II. PAVEMENT ENGINEERING AND PAVING MATERIALS

2. FLEXIBLE PAVEMENT

A. ON GOING PROJECTS
2. Laboratory Study for Suitability of Chalk, a By-Product of Nitro-Phosphate Fertilizer Plant for Road Construction
Date of Start:

October 2005
(i) Central Road Research Institute, New Delhi (R)
(ii) Rashtriya Chemicals & Fertlizer Limited, Mumbai (S)

 

Present Status and Progress
Report finalization in progress.
 
Findings/ Conclusions
(i) The impure chalk has potential as fine for bituminous mixes and can be used in 3-5 % by weight of aggregates in different bituminous mixes in base course as well as wearing courses such as Bituminous Macadam (BM), Dense Bituminous Macadam (DBM), Semi Dense Bituminous Concrete (SDBC) and Bituminous Concrete (BC).
(ii) The impure chalk can be used in SDBC and BM with emulsion, which can facilitate the construction without heating process and use of chalk in wet condition.
(iii) The use of chalk as a partial replacement of sand did not affect the workability of the mix. The moisture (7.9 %) present in the chalk compensated for the extra water required due to the finer size of chalk than sand.
(iv) Five percent replacement of sand by chalk in Pavement Quality Concrete increased the compressive strength of the concrete at the age of 7 and 28 days. The increase in compressive strength was about 3 and 8 % at 7 and 28 days respectively.
 
Interim Conclusions
Detailed study required and full scale field trials for validation of laboratory results.
 
Recommendations
(i) Detailed studies for suitable utility of impure chalk in bituminous mixes may be undertaken to study the binder oxidation with chalk, rheological behavour of binder with chalk, soil stabilization etc.
(ii) Field trials are required to validate the preliminary laboratory studies and before its use in road construction.
(iii) Impure chalk in damp condition can be used in SDBC and BM with emulsion based cold mix technology, which can facilitate the construction without heating process and use of chalk in wet condition.
(iv) Results of this limited study have indicated that there is some potential of using chalk in both pavement quality concrete and dry lean concrete.