A comparable construction is offered by the creation of the joint intermediate layers and surrounding the manhole top with mastic asphalt with the use of a metal manhole shell .

Mastic asphalt is a dense mass of crushed stones, sand, fillers and road construction bitumens, the mineral compound of which is composed nearly free of cavities. The content of binders is adjusted to the …

In order to include the manhole top into mastic asphalt, the side bedding of the frame of the manhole top as well as the intermediate gap between the frame of the manhole top and the manhole taper is carried out by means of the same material – mastic asphalt.

Mastic asphalt is a good alternative for the rehabilitation of manhole tops due to its sufficient strength and good resistance to loads deriving from frost alternations or from the application …

The application of steel spring elements for the height regulation of manhole tops has the following aims:

• substitution for mortar joints and bearing rings,
• height regulation during operation,
• damping of dynamic traffic loads.

Other processes for re-installation and rehabilitation of manhole tops, in the case of a height levelling with cover removal, have the aims of a relief of the bedding of the frame of the manhole cover by transferring its loads to the bordering carrier layer of the street surface. The purpose of this is to achieve a longer useful life.

Load removal above manhole top

Reinsertion of cover and carrier layer:

• paving the frame by casting the joints with bitumen
• inclusion with mastic asphalt without and with the application of meltable or self-adhesive bitumen joint strips

Example: Paving the frame by casting the joints with bitumen

Bitumen joint strips serve to improve the connection between different materials, e.g. "splittmastix" and mastic asphalt and thus to prevent the formation of cracks and opening seams.

For conventional bitumen joint strips, an even edge is required as contact area [ZTVFugStB01]. The removal of the surrounding cover and carrier layer should be carried out by milling and boring. Before the joint strip is applied, the edge must be cleaned and pre-treated …

One of the most frequent rehabilitation failures is the use of mortar systems of unsuitable compositions and/or their unprofessional application on the construction site.

The reason for this is that the different types of cement mortar applied in practice have significantly different material properties. This regards especially insufficient resistances to frost-dew changes and/or frost and thawing salts.

Possible sources of …

The compound of the old and new concrete frequently represents a weak point. Therefore, it is advisable to dowel the new step irons into the manhole wall instead of cementing them in. This leads to a better compound of the new step iron and the existing manhole wall. That is why a dowelled step iron can bear higher loads than a cemented one.

Damages according to DIN EN 13508

• damaged steps (DAQ)
  • loose …

The dowels should be of stainless steel, steel group A4 according to DIN EN ISO 3506 [DINENISO3506-1:1998]. The corresponding bolted joint is described in DIN 1211-3 [DIN1211-3:2003] and 1212-3 [DIN1212-3:2003]. In order to guarantee the tightness of the manhole wall, it must either not be drilled through or the dowels must be inserted into plastic-modified mortar.

With reinforced …

When the step irons are directly cemented in by means of plastics-modified mortar, the ground must be thoroughly cleaned and be provided with an adhesive layer.

In all cases it must be made sure that the material, the shape and step height per manhole are standardised and that, from a static point of view, the condition of the manhole wall allows for a replacement.

Measures for the restoration of defective regions in the inside of sewers of concrete, reinforced concrete and pre-stressed concrete have the aim, depending on the selected repair grout, among others of [DAfStBb] :

• The maintaining and replacement of the corrosion protection of the reinforcement;
• Replacing / supplementing the concrete cross section with or without requirements of stability;
• Replacing or increasing the resistance of the concrete surface …

Suitable materials for the repair of reinforced and un-reinforced concrete pipes are:

• Cement grout, concrete, spray concrete (Cement Concrete - CC);
• Plastics-modified cement grout (Polymer Cement Grout - PCC);
• Reaction resin grout (Polymer concrete - PC) based on epoxy resins, unsaturated polyester resins, polyurethane or polymethyl-acrilate resins.

An in-between position between cement and reaction resin grouts is occupied by the mineral grouts with water emulsion epoxy resin additives, whose hardening properties depend to a great extent on the exact agreement of the speed of the reaction of both binder materials [BDZ89].

Although the repair grouts are disadvantaged in comparison with concrete due to a lower modulus of elasticity for damage elimination measures that require a static participation, they are normally advantageous due to their greater ability to deform for protective measures for ensuring durability and utility in the near-surface region.

Plastic-modified cement grout (PCC) and reaction resins (PC)

Cement-bound grout
 

For repairs that only affect the …

Concrete surfaces that are to be the foundation for a repair measure must always consist of undamaged concrete, i.e. they must be free from dirt, old paints that cannot carry loads, floury fine grout layers and all other substances that can reduce a bonding effects (e.g. damaging salts such as sulphates, nitrates).