- 109 - EFFECT OF ADMIXTURES ON COMPACTIBILITY AND PROPERTIES OF GROUT Osamu Senbu Senior Researcher, Dr.-Engineer Construction Techniques Division Building Research Institute, MOC Tsukuba, Japan Michihiko Abe Head, Dr.-Engineer Organic Materials Divi sio n Building Research Institut e, MOC Tsukuba, Japan Yasuyuki Ma tsushima Researcher Construction Techniqu es Division Building Research Institute, MOC Tsukuba, Japan By Akio Baba Head, Dr.-Engineer Construction Techniques Division Building Research Institute, MOC Tsukuba, Japan Masasi Sugiyama Chif Engineer, Dr.-Engineer Concrete Research Labo. Fujizawa Pharmacential Co.,Ltd Tsukuba, Japan ABSTRACT The water absorption of masonry units makes flaws in the grout. To mitiga te flaws and to get satisfac tory compactibility, various grout admixtures are u se d. This paper reports the results of test conducted to eval ua te the effects of admixtures . In this experiment, density of crackings in the sawcut sectio n and compressive strength of grout in masonry walls were examined. And a non-destructive testing method, that is an ultrasonic method, was used in order to detect the flaws without sawcutting. As a result, a proper expansive action of grout by using some admixtures improved properties of masonry walls. INTRODUCTION In the case of high-lift grouting of masonry walls, satisfactory co mpactibility is obtained by wetting masonry walls befor e grouting and/or usi ng high-slump grout. How ever , it is generally difficult for masonry wall to be wetted completely on site. It is considered to use appropriate admixtures for grout. As the types of flaws in grout, grout-block separation, settlement cracks forming grout br{)dges and poor compactness are observed in the authors' previous study . These flaws of grout occur mainly because of water absorption of masonry uni ts. The wa ter absorption of masonry uni ts takes water away from grout to decrease the volume of grout. From these facts, expansive action and high water retention shall be required as the properties of admixtured masonry grout. In this paper, compactibility and properties of grout are examined for various grout admixtures. A non-destructive testing method, that is an ultrasonic method was adopted in order to detect the flaws and to check the quality of grout without sawing. As a result, the proper expansive action of grout made flaws less, the properties of grout in the wall were improved by water absorption curing effect of masonry units .
Transcript
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EFFECT OF ADMIXTURES ON COMPACTIBILITY AND PROPERTIES OF GROUT
Osamu Senbu Senior Researcher, Dr.-Engineer Construction Techniques Division Building Research Institute, MOC Tsukuba, Japan
Michihiko Abe Head, Dr.-Engineer Organic Materials Divi sion Building Research Institute , MOC Tsukuba, Japan
Yasuyuki Ma tsushima Researcher Construction Techniques Division Building Research Institute, MOC Tsukuba, Japan
By
Akio Baba Head, Dr.-Engineer Construction Techniques Division Building Research Institute, MOC Tsukuba, Japan
Masasi Sugiyama Chif Engineer, Dr.-Engineer Concrete Research Labo. Fujizawa Pharmacential Co.,Ltd Tsukuba, Japan
ABSTRACT
The water absorption of masonry units makes flaws in the grout. To mitiga te flaws and to get satisfac tory compactibility, various grout admixtures are use d. This paper reports the results of test conducted to eval ua te the effects of admixtures . In this experiment, density of crackings in the sawcut sectio n and compressive strength of grout in masonry walls were examined. And a non-destructive testing method, that is an ultrasonic method, was used in order to detect the flaws without sawcutting. As a result, a proper expansive action of grout by using some admixtures improved properties of masonry walls.
INTRODUCTION
In the case of high-lift grouting of masonry walls, satisfactory co mpactibility is obtained by wetting masonry walls before grouting and/or using high-slump grout. However , it is generally difficult for masonry wall to be wetted completely on site. It is considered to use appropriate admixtures for grout.
As the types of flaws in grout, grout-block separation, settlement cracks forming grout br{)dges and poor compactness are observed in the authors' previous study . These flaws of grout occur mainly because of water absorption of masonry uni ts. The wa ter absorption of masonry uni ts takes water away from grout to decrease the volume of grout. From these facts, expansive action and high water retention shall be required as the properties of admixtured masonry grout.
In this paper, compactibility and properties of grout are examined for various grout admixtures. A non-destructive testing method, that is an ultrasonic method was adopted in order to detect the flaws and to check the quality of grout without sawing. As a result, the proper expansive action of grout made flaws less, a~~ the properties of grout in the wall were improved by water absorption a~d curing effect of masonry units .
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TEST PROGRAM
Figure 1 shows a conceptual shape of prism specimen. The quality and flaws of grout were evaluated by the ultrasonic method before cutting. After the cutting, vertical sections of t he specimens were observed and Scm cores were cut from the grout.
In this experiment, fo ur unit types, two states of water contents in the units (air-dry and wet) and various grout types including five kinds admixtures were selected. The test program is shown in Table 1.
TEST METHOD Material
The shapes and the properties of units are shown in Figure 2. and Table 2 respectively. The water absorption of a clay unit is the highest of alI, and the ul trasonic velocity of the clay unit is lower in comparison with the concrete units.
Table 1 Test Program
Croul type ttoriar Concreta
H/C (l) 57 ~ 57 68 80
SIUIIP(~) 21 21 21 25 21 25
AdIIixture .1 P GA2 GA2 AE GAl CA2 F Ha AE GI2 GAl AE GA2
Co6crele O" O" Block S O O O O O O O O O
eo.c", .. IIlock T O O
ela)' O" O" 8Jock " O O O O O O O O O O
Concrele BlocIo I O O O
.1 P : Plane AE: AI! A,etll (iA!: Grout Aid (type 1) GA2: Groul Aid (type 2) F ! friat Production NB: Non-Bleedlnl Apftt
.. I Refore Croati",. ConditiOll of UnHa Is Wet
Table 2 Properties of Units
Un it Type Yolu.o( Vol...,tric AblloluleDry .... , Air Dr)' Hatar UI trasOftie Unlt (ai) RaUoof SpecHic Absorplion eo.lent Velocity
Solld Gr.\lity by vo l_ro by vól .. OO (U/sec.)
Concrele Blod: S 5:168 0.381 2.198 ll.~ 6.32 3.85
Concrtlte Block T - 0.365 2.251 9.58 6.71 4,42
CI .. , Block " 2315 0.467 1.985 19.56 l.41 2.20
Concrete 8lod: A 4387 0.196 2.300 9.13 7.53 3.97
Cut
Core Cut (5~xlOcm) and
Compres s i ve Strength etc.
Figure 1 Shape of Prism
Specimens
xx g~ I 290 I 19QJ
Clay Block M
JDC :O~]1 ( l6~ De 13~ I 390 I I 190 I I 390 I I 190 I I 300 I ~
Concrete B 1 ock S Concrete Block T Concrete Block A
Figure 2 Shapes and Size of Units
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The grout admixtures used in this experiment are listed in Table 3. These admixtures were selected by a preliminary test of which ma in item of examination was the expansive action of admixtured mortar. The watercement ratio of mortar is 0.57, and c:s=1:3 by ' weight. The amount of expansion was measured by the dial gage. The result of the preliminary test is shown in Figure 3.
Construc tion of Specimen . Laying the blocks was performed by professional masons. The mix
proportion of joint mortar was c:s=1:2 . 5 by weight. Prior to laying, the high absorption clay unit was wetted in a pool for about 10 hours. This procedure is supposed to keep th~ clay unit from drawing water from the joint mortar.
Prior to grouting, the wetted state of the specimens was obtained · by scattering water, and the air -dried state was attained indoors without any artificial heat.
The mix proportions of grout are listed in Table 4. After mixing grout , slump and air content tests for fresh concrete were performed. And then grout was poured in to the prism specimens. A flexible vibrator with the diameter of 28mm was used to compact grout. As soon as grouting was finished , the top of specimen was flatten with a trowel .
Mesurment and Observation The ultrasonic velocity method was
used for checking the compactibility of grout and for predicting the properties of grout. The ultrasonic velocity of walls was calculated using that of the face shell and that of the grout .
Soan4-Aure,ate I!ni tll'.lter "-oi Fine Coarse A.ount of Act.illure btlo (1) Contell «&1001) lu. lU. Aclive .'HI
(l/oi) ('&1001) ('&1001) CX 01 ce.en t)
100 263 461 1m O o 100 260 456 1462 O 1.0(&12)
48 200 444 773 1165 1. O (CI2)
50 200 351 852 864 0.015UE)
50 200 351 852 864 1.0(CIl)
50 207 363 839 850 O.95(CIV
50 200 351 852 864 0.6«8)
50 200 351 852 864 O.l<Fl
54 22S 395 1165 741 O.03<>E)
54 22S 395 1165 741 1. O (CI2)
52 198 291 892 8S7 1.0(C'2)
60 235 294 991 613 O.025<1E)
60 235 294 991 613 1.0("2)
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Conversely, the uI trasonic velocity of the grout was ca lcula ted using tha t of the two face s hel l s and that of the wal ls . For cutt i ng roa d cutterwas used, a nd the section was observed.
Core specimens with the diame t er of 5cm were c ut fro m the remainder of the pris m specimens. The o bser vation of cracks, t he s pecific gravity and the compressive strength were measured fo r e very core s peci men. These tests a nd measurm ents of ultr aso nic velocity were also co nducted for lOx20c m cylinder s peci me ns with steel mold s.
RESULTS AND DISCUSSIONS
Properties Qf Admi xtured Gr out Th e properties of , rresh an d har dend grout use d in this stud y are
li ste d in Table 5. The air conten t of fresh gro ut was mesured by a pressure me thod(JISA1l28), and that of hardened grout was calculate d by a gravimetric method. In the case of ex pansive admixtures, that was F, GAl or GA2, the air content of har de ne d grout is gr eater t ha n that of fresh one. The diff ere nc e is thought to be caused by t he time dep e nd e nt beha viour of expansion.
The compressive stre ngt h of grout use d ex pe nsive a dmixtur es was s mall. However, these specimens were mad e i n usi ng iron molds withou t a ny water abso rp tio n. As the gro u t in maso nr y walls was a bsorbed , the gro ut in masonry walls is supposed to be stronger than t ha t of cylinder specimens .
In the case of a grout with ex pansive ad mi xtures , the co mpr ess iv e strength of grout i s not a function of wat er-ce me nt ratio . As s hown bn Figure 4, t he compressive strength is r elated to t he cement-void rati0 2 • The ce ment-void ratio (c/v) was calc ulated as fol lows ;
c/ v=(Unit Weight of Ceme nt)/(Unit Water Cont.+ Air Cont.) (1)
Table 5 Properties of Grout
Properties or Fresh. Grout Properlins 01 Hardcned GrOlll "-o, (10' x2Oc- cylinder, sea led cure) Groul
Specified FI .. Air Unit Specitic Air Co.pressive Ullrasonic 51_ (co) Cont, Wei,ht Grlvilr Cont. Strenllh Velosit,
Observation Q[ Cut Section Vercical sections of the prism specimens are listed in Table 6. In the
case of concrete block specimens, the separation between face shell and grout was the typical flaw. And this separation flaw was frequently observed at the upper part of specimen. For the clay block specimens, settlement cracks forming grout bridges were the typical one. This type of cracks was very wide, and one of the widest is about lcm. As a whole, wetting befor grouting, high-slump and expansive action of grout lead to a good compaction.
Measurement of Ultrasonic Velocity Figure S shows typical results of ultrasonic velocity and the
vertical section corresponded to the results. From this figure, the ultrasonic velocity of the sound parts (V ws ) and that of cracking part (V wc ) was measured. As additional measurement, the ultrasonic velocity of grout with steel molds (V.R.lO) and that of face shells (Vf ) were obtained. Using these values, the forlowing values can be calculated,
VwlO ultrasonic velocity of masonry walls calculated with VglO and Vf . Vgs ultrasonic velocity of grout calculated with Vws.
Density of Cracks Using the cut section of the prism specimens, the density of cracks is
calculated with a mesh dividing method. The cut surface was divided by mesh with the spacing of 2.Scm and counted the total number of units devided by mesh and the number of cracking units. The density of crack (D) is calculated as follows;
D= p/ {J2 . a . sin(8 + 7t/4 )} (2)
where, p = anumberofcracked mesh/a numberof total mesh a : size of mesh O : angle of crack to the horizontal
The density of cracks and the ultrasonic velosity and other information are listed in Table 7.
\9 .--r-r-,---,---,.---,
i i I ,
9········, .. ·······!..······ .. ····· I ",'(ured
Capacity of Water Absorbtion In the case of air-dried specimens, masonry units is considered to
absorb water by the difference between water content of surface dry saturated condi tion(Vs) and that of air-dry condition(Vd). In this study, this difference in water content by volume is named "the Capacity of Water Absorption(CWA)," and calcula ted as follows;
CWA=(Vs-Vd)· (1 - P") / P" (3)
where, p":volumetric ratio of grout core
CWA and Density of Cracks Figure 6 shows the relationships between the capacity of water
absorption and the density of cracks. This figure is concerned with the case of w!c=O.57 and slump=21cm. I~ this figure, the greater the capacity of water absorption becomes, the greater the density of cracks becomes. However, some types of grout admixtures and wet state mitigate density of carcks.
CWA and Ultrasonic Velocity Ratio Figure 7 shows the relationships between the capacity of water
absorption and the ultrasonic velocity ratio of sound grout part to lOcm cylinder of grout molded by steel (Vgs!VgIO)' This figure shows that great capacity of water absorption of unlts rmproved the original quality of grout, in the case of using ' expansi ve types of admixtures.
~E
" 58 -~
Õo ,..0 _o 'Vjc .. o
N/C-57"
SI.,"" - 2 1 CIO
.I.N
o ~o~--------~--------~I~O---------7,15~------~20'
CWA (% yoJ)
Figure 6 Relationships between the Capacity of Water Absorption and the Density of Cracks
Figure 7 Relationships between the Capacity of Water Absorption and the Ultrasonic Verosity Ratio
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Properties gi Core-Cut Specimen Figure 8 shows the height
distribution in compressive strength, and Figure 9 shows that in surface dry specific gravity. Although the compressive strength was generally affected by the existance of flaws in the specimen, the compressive strength of the upper part was weaker than that of the lower parto The specific gravity of grout using expansive admixtures becames small in the higher parto This means that the restaint by units and the pressure caused by this might preven t the expansi ve ac tion of the admixtures.
From these facts, it seems to be difficult to forecast the quality of grout in the walls. At present, a corecut from actual grout is thought to be the best method to know the quality of grout in the masonry wall.
CONCLUSIONS
According to the experimental examinations and discussions mentioned above, the following conclusions can be presented.
ªr--O~----------~
Comprosslvo Strongth (MPa)
Figure 8 Height Distribution of the Compressive Strength of Grout
0, ..•
°2~--~2-.1~~2~.~2--~2.~3~~2-.4~~2.5 Specific Gr,avlty
Figure 9 Height Distribution of the Specific Gravity of Grout
(1) In the case of predicting the compressive strength of grout, the cement-void ratio can be applied to alI types of grout including the expansive admixtured grout.
(2) The expansive action of grout and prewetting of units mitigate the flaws in grout. A greater expansive action is needed for the unit which have a higher capacity of water absorption.
(3) The ultrasonic velocity method is use fuI for the non-destructive detecting method. As the width of the crack was greater, the ultrasonic velocity was smaller.
(4) The pro per conbinations of water absorption of masonry units and an expansive action of grout improve the quality of grout and mitigate the flaws.
(5) The upper part of masonry walls is sometimes weak especially in the case of using expansive admixtured grout. In the case of expansive admixtured grout, the compressivee strength and the specific gravity were small where the pressure of grout placed was small.
REFERENCES
1) M.Abe et aI, "Compactibility of Grout Concrete in Masonry Walls", First JTCCMAR, August, 1985
2) A.N. Talbot, "A Proposed Method of Estimating the Density and Strength of Concrete and Proportioning the MateriaIs by the Experimental and Analytical Consideration of Voids in Mortar and Concrete, Proc. ASTM,1921
