Details:

Creators:
Baker, Rob J. ; van Leeuwen, J (Hans) ; White, David J.
Baker, Rob J. ; van Leeuwen, J (Hans) ; White, David J. Less -
Corporate Creators:
Iowa State University
Corporate Contributors:
Iowa. Highway Division ; Iowa. Highway Research Board
Iowa. Highway Division ; Iowa. Highway Research Board Less -
Subject/TRT Terms:
[+]
Lime Recycling Sewage Sludge--Recycling Sewerage Sludge (Deposit) Waste Management Waste Products As Road Materials--Iowa
Publication/ Report Number:
TR-535
Resource Type:
Tech Report
Geographical Coverage:
Iowa
Edition:
Final report.
Corporate Publisher:
Iowa State University
Abstract:
Lime sludge, an inert material mostly composed of calcium carbonate, is the result of

softening hard water for distribution as drinking water. A large city such as Des Moines,

Iowa, produces about 30,700 tons of lime sludge (dry weight basis) annually (Jones et al.,

2005). Eight Iowa cities representing, according to the U.S. Census Bureau, 23% of the

state’s population of 3 million, were surveyed. They estimated that they collectively produce

64,470 tons of lime sludge (dry weight basis) per year, and they currently have 371,800 tons

(dry weight basis) stockpiled. Recently, the Iowa Department of Natural Resources directed

those cities using lime softening in drinking water treatment to stop digging new lagoons to

dispose of lime sludge. Five Iowa cities with stockpiles of lime sludge funded this research.

The research goal was to find useful and economical alternatives for the use of lime sludge.

Feasibility studies tested the efficacy of using lime sludge in cement production, power plant

SOx treatment, dust control on gravel roads, wastewater neutralization, and in-fill materials

for road construction. Applications using lime sludge in cement production, power plant SOx

treatment, and wastewater neutralization, and as a fill material for road construction showed

positive results, but the dust control application did not.

Since the fill material application showed the most promise in accomplishing the

project’s goal within the time limits of this research project, it was chosen for further

investigation. Lime sludge is classified as inorganic silt with low plasticity. Since it only has

an unconfined compressive strength of approximately 110 kPa, mixtures with fly ash and

cement were developed to obtain higher strengths. When fly ash was added at a rate of 50%

of the dry weight of the lime sludge, the unconfined strength increased to 1600 kPa. Further,

friction angles and California Bearing Ratios were higher than those published for soils of

the same classification. However, the mixtures do not perform well in durability tests. The

mixtures tested did not survive 12 cycles of freezing and thawing and wetting and drying

without excessive mass and volume loss. Thus, these mixtures must be placed at depths

below the freezing line in the soil profile. The results demonstrated that chemically

stabilized lime sludge is able to contribute bulk volume to embankments in road construction

projects.


Format:
PDF
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:573a056c12dd0613c89113d5a93564bceedbab2e31b23807b6d2478ff598f083
Download URL:
https://rosap.ntl.bts.gov/view/dot/23458/dot_23458_DS1.pdf
File Type:

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