University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 1

Determination of Soil Stabilizer Content Using X-Ray Fluorescence

(An Unplanned, yet Fortuitous Product of SPR 2195 and 2207)

Amy Cerato & Gerald (Jerry) Miller (OU)

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 2

Motivation

How do we make laboratory samples that have an

identical stabilizer content as the field site so that we

could compare field strength with lab strength?

SPR 2195: Evaluation and Field Verification of Strength and

Structural Improvement of Chemically Stabilized Subgrade Soil (in

collaboration with Dr. Donald Snethen)

SPR 2207: Validation and Refinement of Chemical Stabilization

Procedures for Pavement Subgrade Soils in Oklahoma (in

collaboration with Dr. Donald Snethen)

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 3

Motivation

How do we know exactly how much stabilizer is in the field sample? Devise a method that could pinpoint the amount of stabilizer present in the

soil.

Construction Quality Control ODOT can inspect stabilized subgrade and make a

determination if enough stabilizer has been used and have any issues fixed before the pavement is laid.

Forensic Geotechnical Investigations ODOT inspectors can collect samples during construction and

keep them in case a roadway performs poorly in the future.

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 4

Background Existing Methods to Estimate Stabilizer (CaO) Content in Soils

ASTM D3155 – Standard Test Method for Lime Content of Uncured Soil – Lime Mixtures Titration process, cumbersome, lots of chemicals, operator dependent

Lime fixation capacity method Initial Consumption of Lime (ICL) Unconfined Compressive Strength test (UCS)

Indicator Tests! - Cannot be retroactively used to pinpoint how much stabilizer is actually present in the soil!!!!!

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 5

X-Ray Fluorescence (xrf) Used extensively in environmental applications to measure elemental content in

soils, sediments, water sources, and even foods; however has not been used in soil stabilization applications.

Test measures elemental content as accurately as 0.01 – 100%.

The Whole Rock Analysis Method using XRF was performed by ALS Laboratory Group in Reno, NV.

Used to measure Calcium Oxide (CaO) content of natural soils (CaO0), chemical additives (CaOC.A.), and treated soils (CaOf).

100..0..

0

CaOCaO

CaOCaOCS

AC

f

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 6

Test Soil

Site # Soil NameAASHTO

Group USCS Group

Percent Clay (%)

Liquid Limit (%)

Plastic Limit (%)

Plasticity Index (%)

Shrinkage Limit (%)

Linear Shrinkage

(%)

1 and V1

^US 281 A-4 ML 10.3 18 NP* NP 2.2 2.7

2^Penn Ave.

A-6 CL 34.9 40 18 22 14.3 6.2

3 ^US 177 A-7-6 CH 36.5 54 20 34 16.8 7.1

5 ^US 81 A-4 ML 14.0 16 NP NP 1.4 2.6

V2 ^SH7 A-6 CL 22.3 35 14 21 11.7 3.8

V3$Kirkland Pawhuska

A-6 CL 28.6 39 17 22 10 12

V4+Hickory

ClayA-7-6 CH 63.6 71 32 39 19.5 11.5

^ Data from Holderby 2010$ Data from Hussey 2010 and Tabet 2012+ Data from Adams 2008 and Campbell 2010*NP – Non Plastic

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 7

Mixed Amount of Stabilizer

0 2 4 6 8 10 12 14 16 18 20

Mea

sure

d S

tabi

lize

r A

mou

nt b

y X

RF

(%

)

0

2

4

6

8

10

12

14

16

18

20

OHC (White = Lime; Black = CKD; Grey = FA)Kirkland-PawhuskaUS 281US SH7

y = .96x+.15; r2 = .9995% Confidence Band 95% Prediction Band

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 8

Stabilizer Regression r2

Combined y=0.96x+0.15 0.99

Lime y=1x+0.05 0.98

CKD y=0.96x 0.99

Fly Ash y=0.96x+0.16 0.98

Validation Results

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 9

Site #1 Site #2 Site #3 Site #4 Site #5

Class C Fly Ash Quick Lime

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 10

Application to Field Sites

Site Number

Soil NameType of

Stabilizer

Design Specified

Content (%)

XRF Determined Content (%)

Predicted XRF

Content from

Validation Study (%)

#1 US 281 CFA 14 15.4 15.7-16.3

#2 Penn Ave. CFA 12 13.4 13.6-14.1

#3 US 177 Quicklime 2.7 2.3 2.0-2.4

#5 US 81 CFA 14 12.2 12.4-12.8

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 11

Conclusions

• The “Whole Rock Analysis” Method using XRF technique could be an extremely useful tool to use for quality control applications or during forensic investigations, where the presence or lack of additive in a stabilized layer is in question.

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 12

Conclusions

• Portable field XRF units seem like a promising method to get a fast and accurate measurement, as well as spatial heterogeneity assessment, of the stabilization of a subgrade before the pavement is laid.

• If problem areas are identified, the subgrade can be remixed and compacted in a timely manner.

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 13

Recommendations

• For projects involving chemical stabilization, samples of additives, untreated soil, and treated soil (after compaction and final grading) should be obtained at three or more representative locations and representing the full design depth of the stabilized layer. • The samples are small and can be retained for

future testing should disputes arise, or they can be incorporated into the quality control program – recognizing the testing times and limitations involved.

University of Oklahoma - School of Civil Engineering and Environmental Science

2013 ODOT – OkTC Research Day, Thursday, September 12 Slide 14

www.geotech.ou.edu

Questions?REFERENCE: Cerato, A.B. and Miller, G.A., “Determination of Soil Stabilizer

Content Using X-Ray Fluorescence,” Geotechnical Testing Journal, Vol. 36, No.5, 2013, pp.781–785, doi:10.1520/GTJ20120186. ISSN0149-6115.