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AGGREGATES Presentation Transcript
1.AGGREGATES
2.FINE AGGREGATE (SAND)
Should satisfy the requirements of IS:383 e.g. Silt < 3 % ( by wt.) or < 8 % ( by volume) (As per CPWD Specification)
Zone IV sand should not be used in R.C.C.
unless tests have been made to ascertain
the suitability of the proposed mix proportions.
Should satisfy the requirements of IS:383 e.g. Silt < 3 % ( by wt.) or < 8 % ( by volume) (As per CPWD Specification)
Zone IV sand should not be used in R.C.C.
unless tests have been made to ascertain
the suitability of the proposed mix proportions.
3.LIMITS OF DELETERIOUS MATERIALS IN AGGREGATES
4.COARSE AGGREGATE GRADING
5.REQUIREMENT FOR COMBINED GRADING
6.Grading Requirement for 75 mm MSA
7. Grading Requirement for 150mm MSA
8.Concrete with higher size aggregate is to be wet – screened through 40 mm size sieve for casting cubes.
Such wet – screening results in increase in 28 – day compressive strength by about 17 to 29 %.
Such wet – screening results in increase in 28 – day compressive strength by about 17 to 29 %.
9.FINE AGGREGATE GRADING REQUIREMENTS
10.COMBINING DIFFERENT FRACTIONS OF C.A
11.EXAMPLE OF COMBINED GRADING
12.COARSE AGGREGATES-MECHANICAL PROPERTIES
13.Reactive constituents of Aggregate
14.INNOCUOUS MINERALS
15.ALKALI – SILICA REACTION
16.ALAKLI – SILICATE REACTION
17.ALAKLI-CARBONATE REACTION
18.Prevention of Alkali – silica Reaction
19.American Recommendations
Only low alkali OPC (less than 0.60% as Na2O equiv.) is not sufficient
The cement system is to include a cement replacement of at least 25 % class F flyash or at least 50% ggbs
Current practices of using 15% flyash as cement replacement may worsen ASR expansion, even with class F flyash.
For very reactive aggregates, lithium nitrate may be needed in addition to classF flyash.
Silica fume should be added only in slurry form. A 10% replacement has shown to mitigate moderate reactivity.
Class C flyash, lithium carbonate and lithium hydroxide are not recommended for ASR mitigation
Only low alkali OPC (less than 0.60% as Na2O equiv.) is not sufficient
The cement system is to include a cement replacement of at least 25 % class F flyash or at least 50% ggbs
Current practices of using 15% flyash as cement replacement may worsen ASR expansion, even with class F flyash.
For very reactive aggregates, lithium nitrate may be needed in addition to classF flyash.
Silica fume should be added only in slurry form. A 10% replacement has shown to mitigate moderate reactivity.
Class C flyash, lithium carbonate and lithium hydroxide are not recommended for ASR mitigation
20.Proposed Amendments to IS1489(PPC)
Limit on alkali
Use of PPC with alkali content less than 0.80%(as Na2O equiv.) is recommended
Such cement shall be manufactured with low alkali OPC( less than 0.6% asNa2O equiv.) and with at least 25% flyash conforming to IS:3812 (Part1)
Limit on Heat of Hydration
Heat of Hydration of PPC:
At 7 days : less than 250 KJ/Kg
At 28 days : less than 290 KJ/Kg
21.Proposed Amendments to IS 455 (PSC)
Limit on alkali
Use of PSC with alkali content less than 0.90%(as Na2O equiv.) is recommended
Such cement shall be manufactured with low alkali OPC( less than 0.6% asNa2O equiv.) and with at least 50% slag conforming to IS:12089
Limit on alkali
Use of PPC with alkali content less than 0.80%(as Na2O equiv.) is recommended
Such cement shall be manufactured with low alkali OPC( less than 0.6% asNa2O equiv.) and with at least 25% flyash conforming to IS:3812 (Part1)
Limit on Heat of Hydration
Heat of Hydration of PPC:
At 7 days : less than 250 KJ/Kg
At 28 days : less than 290 KJ/Kg
21.Proposed Amendments to IS 455 (PSC)
Limit on alkali
Use of PSC with alkali content less than 0.90%(as Na2O equiv.) is recommended
Such cement shall be manufactured with low alkali OPC( less than 0.6% asNa2O equiv.) and with at least 50% slag conforming to IS:12089
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