Hydration behaviour of lime–co-calcined kaolin–petroleum effluent treatment plant sludge

Cement and Concrete Research, no. 2 (2002): 297-302

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摘要

Petroleum effluent treatment plant (ETP) sludge contains hydrocarbons and its ash is pozzolanic in character. The hydrocarbon may be utilized in the calcination of clay. The present communication reports on the hydration behaviour of lime–metakaolin mixtures produced in the presence of the sludge. The hydration products were characterized...更多

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简介
  • Blended cements are produced by intermixing/intergrinding different amounts of various supplementary cementing materials and Portland cement.
  • The blending materials may be either pozzolanic in nature like fly ash, calcined clay, silica fume, rice husk ash, etc.
  • Metakaolin produced by thermal activation of kaolinite clay in the temperature range of 650– 800 °C is an established pozzolana.
  • It is an ‘ultrafine,’ highly reactive pozzolana similar in properties to condensed silica fume.
  • Metakaolin is chemically different from many other pozzolanas as it has a very high alumina content and its reaction products with Ca(OH) (CH) include C – S –H, C– A – S –H gel, C2ASH8 and C3AH6 [2,3]
重点内容
  • Blended cements are produced by intermixing/intergrinding different amounts of various supplementary cementing materials and Portland cement
  • The CH contents of the 1-day hydration products of the co-calcined mixtures prepared using 20% sludge is much lower than that prepared using 10% sludge or without the sludge but at 28 day, it is approximately same for all the mixtures
  • The change in CH and combined water (CW) in the hydration products of the mixtures suggests that utilization of the sludge in the calcination of kaolin enhance the early hydration rate of a metakaolin –lime mixture
  • The intensity of the band at 970 cm À 1 in all the hydrated products increases with hydration period indicating increased formation of C – S –H
  • The 7-day hydration products exhibit an additional peak at 1025 cm À 1, which may be due to formation of new C – S – H phase or transformation of C –S – H phase
  • The peak due to CH, which disappeared in metakaolin –lime hydration products after 7-day hydration, is observed as a weak shoulder in the co-calcined kaolin– sludge– lime mixture
方法
  • The sludge was collected from the ETP of Lakwa oilfield, Assam, India.
  • The kaolin and the mixtures were mixed with Ca(OH) in the lime:mixture ratio of 6:4 and homogenized in a laboratory size ball mill.
  • These lime mixtures were calcined at 750 °C for 1 h in an electrically heated chamber furnace in air atmosphere and stored in a CO2-free atmo-
结果
  • Results and discussion

    Chemical analysis (Table 1) reveals that the sludge ash sample is relatively poor in SiO2 and rich in Al2O3, Fe2O3, CaO and K2O + Na2O compared to the metakaolin. 10 and 20 wt.% replacement of kaolin by sludge slightly lowers the total Al2O3, SiO2 and Fe2O3 content but it is well within the requirement ( > 70%) stated in ASTM for a natural pozzolana [7].
  • The CH contents (Fig. 1) of the co-calcined kaolin– sludge –lime mixtures after hydration are lower than those from metakaolin – lime mixtures and decrease with the amount of sludge.
  • The trend in the change of the amount of CW in the pastes (Fig. 2) of different compositions is the opposite of the change in the CH contents
  • It increases with increase of curing time as well as with the amount of replacement of kaolin by sludge in the compositions.
  • The change in CH and CW in the hydration products of the mixtures suggests that utilization of the sludge in the calcination of kaolin enhance the early hydration rate of a metakaolin –lime mixture
结论
  • The results can be summarized as follows:

    C – S– H gels. The calcined products of the mixture containing 20% sludge exhibit comparatively weak peak at 3645 cm À 1 indicating consumption of higher amount of CH during hydration.

    The intensity of the band at 970 cm À 1 in all the hydrated products increases with hydration period indicating increased formation of C – S –H.
  • The calcined products of the mixture containing 20% sludge exhibit comparatively weak peak at 3645 cm À 1 indicating consumption of higher amount of CH during hydration.
  • The 7-day hydration products exhibit an additional peak at 1025 cm À 1, which may be due to formation of new C – S – H phase or transformation of C –S – H phase.
  • The peak due to CH, which disappeared in metakaolin –lime hydration products after 7-day hydration, is observed as a weak shoulder in the co-calcined kaolin– sludge– lime mixture.
  • The FTIR patterns of the 28-day hydration products of all the mixtures are almost the same
总结
  • Introduction:

    Blended cements are produced by intermixing/intergrinding different amounts of various supplementary cementing materials and Portland cement.
  • The blending materials may be either pozzolanic in nature like fly ash, calcined clay, silica fume, rice husk ash, etc.
  • Metakaolin produced by thermal activation of kaolinite clay in the temperature range of 650– 800 °C is an established pozzolana.
  • It is an ‘ultrafine,’ highly reactive pozzolana similar in properties to condensed silica fume.
  • Metakaolin is chemically different from many other pozzolanas as it has a very high alumina content and its reaction products with Ca(OH) (CH) include C – S –H, C– A – S –H gel, C2ASH8 and C3AH6 [2,3]
  • Methods:

    The sludge was collected from the ETP of Lakwa oilfield, Assam, India.
  • The kaolin and the mixtures were mixed with Ca(OH) in the lime:mixture ratio of 6:4 and homogenized in a laboratory size ball mill.
  • These lime mixtures were calcined at 750 °C for 1 h in an electrically heated chamber furnace in air atmosphere and stored in a CO2-free atmo-
  • Results:

    Results and discussion

    Chemical analysis (Table 1) reveals that the sludge ash sample is relatively poor in SiO2 and rich in Al2O3, Fe2O3, CaO and K2O + Na2O compared to the metakaolin. 10 and 20 wt.% replacement of kaolin by sludge slightly lowers the total Al2O3, SiO2 and Fe2O3 content but it is well within the requirement ( > 70%) stated in ASTM for a natural pozzolana [7].
  • The CH contents (Fig. 1) of the co-calcined kaolin– sludge –lime mixtures after hydration are lower than those from metakaolin – lime mixtures and decrease with the amount of sludge.
  • The trend in the change of the amount of CW in the pastes (Fig. 2) of different compositions is the opposite of the change in the CH contents
  • It increases with increase of curing time as well as with the amount of replacement of kaolin by sludge in the compositions.
  • The change in CH and CW in the hydration products of the mixtures suggests that utilization of the sludge in the calcination of kaolin enhance the early hydration rate of a metakaolin –lime mixture
  • Conclusion:

    The results can be summarized as follows:

    C – S– H gels. The calcined products of the mixture containing 20% sludge exhibit comparatively weak peak at 3645 cm À 1 indicating consumption of higher amount of CH during hydration.

    The intensity of the band at 970 cm À 1 in all the hydrated products increases with hydration period indicating increased formation of C – S –H.
  • The calcined products of the mixture containing 20% sludge exhibit comparatively weak peak at 3645 cm À 1 indicating consumption of higher amount of CH during hydration.
  • The 7-day hydration products exhibit an additional peak at 1025 cm À 1, which may be due to formation of new C – S – H phase or transformation of C –S – H phase.
  • The peak due to CH, which disappeared in metakaolin –lime hydration products after 7-day hydration, is observed as a weak shoulder in the co-calcined kaolin– sludge– lime mixture.
  • The FTIR patterns of the 28-day hydration products of all the mixtures are almost the same
表格
  • Table1: Oxide compositions of clay, sludge ash and clay – sludge mixtures
  • Table2: FTIR vibrations of hydrated products
Download tables as Excel
基金
  • The authors are grateful to the Ministry of Environment and Forest, New Delhi and ERBC, ONGCL, Nazira, Assam, for financial grant and providing the sludge sample respectively
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