced hydration reactivity at small content, and other divalent cations exhibited detrimental or negligible effect on hydration. Bazzoni et al.17) mentioned no clear link was present between crystal structure polymorphs and reactivity based on pure or MgO or ZnO-doped C3S study. Similar tendencies were observed in this cement study, which indicated that chemical composition would play more important roles in C3S hydration than crystal polymorphs.

(2) Compressive Strength Fig.20 shows the compressive strength of all

small mortars at 3, 7 and 28 days. In group Ⅰ, MgO and NiO show a s l ight ly reduced compressive strength from the level of the blank due to the lack of changes in cement hydration. MgO at 3% and 4% showed lower strength at 28 days than the blank. In group Ⅱ, CuO showed significant losses in strength at all ages due to the lower cumulative heat generation. The 1.71% CuO samle was too soft to be removed from the mold for testing due to the induction period lasting 84 hours. Similarly, the 1.91% ZnO sample was removed from the molds on the 3rd day and recorded losses in 3-days strength. However, at later ages this mortar developed the highest

compressive strength out of all mortars. At 7 and 28 days, all ZnO samples had an average compressive strength higher than the reference. The calorimetry showed that addition of ZnO resulted in increase hydration rates which aided in the strength development in the mortar samples. ZnO ≤ 0.97% might be effective for counteract to detrimental element. In group III, P2O5 and TiO2 exhibited loss in strength which corresponded to the decrease in C3S and subsequent hydration loss observed in the calorimetry. At 28 days the loss in strength was less prominent in the P2O5 samples due to the increase in C2S, which was known to influence late strength development. 4. THRESHOLD LIMIT OF MINOR ELEMENTS For effective utilization of waste and by-products, threshold limit were determined based on the compressive strength and the retarding effect on hydration which are related to the setting of cement. In group Ⅰ, MgO ≤ 2.00% and NiO ≤ 1.95% exhibited negligible change in hydration and compressive strength. MgO > 2.00% showed reduced strengths at 28 days. In group Ⅱ, a large amount of ZnO or CuO caused a significantly retarded hydration and loss in strength. For safe use, these elements should be handled with caution. CuO ≤ 0.48% had negligible effects on Fig. 20 Compressive strength of small mortar at 3, 7 and 28 days

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cement hydration. ZnO ≤ 0.97% showed an accelerated hydration and had beneficial effects on strength gain. In group Ⅲ, TiO2 and P2O5 exhibited detrimental effects on strength. P2O5 also retarded C3S hydration. TiO2 ≤ 0.5% and P2O5 ≤ 0.91% were likely to have only egligible effects. 5. CONCLUSION

In this study, six minor elements were evaluated in regard to their effects on clinker minerals and cement properties. The minor elements were differentiated into three groups based on their similarity in the effects on clinker minerals.

Group Ⅰ , comprised of MgO and NiO, was characterized by an increase in f.MgO or f.MgO- like crystals.

Group Ⅱ , comprised of CuO and ZnO, was characterized by negligible changes to the silicate phases and formation of their simple oxides which acted as a retarder. ZnO altered C3A polymorph from the cubic to the orthorhombic phase.

The two first groups promoted M3 type C3S formation and reduced the amount of C3A.

Group Ⅲ , comprised of TiO2 and P2O5, was characterized by a decrease in C3S. TiO2 increased the amount of C3A by replacing Al2O3 in C4AF. P2O5 had negligible effects on the interstitial phase and greater effects on the amount of C3S as compared to TiO2.

Based on the cement properties, the following recommended limits for minor elements were determined: 1. CuO ≤ 0.48% has negligible effects on cement

hydration. Exceeding this limit leads to a significant retardation in cement hydration and a loss in strength.

2. ZnO ≤ 0.97% had accelerates hydration and improves strength development. Exceeding this limit further improves strength development. However, the effect is accompanied by undesirable delays in hydration and loss in 3-days strength due to f.ZnO which acts as a retarder.

3. MgO ≤ 2.00% has negligible effects on strength and reduces the amount of, and thus the hydration of, C3A.

4. NiO ≤ 1.95% has negligible effects on strength. 5. TiO2 ≤ 0.5 % has negligible effects. Surpassing

this limit increased amount of C3A by replacing with Al2O3 of C4AF phase.

6. P2O5 ≤ 0.91% has negligible effects. Additional P2O5 leads to delays in heat of hydration which corresponds to their loss in C3S and loss in 3 and 7 days strengths.

Most of the minor elements exhibited negligible

or detrimental effects on cement hydration. However, ZnO improved strength gain at low addition rate. In order to promote further use of alternative resource, ZnO might be effective for counteracting detrimental minor elements.

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Documents

The Effect of Minor Elements on Clinker Minerals … 太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第172号(2017)：曽我 他 effects on clinker minerals and cement

The Effect of Minor Elements on Clinker Minerals … 太平洋セメント研究報告(TAIHEIYO CEMENT KENKYU HOKOKU) 第172号(2017)：曽我他 effects on clinker minerals and cement