Profundidad de campo en cámaras Scheimpug

Concrete shall be of the grade shown on the Drawings and shall comply with the relevant requirements of Section 9 of this Specification.

5.3.2 Equipment

All equipment used such as batching plant and mixers shall comply with the relevant requirements of Section 9 of this Specification.

5.4 CONSTRUCTION

5.4.1 Preparation of Subgrade or Subbase Prior to placing concrete pavement, the underlying subgrade or subbase shall have been shaped and

compacted in accordance with the provisions of Sub-Sections 2.2.7 or 4.1.2 as appropriate and the waterproof membrane laid as required in the Drawings.

Notwithstanding any earlier approval of finished subgrade or subbase, any damage to or deterioration of the subgrade or subbase shall be made good to the satisfaction of the S.O.

before the waterproof membrane is laid and the concrete pavement constructed.

5.4.2 Construction by Machine The concrete slab shall be

constructed either by fixed form or by slip form paving plant in a continuous process in either one or two layers, as approved by the S.O.

Prior to the placing of concrete, all of the required joint assemblies such as dowel bars, tie bars, etc., shall be installed in accordance with the requirements of Sub-Section 5.5. In one-layer construction, the slab reinforcement shall also be installed and fixed in accordance with the relevant requirements of Section 9.

In two-layer construction, the thickness of the top layer shall be not less than 50 mm or twice the maximum size of the coarse aggregate, whichever is the greater, and shall be at least 15 mm thicker than the depth of the groove former, if used. Placement of reinforcement and concreting of the top layer shall be done immediately, and in any case not more than 30 minutes, after the completion of the bottom layer.

5.4.2.1 Fixed Forms, Rails and Guide Wires For Machine Construction (a) Fixed Forms and Rails All forms and rails shall be made of steel and be sufficiently robust and rigid to support the weight and pressure caused by the paving equipment. Side forms for use with wheeled paving machines shall incorporate metal rails firmly fixed at a constant height below the top of the forms.

The forms shall be secured by using not less than three pins for each 3 m length, having one pin fixed at each side of every joint.

Forms shall be tightly joined together by a locked joint, free from play or movement in any direction.

Forms shall be cleaned and oiled immediately before each use.

The rails or running surfaces shall be kept clean in front of the wheels of any paving machines.

The forms shall be straight within a tolerance of 3 mm in 3 m.

The forms shall be bedded on low moisture content cement mortar and set to the pavement surface level as described in the Contract within a tolerance of ±3 mm. The bedding shall not extend under the slab. There shall be no vertical step between the ends of adjacent forms greater than 3 mm. The horizontal alignment for forms shall be to the required alignment of the pavement edge as described in the Contract within a tolerance of

±10 mm. The mortar or

concrete bedding shall be broken out after use.

Prior to concreting, the forms shall be approved by the S.O.

Forms shall not be removed earlier than 6 hours after the completion of the construction of the slab. Care shall be taken to prevent damage to the concrete and any projecting tie bars during the removal of the forms. If the removal of forms results in any damage to the concrete the period of 6 hours shall be increased to that which is necessary to avoid further damage and the

Contractor shall make good the damaged areas.

b) Guide Wires

Unless otherwise agreed by the S.O., a guide wire shall be provided along each side of the

form paving plant. (Each guide wire shall be at a constant height above and parallel to the required edges of the slab within a vertical tolerance of ±3 mm. In addition, one of the wires shall be at a con stant horizontal distance from the required edge of the pavement within a lateral tolerance of ±10 mm.

The guide wires shall be supported from stakes not more than 8 m apart by connectors capable of fine horizontal and vertical adjustment. The guide wire shall be tensioned on the stakes so that a 500 gramme weight shall produce a deflection of not more than 20 mm when suspended at the mid-point between any pair of stakes. The ends of the guide wires shall be anchored to fixing points which shall be not closer to the edge of the slab than the row of stakes and in no circumstances shall a guide wire be anchored to a stake.

The stakes and guide wires shall be checked and approved by the S.O. prior to concreting.

5.4.2.2 Construction by Fixed Form Paving Machine

A fixed form paving train shall consist of separate powered machines which spread, compact and finish the concrete in a continuous operation.

Concrete shall be discharged without segregation into a hopper spreader which is equipped with the means to control its rate of deposition on to the subbase or on to the lower layer. . The con

without segregation and to a uniform uncompacted density over the whole area of the slab.

The deposited concrete shall be struck off to the necessary level by the underside of the hopper as it is traversed across the

spreading machine. The machine shall be capable of being rapidly adjusted for changes in average and differential surcharge necessitated by changes in slab thickness or crossfall.

Prior to being compacted, the surface level of each loose spread layer shall be adjusted to the correct surcharge by means of rotating strike off blades or a screw device.

The concrete shall be compacted by vibration or by a combination of vibration and mechanical tamping so as to comply with Sub-Section 5.3.1 throughout the full depth of the slab. Poker vibrators shall be used adjacent to the side forms and the edge of previously constructed slabs.

The initial regulation and finish to the surface of the slab shall be effected by means of a beam oscillating transversely or obliquely to the longitudinal axis of the pavement. This beam shall be readily adjustable for both height and tilt.

Joint grooves shall be constructed in compliance with Sub-Section 5.5. The concrete shall be recompacted around the former by a hand held vibrating plate compactor drawn along or on each side of the joint, prior to regulation of the surface by the

The regulation and finishing of the surface of the slab shall be carried out by a machine which incorporates twin oblique oscillating finishing beams which shall be readily adjustable for both height and tilt. The beams shall weigh not less than 170 kg per linear metre, be of rectangular section and span the full width of the slab. The leading beam shall be vibrated. The beams shall be supported on a carriage, the level of which shall be controlled by the average level of not less than four points evenly spaced over at least 3.5 m of the supporting rail, beam, or slab, on each side of the slab that is being constructed.

The final regulation and surface finishing of the slab shall be carried out after any wet forming of joint grooves. After the final regulation and before texture is applied, any excess concrete on top of the groove former shall be removed.

When a concrete slab is constructed in more than one width, flanged wheels on the paving machines shall not be run directly on the surface of any completed part of the slab. The second or subsequent slabs shall be constructed either by

supporting machines with flanged wheels on flat- bottom section rails weighing not less than 15 kg/m laid on the surface of the completed slab, or by replacing the flanged wheels on that side of the machine by smooth flangeless wheels. Before flangeless wheels or rails are used, the surface regularity of the slab over which they are to pass shall comply with Sub-Section 5.4.1 and its

all extraneous matter. Flangeless wheels or rails shall be positioned sufficiently far from the edge of the slab to avoid damage to that edge.

5.4.2.3 Construction by Slip Form Paving Machine

A slip form paving train shall consist of powered machines which spread, compact and finish the concrete in a continuous operation.

A slip form paving machine shall compact the concrete by internal vibration and shape it between sliding side forms or over fixed side forms by means of either a conforming plate or by vibrating and oscillating finishing beams.

The concrete shall be deposited without segregation in front of the slip form paver across its whole width and to a height which at all times is in excess of the required surcharge. The deposited concrete shall be struck off to the necessary average and differential surcharge by means of a strike-off plate or a screw auger device extending across the whole width of the slab. The equipment for striking off the concrete shall be capable of being rapidly adjusted for changes in the average and differential sur charge necessitated by changes in slab thickness or crossfall.

The level of the conforming plate and finishing beams shall be controlled automatically from the guide wires by sensors attached at the four corners of the slip form paving machine. The alignment of the paver shall be

guide wires by at least one sensor attached to the paver. The alignment and level of ancillary machines for finishing, texturing and curing of the concrete shall be automatically controlled relative to the guide wires or to the surface and edge of the slab.

Slip form paving machines shall have vibration of variable output, with a maximum energy output of not less than 2.5 kW per metre of slab per 300 mm depth of slab for a laying speed of up to 1.5 m per minute or pro rata for higher speeds. The machines shall be of sufficient mass to provide adequate reaction on the traction units to maintain forward movements during the placing of concrete in all situations.

Joint grooves shall be constructed in compliance with Sub-Section 5.5. The concrete shall be compacted around the former by a separate vibrating plate compactor with twin plates. The groove former shall be

compacted to the correct level by another vibrating float which may be included with the transverse joint finishing beam. In addition a hand held vibrating float, at least 1 m wide, shall be drawn over the surface along the joint.

Any excess concrete on top of the groove former shall be removed before the surface is textured.

Where a concrete surface slab is constructed in more than one width or where the edge needs to be matched for level to another section of surface slab, and the surface levels at the edges are not achieved, paving shall be carried out over separate fixed side forms supporting the edge to the

5.4.3 Construction by Hand-Guided Method

Areas to be constructed by hand-guided method shall be agreed with the S.O. The slabs shall be

constructed in one layer. Dowel bars, tie bars and reinforcement, if specified, shall be fitted in position as shown on the Drawings.

The concrete shall be spread uniformly without segregation or varying degrees of precompaction, by conveyor, chute or by other means approved by the S.O. The concrete shall be struck off by a screed so that the average and differential surcharge is sufficient to ensure that after compaction the surface is to the required level.

The concrete shall be compacted by vibrating finishing beams. In addition, internal poker vibration shall be used for slabs thicker than 200 mm and may be used for lesser thicknesses. When used, the pokers shall be at points not more than 500 mm apart over the whole area of the slab, and adjacent to the side forms or the edge of a previously

constructed slab.

The surface shall be regulated and finished to the level of the top of the forms or adjacent slab or pavement layer by using twin vibrating finishing beams. The beams shall be metal with a contact face at least 50 mm wide and a vibrating unit having a minimum centrifugal force of 4 kN with a frequency recommended by the manufacturer or an equivalent compactive effort. The vibrating beams shall be moved forward at a steady speed of 0.5 m to 1 m per minute whilst vibrating over the

Details of joints shall be as shown on the Drawings. Joint grooves shall be constructed in compliance with Sub-Section 5.5. Any irregularities at wet formed joint grooves shall be rectified by means of a vibrating float at least 1.0 m wide drawn along the line of the joint. The whole area of the slab shall be regulated by two passes of a scraping straight edge not less than 1.8 m wide or by a further

application of a twin vibrating finishing beam. Any excess concrete on top of the groove former shall be removed before the surface is textured.

The surface shall be brush-textured as described in Sub-Section 5.6.

The concrete shall be cured in compliance with Sub-Section 5.8.

5.4.4 Manual Construction

Areas to be constructed by manual method shall be agreed with the S.O.

The slabs shall be constructed in one layer. Dowel bars, tie bars and reinforcement, if specified, shall be fixed in position as shown on the Drawings.

The concrete shall be spread uniformly without segregation or varying degrees of pre-compaction, by conveyor, chute or by other means approved by the S.O. The concrete shall be struck off by a screed so that the average and differential surcharge is sufficient to ensure that after compaction the surface is to the required level.

The concrete shall be compacted by internal poker vibrator or other means approved by the S.O. The

area of the slab, and adjacent to the side forms or the edge of a

previously constructed slab.

The surface shall be regulated and finished to the level of the top of the forms or adjacent slab or pavement layer by using an approved portable hand screed. The screed shall be at least 600 mm longer than the width of the slab to be struck off and compacted. It shall be of approved shape, sufficiently rigid to retain its shape and constructed either of metal or of other material shod with metal.

Compaction shall be attained by raising and dropping the screed in successive positions until the required compaction and reduction of surface voids is secured.

The screed shall then be placed on the forms and slid along them, with out lifting, in a combined

longitudinal and transverse shearing motion moving always in the direction in which the work is progressing. If necessary, this shall be repeated until the surface is of uniform texture, true to grade and contour, and free from porous areas.

After the concrete has been struck off and compacted, it shall be further smoothed, screeded and compacted by means of a longitudinal hand float or other equipment as approved by the S.O.

Details of joints shall be as shown on the Drawings. Joint grooves shall be constructed in compliance with Sub-Section 5.5. Any irregularities at wet formed joint grooves shall be rectified by suitable means approved by the S.O.

The concrete shall be cured in

As soon as surplus water has risen to the surface, the pavement shall be given a broomed finish.

5.4.4.1 Side Forms for Manual Construction

All side forms shall be made of steel and be sufficiently robust and rigid to withstand

construction forces. Timber forms shall only be used for work which is less than 200 m in length.

The forms shall comply with other requirements of Sub-Section 5.4.2.1 as appropriate.

5.5 JOINTS

Joints shall be constructed as specified herein and/or as directed or approved by the S.O. Before any joint materials are set in place, the underlying pavement course at those locations shall have been approved by the S.O.

Preformed expansion joint filler shall be placed around each structure which extends into or through the pavement over the full interface with the concrete pavement slab before concrete is placed.

5.5.1 Transverse Expansion Joints

The components for each transverse expansion joint shall be assembled in advance and placed in position as a unit.

Each assembly shall consist of an installing template, preformed joint filler of the required dimensions in a single piece, dowel bars and sleeves of the required sizes and lengths at the required locations, and spacing and supporting elements for the dowel bars, as shown on the

The installing template shall be metal plate of adequate rigidity approved by the S.O., cut to the required depth and crown of the slab and having a length 10 mm less than the required length of the joint. It shall be slotted from the bottom as necessary to permit removal.

Suitable means shall be provided on the template for facilitating its removal.

One half length of each dowel bar shall be thoroughly coated with a 200 pen bitumen blended with creosote oil or other material as approved by the S.O. A dowel sleeve shall be fitted on to the coated end of each dowel.

The dowel supports shall be constructed so as to hold dowels in correct alignment, both vertically and horizontally, subject to a tolerance of not more than 1 in 100.

When assembled, the top of the installing template shall be about 5 mm above the top of the preformed filler. The filler shall be vertical and shall be in a plane at right angles to the centre line of the road, subject to a tolerance of not more than 1 in 500.

The joint assembly shall be placed so that the installing template is on the side of the filler remote from pouring operations. The top of the filler shall be 10 mm below the required con crete surface, and the bottom shall rest on or extend slightly into the underlying pavement course. The assembly and its installation shall have been approved by the S.O.

before any concrete is placed against it.

Stakes for supporting the installing template shall be of a cross-section and length satisfactory to the S.O.

5.5.2 Transverse Contraction Joints Transverse contraction joints shall consist of planes of weakness created by forming or cutting grooves in the surface of the pavement and, when shown on the Drawings, shall include load transfer dowel bar assemblies.

5.5.2.1 Planes of Weakness (a) Sawn Grooves

When sawn grooves are specified they shall be sawn in the con crete after its initial set.

Grooves shall be at right angles to the centre line of the

pavement, shall be true to line and shall have the width and

pavement, shall be true to line and shall have the width and