Effect of Formaldehyde As an Additive on Some Properties of Magnesium Oxysulphate Cement

Material Science Research India Vol. 5(2), 313-320 (2008)

Effect of formaldehyde as an additive on some properties of magnesium oxysulphate cement

RITU MATHUR¹, SANJAY K. SHARMA²* and M.P.S. CHANDRAWAT³

¹PG Department of Chemistry, RR College, Alwar (India). ²Department of Chemistry, Institute of Engineering & Technology, Alwar (India). ³IET Biotechnology Institute Alwar (India).

(Received: October 06, 2008; Accepted: November 16, 2008)

ABSTRACT

A French scientist Sorel S.T., discovered magnesium oxysulphate cement (magnesia / Sorel’s Cement) in 1867. In this work the effect of formaldehyde as an additive is studied on some properties of Sorel’s cement. It is found that incorporation of formaldehyde in the matrix increases setting periods but does not contribute to the water tightness of the cement, though compressive strength of the product improves by its incorporation in small amount. Minor contractions in the linear beams are also noticed with passage of time.

Key words: Magnesium oxysulphate cement, Compressive strength, Water tightness, Setting periods, Weathering effects, linear changes.

INTRODUCTION Its chief drawback is its poor water resistance, making it unsuitable for construction Sorel cement, which is named for its applications. Additionally, it is expensive compared inventor, Frenchman Stanislas Sorel who first to standard concrete and gypsum. produced it in 1867, is a hydraulic cement mixture of magnesium oxide (burnt magnesia) and Sorel has highlighted the use and potential magnesium chloride with the approximate chemical of Magnesium oxysuphate as a binder material formula Mg4Cl2(OH)6(H2O)8, corresponding to a since the invention of magnesia cements in 1,2,10 weight ratio of 2.5-3.5 parts MgO to one part MgCl2¹. 1867 . Sorel cements show many properties that This material, which is also called “Magnesia are superior to those of OPC¹¹. For example, it has Cement,” is usually combined with filler materials high fire resistance, low thermal conductivity, high such as sand or crushed stone. Magnesia cements abrasion resistance, high transverse and crushing are a variety of cements based on magnesium oxide strengths and does not require wet curing. It is being (MgO). This variety includes magnesium oxychloride considered for nuclear applications also9,12-13. cement1,2, magnesium oxysulphate cements³, Magnesium oxysulphate cement has a very distinct magnesium phosphate cements4-6. Morovere, adding difference from Oxychloride cement that it does not magnesium oxide to Ordinary Portland Cement present a potential source for corrosion of (OPC), yields more durable composite reinforcing steel. Magnesium oxysulphate cements, cement7,8.Magnesite cements (or magnesium formed by the reaction of magnesium sulphate carbonate) is one of the more promising magnesia solution with magnesium oxide, have similar cements that has recently attracted considerable properties, as of magnesium oxychloride cements³. interest from industry9. 314 Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008)

According to temperature ranges and In this study, formaldehyde is tried as an preparation conditions, five types of Oxysulphate additive for magnesium oxysulphate cement. The cements are known. They are 5Mg(OH)2. molecular formula of formaldehyde is HCHO. It is

MgSO4.3H2O (or2H2O), 3Mg(OH)2.MgSO4.8H2O, highly water soluble and low boiling gas.

5Mg (OH)2.MgSO4.8H2O, Mg(OH)2.MgSO4.5H2O Commercially it is available as formalin (40% and Mg(OH)2.2MgSO4.3H2O [14,15]. Hall et. al has solution in water containing a small amount of also identified the presence of 5Mg(OH)2. MgSO4. methanol). It is very reactive and prone to

3H2O [16]. Magnesium Oxysulphate cement of polymerization on account of the absence of bulky

5Mg(OH)2.MgSO4.8H2O composition is most groups. This may contribute to some properties of commonly found17-19. magnesia cement. That is why formaldehyde has been tried as an additive for oxysulphate cement in The Oxysulphate cement category is the present work19. normally considered to be weaker than the oxychloride types of cement. But studies reveal that The object of this study was to determine many weak cementing materials can be made to the effect of formaldehyde as an additive on have higher strengths by modifying certain Magnesium Oxysulphate Cement. Effect of conditions of manufacture or preparation20,21. In case formaldehyde on some properties of magnesium of Portland Cements²², strength remains unchanged oxysulphate cement was studied by incorporating during its exposure to water23,24. The oxysulfate it in different amounts in the dry –mix (1:2 dry mix cement system is not in the wide use because of was prepared by weight of magnesia and dolomite), loss of strength on prolonged exposure to water. on the basis of: (i) Setting time investigations, (ii) Weathering effects, (iii) Moisture ingress (Steam Additives or admixtures play an important tests), (iv) Compressive strength tests and (v) Linear role to modify the properties of oxysulphate cement changes (for soundness). The results are reported either in positive or in negative direction and also in the present article. nullify the pernicious effects of the impurities present in the raw materials. Incorporation of Green EXPERIMENTAL additives has been reported for sustainable cement production to improve its properties25. Green Raw materials Chemistry is placed in the frontier areas of research The raw materials used in the preparation and has been focused for considerable recent of magnesium oxysulphate trial blocks are research26. Use of green additives involve magnesium oxide, magnesium sulphate and inert considerable decrease in emissions of green house filler, dolomite³². gases (CO2 and SO2) during the production of cement27,28. It opens new doors of possibilities to Magnesia (magnesium oxide) produce sustainable cements. Commercial grade magnesium oxide of Salem origin is used in the study with the following Changes in properties of Magnesium characteristics (i) MgO – 92% (ii) Active lime (CaO) oxysulphate cement on admixing sodium < 1.9% (iii) Iron oxide (Fe2O3) < 1.4% (iv) Silica bicarbonate as an additive have been studied (SiO2) < 8.2% (v) Alumina (Al2O3) 0.2 – 0.4% (vi) separately, which reveals that sodium bicarbonate Bulk density 0.85 kg/I (vii) 95% passing through 75 increases setting periods in all proportions within micron (200 mesh) IS sieve (viii) Ignition loss 2.5 ± the experimental limits. It also improves the water 0.5% at 110°C. tightness and strength of the cement when is added in powdered form. But in the form of saturated Inert Filler (Dolomite- CaCO3.MgCO3) solution sodium bicarbonate is not a good additive29. Uncalcined dolomite powder passing In our research group we have tried many additives through 150-micron sieve and retained 50% on 75- to magnesium oxysulphate cement and studied their micron sieve is used as inert filter in the preparation effects on its various properties29-31. of magnesia cement³³. It was checked for reactive impurities like lime before use. Its incorporation in Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008) 315 the matrix absorbs the heat evolved during the Moisture ingress exothermic formation of magnesia cement, which In order to find out the effect of reduces thermal shocks in the structure. It contains formaldehyde on moisture ingress of oxysulphate 28.7% CaO, 20.8% MgO, insoluble and other cement, all the setting time blocks with different sesquioxide contents less than 1.0 % and loss on proportions of the additive were cured for 2 months ignition 50%. under identical conditions and then subjected to boiling water for at least 30 hrs as per standard Magnesium Sulphate (Epsom Salt) procedure in a closed steam bath. Their relative

MgSO4.7H2O – Magnesium sulphate used moisture sealing efficacies were then studied as a in the study was according to Indian Standard function of time. Moisture ingress and soundness Specifications34. Technical grade magnesium are inversely proportional37-40. Results are shown in sulphate is used in the study. On chemical analysis, Table 3. magnesium sulphate content was found to be more than 98%, chlorides (as Cl), Lead (as Pb), Arsenic Compressive strength

(as As2O3), Iron (as Fe), Zinc and matter insoluble To study the effect of formaldehyde on in water were found to be present in traces. compressive strength of oxysulphate cement, standard 50 cm3 cubes were prepared from the Formaldehyde standard consistency pastes having formaldehyde Which is commercially available as in different amounts. These cubes were tested after Formiline. 30 days of curing under identical conditions with the help of compressive strength testing machine METHODS as per standard procedure35. The practical out comings are recorded in Table 4. Effect of formaldehyde on setting, strength an moisture resistance of oxysulpahte cement was Linear changes studied by incorporating it in different amounts in The effect of formaldehyde on linear the wet-mix and following experiments were changes of magnesia cement was studied by conducted according to IS specifications [33-36]. preparing wet mixes having varying quantities of the additive and then filled into standard sized Setting periods moulds (200mm× 25mm×25mm). Trial beams were Effect of formaldehyde on setting then kept under 90% relative humidity and 30±20C characteristics of the cement was studied by mixing temperature for 24 hrs. Initial length (after 24hrs) formaldehyde in the gauging solution in varying and final length (after 28 days) of the beams were proportions. The quantity of the additive was measured using micrometer scale and then calculated by volume of gauging solution. Setting difference between the two was determined. This periods and consistency of the wet-mixes prepared shows the linear change in the product by the by 1:2 dry mixes (1 part weight of magnesia and 2 incorporation of the additive37. Results are parts by weight of dolomite) with magnesium enumerated in Table 5. sulphate solution of 25° Be having different quantities of additive were determined adopting the RESULTS AND DISCUSSION standard procedure by Vicat needle apparatus35. The observed results are summarized in Table 1. The effect of mixing formaldehyde on setting characteristics of oxysulpahte cement is Weathering effects summarized in Table 1. Incorporation of Variation in weights of the setting time formaldehyde in the matrix increases initial setting blocks were recorded after 24 hrs, 7 days, 30 days periods. So is the case with final setting periods. and 45 days respectively. Different weathering Absence of steric hindrance in formaldehyde, its effects may increase or decrease the weights of high reactivity and small size interfere with the the trial blocks with passage of time. Experimental normal setting process of oxysulphate cement. findings are summarized in Table 2. Also, at higher pH values, formaldehyde undergoes 316 Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008) autopolymerization to produce linear chains of After final setting of the product, some polyformaldehyde (Eq 3). These chains entangle uncombined moisture and formalin remain with lattice formation process and crystallization entrapped in the matrix, which may be given out process of the product. During the crystallization with passage of time and results in decrease in process, position of water molecules may be weights of the trial blocks (upto 30 days) as is replaced by small sized formaldehyde molecules, evident from the data shown in Table 2. At later which in turn indirectly interfere with the setting stages, slight increase in weights is noticed. This process. Cumulative effects of all the above process may be due to factors like hydration, carbonation, retard setting process and increase setting periods. etc of the unreacted or freely available basic

Table 1: Effect of formaldehyde on setting Characteristics of oxysulphate cement

Conc. of g.s = 25O Be Dry –mix composition …… 1:2 Volume of g.s. = 70 ml (a) One part by weight of magnesia [g.s. of 25O Be + additive] (b)Two parts by weight of dolomite Temperature … 30 ± 2OC Quantity of dry mix …200 gm Relative humidity …above 90%

S. Dry Mix (% Additive) Setting Time No Composition Initial (Min) Final (Min)

1 0% 30 133 2 5% 32 223 3 10% 33 257 4 15% 35 275 5 20% 40 307

g.s. = Gauging solution

Table 2: Effect of formaldehyde on weathering characteristics of oxysulphate cement

S. Dry Mix Weight of Blocks in gm after No Composition 24 hrs 7 days 30 days 45 days (% Additive)

1 0% 258.870 251.163 243.322 241.440 2 5% 252.030 239.500 231.750 232.270 3 10% 255.360 242.100 231.100 231.500 4 15% 264.760 250.570 243.380 243.820 5 20% 246.350 231.200 224.090 224.800 g.s. = Gauging solution Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008) 317 ingredients of the matrix, which are responsible for compressive strength of the cement due to gaining weights. simultaneous formation of polyformaldehyde chains, which interlace and entangle with the main network Very poor watertightness is observed if of magnesia cement (Eq 3). On subsequent formaldehyde is mixed as an additive in magnesia additions of the formaldehyde in the matrix, beyond cement (Refer Table 3). Formaldehyde is highly optimum proportion, strength data show decreasing water soluble and volatile compound. It is given trends. This is attributable to the decreasing out at high temperature during the steam test. This quantities of gauging magnesium sulphate solution results in the formation of voids and makes the with increasing additive proportions. Chances of product less watertight on account of increased formation of strength giving composition chances of moisture ingress. (magnesium oxysulphate) are thus reduced (Eq 5), which in turn reduce the mechanical strength of Table 4 shows that incorporation of formaldehyde oxysulphate cement. upto an optimum proportion (about 5%) improves

Table 3: Effect of formaldehyde on moisturing ingress characteristics of oxysulphate cement

S. Dry Mix Trial blocks kept in boiling water for N Composition 0-5 5-10 10-15 15-20 20-25 25-30 (% Additive) Hrs Hrs Hrs Hrs Hrs hrs

1 0% N.E. N.E. N.E. N.E. C - 25%C----- 310%C----- 415%C----- 520%C-----

g.s. = Gauging solution, N.E. = No effect, C = Cracked

Table 4 : Effect of formaldehyde on compressive strength of oxysulphate cement

Conc. of g.s = 25O Be Dry –mix composition …… 1:2 Volume of g.s. = 200 ml [g.s. of 25O Be+ additive] (a) One part by weight of magnesia Temperature … 30 ± 2OC (b) Two parts by weight of dolomite Relative humidity…above 90% Quantity of dry mix … 565 gm

Dry Mix Composition 0% 5% 10% 15% 20%

Compressive Strength (Kg/cm2) 275 340 310 300 270

g.s. = Gauging solution 318 Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008)

Table 5: Effect of formaldehyde on linear changes of oxysulphate cement

Conc. of g.s = 25O Be Dry –mix composition …… 1:2 Volume of g.s. = 105 ml [g.s. of 25O Be+ additive] (a) One part by weight of magnesia Temperature … 30 ± 2OC (b) Two parts by weight of dolomite Relative humidity…above 90% Quantity of dry mix … 300 gm

S. Dry Mix Length of Beams (mm) Change in No. Composition Length (mm) (% Additive) Initial Final

1 0% 200.00 200.02 0.02 2 5% 200.00 199.37 0.63 3 10% 200.00 199.41 0.59 4 15% 200.00 199.48 0.52 5 20% 200.00 199.51 0.49

g.s. = Gauging solution

Steric effects being less pronounced in case of (Strength giving formaldehyde, causes contraction in volumes, for compositon) similar reasons (more association, more compaction) to greater extents (Eq 4). This is CONCLUSIONS evident from the data shown in Table 5. 1. Incorporation of formaldehyde increases The following probable chemical changes are helpful setting periods (initial and final, both). in explaining the above discussion 2. Formaldehyde does not contribute to water tightness when mixed in the matrix. → CaO + H2O Ca(OH)2 ...1 3. Addition of formaldehyde improves → MgO + H2O Mg (OH)2 ...2 mechanical strength of the product upto an optimum proportion (about 5%). pH>7 4. Minor contraction in trial beams is noticed → nHCHO […..HCHO…..]n ...3 on mixing formaldehyde in the matrix. Linear polymeric chain (hydrophobic) ACKNOWLEDGEMENTS Magnesium Oxysulphate + → Mag.O.S-Formaldehyde- Authors are thankful to Dr. M.P.S. Mag.O.S ...4 Chandrawat, Principal, IET Biotechnology Institute, Formaldehyde Association (Compaction) alwar for providing them valuable guidance and sparing his time for the present work. Author (SKS) → 5Mg(OH)2+MgSO4.7H2O+H2O 5Mg(OH)2.MgSO4.8H2O is very grateful to Dr. V.K. Agarwal, Chairman, IET ...5 Group of Institutions, Alwar, India, for providing the Magnesium basic facilities. Oxysulphate Cement Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008) 319

REFERENCES

1. Sorel S. T., C.R. Acad. Sci, Paris, 65: 102 18. George S. Brady : Materials Hand Book, (1867). McGraw Hill, Fifteenth Edition, 17 (2002). 2. Maravelaki Kalaitzaki P, Moraitov G, Cement 19. Walker, Formaldehyde, ACS Monograph & Concrete Res, 29(12): 1929-1935 (1999). 159, Reinhold 1964, New Expansions, C & 3. Daspoddar K., Chowdhury B.N. and Basu EN, 6: 25 (1964). R., J. Indian Chem. Soc., 69: 550 (1992). 20. Ramchandran, V.S., and Feldman, R.F., 4. Kingery W., J. Am. Ceram. Soc., 33: 242 Cem. And Concrete Research, 3: 729 (1973). (1950). 21. Feldman, R.F., and Ramchandran, V.S., J. 5. Sugama T. and Kukacka L., Cem. Concr. Amer. Cer. Soc., 49: 268 (1966). Res., 13: 407 (1983). 22. Young J.F. and Mindess S., Concrete, 6. Soudee E. and Pera J., Cem. Concr. Res., Prentice hall, Upper saddle river, NJ,USA, 30: 315 (2000). 2nd. Edn., (2003). 7. Fernandez L., Alonso C., Hidalgo A. and 23. Soroka, I., and Sereda, P.J., J. Am. Cerem. Andrade C., Adv. Cem. Res., 17: 9 (2005). Soc. 51: 337 (1968). 8. Paya J., Borrachero M.V., Monzo J. and 24. Beaudoin, J.J. and Ramchandran, V.S., Cem. Bonilla M., Waste Manage., 19: 1 (1999). And Concrete Research, 5: 617 (1975). 9. Harrison A.J.W., Reactive magnesium oxide 25. Phair J.W., Green Chem., 8: 763-780 (2006). cements, US Pat.2003/0041785A1 (2003). 26. Sharma S.K., Chaudhary A. and Singh R.V., 10. British Cement Association: Different Types Rasayan J. Chem., 1(1): 68-92 (2008). of Cements, www.azobuild.com, Artilce Id 27. Penttala V., ACI Mater. J., Sept-Oct, 409 7959 (2006). (1997). 11. Singh D., Wagh A.S., Cunnane J.C. and 28. Wischers G., Betonwerk+Fertigteil-Tech., 1: Mayberry, J.L., J. Environ. Sci. Health, Part 103 (1994). A, 32: 527 (1997). 29. Mathur R and Sharma S K, Rasayan J. 12. Beaudoin James J. Ramchandran Vangipuram Chem, 1(3): 620 (2008). S & Feldman R.F, American Ceramic Society 30. Mathur Ritu, Sharma S.K., “Effects On The Bulletin, April, 424 (1977). Setting, Strength, Moisture Resistance & 13. Vangipuram S.R, Ralph M.P., Baeudoin J, Linear Changes of Magnesium Oxysulphate Delgado A.H, Handbook of Thermal Analysis Cement (Sorel Cement) On Mixing Portland of Construction Materials (William Adrew Inc) Cement As AnAdditive”,accepted in E 359 (2002). Journal of Chemistry , Vol 6 (In Press). 14. Demediuk, T. and Cole, W., Aust. J. Chem., 31. Mathur Ritu, Sharma S.K., Effect of Copper 10: 287 (1957). Sulphate as an Additive on Setting Strength 15. Newman, E.S., J. of Research, Nat. Bur. Std. and Durability of Magnesium Oxysulphate A, 68A: 645 (1964). Cement , Unpublished Results. 16. Hall,G., Read,G. and Bradt,R., Paper 32. Satya Prakash, Madan R.D., Modern presented at 78th. Meeting American Ceremic Inorganic Chemistry (S Chand) 906 (2005). Society, Cincinnati, May (1976). 33. Indian Standard : 1760 (1962). 17. Mathur R, Chandrawat M.P.S., Nagpal K.C., 34. Indian Standard : 2730 (1977). Res & Ind, 29: 195-201 (1984). 35. Indian Standard : 10132 (1982). 320 Mathur et al., Mat. Sci. Res. India., Vol. 5(2), 313-320 (2008)

36. Indian Standard : 657 (1982). 39. Chandrawat M.P.S., Ojha T.N., Yadav R.N., 37. Chandrawat M.P.S.,Yadav R.N., Mathur Ritu, Bull. Mater. Sci. 24(3): 313-316 (2001). Res & Ind, 39: 18-21 (1994). 40. Mathur Ritu, Effect of Some Additives on 38. Gupta Y.K., Chandrawat M.P.S., Yadav R.N., Bonding Characterstics of Magnesium Res & Ind, 35: 191-193 (1990). Oxysulphate Cement (Ph.D Thesis, University of Rajasthan) (1993).