state-of-the-art on design and construction of...

“Gh Asachi” Tehnical University of Iasi FACULTY OF CIVIL ENGINEERINGFACULTY OF CIVIL ENGINEERING

State-of-the-art on design and construction of LLRP


Road concrete projects with extended life has been achieved based on significant changes in:

- materials and concrete technologies- overall pavement thickness design- construction requirements- validation of performance by using Accelerating Load Testing -ALT facilities


Road projects with extended life concrete designs

Long-life concrete pavements have been attainable for a long time (an important number of very old pavements are still in service).

Significant approaches:

Increase the specified aggregate size from 19 mm to 32 mm /or 15 to 25mm, to improve flexural strength without significant increases in cement content.

Devise these layers within the one-slipformed layer rather than a multilayer approach that might lead to delamination.

Continue to provide incentives to contractors to encourage pavements to be constructed to lower tolerances or to better medium-term performance measures.

Road authorities are supporting training of engineers and paving crews to promote the adoption of best practices.


Road projects with extended life concrete designs(European Experience)

Project E5 Brussels–Liège : a significant example of a motorway construction, with extended life pavement , in service for 34 years.

-Traffic intensity: 112,000 vehicles per day ( year 2000) with 14 percent heavy traffic

- Low Maintenance during the first 30 years: replacing the joint fillings

-Road pavement structure still in good condition, no structural maintenance or renewal is planned yet, expected life span of 40–50 years.


Structure of E5 motorway : continuously reinforced concrete comparison to an asphalt structure


Defining the concept of long life rigid pavements LLRP

The concept of Long Lasting Rigid Pavements can be defined only in conjunction with the world wide evolution of modern paving in terms of design, materials, specification and construction, maintenance


LIFE CYCLE COSTING—CONCRETE VERSUS ASPHALTStudy undertaken looking at maintenance costs of concrete

pavements compared with asphalt pavements (AC) length on a main highway (Australia).

Comparative maintenance costs between Asphalt, PC and CRC Pavements

Low-maintenance costs are indicative of long-life pavements.


The quality of the concrete is a major factor in seeking long-term performance.

Evolution of coefficient of variation data on paving projects from 1975 to 2005 in Australia


Improvements in overall pavement thickness design :

Besides the increase of the minimum recommended thickness, the fallowing aspects have been also reconsidered in the design of long – life concrete pavements:

Developing more refined thickness design procedure

Change from nomographs to computer programs and spreadsheet analysis in order to reduce human error.

Increase the skew to transverse contraction joints from 1:6 to 1:10.

Better collection of heavy traffic data provided better input into fatigue analysis.

Minimum base layer thickness for different pavement types have been introduced in the last years.

Development of various design catalogues for heavy-duty pavements.


Improvements in construction requirements

Tolerance for thickness and strength was modifiedto ensure that more of the pavement was built above the minimum limit rather than an average around the design requirement.

Better preparation of materials, reduced the risk of construction.

Significant improvements to the slipform pavers and better training of staff at all levels conducted prior to construction.


Accelerating loading test (ALT) for validation of various LLRP options

ALT –LIRA track test (COST 347 –Improvements in Pavement Research with Accelerated Load testing – Final Report,

2005)


Typical Rigid Pavements

&

Materials, technologies and experiences on

design and construction of extended life concrete pavements around the world



Jointed Plain Concrete Pavement (JPCP)

* Jointed plain concrete pavement is the most common type of rigidpavement.

* JPCP controls cracks by dividing the pavement up into individual slabs separated by contraction joints. Slabs are typically one lane wide and between 3.7 m and 6.1 m long.

* JPCP does not use any reinforcing steel but does use dowel bars and tie bars.



Jointed Reinforced Concrete Pavement (JRCP)

* Jointed reinforced concrete pavement controls cracks by dividing the pavement up into individual slabs separated by contraction joints.

* Jointed reinforced concrete pavement uses contraction joints and reinforcing steel to control cracking within the slab;

* Dowel bars are typically used at transverse joints to assist in load transfer while the reinforcing steel/wire mesh assists in load transfer across cracks.



Full-scale Continuously Reinforced Concrete Pavement (CRCP)* Continuously reinforced concrete pavement uses reinforcing steel rather than contraction joints for crack control. Continuously reinforced concrete pavement does not require any contraction joints.

* Cracks typically form at intervals of 1.1 - 2.4 m. Reinforcing steel usually constitutes about 0.6 - 0.7 percent of the cross-sectional pavement area and is located near mid-depth in the slab.


Recent Advances in Concrete Technology favourable to the development of Long Life Rigid

Pavements

High Performance Concrete

* High Performance Concrete (HPC) may be defined as any concrete that provides enhanced performance characteristics for a given application such as substantially improved durability under severe service conditions, extraordinary properties at earlier ages, or better mechanical properties

* These type of concrete may contain materials such as fly ash, granulated slags, fibres, chemical admixtures, and other materials, individually or in various combinations.


Potential applications of HPC

Concrete Type Potential

Applications VES

(A)

VES

(B) HES VHS

New pavement X X

Full-depth pavement patch X X X

Pavement overlay X X X X

New bridge deck X X

Full bridge deck replacement X

Bridge deck overlay X X X

Bridge girders X X

Precast elements X X X

Prestressed piles X X X

Columns and piers X X


Recent Advances in Concrete Technology favourable to the development of Long Life Rigid Pavements

Fibre Reinforced Concrete Pavements

* Fibre-reinforced concrete (FRC) is made of hydraulic cements containing fine or fine and coarse aggregates, and discontinuous, discrete fibres. Fibres used in concrete pavements are typically made from steel or plastic and are available in a variety of lengths, shapes, sizes, and thicknesses. They are added to fresh concrete during the batching and mixing process.

* Advantages to reinforcing concrete with uniformly dispersed and randomly oriented fibres, including improvement in ductility, impact resistance, tensile and flexural strength, fatigue life, durability and abrasion resistance.


Polymer fibre reinforced concrete pavements

Synthetic Fibres for concrete pavements

The most commonly used synthetic fibres in concrete pavements are made of fibrillated polypropylene. They are normally used inconcrete at a rate of at least 0.1% by volume. According to relative recent SHRP research, it was found that mixtures containing 1 or2% by volume of propylene fibres showed deterioration in compression stress-strain response when compared with the control mixture


Steel fibre reinforced concrete (SFRC)

SFRC with steel fibres industrial produced

The most significant effect of incorporating steel fibres in concrete is to delay and control the tensile cracking of concrete. These properties, besides the increased resistance to impact and repeated loading, make SFRC an adequate material for pavement construction.

Steel fibres: with hooks (left) and crimp-shaped (right)


Potential applications of SFRC

Steel fibres reinforced concrete can be used for reinforcementof existing deteriorated Portland Cement Concrete Pavements

(PCC Pavements)

Full scale experiment was carried out in Great Britain, on a length of reinforced concrete carriage way on the M10 Motorway( three fibre contents have been

used:2.7, 2.2 and 1.3 per cent by weight

*Steel fibres reinforced concrete used for new SFRC pavements

Jowa USA exeperiment (1973):Three fibre contents 35, 59 and 94 kg/m3 – and two overlay thickness-2 and 50 and 75 mm – were considered.


Recent Advances in Concrete Technology favourable to the development of Long Life Rigid Pavements

Roller Compacted Concrete (RCC)Roller compared concrete (RCC), is a composite

material made from the combination of three main constituents: aggregates, water and binder, that are the same as for conventional concrete, but are mixed with different proportioning resulting to a material with distinctive properties and behaviour.


Distinction between the different types of concrete based on the cement content and water ratio


Options for the LLRP structural concepts envisaged for the EcoLanes

Project


Options for the LLRRP structural concepts envisaged for EcoLanes Project

Option A1: the rigid pavement structure is composed by a slab constructed from steel fibres reinforced concrete (SFRC) surfacecourse, having a reinforcement percentage resulted from previouslaboratory study conducted for SFRC mix design, laid on cement stabilized or low-strength concrete base course.

Cement stabilized base course

SFRC surface

Subgrade/improved subgrade

Subbase (Foundation layer)



Option A2: the rigid pavement structure is composed by a slab constructed from steel fibres reinforced concrete (SFRC) surfacecourse, having a reinforcement percentage resulted from previouslaboratory study conducted for SFRC mix design, laid on a relative thin asphalt layer constructed over a base course granular supported by a classic foundation.


Subbase (Foundation layer)

Granular base course

SFRC surface

Intermediate asphalt layer


Options for the LLRRP structural concepts envisaged for EcoLanes ProjectOption B - two-lift construction.Option B1: a concrete slab realised by two lift construction from a SFRC surface course with a percentage by weight of reinforcing fibre resulted from laboratory studies, and having a minimum thickness of 6cm, and a Portland cement concrete (PCC) base course. This concrete slab is laid on a cement stabilised subbase supported by a classical foundation and subgrade or improved subgrade.


Foundation layer

Cement stabilized subbase

SFRC surface

PCC base



Option B2: a two-lift constructed concrete slab, both layers from SFRC, with different reinforcement percentages by weight (for example, minimum 2.0% for the upper layer, and minimum 1% for the bottom layer). This slab will be laid on a cement stabilized or a low strength concrete subbase course, supported by a classical foundation and subgrade or improved subgrade.


Foundation layer

Cement stabilized subbase

SFRC surface, min 2%

SFRC surface, min 1%



Option B3: a concrete slab realised from a SFRC surface layer, of a minimum 6 cm thickness and a RCC layer, laid on a granular base course, supported by a classical foundation and a subgrade or improved subgrade.


Foundation layer


SFRC surface

RCC layer


Options for the LLRRP structural conceptsenvisaged for EcoLanes Project

Option B4: a concrete slab realised from a SFRC surface layer, of a minimum 6 cm thickness and a FRRCC (Fibre Reinforced Rolled Compacted Concrete) layer, laid on a granular base course, supported by a classical foundation and a subgrade or improved subgrade.


Foundation layer


SFRC surface

FRRCC layer



Option C: composite pavement structuresOption C1: a bituminous surface course is laid on a RCC (Rolled Compacted Concrete) base, supported by a granular base course, a classical foundation, and a subgrade or improved subgrade.


Foundation layer


Asphalt surface

RCC layer



Option C2: the bituminous surface course is laid on a SFRRCC (Steel Fibre Reinforced Rolled Compacted Concrete) base, supported by a granular base course, a classical foundation, and a subgrade or improved subgrade.


Foundation layer


Asphalt surface

FRRCC layer


Thickness design methods envisaged for the EcoLanes Project

Thickness design methods – general considerations- Empirical design methods- Mechanistic – empirical methods

Several design methods have been developed over the years, some of which are based on the results of full-scale road tests, others on theoretical developments on stresses on layered systems and others on the combination of the results of tests and theoretical developments.

However, for the objective of the Ecolanes project, seeking the development of the LLRP concept, at least three methods are envisaged to be used for each option, except for option C, which is considered as a composite structure.


Empirical design methods

* The American Association of State Highway and Transportation Officials (AASHTO-1993)

* The Portland Cement Association (PCA)


Mechanistic – empirical methods

* NCHRP Mechanistic –Empirical Design Method ( USA-2004)

* The Highway Agency Design Method ( UK-2006)

* Rigid Pavements Design ( Romanian Standards: NP 081 – 2002)


Thickness design methods envisaged for the EcoLanes LLRP options

For each of the envisaged A and B options, mentioned before at least three alternative methods of thickness design, including the Romanian method, are intended to be used.Finally the best fitted one will be selected, taking into consideration various extensions of design life, based on technical and economical criteria, in order to be proposed for the various EcoLane demo projects.


Thickness design methods envisaged for the EcoLanes LLRP options

For options C, by adopting the assumptions that, between the asphalt surface and the concrete base there is no bonding, it ishighly recommended that, for the thickness design of the whole structure, the design studies to be conducted separately for each layer, according the specific existing norms (Romanian and other), as fallows:

- concrete base: “Technical Norm for Structural Design of Concrete Base for Pavements”, NP 111-04, 2005 [55] and Ecolanes internal reports recommendations.

- Asphalt Institute Design Method and the Romanian method will be used, for the asphalt surface layer.


Other Romanian norms intended to be used :

Construction of plain, reinforced and prestressed concrete pavement layers (NE - 012 – 1999),

Construction of PC pavement layers with fixed and sliding forms (NE – 014 – 2002),

Design of rigid pavements (NP 081 – 2002)

Code of practice for establishing the performance criteria and composition of SFRC (GP 075 – 2002)


Conclusions & Recommendations

* Concrete base with a minimum compressive and flexural strength of 35 MPa and 4.5 MPa, respectively, at 28 days age are strongly recommended ;

* It is recommended to use of concrete tied shoulders with a width of 2 to 3 m in the curb lane and 0.6 m in the median lane.

* It is recommended to provide appropriate joint layout , in order to reduce corner stresses and to allow heavy vehicles to travel in the “middle” of the slab.

* It is recommended to provide a stabilized upper formation to provide a sound long-term support.

.


Conclusions & Recommendations

* It is recommended to provide a thin layer of 100 mm of HMA (High Mixed Asphalt) over 100 mm of aggregate base in order to limit base deflection and pumping.

* The original concrete pavements omitted dowel bars; however, they are now consistently recommended to be used to minimize faulting potential.

* The lengthy life and maintenance impacts may make alternate concrete surfaces such as SFRC and prestressed concrete more attractive than they are under current design concepts.

state-of-the-art on design and construction of...

Documents