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Aluminum Sulfate Hydration Retarders for High-Calcium Fly Ash Used in Highway Construction

Published online by Cambridge University Press:  25 February 2011

M. Tohidian  and
Joakim G. Laguros
M. Tohidian
Affiliation:
Standard Testing and Engineering, Oklahoma City, Oklahoma
Joakim G. Laguros
Affiliation:
School of Civil Engineering and Environmental Science, The University of Oklahoma, Norman Oklahoma 73019, USA
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Abstract

The rapid hydration and setting associated with the use of high-calcium fly ash as an additive in soil and aggregate base stabilization in highway construction imposes certain limitations in regards to operational time and volume of work executed. Aluminum sulfate and its ammonium salt were evaluated as hydration reaction retarders. Mixtures of Ottawa sand and Class C high lime fly ash in a 1:1 weight ratio were used for the evaluations. These additives minimized the adverse effects of delayed compaction by recovering some of the compressive strength lost to the rapid hydration, although in all cases the density of the mixes decreased. The recovery of strength was related to the heat of hydration, wherein the peak temperature was reduced from 90°F to the range of 86–78°F at 2 hours; further temperature decreases were observed as reaction time increased. The availability of the sulfate ions, as manifested by the presence of ettringite, helps the hydration process continue, minimizes the adverse effects of delayed compaction and assists positively in the reduction of the void area of mixes and in stratlingite formation, which contributes to a strong crystalline framework.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 86: Symposium N – Fly Ash and Coal Conversion By-Products III , 1986 , 171
Copyright
Copyright © Materials Research Society 1987

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References

REFERENCES

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