The strength effect of mineral admixture on cement concrete

CEMENT and CONCRETE RESEARCH. Vol. 18, pp. 464-472, 1988. Printed in the USA. 0008-8846/88 $3.00+00. Copyright (c) 1988 Pergamon Press plc

THE STRENGTH EFFECT OF MINERAL ADMIXTURE ON CEMENT CONCRETE

Feng Nai-qian, Yang Hsia-ming and Zu Li-hong Building Material Laboratory, Department of Civil Engineering Tsinghua University, Beijing, China

(Communicated by Wu Zhong-wei) (Received Nov. 2, 1987)

ABSTRACT This paper presents the strength effect of the F mineral admixture (FMA) which is made of the finely divided powder of natural Zeolite Rock ground with a bit of other inorganic material. Test results indicate that a concrete mixing with 450 kg/m3 of ordinary portland cement (OPC), 50 kg/~ of FMA and W/C(=W/C+FMA)=35% can have a compressive strength above 80 MPa, while the compressive strength of the corresponding concrete mixing with 500 kg/m3 of OPC is only 70 MPa. Test results also conclude that, when a 5-10% of cement in the concrete is displaced by FMA under the condition of using superplasticizer (HRWR) and w/c=0.31-0.35, the strength of this concrete is 10-15% higher than that of the corresponding concrete mixing with pure OPC. The mechanism of strengthening effect on concrete strength by FMA is also studied and discussed. This strengthening effect by FMA occurs only at lower water-cement ratio with HRWR and fineness of FMA lower than that of cement. The strengthening effect of concrete by FMA to slag portland cement concrete is also similar.

INTRODUCTION The F mineral admixture (FMA) used in this study is a fine powder of natural Zeolite rocks ground with a bit other inorganic materials. The principal mineral composition of this admixture is Clinoptilolite and Mordenite whose content is about 60%. When FMA is used to displace 5 to 10% (by weight) of the ordinary portland cement (strength grade 5251) used in the concrete mixed with a suitable amount of naphthalene-based water reducer (HRWR) and water-cement ratio (w/c) about 0.35. A high-strength fluid concrete with compressive strength about 80 MPa and slump about 160-180 mm can be obtained. The raw material of FHA in China is very plenty in deposit which is wide in distribution and easy to exploit. This FMA is an ideal inorganic strengthening admixture of concrete. In this study, the FMA to the strengthening role of cement concrete and 464

Vol.

18, No.

3

465 M I N E R A L ADMIXTURE,

ZEOLITE,

STRENGTHENING

its s u i t a b i l i t y for different types of cement are studied, and the m e c h a n i s m by which FMA improves the strength of concrete is also investigated. The c o n c r e t e with an actual compressive strength about 80 MPa is called a s u p e r - h i g h strength concrete [i]. Although here are several methods to get it in other countries, but at the present time, these methods are very difficult to put into practice in China, because there is lack of autoclave- treated equipments, and the finely divided silica fume is too costly and will pollute the envlrnment. Therefore, the FMA is naturally a suitable addition for the f l u i d - s u p e r h l g h - s t r e n g t h concrete in China.

MATERIALS

USED

The FMA used is made respectively of two different types of natural Zeolite rocks exploited individually from the North and Northeast China. Their chemical c o m p o s i t i o n s are shown in table-l. TABLE-1. Original

CHEMICAL C O M P O S I T I O N S OF THE F~:A

~

Chemical .

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composition

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(%,by wt.)

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Deposit ¶ SiO ¶ A ~ O 3 ~ Fe205 ¶ CaO ~ MgO q KIO ~[ NazO ~[ Ignition Loss .......... ¶ ....... ~ ....... ~ ....... ¶ ...... ¶ ...... ~ ...... ~ ...... ~ ............... N o r t h e a s t ¶ 66.82 ¶ 13.70 ¶ 1.38 ¶ 3.73 ¶ 1.09 ¶ 1.95 ~ 0.64 ~ i0.00 China ~ ¶ ¶ ~ ~ ~ ~ .......... ~ ....... ~ ....... ~ ....... ¶ ...... ~ ...... ~ ...... ~ ...... ~ . . . . . . . . . . . . . . . North China .

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~ 60.90 ~ 13.67 ~ 1.46 ~ ~[ ¶ .

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¶ 3.66 ~ 1.83 ~ 2.54 ~ 0.49 ~ ~ ~ ~ ~ .

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14.~7 .

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The result of N i t r o g e n (Nz) a d s o r p t i o n bv BET method analysis indicates that FMA is such a material that contains lots of microporous crystalline phases with large amount of internal surfaces and a very high BET value of N i t r o g e n (Nz) a d s o r p t i o n (table-2), and thus the FHA has a much better ability of h y d r a t i o n reaction. TABLE-2.

S O L U B I L I T Y OF SILICA.

Original ~Solubility~solubillty¶ N Deposit ~ SiOz II A 1 2 0 3 ¶

ALUMINA AND PORE PROPERTY OF FMA

adsorption BET

¶ Max. possible ~ Mean diameter ¶ pore diameter ~ of grains (%) ~ (%) ~ (mX/g) ¶ (~) ¶ CUm) ......... ~ .......... ~ .......... ~ . . . . . . . . . . . . . . . ~[. . . . . . . . . . . . . . . q ..............

Northeast~[ 3.0765 ~ 6.2002 ¶ 19.54 ¶ 25.0 ¶ 5.00 China ~ ~ ~ ~ ¶ ......... ¶ .......... ~ .......... ~ ............... ~ ............... ~ .............. North China .

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Two cement is slag The sand. The NF, UNF

~T ~ .

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3.2056 .

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5.9321 .

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~[ ~ .

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34.30 .

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23.3 .

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5.90 .

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different types of cement are used. One is the ordinary Portland ( O P C - - s t r e n g t h grade 525#) with 28 days strength 61 HPa. The other one Portland cement with 28 days strength 36 MPa. coarse aggregate is crushed gravel and the fine a~gre~ate is river o r d i n a r y drinking water and the N a p h t h a l e n e - b a s e d produced in China are used.

water reducer

(HRWR)

466

Vol. Feng

TESTING

Nai-qian,

SERIES

18,

No.

3

et al.

AND

SAMPLE

PREPARATION

Five t e s t i n g s e r i e s of c o n c r e t e s w i t h and w i t h o u t m i n e r a l admixture have been performed in this s t u d y for the p u r p o s e to see the concrete strength influenced by various factors. T h e m a t e r i a l s u s e d in e a c h series and its c o r r e s D o n d i n g o b j e c t i v e a r e s h o w n r e s p e c t i v e l y in t a b l e - 3 . TABLE-3.

TESTING

SERIES

AND

OBJECTIVE

..............................................................................

4 Material/m ~ (kg) 4 No.4 ...................................... 4 Objective 4Cement4Admixture4Water4Sand4Gravel4 NF4 ---~; . . . . . . 4 . . . . . . . . . 4 ..... ¶ .... ¶ . . . . . . 4 - - - ¶ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 500 4 4 ¶ 4 4 4 S t r e n g t h e f f e c t of FMA, F l y - a s h A 4 . . . . . . ~I. . . . . . . . . ¶ 175 4 5 6 0 4 1207 4 5 . 0 ~ and slag powder on concrete 4 450 4 50 ¶ ¶ 4 4 ¶ respectively. ---4 . . . . . . 4 . . . . . . . . . ~ . . . . . 4 .... ¶ . . . . . . 4- --4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 500 4 4 ¶ 4 4 ¶ Strength effect of FMA with B 4 . . . . . . ¶ . . . . . . . . . 4 150 4 5 7 4 4 1 2 1 9 ¶ 7 . 0 4 d i f f e r e n t f i n e n e s s on concrete ¶ 450 4 50 ¶ ¶ 4 4 4 respectively. ---4

. . . . . .

4 . . . . . . . . .

4 . . . . .

4 ....

¶ 500 4 4 4 C 4 . . . . . . 4 . . . . . . . . . ¶ 150 ¶ 5 7 4 ¶ A ¶ B 4 ¶

...................................

4 . . . . . .

'iT---4

~ 4 1219

4 4 47.0¶

4

4

4

A = 475, 450, 425, 400 kg with corresponding B=25, 50, 75, I00 kg r e s p e c t i v e l y .

- - - ¶ . . . . . . 4 . . . . . . . . . ¶ . . . . . ¶ .... ¶ . . . . . . ¶- --¶ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 4 250 4 5 4 4 4 1 1 5 6 4 4 Strength effect of FMA on ¶ 4 ¶ ..... 4 .... 4 . . . . . . 4 - - - ¶ concrete with different water4 500 4 4 D 4 ...... 4 ¶

¶ 450 4 4 -- -4 . . . . . . 500 E ~ ...... 4

400

4 4 4 ¶ ......... 4

4 215 4 ..... 4 200 4 ..... ¶ 185

¶555 4 .... 4560 ~ .... 4565

4 1180 4 ...... ¶ 1190 4 ...... 4 1200

4 4 4---4 42.0¶ ~---4 43.04

4

¶ .....

¶ ....

¶ ......

4- --4

4 50 4 4 4 ......... 4 4 .........

g 170 4 ..... 4 155 4 ..... ¶ 215 4 .....

4570 4 .... ~574 4 .... ¶ ~531

4 1210 4 ...... ~[ 1 2 2 1 4 ...... 4 4 1239

44.04 4- - -4 46.04 4 - - -¶ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ¶ ¶ S t r e n g t h e f f e c t of F M A on slag ¶ 4 Portland cement concrete.

¶

4 194

4

4

¶

50

cement

ratio.

¶

..............................................................................

A 5 0 - 1 i t e r m i x e r w i t h f o r c e d m o v e m e n t is u s e d for the m i x i n g of concrete. T h e F M A is fed i n t o the mixer with o t h e r dry ingredients, b u t the H R W R is added by a post-incorporating method. T h e t o t a l m i x i n g time is a b o u t 2.5-3 minutes. T h e t e s t i n g s a m p l e s w i t h i 0 " i 0 " i 0 cm a r e c u r e d u n d e r s t a n d a r d c u r i n g condition

till

i. S t r e n g t h The standard these

they

Effect

are

tested

under

TEST

RESULTS

of D i f f e r e n t

compression.

AND DISCUSSIONS

Powdered

Mineral

Admixture

c o m p r e s s i v e s t r e n g t h of s e r i e s A c o n c r e t e s for 3, 7, 28 d a y s under c u r i n K c o n d i t i o n a r e s u m m a r i z e d in t a b l e - 4 . T h e r e l a t i v e s t r e n g t h of

concretes

are

comoared

in F I G . I .

Vol.

18, No.

3

467 MINERAL

ADMIXTURE,

ZEOLITE,

STRENGTHENING

TABLE-4. C O M P R E S S I V E S T R E N G T H OF C O N C R E T E WITH D I F F E R E N T P O W D E R E D M I N E R A L A D M I X T U R E

Concr.ete

Group

~ q

........................... Concrete

with

pure O P C

symbol

~ C o m p r e s s i v e strength q ....... ................................ ~ R3 ~ R7 ~

Concrete

with

FMA

~ ........

q

with

with

59.5

(1007.)

q

70.8

~

(I00%)

~ 52.4 ¶ 62.0 ~ 80.0 c o ¶ (110.4%) ~ (104.1%) ~ (113%) ~ .......... ¶ . . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . . 40.9

(86.0%)

~

~

. . . . . . . . . .

43.4

(91.3%)

51.6

(86.7%)

q q

66.1

(93.3%)

l..................__J 7

¶

51.2

~

¶

(86%)

~

66.7 (94.2%)

1 FIG.I.

3

¶

¶

~ .......... ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . .

slag p o w d e r ¶

¶

'°°t

g

~

~ .......... ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . .

q e- .... -e ~ ¶

PFA

........................... Concrete

47.5

(i00"7.)

~

........................... Concrete

R28

¶ .......... ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . ~ . . . . . . . . . . . . .

~ ...........................

(MPa)

28 DAYS

C O M P A R I S I O N OF R E L A T I V E STRENGTH FOR CONCRETE WITH D I F F E R E N T MINERAL A D M I X T U R E AT DIFFERENT AGES

AGE

E v i d e n t l y from table-4 and FIG.I, w h e n 10% c e m e n t (by wt.) used in the OPC concrete is d i s p l a c e d by FMA, its c o m p r e s s i v e s t r e n g t h at any age is higher than that of the pure O P C concrete. Therefore, F M A has a good s t r e n g t h e n i n g effect to cement concrete.

v Z (-

130

~

120 od

a 12%

1]0

28 DAYS

12o

110

27.

100

//~

7 DAYS

110 100

I

,i

7

28 DAYS

t

2%

ACE

RELATION

BETWEEN

L

7%

12%

FINENESS OF FNA

(a) R E L A T I O N B E T W E E N C O N C R E T E STRENGTH AND AGE WITH D I F F E R E N T F I N E N E S S OF FMA FIG.2.

~"

CONCRETE

(b) R E L A T I V E CONCRETE FINENESS STRENGTH

STRENGTH OF ~ITI] D I F F E R E N T OF FMA

AND FINENESS

OF FMA

468

Vol. Feng Nai-qian,

2. Strength

18, No.

et al.

Effect of Concrete by FHA with Different Fineness 4

Testing results for series B concretes are shown in FIG.2. The partial replacement of cement for each concrete by three different fineness of FMA is also 10%. The strength of the concrete made of these three different fineness material for 7 and 28 days i s all higher than that of the pure OPC concrete, and the strengthening effect of fineness 7% (4900-mesh sieve residues) is much better. 3. Relation Between Concrete Strength and Cement Displacement Results of series C concretes are shown in FIG.3. When FMA is used to displace 5~ of the cement used in the concrete, the concrete strengths of 3, 7 and 28 days are all higher than the corresponding values of pure OPC concrete.

~ 3

,4

-r" ul

DAYS

DAYS

~ ma6

FIG.3.

~ Ipe

m

.

5

o

LO

15

.

m

ZO

25

RELATION BETWEEN CONCRETE STRENGTH AND THE AMOUNT OF CEMENT DISPLACED BY FMA

AMOUNT OF CEMENT DISPf,ACEMENT BY FHA (%)

4. Strength Effect of FMA on Concrete "~'ith Different W/C Ratio Test results of series D concretes are given in FIG.4. The partial replacement of cement by FMA for each water-cement ratio concrete is 10%. When C/W<2.25 (W/C>45~). the relative strength of the concrete with FMA is lower that, that of the basic concrete (without FMA), this means that the strengthening effect is lost. Therefore, water-reducer (HRWR) should be used in coucrete with FMA to stimulate its strengthening effect. 5. Strength Effect of FMA to Sla~ Portland Cement The test results of series E concretes are summarized in table-5. i-2 have the same water-cement ratio (W/C=43%), but the slag portland

(to

~

~

'

S

~

7 nAYS FIG.4.

/ ,-4

/ "

Z.O

/

STRENGTH EFFECT OF CONCRETE WITH OR WITHOUT FMA UNDER DIFFERENT WATER CEMENT RATIO -

"

•

a

|

I-i and cement

I

Z.2 Z.& 2 . 6 2 . 8 3 . 0

•

3.Z

C/W

3

Vol. 18, No. 3

469 MINERAL ADMIXTURE, ZEOLITE, STRENGTHENING

used in i-2 is i00 k g / ~ less under the condition of incorporating 50 k~/~. of FMA. The steam curing strength of i-2 is 11% higher than that of l-l, but their strength for 28 days under standard curing condition are about the same. TABLE-5. STRENGTHENING EFFECT OF FMA ON SLAG CEMENT ¶ No. ¶

Type and Grade of cement

¶ Admixture of ¶ ¶ FMA ~

Steam CurinR ¶ Standard Curing Strength ¶ Strength for 28 days ¶ ~ (kg/m3) ¶ (MPa) ¶ (MPa) ..... ¶ .................. ¶ .............. ~ ................ ¶ ..................... i-I ¶ Sla~ Portland ¶ ~ 238 (100%) ~ 351 (100%) ¶ Cement 325# ¶ ¶ ¶ ..... ¶ .................. ~ .............. ~ ................ ~ ..................... I-2 ~

Same as above

¶

50

¶

265

(111%)

¶

360

(102%)

MECHANISM IMPROVING CONCRETE STRENGTH BY FMA I. Reaction of FMA and Ca(OH) z In the process of cement hydration, a large amount of Ca(OH) z is liberated. The structure of this compound is a flake-like crystalline material, in which crystalline layers are bonded together by the very weak molecule chain bond force between layers, and thus, this material contributes little to the strength of the hardened cement paste. However, the formation and growth of large amount of CSH gel-crystalline nets can contribute the strength of the cement paste continuously. In the laboratory test, testing samples are prepared as follows: F M A : C a ( O H ~ :water=3:l:2.6, and a standard curing (20°C) for 28days is adopted. The results of XRD. TG-DSC and SEM analyses are shown respectively in FIG.5, FIG.6 and FIG.7. The result of XRD analysis (FIG.5) indicates that the FMA can react with the Ca(OH) 2 to produce C-S-H. From FIG.6 and FIG.7, it is clear that the reaction of FMA and Ca(OH) a can also produce C4AH,B besides the formation of C-S-H. The XRD spectral curves of the cement paste with and without 20~ of FMA at the age of 90 days are compared as shown in FIG.8. Comparing with the XRD pattern curves in this figure, it is noted that when a 20% of FMA is added, the characteristics peak of CSH is raised, but the peak of Ca(O}{)Z is lowered. Hence, the addition of FMA can absorb C a ( O H ~ , and thus the formation of CSH phase is produced and the strength of cement concrete is increased.

04

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c'J

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10°

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£

f

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20+

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~

30° 2~ (Cu

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]

I

*

I

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~

I

40+

I.(~)

FIG.5. XRD PATTERN FOR THE HARDENED MIXTURE OF FMA AND Ca(OH)2

470

Vol. 18, No. 3 Feng Nai-qian, et al.

TGA ?.2.

1,6

Gllrib

6.0

E 4-~ C£ *~

~

3.6

C-S-H AND

2.4

)

6.4,~

SC

\x

Ca(OH)2

""

~J

~'~"

FMA

3.:Z

[.2. TGA

O

; 0

?0

I 4,0

,,

I

I

I

I

2t 0

.2~0

3~;0

4,~0

temperature

.

~

¢

i

~f$O

~;60

630

-1 . 6 '00

('C)

FIG.6. RESULT OF TG-DSC CURVES FOR THE HARDENED MIXTURE OF FMA-Ca(OH) 2 - H 2 0

5

(* a)

FIG.7. SEM IMAGE FOR THE HARDENED MIXTURE OF FMA-Ca(OH)2-HzO

'

t

i

CENENT+2.0%FMA+WATER

2 fl (C u

E ~)

FIG.8. ~RD PATTERN OF THE HARDENED CEMENT PASTE WITH ANI) WITHOUT 20% F ~ As for the diameter of pore in cement paste, it is known that only pores with diameter greater than IO00A (>1000~) are harmful to the strength and permeable resistance [2]. The pore with diameter smaller than 500~ (<500~) probably belongs to the inner micro-pore of the hydration product which is mainly made of the cement-gel. Hence, the number of pores smaller than 500~ can indicate the number of the cement-gel, and thus, the more the hydration product developed, the higher the strength and, the better the impermeability reached. In this study, two testing samples are prepared: one is a pure cement paste with W/C=30%, another is a cement paste in which 5% of cement is

E

Vol.

18, No.

3

471 M I N E R A L ADMIXTURE,

ZEOLITE,

STRENGTHENING

displaced by FHA with the same w a t e r - c e m e n t ratio (WIC+FHA=30%). The content of pore and its d i s t r i b u t i o n of these two samples are then measured at the age of 3. 7, 28 days respectively. The results of these m e a s u r e m e n t s are given in table-6. TABLE-6.

PORE D I S T R I B U T I O N AND C O N T E N T OF CEMENT PASTE

¶

Pore D i s t r i b u t i o n

and Content

...........................................................

~] 3 days ¶ 7 days ¶ 28 days ~ . . . . . . . . . . . . . . . . . . . :[.... ; ......... ..... ~[. . . . . . . . . . . . . . . . . . . ~ < 5 0 0 ~ [ > i 0 0 0 ¶ Pore ¶ < 5 0 0 A ~ > I O 0 0 ¶ Pore ~ < 5 0 0 ~ ¶ > I 0 0 0 ¶ Pore ~[ (~) ¶Content~ ¶ (~) ~ C o n t e n t ¶ ¶ (~) ¶Content (7.) ~ (7.) ¶ (mllg)¶ (7°) ~ (%) ~ (mllg)~i (%) ~7 (7.) ¶ (ml/g) . . . . . . . . . . . . . . . . . . ¶ ..... ~ ..... ¶ ....... ~ ..... ~ ..... ~i ....... ~ ..... ~ ..... ~ ....... Pure Cement Paste ~93.21¶ 4 . 9 6 ¶ 0 . i I 1 7 7 ¶ 9 6 . 2 4 ~ 3 . 2 9 ¶ 0 . I 0 3 2 2 ¶ 9 6 . 0 2 ~ 2.91~;0.09477 . . . . . . . . . . . . . . . . . . ~ ..... ¶ ..... ¶ ....... ¶ ..... ~ ..... ¶[....... ¶ ..... ¶ ..... ¶ ....... Sample

FHA+Cement

Paste

¶95.16¶

3.86~0.i1650~96.64~

2.51¶0.I0076~[96.41~

2.67¶C.09131

Test results indicate that the contents of pore larger than 1000A of the cement paste with FMA for 3, 7 and 28 days are less than the c o r r e s p o n d i n ~ value of the pure cement paste respectively, but for the pore samller than 500~ (<500~), the c o r r e s p o n d i n g content of the forn,er is more cr less higher than that of the later. This means that the FHA can cause the cement to produce more hydration product, and c o n s e q u e n t l y , the number of the inner m i c r o - p o r e s is increased. Therefore, the strength and the impermeability of the cement paste are improved. 3. I m p r o v e m e n t

of Interface Structure

in C o n c r e t e

by FHA

The interface transition zone of the concrete (WIC=30Z) at the age of 28 days has been studied by EDAX (spectra) analysis. The contents of elements and oxides are measured from the aggregate to the cement paste. The curves shown in FIG.9 are the c o r r e s p o n d i n g change of SiO2/CaO (wt. ratio) in the interface transition zone of concretes with and without FMA. As shown in FIG.9, it is apparent that the S i O z / C a O ratio in the interface trasition zone of concrete with FMA is higher than that of the basic concrete. The large amount of S~*-lon existing in the interface transition zone causes to increase the content of the C-S-H gel and to d e c r e a s e the o r i e n t a t i o n of flake-like Ca(OH)z. The SEH image of observation supports the above point of INTERFACE (TRANS 1TION ZONE)

CEMENT PASTE

to.72

•b / /

A

,a

/

0.s ~"

\

0.5* "" ,"

\

J/

',\

0.4

/

0.3 ~ FIG.9. R E L A T I O N OF S l O a / C a O R A T I O IN T H E INTERFACE (TRANSITION ZONE) OF CONCRETES WITH AND WITHOUT FMA

----=0.2

,~ 0

X----~

BASIC

o

CONCRETE

-' o

4.0

, 8.0

CONCRETE

0.1

WITH

12.0

FHA

, L 16.0

0

20.d

(urn)

472

Vol.

18, No. 3

Feng Nai-qian, et al.

view. The SEM images of interface transition zone for without FMA are shown in FIG.10 respectively.

(a) Basic Concrete

above*300 bottom*f500

concretes

(b) Concrete with FMA

with

and

above*300 bottom*1500

FIG.IO. SEM PHOTOGRAPHS OF THE INTERFACE TRANSITION ZONE OF CONCRETE WITH AND WITHOUT FMA CONCLUSIONS (i) A partial displacement of cement by FMA can more effectively make high strength and super-high strength concrete above 80 MPa. When i0% cement is displaced by FMA, the strength of this concrete can increase about I0-15%, and thus not only the cement is saved but also the strength is raised. (2) The strengthening effect of the FMA is suitable not only to the ordinary portland cement but also to the slag portland cement. (3) Water-reducer (HRWR or superplasticizer) should be used in concrete with FMA to stimulate its strengthening effect. (4) The strengthening effect of FMA is determined by it's chemical compostlon and mineral components; as the natural Zeolite rock is the main raw material of FMA, thus the content of Zeolite in this rock should be above 60Z, and its content of soluble silica and alumina is respectively about 10Z. Besides, the fineness of the FMA is also another principal factor determing the ability of strengthening effect. The ability of improving strength increases only when FMA is finer than cement. (5) The FMA can increase the amount of micro-pore (d<500A) in the cement paste and decrease the amount of harmful large pore (d>lO00A), and hence, the strength of concrete is increased and its other properties are improved. Furthermore, FMA can raise the SiOz/CaO weight ratio in the transition zone, increase its CSH phase, and decrease its flake-like crystals, and thus, the structure of transition zone is improved. Consequently, the strength and permeable resistance of the concrete are increased. REFERENCES [i] ACI Committee 363, ACI Journal, July-august, 1984, 364-411 [2] P.K.Mehta and D.Manmohan, "Influence of Pozzolanic, Slag, and Chemical Admixtures on Pore Size Distribution and Permeability of Hardened Cement Pastes", Vol.3, No.l, (1981), P63-67.