WHITE TOPPING

Presented by P.JAGATH CHANDRA

INTRODUCTION Concrete roads were first built by romans

(300 BC-476AD).Pozzolana cement from the village pozzouli near Italy ,horse hairs as fibres in concrete ,admixtures in their primitive from(like animal fat ,milk & blood).

What is whitetopping ?

Portland cement concrete (pcc) overlay on an existing bituminous pavemant is commonly known as white topping.

Types of white topping

Conventional white topping(CWT) Thin white topping(TWT) Ultra-thin white topping(UTWT)

Conventional white topping

Which consist of PCC overlay of thickness 200mm or more, which is designed & constructed without consideration of any bond between existing overlay & underlying bituminous layer

Thin white topping Which has PCC overlay between 100-

200mm. It is designed either considering bond between overlay & underlying bituminous layer or without consideration of bond.

High strength concrete (M40 or higher) is normally used to take care of flexure requirement.

Joints are at shorter spacing of 0.6 to 1.25m

Ultra-thin white topping (UTWT)

Which has PCC overlay of less than 100mm.bonding between overlay & underlying bituminous layer is mandatory.

Joints are provided at a spacing of 0.6 to 1.25m

ADVANTAGES Reduced thickness Fast –track contraction Reduced maintenance Cost –effective Improved service life Little pre-overlay repairs Improvement in safety Reduction in operational costs and lower

adsorption of solar energy Improving the environmental benefits

DETAILS OF THE PROJCET TESTSS.NO VALVES1 C B R 8 to 102 Commercial vehicles per day 10003 Temp differential at bangalore 17.3 deg C4 Thickness of bituminous layer 4” to 7”5 Base(40mm metal thickness) 4” to 9”6 Road width 100’7 Length of road 350m8 Concrete grade M459 Axle load 16T

DESIGN OF PAVEMENT AND CONCRETE MIX

Design of the overlay was carried out using westergaaed’s equation and warping stress as per IRC: 58-2002 and IRC:SP:76-2008.

Concrete mix design was arrived at by evaluating trial mixes and the design mix was arrived at with a cement content of 430kgs ,fly as-30kgs,W/C ratio of 0.283 achieving a slump of 40-60mm at site

DETAILS OF CONSTRUCTION

Production of concrete in a RMC plant or a dedicated batching plant

Using either fixed from or slip form mechanical pavers

Strict quality control at site including testing of fresh , hardened and extracted specimens of concrete and tests on pavement qulity

SALIENT FEATURES OF CONSTRUCTION

Surface preparation : in case of TWT, bond between PCC overlay & existing bituminous pavement is atleast partly desirable ;

In case of UTWT , effective bond is essential . To ensure this any of the following method can be adopted.

Milling is used to remove surface distortion like cracks in the top portion and adjust cross slopes. Range 25to 50mm

TEST RESULTS

NO SAMPLE SIZE

1-DAY STRENGTH(MPA)

3-DAY STRENGTH (MPA)

7-DAY STRENGTH(MPA)

28-DAY STRENGTH (MPA)

60 CUBES PER TEST

MAX:24.1MIN:21.1AVG:22.05

MAX:48.2MIN:38.4AVG:43.2

MAX:55.2MIN:48.4AVG:51.02

MAX:67.2MIN:57.4AVG:61.8

COMPRESSIVE STRENGTH OF CONCRETE CUBES

NO SAMPLE SIZE 28-DAY STRENGTH(MPA)

60 PER TEST MAX:61.4MIN:43.7AVG:52.45

COMPRESSIVE STRENGTH OF CONCRETE CYLINDER(TOTAL NO. OF SAMPLES 60)

NO SAMPLE SIZE 28-DAY STRENGTH60 per test Max:7.35

Min:6.2Avg:6.3

FLEXURAL STRENGTH OF CONCRETE

NO SAMPLES SIZE 28-DAY STRENGTHQ

60 per test Max:4.01Min:2.92avg:3.36

SPILT TENSILE STENGTH OF CONCRETE

CONCLUSIONSDue to advances in the area of

mechanization and fast track contraction, concrete roads and white topping provide a sustainable as well as cost effective option for pavement contruction.

THANK YOU.