Frequently Asked Soil-Cement Questions
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FAQs > Cement vs. lime slurry
How does cement slurry compare with lime slurry?
Although the application of cement and lime are relatively similar,
there are some distinct differences on how each works. In most cases,
slurry products are applied through the use of a modified water
truck. A rearmounted distributer bar applies the slurry by gravity
onto the desired surface. Also, application by means of a drum-mounted
sprayer bar on pulverization equipment is available.
The differences are noticed in several ways. The water to cement
ratio in cement slurry varies from 1:1 to 1.5:1. This is not the
case with lime slurry. A large tank with an internally mounted mixing
paddle is used in the “slaking” (hydration) of the dry
lime and at the very least 2.5 times the amount of water to dry
lime is needed for proper hydration. This means 40% more water is
needed in lime slurry production. The exothermic reaction of hydrating
lime can produce temperatures as high as 212° F whereas temperatures
of cement slurries can range from 70° F to 120° F. Heat
burns can occur to skin quickly at temperatures exceeding 120°
F.
The engineering benefits of cement slurry are superior also. While
both portland cement and lime are capable of providing calcium,
the primary ingredient necessary for stabilizing a clay soil, they
differ in their chemical nature, mode of reaction in the presence
of water, and resulting reaction products. Although both portland
cement and lime produce the pozzolanic reaction to form calcium-silicate-hydrate
(C-S-H) and calcium-aluminate-hydrate (C-A-H), portland cement has
the capability to form C-S-H and C-A-H immediately similar to portland
cement concrete. This characteristic allows cement treated soils
to produce higher strengths and work more effectively with a broader
range of soils. The PCA publication, Evaluating
the Performance of Soil-Cement and Cement-Modified Soil for Pavements:
A Laboratory Investigation, RD120, shows higher unconfined
compressive strengths are produced by cement slurry when compared
to lime slurry in sample clay materials (refer to figure below).
When considering the use of a slurry product for modification, stabilization
or reclamation, cement slurry has distinct advantages over lime
slurry in economic, health and engineering aspects.
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