1 Introduction
2 Experimental Details
2.1 Materials
Composition | Slag | Plaster of Paris | Lime | Composition | Slag | Plaster of Paris | Lime |
---|---|---|---|---|---|---|---|
MgO | 9.52 | 1.92 | 2.47 | Fe2O3 | 1.37 | 0.852 | 0.381 |
Al2O3 | 21.86 | 1.13 | 0.68 | Na2O | 0.088 | 1.55 | 1.54 |
SiO2 | 30.82 | 0.916 | 2.75 | MnO | 0.14 | – | – |
K2O | 1.04 | 0.661 | 0.9 | TiO2 | 1.04 | – | – |
P2O5 | – | 0.58 | – | SO3 | 0.66 | 39.88 | – |
CaO | 32.42 | 41.45 | 90.26 | Loss on Ignition | 1.0 | 6.25 | 0.84 |
2.2 Methodology
2.2.1 Physical Properties
Sample code | Proportion (%) slag + lime + plaster of Paris | Sample code | Proportion (%) slag + lime + plaster of Paris | Sample code | Proportion (%) slag + lime + plaster of Paris | Sample code | Proportion (%) slag + lime + plaster of Paris |
---|---|---|---|---|---|---|---|
A | 95 + 5 + 0 | A1.5 | 95 + 5 + 1.5 | A2.5 | 95 + 5 + 2.5 | A10 | 95 + 5 + 10 |
B | 90 + 10 + 0 | B1.5 | 90 + 10 + 1.5 | B2.5 | 90 + 10 + 2.5 | B10 | 90 + 10 + 10 |
C | 85 + 15 + 0 | C1.5 | 85 + 15 + 1.5 | C2.5 | 85 + 15 + 2.5 | C10 | 85 + 15 + 10 |
D | 80 + 20 + 0 | D1.5 | 80 + 20 + 1.5 | D2.5 | 80 + 20 + 2.5 | D10 | 80 + 20 + 10 |
E | 70 + 30 + 0 | E1.5 | 70 + 30 + 1.5 | E2.5 | 70 + 30 + 2.5 | E10 | 70 + 30 + 10 |
F | 60 + 40 + 0 | F1.5 | 60 + 40 + 1.5 | F2.5 | 60 + 40 + 2.5 | F10 | 60 + 40 + 10 |
A1 | 95 + 5 + 1 | A2 | 95 + 5 + 2 | A5 | 95 + 5 + 5 | ||
B1 | 90 + 10 + 1 | B2 | 90 + 10 + 2 | B5 | 90 + 10 + 5 | ||
C1 | 85 + 15 + 1 | C2 | 85 + 15 + 2 | C5 | 85 + 15 + 5 | ||
D1 | 80 + 20 + 1 | D2 | 80 + 20 + 2 | D5 | 80 + 20 + 5 | ||
E1 | 70 + 30 + 1 | E2 | 70 + 30 + 2 | E5 | 70 + 30 + 5 | ||
F1 | 60 + 40 + 1 | F2 | 60 + 40 + 2 | F5 | 60 + 40 + 5 |
2.2.2 Chemical Bonds and Hydration Products
3 Results and Discussion
3.1 Consistency
3.2 Setting Time
3.3 Soundness
3.4 Chemical Bonds and Hydration Products
4 Conclusions
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The normal consistency values of slag-lime-plaster of Paris mix increase with either increase in lime or plaster of Paris content. The consistency values for the present raw material compositions vary over a wide range from 28.8 to 37.7 % as compared to about 30 % of ordinary Portland cement (OPC).
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The initial and final setting times of the mixes decrease with either increase in lime and/or plaster of Paris content. In general, the initial and final setting times of the mixes are lesser than that of the value prescribed for ordinary Portland cement. An addition of borax retards the setting time and a borax content of 0.4 % by mass gives the setting time that is normally prescribed for OPC.
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The soundness of this binder varies between 1 and 3 mm, which is lower than that of the value prescribed for ordinary Portland cement by Bureau of Indian Standards.
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X-ray diffraction analysis shows a series of crystalline compounds such as calcium–sulfate–hydrate, portlandite, calcium–silicate–hydrate and calcite.
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SEM analysis also confirms the existence of these components in the hydrated specimens as calcium–sulfate–hydrate gel and calcium–alumina–iron oxides. In the early stages of setting C–A–S–H gels are found in this cementing material instead of only C–S–H gel, as normally found in hydration products of OPC. However, after 24 h of setting both C–S–H and C–A–S–H phases are found.
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FTIR analysis shows a shift of S–O and O–H bands with wave number, indicating that the hydration process continues with setting time and confirms the formation of calcium–sulfate–hydrate gel during the reaction.
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The increase in stiffness of the pastes during setting is due to the intensification of crystalline compounds such as calcium hydroxide, calcium–sulfate–hydrate, portlandite, gypsum and calcium–silicate–hydrate with setting period.