EFFECT OF SELF HEALING PROMOTED MATERIALS BLENDED …extras.springer.com/2007/978-1-4020-6250-6/documents/95.pdf · EFFECT OF SELF HEALING PROMOTED MATERIALS BLENDED WITH CARBOXYLIC

Proceedings of the First International Conference on Self Healing Materials 18-20 April 2007, Noordwijk aan Zee, The Netherlands You Youkun et al.

1 © Springer 2007

EFFECT OF SELF HEALING PROMOTED MATERIALS BLENDED WITH CARBOXYLIC ACID ON

PERMEABILITY

You Youkun a,b,c , Qian Chunxiang a, Miao Changwen b, Ye Guang c, K. van Breugel c

a Southeast University, Nanjing 210018, China

b Jiangsu Provincial Building Institute , Nanjing 210008, China c Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1,

2628 CN Delft, The Netherlands

A kind of calcite crystalline proliferation cementitious mixture consisting carboxylic acid and carbonate salts used as self healing promoted materials (SHPM) was presented. Study was focused upon formulating the leaching and deposition equilibrium process of calcite crystals proliferated by SHPM during direct hydraulic permeability test. Results of permeability experiments and Environmental Scanning Electron Microscopy (ESEM) observation confirmed the properties of self healing of the materials. Comparing to blank paste sample, the permeability of paste coated with SHPM reduced significant with the elapse of time, while the permeability of paste blended with magnesium salt and cured in dilute carboxylic acidic solution dramatically increased during the leaching period. Compared to maleic acid and malic acid, tartaric acid mixed in SHPM had a high efficiency to modify the crystalline morphologies of deposited calcite and aragonite. Study is aimed to give a comprehension of self healing process of concrete in ambient weak acidic saturated environment.

Keywords: Self-healing, Carboxylic Acid, Calcite, Carbonate, Crystals, Precipitation, Permeability

1 Introduction Durability of concrete structures exposed to different environments has become a predominant concern in the concrete industry. The durability depends both on the ability of concrete to resist the penetration of aggressive substances from the environment, and on its self healing ability. Degradation products might be produced and deposited in cementitious materials in an aggressive environment. However, some of these reactions might play a role of self healing properties on the contrary. As some researcher pointed out, self healing is largely attributed to the dissolution and redeposition of hydrates or crystals in cracks or macroporos[1,2]. According to Natalya Hearn [3], Dissolution, deposition and crystallization is the main mechanism of self-healing in mature concretes, while carbonation has a low degree of influence on the performance. However, Carola Edvardsen[4] denoted that calcium carbonate crystals deposited in cracks might be almost the sole cause for the self healing. The mechanism of self healing during the carbonation might be assumed as follows: Concrete carbonation process involves the chemical reaction of portlandite, and calcium silicate hydrate, C-S-H, in the cement matrix with carbon dioxide gas leading to calcite, CaCO3 and other metal hydroxides give carbonates.


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The calcite mineral is 17% larger than the portlandite mineral, hence it may reduce the permeability and porosity especially in poor quality concrete [5]. Practically, concrete seldom suffer from single aggressive chemical substance attack in a natural environment. Some species immigrated from outer environmental might also play a self healing promote role in some occasions. Recent report manifests that [6-8] concrete aged in the mild acidic environment did not result in any detrimental effect and in some cases even a positive influence was observed. Some natural organic acids (e.g. humic and fulvic acids),which have chelating or complexing function with divalent cations or multivalent metal cations in cementitious alkaline pore solution. With the aid of chelating carboxylic acid, divalent or multivalent cations are more transportable in the global porous system and feasible to precipitate in macroporoes or cracks. The self healing process might be proceeding continuously in the materials. On the other hand, if the cementitous materials is immerged in flow water circumstance,the higher migration rate of metal cations ,the more leaching of the cations from the materials. In this case, the carboxylic acid would play an corrosive degradation role on the materials. Leaching of alkaline would increase permeability while crystalline deposition produced during the reaction between carbonation anion and divalent metal cations in pore solution might reduce the permeability of cementitious materials. During the equilibrium process, carboxylic acids might also play contradiction roles. Firstly, as effective crystal growth inhibitors, carboxylic acids improve the permeable alkaline leaching; secondly, once the carboxylic group released from the chelated divalent alkaline cations in solution, the alkaline reaction crystals re-deposition would be transferred in the microcracks or marcroporos elsewhere. Thus, carboxylic acid might have a positive contribution to self healing efforts. However, investigation on the mechanism of self healing incorporate the synergetic effect of multiple corrosive chemicals has not yet attached more attention. In this article, different SHPM are experimental compared in direct hydraulic permeability test. Three carboxylic acids, i.e. maleic acid (ME),malic acid (MA) and tartaric acid(TA), were compared in fabricated self healing promoted materials. The material was coated on the paste to investigate paste permeability during a long time elapse of test.

2 Materials and methods

2.1 Materials and preparing

The composition of the cement paste tested is w/c =1/2. The cement used is of type CEM-I 32.5R according to European Norms (EN 197-1). Its chemical composition is given in Table 1.

Table 1: the chemical properties of CEM I 32.5R (%) CaO SiO2 Al2O3 Fe2O3 MgO K2O Na2O SO3 C3S C2S C3A C4AF 63.4 21.0 5.03 2.83 2.0 0.65 0.24 3.0 63.0 13.0 8.0 9.0

The mineral composition of CEM I 32.5R is calculated with modified Bogue equation[9] . The Blain value of the cement is 283m2/g and 3150 kg/m3 of its density. A high porosity concrete sample coated with SHPM (Mixed with TA) was also laboratory prepared for observation of crystalline morphologies and measurement of porosity transfer. The ratio of cement to water of W/C=0.75, and the ratio of sand to cement is sp=40%.The maximum of aggregate size is 20mm.The curing regime is same as paste and the measurement is at 56 days ageing.


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The SHPM are consisted of the following components: one of three alternative carboxylic organic acids, carbonate salt and calcium or magnesium salt. All these materials were mixed with CEM I 32.5 R cement in a constant weight ratio of 30%, and the Portland cement is used as inorganic binder for coating cementitious materials. The chosen carboxylic acids have different number of hydroxyl groups in a same two carboxylic group in a molecular. The molecular structures of three carboxylic acids are shown in Fig.1.

OH

OH

O

O

OHHO

O

O

HO

OH

O

O

OH

HO

OH

maleic acid tartaric acidmalic acid

Figure 1: three carboxylic acids molecular structures The paste samples used for permeability test parallel coated with a layer grout of above mentioned self healing promote mixture, which consisted of a kind of carboxylic organic acid, lithium carbonate and cement .The coated grout is mixed with water in a ratio of W/B=0.3(B: binder solider mixture material ). The amount of self healing promote material coating on one side of paste was a constant of 1.5kg/m2 for test paste samples. In the procedure of the sample preparation for permeability, in order to prevent bleeding, the samples were cast into 1000 ml plastic pipe with the internal diameter of 95mm and rotated at a speed of 5 rpm in a room with temperature of 20°C. After 24 hours rotation, the samples were still kept in the plastic bottle and stored in the curing room with temperature of 20°C for 28 days. After 28days ageing paste disk samples were sawn from the paste column with a thickness of 10 mm. The accurate thickness was measured to calculate the permeability. The paste samples coated with SHPM were cured in a water filled box, keeping the base paste immerged in water while the level of curing water is lower than the coating SHPM for an assign curing age, e. g 7days and 28days respectively. The complex curing regime is set up so that deposition crystals yielded by SHPM could penetrate into the inner of paste with water suction function and reduce the paste permeability with physical clogging efforts. The main penetrable crystals are assumed as calcium carbonate or magnesium carbonate, in a crystalline formation of calcite or aragonite. The crystalline penetration process combines the two self healing mechanism of carbonation and re-deposition of crystals. In addition, carboxylic acid was mixed in SHPM to improve the characteristics of crystalline penetration. The self healing quality is characterized by the permeability of paste samples coated by SHPM. Before the permeability experiment, the coat of SHPM was removed to avoid its effect on paste permeability. In this paper, the effort of deposited crystalline calcite yielded by SHPM on porous microstructure and permeability characteristics is contrast manifested by acceleration leaching of magnesium salts from the paste samples. According to T. Van Gerven [10] diffusion test results, concrete carbonation process decreases leaching of Na, K, Ca while increases leaching of magnesium in concrete. The different leaching rate of magnesium and calcium cations should have an effect on the permeability performance during the artificial self healing promoted carbonation deposition process.


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Paste samples blended with 5% weight of cement magnesium salt were prepared with same cement to water ratio of 0.5 and same curing regime. Contrasting, these samples without SHPM coating, cured in three carboxylic acid dilute solution(1gl-1) for 28days.The contrasted permeability experimental results might show the significant difference between self healing efforts and pure leaching efforts. The experiments were set up to reveal the self healing mechanism. Additionally, three different morphologies of precipitated calcite crystals were respectively obtained by mixing two solution, one is calcium chloride (500 mmol l−1), and another is lithium carbonate (500 mmoll−1) solution, in which dissolute a certain above mentioned carboxylic acid with a concentration of 5mmol. l−1. The calcite crystals were simulated precipitated after the two solution mixed and then filtered off, washed using distilled water and dried at 105 oC. The analytical grade chemicals were used (ACS Reagent, Sigma) for the calcite crystals precipitate experiments.

2.2 Methods

A direct hydraulic water permeability test system was adopted for permeability measurement [11]. The thicknesses of paste samples were accurately measured with gauges of HEIDENHAIN MT25. After saturation and lateral proofing, each sample was placed in a device in which the water flows under a controlled pressure gradient of 0.4~0.6MPa and temperature of 25oC. The permeability coefficient was calculated with the Darcy’s law.

3 Results and analysis With different complexing ability and release ability, the carboxylic acid in SHPM has not only an influence on the deposition crystal migration rate but also deposition crystalline morphologies in porous cementitious material, which determine the self healing characteristics of SHPM. To reveal the complicated crystalline penetration and deposition process and their physical clogging effects on cementitious materials, direct hydraulic permeability system set-up is used to measure the permeation quality of maturated paste samples coated with SHPM.

Figure 2: the Cumulative flow against time for paste samples


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The cumulative flow evolutions as functions of time are shown in Fig.2. For all samples, a dozen hours are necessary for reaching steady state when permeability is calculated by the application of the Darcy’s law. In Fig.2, the upper three curves represent the permeability characteristics of paste samples blended with 5% weight percent of cement with magnesium salt. These samples were cured in three dilute carboxylic acidic solutions (1gl-1) for 28days.Without carbonation salt deposition supplied by SHPM, the samples procedure a running water leaching process during the direct hydraulic test. In the figure, a distinguish difference permeability characteristics between self healing efforts and leaching efforts were shown.

blank ME MA TA0.0

0.5

1.0

1.5

2.0

2.5

3.0

Per

mea

bilit

y(*1

0-12 m

/s)

Paste Samples

initial stage lateral stage

Figure.3: the permeability of initial and later stage of paste samples coated with SHPM

The calculated permeability of paste samples coated with SHPM are shown in Fig.3.The initial stage permeability of paste without SHPM coating is 2.81×10-12m/s, with the evolution of permeation time, it decreases to 1.99 ×10-12m/s.Comparing to the blank paste sample, all the paste samples coated with SHPM show a lower permeability and a higher decrease of later permeability to initial ones. The initial permeability of paste coated with SHPM(ME) is 2.78×10-12m/s, SHPM(MA)1.71×10-12m/s, SHPM(TA)with an initial negligible permeability value. During the later permeation stage about 150 hours, the permeability of past coated with SHPM (ME) and SHPM (MA) reduced to 1.15×10-13m/s and 1.05×10-13m/s respectively, while the sample coated with SHPM(TA) show a small cumulative flow during the later permeation stage, with a calculated permeability of 0.93 ×10-12m/s according to its permeation period. Comparing to the blank paste, the permeability of pastes coated with SHPM is efficiently reduced. Among the three carboxylic acids, tartaric acid has a lowest permeability during the initial permeation stage and a lest cumulative flow amount during the total permeation test. The paste permeation measurement results might be assumed be correlate to the penetrable ability and the degree of deposition of proliferated crystalline calcite and its modified crystalline morphologies. Past samples coated with SHPM show a relative lower water flow rate and cumulative amount than the parallel blank paste samples without SHPM coating. Three carboxylic acids also show the similar tendency of permeability, water flow rate and cumulative flow amount. The paste samples coated with SHPM mixed with tartaric acid have a lowest permeability.


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The result might be interpreted the near round calcite crystals having a high penetration ability and deposited in most macroporos and mesoporos in a deeper depth under the coating surface. Once all pores under critical porous radius are physical clogged, the paste might show water impermeable under the experimental hydraulic pressure. Both of samples coated with SHPM mixed with maleic acid or malic acid show a lower cumulative flow rate than blank paste sample without SHPM coating. The self healing effort was manifested as assumption of proliferated penetrable calcite crystalline deposition mechanism. The effort of self healing provide by SHPM is aggravated by combined the carbonation and penetrable proliferated crystalline deposition processes to density the cementitious materials. Penetrable crystalline deposition proliferated by the coated SHPM is supposed to be the main cause of self healing and main factors effect on permeability characteristics of paste. Three organic carboxylic acids in SHPM introduced to the crystallization processes of CaCO3 modify the shapes of crystals, retard nucleation and growth rate, and control polymorphism [12, 13]. The penetrable crystal morphology and its penetration rate are both significant characteristics s of self healing efficiency and physical clogging efforts in porous material. In the study, ESEM is used to observe the crystalline size and morphologies. The three calcite crystals precipitated in saturated calcite carbonate salt solutions mixed with ME; MA and TA are shown in Fig.4:

(a) (b) (c)

Figure 4: ESEM microphotographs of the calcite particles precipitated in three carboxylic acid solution: (a)ME, (b) MA, (c) TA The original calcite, CaCO3, has a trigonal crystal structure, a space group R-3c, a punctual group of symmetry -32/m and a=b=4.990 Å, c=17.061Å, α=β=90o and γ=120o [14].From the ESEM microphotographs of the calcite particles precipitated in three carboxylic acid solution shown in Fig.4, the tartaric acid has the highest efficient to modify calcite morphology from single distributed trigonal crystal to almost round of binary combined particles. However, the maleic acid, with no hydroxyl group in the molecular, the deposited calcite morphology is most near to the original calcite crystal trigonl morphology. It demonstrates that the number of hydroxyl in carboxylic acid has a strong influence on the deposition crystals morphologies in cementitious pore solution and fine cracks. It could also be hypothesized that the tartaric acid has a highest complexing interaction with the calcite crystals among the three acids.


7 © Springer 2007

blank ME-Mg MA-Mg TA-Mg

0

2

4

6

8

10

Paste Samples

Per

mea

bilit

y(*1

0-12 m

/s)

lateral stage

Figure 5: the permeability of initial and later stage of paste samples blended with magnesium salt

The calculated permeability of paste samples blended with magnesium salts are shown in Fig.5.Comparing to the blank paste sample, the test samples all have a higher initial permeability and higher later stage permeability. The curing dilute acidic solution also has an effect on the permeability of paste samples. The permeability of samples cured in tartaric acid dilute solution has a highest value of initial and later stage permeability; while samples cured in maleic acid dilute solution has a smallest value of permeability among the three acidic solutions. Considering there is no calcite provided by SHPM, the permeation test results in a leaching process of alkaline ions from the paste. The quantification of alkaline crystalline deposition in the leached solution revealed that the sample cured in tartaric acidic dilute solution has a highest value, which means it had high chelating interaction with the cementitious materials. Literatures have demonstrated that the dissolution of calcium hydroxide and a progressive decalcification of C-S-H in a running water leaching system are the essential processes governing degradation of cementitious materials [15]. For a paste blended with magnesium salt and cured in dilute acidic solution, this deterioration might be aggravated in the leaching process. With high migration rate of magnesium cations and solubility of magnesium salts, the paste samples show high permeability. The acid sorts also has an effect on the migration of magnesium ions and its crystalline morphologies. To investigate the this difference, ESEM is parallel used to observe the crystalline morphologies of MgCO3 deposited in three acid solutions as shown in Fig.6.

(a) (b) (c)

Figure 6: ESEM microphotographs of the MgCO3(aragonite) particles precipitated in three carboxylic acid solution: (a)ME-Mg, (b) MA-Mg, (c) TA-Mg


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From Fig.6, aragonite has a smaller particle size comparing to calcite crystals which shown in Fig.4.The three carboxylic acids show a similar modify effort on crystalline morphologies. The modification ability of tartaric acid is still the most efficiency one among three acids. Nevertheless, the binary phenomenon in calcite disappeared in aragonite crystals. They are single distributed separately. The different permeability characteristics between pastes coated with SHPM and paste samples blended with magnesium salts might be attributed to the following factors: Firstly, the two kinds of carbonate crystals have different particle size. The smaller crystals have a lower efficiency of physical clogging efforts. Secondly, according to literature data [16], the aragonite crystals( lgK sp,aragonite=-8.36) have a bigger dissolution than calcite( lgK sp,calcite=-8.475).During the Saturated permeability test, water continuously flow through the paste samples, there is an equilibrium between dissolve and deposition process. The aragonite crystal with high dissolution would induce a large amount of solute aragonite leached from the outlet of permeability experimental setup. So it has a higher permeability during the initial permeation stage. During the aragonite leaching process, the decalcification process might be accompanied. The permeability of paste sample would remain a stable high value for its high porosity formed by dissolve of alkaline ions. On this occasion, self healing function is no long exist in an “opening” running water leaching environment. From above discussion, the self healing process is supposed to have relation to cementitious component, environment chemical substance sorts and the system characteristics of “open” or “closed”, which determinate the dissolution and deposition equilibrium. In view of self healing promoted mechanism, some artificial SHPM might be applied as cementitious surface densify materials, where required a detail investigation on situ cementitious component and environmental condition etc. In practical, the self healing effort of SHPM coated on the maturated poor quality concrete surface might be significant due to coarse pores, fine shrinkage cracks and interfacial transition zone (ITZ) between aggregate and cement hydrates. These defects of microstructure provide enough capacity for crystalline deposition and high connective of microstructure for chelating agent and divalent cations penetration: there are two essentials process for the self healing performance.

4 Conclusions A kind of Self healing promoted materials (SHPM) consisting carboxylic acid and carbonate salt is proposed in this article. The permeability characteristics of SHPM are investigated and the morphologies of chelated crystalline deposition are detailed compared. With the aid of chelating interaction between carboxylic acid and divalent cations, proliferated crystalline deposition, e.g. calcite or aragonite, penetrate into the internal of cementitious porous materials, change the permeability characteristics of materials. The penetrable ability is concerned with the deposited crystalline morphologies. Different carboxylic acid has different modification efficiency. The number of hydroxyl group in carboxylic acid molecular has an effect on the crystal morphologies. Compared to malic acid and maleic acid, tartaric acid, with two hydroxyl groups in a bicarboxylate acid molecular, has the highest crystalline morphologies modify efficiency, yielding almost round calcite particle modified morphologies. Paste samples coated with SHPM consisting of tartaric acid has a lowest permeability comparing to the ones consisting of malic and maleic acid, while for the paste samples blended with magnesium salt and cured in tartaric acid dilute solution, the permeability coefficient is highest among the three ones. The result of permeability experiments indicates that the characteristics of carboxylic acid have influence on carbonate salts deposition efficiency and its dissolution migration ability.


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The high migration rate promoted the proliferation of deposited precipitation products in cementitious capillary pores and fine cracks. In a leaching circumstance, there is equilibrium between deposition and decalcification of leaching process, which determines the materials permeability characteristics and durability performance. Particularly, in a weak acidic drying-wetting cycles circumstance, there is an equilibrium of self healing of carbonate deposition and degradation of decalcification in cementitious materials. The test results in this research confirmed that the leaching of alkaline ions from cementitious materials via dilute acidic solution, without a contrary process of crystalline deposition, would significant aggravate the materials degradation progress. Compared to calcium carbonate, magnesium carbonate is more inclined to leach out from cementitious materials for its tiny particle morphologies and higher solubility, and more feasible to be suffered from acidic chemical attraction.

ACKNOWLEDGEMENTS

Authors would like to thank Doctorial candidate J. Zhou for his assistance on the permeability experiment. Jiangsu Provincial Institute of Building also expresses his gratitude to the Department of Education of Jiangsu Government for a grant allowing him a research visit to TU Delft.

REFERENCES 1) Nataliya Hearn, Self-sealing, autogenous healing and continued hydration what is the difference? Materials

and Structures, 1998, 31,563-567 2) Sébastien Granger, Ahmed Loukili , Gilles Pijaudier-Cabot and Mouloud Behloul ,Self healing of cracks in

concrete from a model material to usual concretes,2nd International Symposium on Advances in Concrete through Science and Engineering,2006, 11-13

3) Natalya Hearn and C. T. Morley,Self-sealing property of concrete—Experimental evidence, Materials and Structures, 1997, No. 30,404-411

4) Carola Edvardsen ,Water Permeability and Autogenous Healing of Cracks in Concrete, ACI Materials Journal, 1999, 96, No. 4,448-455

5) Peter A. Claisse, Hanaa El-Sayad, and Ibrahim G. Shaaban ,Permeability and Pore Volume of Carbonated Concrete, ACI Materials Journal, 1999. 96, No. 3,378-382

6) R. Wasserman and A. Bentur, Effect of concrete composition on durability in natural acidic environment ,Advances in Cement Research, 2006, 18, No. 4,135-143

7) A. Bertrona, G. Escadeillas, and J. Duchesne, Cement pastes alteration by liquid manure organic acids chemical and mineralogical characterization, Cement and Concrete Research, 2004, No. 34, 1823-1835

8) A. Bertron, J. Duchesne and G. Escadeillas, Attack of cement pastes exposed to organic acids in manure,Cement & Concrete Composites 2005, No. 27 ,898-909

9) Taylor, H. F. W, Modification of the Bogue calculation, Advances in Cement Research, 1989, 2, No.6. 73-77.

10) T. Van Gerven, D. Van Baelen, V. Dutré and C. Vandecasteele, Influence of carbonation and carbonation methods on leaching of metals from mortars, Cement and Concrete Research, 2004, 34, No. 1, 149-156

11) Ye, G. Experimental study and numerical simulation of the development of the microstructure and permeability of cementitious materials, Ph.D. thesis, Delft University of Technology, Delft, 2003.

12) Norio Wada, Kimihiro Yamashita and Takao Umegaki, Effects of carboxylic acids on calcite formation in the presence of Mg2+ ions, Journal of Colloid and Interface Science 1999, 212, No. 2,357-364

13) An-jian Xie, Yu-hua Shen, Xiao-yan Li, Zong-wei Yuan, Ling-guang Qiu, Chun-yan Zhang and Yuan-feng Yang, The role of Mg2+ and Mg2+/amino acid in controlling polymorph and morphology of calcium carbonate crystal , Materials Chemistry and Physics, 2007, 101, No. 1, 87-92

14) Jesús García-Carmona, Jaime Gómez Morales and Rafael Rodríguez Clemente, Morphological control of precipitated calcite obtained by adjusting the electrical conductivity in the Ca(OH)2-H2O-CO2 system, Journal of Crystal Growth ,2003, 249,No.3-4,561-571

15) C. Vernet, C. Alonso, C. Andrade, M. Castellote, I. Llorente, A. Hidalgo ,A new leaching test based in a running water system to evaluate long-term water resistance of concretes, Advances in Cement Research, 2002, 14, No. 4, 157-168


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16) K.-J. Westin, and A.C. Rasmuson ,Crystal growth of aragonite and calcite in presence of citric acid, DTPA, EDTA and pyromellitic acid, Journal of Colloid and Interface Science 2005, 282 , No. 2,359-369

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EFFECT OF SELF HEALING PROMOTED MATERIALS BLENDED …extras.springer.com/2007/978-1-4020-6250-6/documents/95.pdf · EFFECT OF SELF HEALING PROMOTED MATERIALS BLENDED WITH CARBOXYLIC