MAH KALI Age Preprints of the Contributions to the Paris Congress, 2-8 September 1984 ADHESIVES AND CONSOLIDANTS Edited by N.S. Brommelle, Elizabeth, M. Pye, Perry Smith and Garry Thomson Published by The International Institute for Conservation of Historic and Artistic Works 6 Buckingham Street, London WC2N 6BA. fob OW. x3FROM, DC. Peepeiats a ye Conteibutioa ko the Pacis Congres ATT Omver aad Consci dants ; Landon , ASE. INJECTION GROUTING OF MURAL PAINTINGS AND MOSAICS D. Ferragni, M. Forti, J. Malliet, . Mora, J.M. ‘Teutonico and G. Torraca 1 INTRODUCTION When lack of adhesion between plaster and wall threatened the survival of a mural decoration (painting or mosaic), it used t0 be customary to detach the surface layers from the original support and to transfer them onto a new one. More recently, however, historians and architects have become increasingly aware that transfer techniques cause an important change in the treated object and fal to provide a reliable solution of the conservation problem; in fact it hhappens frequently that mural works of art which were transferred in the past undergo new deterioration processes and must be treated again, Re-attachment of plaster may be achieved by injection of mortars or adhesive materials (an operation called grouting in civil engineering) and a slight compression of the surface. If grouting is considered as one step in a process which includes protection and maintenance, it may become the basis of a less disfiguring and less costly conservation policy for mural decorations. 2 IDEAL PROPERTIES OF GROUTING MATERIALS SUITABLE FOR MURAL, PAINTINGS AND MOSAICS Consolidation of plaster by injection is by no means a simple operation and it may be stated that all materials ‘currently used or tested present some shortcomings, in varying degrees, ‘The main difficulties met in such operations may be listed as follows: 1 unreliable setting of mortar when contact with air is difficult or the wall is damp: 2. shrinkage of mortar. or adhesive. upon setting. 3 excessive strength of modern mortars or adhesives, ‘which may impose new stresses on the ancient material (e.g. by differential thermal expansion or by ‘uneven redistribution of mechanical stress); 4 low porosity of modern mortars or adhesives which may hinder water evaporation and cause moisture accumulation; 5 soluble salts present in mortar mixtures which may cause deterioration in the adjoining porous materials. and particularly on the decorated surface; salts formed by mortars used in conservation are mainly sodium and potassium compounds, but one may not rule out the risk that stightly soluble calcium hydroxide may form insoluble efflorescences of calcium carbonate. ‘A research group, composed of former participants of ICCROM courses, supported by staff members and consultants and financed in part by grants from EEC and Unesco, has been active in the ICCROM laboratory since 1979 testing mortars and subsequently carrying out field ‘experiments on mosaics and murals A first series of results was published in two papers presented at a seminar on mortars held at ICCROM in 1981 [1.2] and more recent data were presented at the Aquileia ‘meeting on the conservation of mosaies (3. ‘On the basis ofthe data available in the literature and the initial results of our work, we feel that itis possible to draft a tentative specification which can be used as a guideline in testing injectable mixtures designed to overcome. or 110 ‘minimize. the difficulties mentioned above (see also 2). A frst draft of such a specification is offered here: ‘A. the mortar must set in a reasonable time (e.g. not ‘over 48 hours in the Vieat test: see section 5.3) in both dry and wet conditions, with or without contact, with air B. volume shrinkage (from wet paste to hard solid) should be as small as possible (e.g. not more than 4%): mechanical strength should not be too much above that of traditional mortars (e.g. in the range of 3-8MPa for compressive strength and 0.3-1,2MPa for the Brazilian test; see section 5.4); D the mortar should allow the passage of water vapour (no measurement of vapour permeability is avail- ‘able, 30 no tentative limit may be set); E the amount of extractable sodium and potassium fons should be as small as possible (e.g. not more than 120 milliequivalents per kg of mortar) but also the soluble calcium should be kept reasonably low (e.g, not mote than 60 millequivalents per kg): F the grouting mixture should develop some tackiness soon after injection as this allows one to set back in position superficial fragments which are dangerously Setached. 3. MATERIALS CURRENTLY USED FOR THE RE-ATTACHMENT OF PLASTER. B.A Lime casein “The use of this traditional mixture is amply discussed in [4.Annex!¥-2]. The ratio nine parts lime to one part casein Shows that a relatively small amount of calcium caseinate is formed: it should provide the initial tackiness to the mixture, Casein probably also helps the retention of water in the mixture against the suction of the porous masonry, From the point of view of the tentative specification. lime-easein does not fulfil point A (as it does not set in a ‘moist environment of without air) and point B (because of excessive shrinkage) 3.2 Lime-syntheti resin emulsion “The emulsion isa substitute for casein, providing tackiness and water retention (the latter. probably. because of the presence of water-soluble polymers, such as methylcellulose fr polyvinyl alcohol, added as stabilizers). The adhesive strength of this mixture is probably higher than for lime~ casein but the main defects remain 3.3. Lime-synthetic resin emulsion fluid coke ‘The expansive effect caused by fluid coke. when in contact with water. permits the formulation of injectable grouts ‘which do not shrink but expand slightly on setting [5]. The [problems related to the unreliable setting of lime remain but the control of shrinkage isa positive factor. Fluid coke, hhowever, is not easy {0 purchase in many countries, including Hay. 3.4 Synthetic resin emulsion Slightly diluted emelsions may be injected alone and are ‘quite effective ifthe gap to be filed is narrow and if the load tobe borne by the adhesive is relatively smal.3.5. Cement Water-cement grout is the typical material used to consolidate ancient masonry. It is widely available and easy to use; it obviously complies with point A of the tentative specification and its shrinkage may be controlled by the addition of filles and admixtures. It shows, however, important defects under points C (excessive mechanical strength), D (low permeability to vapour) and E (relatively high content of soluble salts). Addition of synthetic resin cemulsion may be used to develop tackiness and improve water retention, Cement, however, is not a material but rather an entire class of materials with a wide range of properties: it should be possible to pick up formulation which fulfils our specification. For instance, low-alkali cement may be used to reduce the danger caused by alkaline salts [1]. Also, strength and porosity may be modified by suitable fillers. Unfortunately the sheer size of the cement industry makes it diffcute for it to adapt to the stringent requirements of a ‘minor market like conservation 3.6 Thermosetting synthetic resins Materials for injection are made up of fluid resins with catalyst and little or no filler; they undergo very little shrinkage upon setting. Thanks to their great strength and adhesive power, epoxies and polyesters are considered as choice consolidants which are widely used for reinforced conerete structures, in particular when high structural loads are involved, ‘We do not think, however, that their use in the con- solidation of mural paintings, mosaics or stuccos. is justified. Our opinion is based on the fact that, after setting, ‘these resins are exceedingly strong and very lfficule to remove in case of an error in their application, ‘Their thermil expansion is quite large. and, with respect 10 the tentative specification. they would fail not only under point C (excessive strength) but also under point D because they are non-porous and inhibit evaporation, 4 GROUTING MIXTURES TESTED BY THE ICCROM TEAM 41 Binder Experience gained in the first two years of testing led our team to the choice of hydraulic lime as the binder in our routing experiments, Hydraulic limes are manufactured by the firing of ‘marlaceous limestone, or mixtures of lime and clay, at temperatures (1100-1200°C) which are lower than those of cement kilns (1400-150°C). In some cases, however, ‘mixtures of low-strength cement and calcium carbonate filler are marketed as hydraulic lime ‘The main hydraulic component in real hydraulic limes is di-calcium silicate (C38), as tri-calcium silicate (C,) is not formed at the lower temperatures. Our laboratory tests of| 1981 [2] indicated that a French hydraulic lime (chaux blanche by Lafarge) might provide the simplest route to the preparation of mixtures which could full the requirements Of the tentative specification we had set. X-ray diffraction analysis allowed us to establish that itis composed mainly of CyS and calcium hydroxide (Portlandite). Hardening shouid take place by reaction with water and decomp- sition of C,$ into hydrated calcium silicates, gels or fibrous crystals, and calcium hydroxide (see [6]). Inour tests, chaux blanche yielded mortars which showed lower strength and alkali content than two hydraulic limes am available on the Italian market; soluble alkalis are much below those formed inthe set of Portland cement. “The alkali content of cements and limes is due both to the raw materials used and to the fuel; if the dust obtained from the purification of the smokes is added to the final product the alkali content is further increased. Therefore the alkali content may vary considerably from one plant to another, even forthe same type of cement, and may vary in time, in the same plant. Periodical contol of the quality of the product is, therefore, mandatory and it should be carried out on the basis of a standard procedure agreed tupon by all parties involved. A first step in this direction vwas taken when the Laboratory ofthe Istituto Centrale del Restauro set up a tentative standard to analyze the samples produced by our research team (see (7). 42. Filler ‘The use of a filler in grouting mixtures is desirable in order to reduce shrinkage and to control mechanical strength, Some materials which are frequently designated as fillers are not chemically inert, however, because they ean react with calcium hydrotide at room temperature (pozzolanic behaviour). Tn our study, we tended to prefer reactive (pozzol fillers on the assumption that calcium ions from slightly soluble calcium hydroxide might themselves cause some Lwouble by forming insoluble calcium carbonate efor cescence, less dangerous than the alkaline salts as a source of crystallization stress but objectionable from the aesthetic point of view Pozzolanie filers can block soluble calcium in part or completely; pozzolana itself cus it down to almost nothing when added to mortars in sufficient amounts, Unfor- tunately it forms in the reaction a sizeable amount of potassium ions. Unpublished information obtained from the laboratory of large lalian manufacturer (Italeementi) indicates that pozzolana is believed to inhibit swelling of alkali-sensitive aggregates, ain effect which, although not explained, suggests that potassium ions formed by pozz0- lanie mortars might not be as dangerous as sodium ions. Unfortunately no proof ofthis hypothesis is available. Crushed brick powder asa filler. represents a reasonable ‘compromise among contrasting requirements. It produces few alkaline ions but it is able to block only part of the soluble calcium formed by the binder. The mechanical strength of these mortars is acceptable for a crushed brick: hydraulic lime ratio between I:1 and 2:1. Unfavourable factors are its red colour and the fact that itis not available jn a fine mesh grade (in Italy) and must be sieved before use (75-150 mesh in our experiments) Diatomaceous earth (diafilter or dicalite) is a whitish «dust which contains very small amounts of alkali and reacts with lime more or less like erushed brick: itis available as a fine powder, requiring no sieving, It reduces the inject- bility of mixtures, however, probably by introducing a tendency to gelling: this limits the amount that can be added to a binder:filler ratio above 2:1 and this, in turn, ‘may cause shrinkage problems. 4.3. Admixtures ‘The use of a fluidizer or water reducer allows one to obtain 1 less viscous slurry at an equal waterisolids ratio or, ‘conversely, to obtain the same viscosity with a lower water ‘addition; a fluidizer acts, presumably, by being adsorbed on the surface of the solid particles and avoiding the formation of clots‘There are many proprietary compounds which are widely used in concrete technology. We preferred a pure chemical, sodium gluconate, which is quite effective but litte used because it slows down the setting of cement (an effect ‘which, in our case, is even desirable). One part by volume ‘of a 10% sodium gluconate solution was used per 1X) parts of hydraulic lime. AAs discussed above, emulsions of synthetic resins can perform the function of easein in the ancient grouts, that i, they reduce water losses to the adjacent pores and confer some tackiness on the mixture. We selected Primal AC33, ‘an acrylic emulsion widely used in conservation, adding 10 parts by volume per 100 parts of hydraulic lime. 5 LABORATORY TESTS 5.1 Preparation of samples Injection mixtures were prepated in a commercial blender (Braun, 100 watts, one litre capacity) as our previous data [1] showed that high-speed mixing was required to achieve 8 satisfactory dispersion of the solid particles in water. Batches of approximately 500m! were prepared for each fest. All solid materials were dried and passed through 754. sieve (in field-work on large surfaces a 150, sieve was used). Proportions were calculated by volume. ‘The water-to-binder ratio was kept as low as possible. in ‘order to minimize shrinkage, but obviously there is a lower limit below which the injectablity of the mixture is too poor for practical use ‘After blending, the mixture was passed through a Marsh cone and then through the colurnn ofthe injection test (see section 5.2), ‘Shrinkage was determined on the residual fraction of the liquid mixture (see Section 5.5). “Mechanical tests were performed on samples produced by cutting the injection test column to pieces after setting (see section 5.4) Analysis of soluble salts was performed on fragments of the broken samples from mechanical testing (see section 5.1). Unused sections of the columns are available for fature porosity tests (see section 5.6) ‘The results obtained fom the testing of 87 mixtures are presented in Tables 1, 2 and 3. The results from 62 other mixtures are not presented because they were considered rot relevant to the present paper for various reasons (such aslow injectability. use of alkali-rich materials ee.) 5.2 Viscosity and injctabilty Injectability depends upon several factors: viscosity of the dispersion, dimension of the dispersed particles, wetting of injeéted materials, wate losses and others. ‘Table 1 Injectability, mechanical strength (Brazilian test), shrinkage and specie gravity (data from 26mm columns) Sample Formation” Waserto Flow __Injecabilay Mchanical Shrinkage Specie gravy ruber binder ratio mumber umber irengih MPa 28.doys 2Bdays Sesolume (@) Binders without firs 3 SLALSWIGE 765 6 16 am 2a 19 9 SLHLBWiGt 165 0 4 ots 360 107 9L LHLR TWiRD os 5 6 a9) 58 116 103 SLHLR7Wisk os w 3 0.130 nm in 10s SCHL W0.O2Pe 75 2 2s 0.108 870 00 Sul aLHIS.SWiG! no 2 ns am 353 2 = aLHIBWict 05 a 98 Orne Bat 129 812 SLHLS.Sw.2PuG1 38 25 ry om 209 os. 17 4cpcawict 589 2 B E10 238 1510 ls 4CPCBWIRD 589 a 4 1637 3B 1.508 119 _4CPCAWISm 569 0 6 un? 37 1516 (©) Crashed brick filer 1m «LHL2BMSWO2PrGL Tae Fry = 0.105 700 103 © SLHIRBAW2PIGI 58 0 7 am 528 0.95 (© Omer filers 124 -SLHUSPIA 6WiGT 15s 7 3 O26 a 126 2s WHUSPe6WiG! 1S am 4% 0389 $8 123 13 ALHL2PAwiG! 22 2 20 70 346 re 6 4LHLRP« WIG! 2 9 21 0239 9 124 I ALHLRPeaWi0.2eGI 122 n 125 om 286 U6 133 SCHLQPM 9Wwin 2PrIGI 125.9 % 2s om om im 12 aLHLaDIsTWiGt tis0 6 38 nm om oss: 1 aLHL2DIe 9w/Gl 15.9 4 3 0176 om nm 136 SLHLSDIe Wo IsPrIG! 1680 a 20 0.188 638. 076 139 SLHLSDIWiDISPHIGL 163.3 0 103 am. rm om 10 SLHLSDSAWin.IsPGL 173'5 0 6 O38 am om Mi SCHLADC7Wn2PHGI 119.0 2 a ou am om (@) Commercial grouting mixture B41 DDS/DDL nowaier 38 17 ae 798 os sede 13s 4DDS3.6W 30.0 36 “ 0.258 1.3 0.98 n2| Table 3 Analysis of soluble matter in grouting mixtures “Sample Formulation pio Conductivity Cameghg” — Nemegke” Kage" Nas K umber Solution Sem meg hg"? 70 UHI. Swit 10s 1000 32 16 ra 1m n ALHUBWIGI 98 800 wz 3 » 7 n ALHLWIGt m2 4650 2 28 5 ” % ALHLABAWiGL 0s 3650 305 2 si a3 8 SLHUSBISWiGI 104 160, 5 8 6 106 4 SLHL2PHWIGL 106 130 6 2 176 28 9s SLHLSPaswicr = 104 730 z 3 108 ir 96 ‘acro2.swict 107 230 100 3 29 27 98 SCABWIGL 109 350, 369 1 ‘8 % 2 SLHLSDiAawict 108 1000 bs 2 2 8 106 SCABADAWIGI ILO 2400 200 0 55 2 no ScrCBBILIWIGI 108 1000. 38 2 144 216 13a. bpsot ns 5200 st 104 5 i * Abbreviations are explained inthe ist of material Viscosity may be evaluated by passing a mixture through ‘a metal cone called the Marsh cone and measuring the time required for the flow of a given volume. Actually, we used volumes around SO0m! and calculated, approximately, the time required for one lite ‘A mote direct evaluation of injectability is possible by means of the test devised by the Laboratoire des Ponts et Chaussées [8] that we had already used in our previous ‘work (1]. This test is based on the injection of the fluid ‘mixture into a Perspex tube (40cm length. 26mm diameter) full of graded sand (1.0-1.7mm) of the type prescribed by Italian specifications on cement testing ‘We modified this apparatus slightly by replacing the screw-in column caps with others held in place by aclamping device. This allowed us to reduce the cost of the Perspex columns by a factor of about 10 because screw fillets were n0 longer required mn the test injectability data are obtained by observing i the injection is possible at all under a pressure of 0.75 bar ‘and, in the affirmative case, by measuring the time required forthe rise through the column and the rate of flow, once the column has been filled. In order to prepare samples for the mechanical and chemical testing of pure mixtures (i.e. without sand) we introduced a further modification in the procedure. The 26mm column was replaced by a 12mm one which was kept empty and the injection was carried out under a pressure of| 0.3 bar. In this ease also the time of rise through the column and the rate of flow may be measured. In order to express in simple figures the heterogeneous data we obtained from these tests, we decided to transfer all data on logarithmic scales which were adjusted to yield similar dispersions for the whole of our data; thus we can describe the behaviour of a mortar in the Marsh cone by ‘conventional flow number and that in the columns by fan injectability number. Results are shown in Tables 1"and 2. Experience shows that easily injectable mixtures should have an injectability number below 50, for the 26mm ‘column, or below 20, for the I2mm column (low numbers indicate low viscosity). 5.3. Setting time Setting time had been measured in our previous work [2] by means of the Vieat needle. As we could assume that the mixtures we employed in this series of experiments would show an acceptable result, the measurement of setting time was waived, 4a S.A Mechanical strength ‘The Brazilian testis carried out by compressing cylindrical samples from the side: it is easy to perform and allows evaluation of the tensile strength. Samples were prepared by sealing with paraffin the columns used in the injection tests and allowing them to set for 28 days. The Perspex columns were then cut in pieces to yield cylinders whose length was twice their basal diameter; six samples were thus obtained from the large column and 15 from the small one In the frst case all six pieces were tested; only five in the second. Maximum and minimum values were always discarded and the others were averaged. Results are shown in Tables 1 and. 5.5. Shrinkage Shrinkage was measured by atest based on ASTM C474-67 Specific gravity of the fluid was calculated by weighing a volume measured by means of a syringe; specific gravity of the slid, after 15 and 28 days, was calculated, as usual, from the weight in air and in kerosene. The volume shrinks calculated from the ratio of the specific gravites ‘Comparison of the apparent with the theoretical specific gravity also provides some information on the entrained ar. 5.6 Water vapour permeability and porasity Fulfilment of the requirement of permeability to water ‘vapour would be best verified by direct measurement for instance with the method recommended by RILEM for stone [9]. Unfortunately, the method was not operative in Rome, until very recently. Tn our previous work [2] an indirect assessment of permeability was obtained through the measurement of pote size distribution by the mercury porosimeter. The data available allow us to suppose that the mixtures tested in the present campaign should have enough medium and large pores (diameters above 14) t0 allow evaporation even if large size pores should be fewer than in lime/sand mortars. Due to temporary difficulties our measurements, which are carried out by Dr P Rossi Doria of CNR Rome, had to be suspended in 1983, but they will be resumed in 1984 to ‘complete our data 5.7 Soluble salts and efflorescences Samples broken in the mechanical tests were finely ground and passed through a 106 sieve. Five gram amounts were ‘extracted with about 200ml cold water for seven days and brought to volume. The electrical conductivity and the“Tle2 Injecability, mechanical strength (Brazilian test), shriakage and specific gravity data fom 12mm columas) ‘Sample Formulation Waterio Flow __Injecabilty Mechanical Shrinkage Spec gravity mabe binder ratio number —pumber’ renin MPa 28 days 7s ‘volume (@) Binders without fos 7 atHUSWIGL 763 ¥ 510 za Tit 1% aLHIS.swict ns 5 oe 333 i Tm aLHUAWicI 63.0 3 raat Se Ga 9% crc swict 88 31 rit 133 Les 98 == SCABIWiGI 30.1 6 vost 48 9 7 aLHUSW2PrGI 16 9 om 238 ox 1% ALHU3W02PrGt 765 2 O95 355 0.99 7 ALHLAWIO.APrGL 63 15 0.195 20 0:56 75 LHI sw00.2PrG1 338 2 0.283 209 089 7% SLHUAW.2PrGI 880 2 0368 292 100 1s 4CPC2.7W0.2PHG et a ost 8 tas 109 4cPCA.7Wn-aPHGL a 2 1320 2.09 ce (©) Crashed brick filer 19 2LHLaBRswict Tass 1 ie 1a 21 SLHUSB2.6WrGi 3 19 ui 030 Cas &3 SEHUSBr swict 133.1 10 435 ts 78 SCHLABAWiGt 020 19 230 133 & | SLHISB4 Swit 1as.0 2 3m £25 6 SLHI2B swiGt 938 2 397 125 50 SLHL2Bwiat 83 » 371 133 @ — SLHLU2BWIGt 83. 3 38. car 6 SLHIQBawiclr 33. 0 sa O 6 ALHISBawici: 33) ro 49 vat 52 SLHLaBrawsk 3 1 3.00 130 S30 4LHIQBAWwiRb 3&3 2 au 130 S| ALHIBw &3 1 am am @ | ALHL2BAawict 3. 0 386 132 © — SLHURB.EWiGL 18 35 356 137 10 3¢PC3B/42WiGt 2's is <0 139 97 SCPCB/4 4WIGL 805 a 34 ra 9% ACABI2B/4 3WIGt 363) is a 140 SS — SLHLSBIgSWoOIsPrIGI 163.3 0 621 ras 7%) ALHL2BAWin.2PeGI 102.0 2 12 120 © SLHLRBISWOAPrGL 127.6 0 1125 00 86 SLHISBIsaWo.IsPeiGI 1333 3 621 Eis 6 SLHIDBTWo2PuGI” 145.9 0 1 528 095 8 SLHIBISWOAPIGI 100.0 i 168 1.06 1m 3CPCBBI2WIOISPIGI 1025 2 $00 130 Ws éCPCRBis.¢wr.2P; 805 a 694 129 13 éCPCRBILaWosPGl 805 5 336 124 (©) Oiber files 32 2LHLaMaSSwiGt Ta To ons is 30 SLHLAM2‘sswict a7 85 036s zB 31 SLHLAM2 eswict 683) 3 0582 336 38 SLHUAM2-sswict 50.1 106 0.705 3 38 1SLIL-SPBMAW.GI fm 3s L130 1.32 146 9s SLHLSPia swict Sa 10 0521 3m us 94 ALHLaPiaWrat 120 7 0355 264 125 5 -SLHUBPAWIGI ut 19 8.900, 3s 125 146 SLHUBPAWO.SPHGL 113.8 35 ovr 390 126 17 SLHUBPs.SWioisPIGI 126.1 2 ost S20 ts 102 3LHLSDiwict 197 2s oat9 on oR 93 ALHLDi.TWIGL 10 os nm ox 448 ALHU2DI6 2WIGt 7 075 om am 106 «CABQDI4.4WiGI & 161 3 Tis 11 -SLALSD/s.¢W0.1sPeGt 6 0359 38 076 100 4LHL2D/8.W.2PrIGI 2 0326 si 086 149 4LHU?DIS. ew. 2PuGI 9 0316 3m 0.94 107 SCAB2D/4.4W0.2PrGL 2 ons 10 in 17 SLHUSQVWiGL 5 0.168 349 120 128 ALHLROMAwict 15 0.186 ous 0 132 SLHLIO#25wiGt B one 310 16 129 SLHUSOWI0.1SPHGI 31 007 30 rr 10 ALHU204.¢wi02PrGI 23 0.105 576 0% (@ Commercial grouting minture 1342 DDS/DDL nowaier 88 5 O38 78 os ‘ded 4008.60 ‘300 36 4 0.486 1.83 0.98 lations are explained inthe list of ma $3 minutes mining + minutes mixing ‘hm = not measured, 13i “Table 3 Analysis of soluble matter in grouting mixtures Formalaion™ pif Conductivity Camaghg” Nameqke” Kmeglg? Nav K fusion Som meg" SCH. SwiGt os 160 rH 16 2 rH SCHUAWIGI 98 0 1 8 » 7 SLHLBWIGl 2 4650 22 2 5 7 SCHLDBAWIGL wos 3050 40s 2 si a3 SLHLSBSWIGI 108 1630 us 3 6 106 ALHL2PAWiGL 06 1330 106, 2 1% 28 SLHUSPASWGL 10 780 2 9 108 ir scPCR. SWIG! 107 2250 100 93 29 a7 ACABAWIGI 109 850, 369 0 8 SLHLDIAWicl 108 tooo 2s 2 21 SCABADMAwiG] ILO 2400 200 a 55 ScrcsBM2WiGl 106 too 3 2 1a bpsippL, us 5200 aa 104 < * Abbreviation ae explained inthe ist of material Viscosity may be evaluated by passing a mixture through ‘a metal cone called the Marsh cone and measuring the time required for the flow of a given volume. Actually, we used volumes around S00m! and calculated, approximately, the time required for one litre ‘A mote direct evaluation of injectability is possible by means of the test devised by the Laboratoire des Ponts et Chaussées [8] that we had already used in our previous work [1]. This test is based on the injection of the fluid rixture into a Perspex tube (40cm length. 26mm diameter) full of graded sand (1.0-1.7mm) of the type prescribed by Italian specifications on cement testing ‘We modified this apparatus slightly by replacing the screw-in column caps with others held in place by aclamping. device. This allowed us to reduce the cost of the Perspex ‘columns by a factor of about 10 because serew fillets were no longer required. In the test, injectability data are obtained by observing if the injection is possible at all under a pressure of 0.75 bar ‘and, inthe affirmative case, by measuring the time required for the rise through the column and the rate of flow, once the column has been filled. In order to prepare samples for the mechanical and chemical testing of pure mixtures (i.e. without sand) we introduced a further modification in the procedure. The 26mm column was replaced by a 12mm one which was kept ‘empty and the injection was carried out under a pressure of (0.3 bar. In this case also the time of rise through the column ‘and the rate of flow may be measured. In order to express in simple figures the heterogeneous data we obtained from these tests, we decided to transfer all data on logarithmic scales which were adjusted to yield similar dispersions for the whole of our data; thus we can describe the behaviour of a mortar in the Marsh cone by ‘a conventional flow number and that in the columns by an injectability number. Results are shown in Tables I'and 2. Experience shows that easily injectable mixtures should hhave an injectability number below 50, for the 26mm column, oF below 20, for the 2mm column (low numbers indicate low viscosity) 5.3. Setting time Setting time had been measured in our previous work [2] by ‘means of the Vicat needle. As we could assume that the ‘mixtures we employed in this series of experiments would show an acceptable result, the measurement of setting time was waived 1s S.A Mechanical strength ‘The Brazilian testis carried out by compressing cylindrical ‘samples from the side; itis easy to perform and allows evaluation of the tensile strength. Samples were prepared by sealing with paraffin the columns used in the injection tests and allowing them to set for 28 days. The Perspex columns were then cut in pieces to yield cylinders whose length was twice their basal diameter; six samples were thus ‘obtained from the large column and 15 from the small one. In the frst case all six pieces were tested; only five in the second. Maximum and minimum values were always discarded and the others were averaged. Results are shown, in Tables 1 and2. 5.5. Shrinkage Shrinkage was measured by a test based on ASTM C474-67. Specific gravity of the fluid was calculated by weighing a volume measured by means of a syringe; specific gravity of the solid, after 1S and 28 days, was calculated, as usual, from the weight in air and in kerosene. The volume shrinkage is calculated from the ratio of the specific. gravities. Comparison of the apparent with the theoretical specific _Eravty also provides some information onthe entrained 5.6 Water vapour permeability and porosity Fulfilment of the requirement of permeability to water vapour would be best verified by direct measurement, for instance with the method recommended by RILEM for stone [9]. Unfortunately, the method was not operative in Rome, until very recently. In our previous work (2] an indirect assessment of permeability was obtained through the measurement of Pore size distribution by the mercury porosimeter. The data available allow us to suppose that the mixtures tested inthe present campaign should have enough medium and large pores (diameters above 1}) to allow evaporation even if large size pores should be fewer than in lime/sand mortars Due to temporary difficulties our measurements, which are carried out by Dr P Rossi Doria of CNR Rome, had to be suspended in 1983, but they will be resumed in 1984 to complete our data 5.7. Soluble ats and efflorescences ‘Samples broken in the mechanical tests were finely ground and passed through a 106u sieve. Five gram amounts were extracted with about 200ml cold water for seven days and brought to volume. The electrical conductivity and the‘Table? Injectabiity, mechanical strength (Brazilian test), shrinkage and specific gravity (data from [2mm columas) “ample Formulation” Wiuerio Flow Inecabilty Mechanical Sri Specie ara ruber Iinderruio rumber number” range tf 2Bdays® Bay volume © Binders without les m aLHUSWiGl 765 ¥ Tsi0 zp 7 4LH3.swior ne a at 333 7” auHUBwiat 0 ‘ 1031 500 ! 96, 4CPCR,SWIGI 458 aL 13 133 i 58 ACABAWiot so 6 rou ss 33 ALALSwo 2Peat 176 8 om 288 ose 34 SLHUSWi0 Prt 765 2 395 355 095 7 {LHLAWo4PeGL 763 5 95, 26 096 33 Le swoaPeGt Be » 285, 20 039 36 {LAU 2PeIc1 0 2 0368 an 100 0s 4CPC2.7Wi0.2riGt 4 a ‘61 as ca 19 __4CPC2.7WA.aPrGl os B 1S0 20 ta (Crashed brick ler 1 2LHUSBrEwicl a3 1 7 ry 13 21 SLHLSB.6wict 83 0 13 030 18 & SLHLSBaSWct 1831 10 5 13s 1s 7% ALHLABAWiG! 020 % 8 230 133 &SLHISBre swict bs. B 5 3a 13s & aLHiaBe swt 338 B iB 397 135 aLHIaBawror 33 » te an 135 @ — dLuiasewet 83 3 6 36 tat & — dLuiapewictr 83 *o 0 Sa io & dLuiapawictt 83 o 0 a9 2 dLui2Bawse 83 ° n 300 3 HiaBiewiRb 53 3 2 at $i SLHV2Baw 53 5 a 4 ALHV2BAWol 83 40 ut Sis 8 4LHUaBAsWiot Sys 38 ” 356 Ho -3éPcr3B42WiGt 12s 8 3 ap 7 4chcaBi awit 808 x rr 3a 5 SCABBI swict 86.3 6 5 ue 8 SLHLSB/SWo.ISPIGL 163.3 on 5) ALHLanwo. abet th # sLUL2B/swo.aPeG! 1135 % —SLHISBieeWosPrict 621 6 aLuizarwo.2PeGi £28 S sLUI2BaWin aPrct Sot 12 3epCSp2Wo.IsPrGi 12s u 00 Ws 4cpcabieawno.2PG! ‘S03 xs 3 13 ScPCABe AWG! 505 D ee (Over fler RB ALHUaM2sSWiGk Bie vor @ as 30 SLHUSM2.swict as s 0 2 3 ALHLAMa@SwiGl 3 9 536 38 SLHUGMa.sswrcl so. 105 8 3a 35 LSU sP5MaW.Gl om se n 1032 SLHLBPI4sWiGt 135 io 2 Sa SCHLAPIwIOL tooo b 5 2s SLHUSPAWGI nga % 5 Ses SLHUSPAWO.ISPeiGI ILS 4s B 390 SLHUBP 4 SWi0ISPrG 1261 a ie 534 SLHUSDi6.aWiG 1087 5 3 on SCHL2Di6 TWIG tiga 0 iH om ScHUADI2WIGt $82 D u o sCABaDIAWIGL a0 3 u 86 SURLSDIAAwn.IsPrGI 149.7 » 6 38 ALHLabiswno2PrGl 1148 a B Bis Scab sw 2PIGI ‘924 is un an SCABADIEWI 2PrIGL 40 2 2B ao SLHLSQ W/o! te 5 i 38 SLHL20 What toes 8 8 oi SLHIZION 25WiGt 62 8 5 310 SLHLBOMWo.IsPeGl 137 2 is sa ACHLAGAWn.2PrGl 1088 z 6 56 {(@) Commercial grouting mintwre 142 DDSIDDL ae 5 oe wa or 1352 __DDsi3.6W 36 “ 0.46 110 098 Abbreviations are explained in the + 2minutes mixing fhm ™ not mensure. 413concentration of sodium, potassium and calcium were ‘measured in the extract. Results are shown in Table 3. ‘Aitect assessment ofthe risk of producing efflorescence might be preferable to chemical analysis but, unfortunately, the literature does not appear to offer a reliable method. We tested a procedure suggested some years ago (10] with no success. Later, following a recommendation of the RILEM committee on gypsum [11], we tried a simple qualitative test by immersing our cylindrical samples in distilled water. to a epth of about Lem, and observing the formation of salt crystals after 30 days. This test, however, detects mixtures with high soluble-salt content but fails to separate mixtures -with medium tolow salt-concentration 6 FIELD EXPERIMENTS: INJECTION ‘TECHNIQUES “The long experience of Italian mural paintings restorers in the use of lime-casein grouts has been extremely useful 10 ‘our group and allowed us to manage the difficult transition from laboratory to field conditions ina relatively short time. In a real wall, several factors which are not easily tested in the laboratory become important and determine the suecess or failure of the grouting technique In 1982 and 1983 the ICCROM research team devoted a considerable proportion of available time 10 field experiments on limited areas of plaster or on entire wall surfaces: 1 Inthe Basilica of Santa Maria Assunta in Tocello, the consolidation of a small section of the mosaic in the apse. 2. Atthe School of Engineering of Rome University. the grouting of an experimental stone masonry pillar Which had been crushed in a mechanical test (it was crushed again, after consolidation, showing a decrease instrength of about 50%), 3. In the Basilica of San Lorenzo in Rome, the re attachment of a large bulge in the thirteenth-century ‘mural paintings of the pronaos, 4 In the Casa del Menandro in Pompeii. the ‘consolidation of the mural paintings on the south side ‘of the plutei ofthe peristye ‘5. Imapalace in Rome (via della Fossa) the consolidation ‘of the sgraffito facade of a fourstorey building, 6 In Assisi, Chiesa Superiore di San Francesco, the sealing of acrack in the Giotto frescoes. 7 In Ostia Antica, an experiment in the consoli of a loor mosaic. 8 In Rome, at the excavations of the Crypta Balbi, the ‘emergency consolidation of a small mortar area. 9 In the Roman Villa at Lauro di Nola, an experiment in the consolidation ofa wall mosaic. In the course of these works our engineers and architects, worked side by side with the restorers in charge and progressively refined their skill in carrying out injections ‘without undue risks to surfaces of high artistic valve. Experience has taught us that proper selection of the injection point and suitable pretreatment are of major importance. Exploration of areas to be treated is carried out by gentle tapping with the knuckles and feeling vibrations (or sounds) which indicate a promising spot Injections are executed through existing cracks or by drilling a 3mm hole in a damaged surface area. Nearby cracks or holes through which the injected fuids may escape are sealed off by inserting dry cotton; also the free space around the needle is sealed in the same way. 1s Pretreatment includes the suction of dust by means of a rubber bulb and the injection of an alcohol-water mixture, alcohol being added to the water to improve wetting of dry, ‘dusty surfaces and so aid penetration. This is followed by several injections of tap-water and by one or more injections of diluted Primal ACS. Prodding and gentle shaking with dental tools may help the penetration of the mixture in difficult cases. Penetration may be eased by dilution, but excess water yields mortars ‘with insufficient strength and high shrinkage. ‘Although we tried a variety of injection equipment, we finally settled on 60ml plastic syringes with Imm needles “which are easy to obtain and relatively inexpensive. Mr Stefano d’Avino, who assisted us in some field experiments, devised and made an adjustable metal strut which may be inserted between seaffolding and wall to provide a gentle, controllable pressure after the injection, Adjustments of the technique were required for almost every new site, as the quality and thickness of the plaster varied, The injection mixture most frequently used was the I: chaux blanehe:crushed brick, with Primal AC33 and sodium gluconate. Immediate results of consolidation were invariably good. adhesion being obtained under slight pressure after @ short time. The deciding factor is penetration: if just one syringe ff fluid can be injected. local consolidation will be achieved Inspection of some of the experiments after one year showed no visible defects, but iti obviously too early to say i some will appear in time. 7. ‘TESTING OF AN EXPERIMENTAL COMMERCIAL PRODUCT ‘In 1982, contacts with the experts of a firm active in the refurbishing of buildings (Damp and Dry, Piombino, Italy) resulted in the production of a two-component grouting compound made up according to a tentative specification drafted by the ICCROM team in cooperation with the laboratory of Italcementi in Bergamo. This laboratory also provided a batch of purified white cement which was the basis forthe new formulation, ‘Columns 134/1, 134/2, 135/1 and 135/2 were injected with this experimental grout. Laboratory results for: alkaline salts appear to be acceptable but some objection could be raised 10 the mechanical strength (which is rather high). the soluble calcium (which is 100 high. but this was not included in our specification at the time) and to the injectability tests (which were not completely satisfactory) Field experiments with the Damp and Dry mixtures were just started at the end of 1983 and reliable information is not yet available. We are confident that in alittle while, all difficulties will be removed. 8 CONCLUSIONS Injectable mortars forthe re-attachment of plasters to walls present contrasting requirements which make it difficult t0 reach a ‘perfect’ formulation. If, for instance, fluidity is increased by the addition of water, low mechanical strength and high shrinkage may result. ‘AS another example, soluble calcium ions, which may ‘cause encrustations, could be removed by pozzolana but this would cause an increase in potassium ions, which are potentially dangerous as a source of crystallization stress. Tis possible, however, to reach a useful compromise and to prepare mixtures which ate far superior in performanceand, hopefully, less dangerous than the ones which are used at present. But, obviously, only the observation of result actual field operations after a reasonable number of years will provide a reliable indication of whether this aim has been achieved or not. ACKNOWLEDGEMENTS. ‘The authors wish to thank the following fr thei contribution to the prese Centrale nt paper: S. Diana, P Sammi and M. Tabaseo (Istituto ‘el Restaur) who carried out the analysis of the soluble salts in the mortars: L. De Julio and A. Crocia (Institute of Construct the execution of the mechanical tests: S. Bonacin tion Science, Engineering School, Rome University) for (Damp and Dry, Piombino) forthe preparation of an experimental grouting LIST OF MATERIALS" 1 Water Wr” Rome tap-vater 2 Binders Lime puty: local supple. CHL Hydraulic lime “Chaux Blanche’, manufsctured by Lafarge; standard mortar resistance: 60 bars. LHI Hydraulic ime “Calce Eminentemente Idraulic Speciale Plastica per Intonachie Murature ‘manufactured by aleementi; standard mortar HU ce caB, 3. Fillers Sand fesistance: 60 bars Hydraulic lime “Calee PlasicaEminentemente draulics’, manufactured by Unicem; standard mortar resistance: Dbars Pomolanic cement ‘Cemento Pozzolanico 325’, ‘manufactured by Colacem standard morta resistance Sisbars White cement Uh ‘Aquila Bianca’, manufactured by ment; standard mortar resistance: 325 bars. Supplied by SISA. Tose del Lago, Italy. Standard sand foccement testing, fraction 1.00.70 gra size. B Crushed brick: local supplier M Crushed marie local supplier, P-—Pozzolana"Pozzolana Superventlata’, manufactured by Pozzolane di Salone. M. Testa, Rome, lal D Diatomaceous carih -Diafiter manufactured by Diatom, Castiglione Teverina, lay © Quartzline ponder: Riedel de Haen. 4 Admictures Br Acrylic resin emulsion ‘Primal AC 39. manufactured by Rohm & Haas, Philadelphia PA, USA, * Abbreviations refer to Tables 13 116 Pe Pobettylene Glycol 400, manufactured by BDH Chemicals Ld, Poole, UK. Gi Fidizer: sodium gluconate 98%, manufactured by (Carl Erba, Milan, aly Rb Fluidize: ‘Rheobuild 561, manufactured by MAC Mediterranea, Treviso, tly Sk Fluidizer: Sikament A 30, manufactured by Sika Italia, Milan, aly. Sm Fluidizer: supplied by local vendor, manufacturer Unknown, S- Commercial grouting mixture DDS" Pre-pack injection misture, solid component, ‘manufactured by Damp and Dry, Piombino, Italy DDL Pre-pack injection" mixtare, liquid." component. smanlfacturedby Damp and Dry, Piombino, REFERENCES . " Ferapn, Del, “Essie de lnboratiesur ds coulis base ‘ cment in Mortar Cement) and Grows. Used inthe Conservation of Hatorke Buldngs, ICCROM, Rome (1982) sso, Feroni Sta, Lime based mortars for the repair of ancient tmasonry and posible subsites in Moras, Cement and Grous Used the Consrvtion of Historie Buldies, TCCHOM, Rome (1982) 6399. ! Fraga Data “insite consolidation of wall and floor Inova by ‘means of injection outing. techniques in Conservation det Monae Inst, (CCROM, Rome (1983) Mora, L- Mora, Band Philip, P, La’ Conservation des Pannes"Muralés, ICCROM, Bologna (1977) 268-273 and atsa0e Philips, MW, “Adhesives for the reatachment of lose plaster, APT Balen XI (1980) 3783. Devin, S20 "Xory difraction and seanaing. cecton rcrotope, analysis of conventional mortars’ In, Mortars. Comenas"and: Grows Used in the Conservation of Historic Buldings,TCCROM, Rome (1982) 1-13. ‘Tibesso, M, Diana, Sy and Sammi, P, “Evaluation of ‘mortars for ein caservaton from the standpoint of rease {SF soluble sale (pronsonal ite) in ICOM Commate for Conervation 7 ena Metin, Copenagen (983). Falre, A.M and Rizolees,YRepration des structures tn ton par injection des plyaties. Esai injectabiite 3 it colonne de sabi Bull de Laason du Labor des Font et Chaustes 96 (978) 123. Unesco RILEM, “Vapour permesbiliy” in Deterioration ond Preservation of Sone Monnens, CEBTR, Pais (1978) Vol. V, ‘as Ritchie, T, ‘Study of efflorescence produced on ceramic wicks by masonry mortars, Journal o he American Ceramic Soil} 351988) 362366 Murat, his “Fnal report on the activity (197-1980) of the RILEM Committee 2.GP on Gypsum Piste, Matriause Conracion 8 (1982).