Hydrated Lime Test of Extracted HMA Using FTIR

Item #: 20240062

CONTACTS

Implementing Organization: Central Materials
Implementation Lead: Radha Ukkiramapandian
Development Team: Radha Ukkiramapandian, Chemistry and Cement Lab Supervisor, UDOT Central Materials Lab

Article Written By: Radha Ukkiramapandian
Innovation Team Coordinator: Quinten Klingonsmith

STATUS

Implementation Date: November 01, 2023
Adoption Status: Fully Implemented
Adoptability Note: Are you using this method to test for lime in your HMA samples?

APPLIES TO

Topic: Construction Practices
Organization(s): Central Construction, Central Maintenance / Facilities Management, Central Materials, Central Preconstruction, Performance and Asset Management, Policy / Legal, Region 1, Region 2, Region 3, Region 4, Research and Innovation, Structures
Job Role(s): Construction Engineer, Materials Engineer, Program Director, Program Manager, Program Specialist, Roadway Operations / IMT
Tags: highway transportation, capital productivity, infrastructure preservation, materials, employee empowerment, economic benefits, expenses, expenditures, inventions, ( process improvement ), contract administration > bids, contracting, solicitations, contracts, ( RFP, FRQ ), governance > auditing, policy making, procedures, compliance, law, ( legal ), Fourier Transform Infrared (FTIR) spectroscopy, Attenuated Total Reflectance (ATR), civil engineering, chemistry, industrial engineering, materials science, asset management, construction, contracting, design, inspection, maintenance, testing > samples, sampling, toluene, trichloroethylene, Federal Highway Administration (FHWA), quality of life

PROBLEM

Lime (calcium hydroxide) is used in Hot Mix Asphalt (HMA) pavement to improve its binding and mechanical properties and to limit damage due to moisture. UDOT needed a testing method to ensure that contractors were using the required 1% lime according to our HMA pavement specification.

The Federal Highway Administration (FHWA) has published a test for lime using Fourier Transform Infrared (FTIR) spectroscopy with an Attenuated Total Reflectance (ATR) accessory. The advantage of this method is that it does not require the extraction of lime from the asphalt mixture.

However, since the lime present in HMA is only around 1% and only a small amount of samples can be loaded in the ATR it is challenging to test very small amounts of lime in HMA samples using this method. Testing older samples using this method is even more challenging because slowly over time lime is converted to limestone (calcium carbonate) in the presence of air.

CHANGE

The UDOT Chemistry & Cement Lab modified the existing FHWA test method by extracting HMA with toluene solvent and testing the extract using FTIR. They attempted to extract the HMA with acetone, methanol, trichloroethylene, and toluene and found that both toluene and trichloroethylene worked.

In this modified method, the lab can confirm the presence or absence of lime-containing samples very clearly, even in small samples of aged pavement.

RESULT

Extraction of HMA with toluene solvent allows the lab to load more samples in the sampler which results in the formation of a larger peak at the 3640 cm-1 wavenumber for hydrated lime and a separate peak at 1390 cm-1 for limestone.

Another advantage is that the test can be performed with the existing FTIR instrument without the requirement of any additional accessories like ATR.

UDOT’s test procedure more effectively and efficiently ensures the proper inclusion of lime in our asphalt pavements which reduces moisture susceptibility, improves the binding of aggregates, resists rutting, improves toughness, improves oxidation of binders, and increases the longevity of HMA pavements. Improving the life of roads will save millions of dollars for UDOT and taxpayers alike.

Next Steps: Now that UDOT knows how to test for the presence of lime in HMA paved roads, the next step is to make improvements to this testing method and to measure quantitatively the total amounts of lime in HMA pavements.

IMPACT

BETTER MOBILITY

The federal highway and Nevada DOT studies conclude that the presence of lime in HMA increases pavement lifetime by 38%
Roads that require less maintenance provide better overall mobility

GOOD HEALTH

CONNECTED COMMUNITIES

STRONG ECONOMY

Extending the service life of roads by ensuring they are constructed correctly will save millions
According to the National Lime Association, using lime results in savings of about $20 per ton of HMA (10% cost saving)

Page updated

Report abuse