APPENDIX A: ALTERNATIVE CEMENTS
Asok Sarkar, formerly of the University of Dayton Research Institute, provided
this analysis of cements other than plain portland cement for potential use in cold
weather. This is not intended to be an exhaustive review but rather to serve as an
introduction to alternative cements.
A considerable amount of effort has been expended both in northern America and Eu-
rope to devise ways by which construction can continue throughout the winter season. In
general, North American concreting practices have tended towards the use of heating and
housing to protect fresh concrete during placement and curing. However, in view of the
cost and logistical problems associated with transporting the equipment needed for heating
and housing, there is a significant need for concreting and repair materials that can function
without elaborate costly protection measures.
Cementitious binder materials can be classified into three broad categories: 1) inorganic
cements, 2) organic polymer resins, and 3) hybrid inorganic-organic binders. The useful
temperature range of regular and blended portland cements can be extended by the use of
various accelerators, antifreezing agents, and combinations thereof. Several inorganic non-
portland cements have also been used for cold weather applications. For any cement mate-
rial to perform effectively at low temperatures, several key properties--such as rapid set-
ting, rapid strength gain, and self-generation of heat--are needed.
For inorganic cements to function at low temperature, the mix water must remain liquid
during both mixing and initial hydration.
The main concerns for cold weather concreting with portland cement are maintaining an
adequate temperature for curing the concrete and protecting the concrete from both freez-
ing and large thermal shocks. There are two ways to overcome the low-temperature limita-
tions of portland cements: accelerating the setting and hydration reaction of the cement,
and depressing the freezing point of the free water in the cement matrix. Both of these
aspects have been discussed in the main body of this report. More research with novel
additives and admixtures is required in this area.
Supplementary and blended cements
Blended cements are made of mixtures of regular Type I portland cement with various
siliceous supplementary cementing materials, for example, blast furnace slag, fly ash, silica
fume, and natural and artificial pozzolans. Besides providing significant cost reduction of
the placed concrete, these replacement materials can act to improve workability; reduce
water/cement ratio; reduce porosity of the concrete; lead to improved durability; and can
reduce the heat of hydration of cement, leading to lower thermal stresses in large concrete
structures. While the reduced heat of hydration of blended cements is advantageous for the
construction of large concrete structures, it is a serious drawback for the construction of
smaller structures at low temperatures. For this reason, blended cements are not normally
selected for use at low temperatures unless heating and housing are available. Work is
needed to find chemicals that will speed up the normally slow hydration reaction of supple-
mentary cementing materials.
Modified portland cements
Modified portland cements are often manufactured because of raw material constraints,
and several have been formulated and produced specifically for low energy consumption