• Resistance to rutting and other deformations of pavement.
• Improve the properties of marginal materials so they can be used instead of premium quality aggregates.

• In-situ stabilisation of modified pavement layers (TNZ B/5)
• In-situ stabilisation of bound sub-base layers (TNZ B/6)
• Manufacture and construction of plant mixed modified pavement layers (TNZ/B7)
• Manufacture and construction of plant mixed bound sub-base pavement layers (TNZ/B8)

More details on cement stabilisation specifications can be found on the NZTA website.

1. Modified: typically <2% cement
   Normally used as an intermediate option, it bridges the gap between an unmodified and structural pavement for improving resistance to deformation and rutting. Other benefits include enabling the use of lower quality aggregates or in-situ recycled materials.
2. Bound: typically >3% cement
   This is normally used to provide a sub-base with high strength over a weak substrate to support the overlying chip seal surfacing on thick asphalt pavement layers. It’s also commonly used under rigid concrete pavements and on high volume or heavily loaded roads.

1. Cement is placed on top of a pre-dampened granular layer or existing road and then mixed in to a specified depth. 
2. Extra water is then applied from a following truck to provide the water needed to hydrate the cement. 
3. Finally, the layers are compacted by several passes of a vibrating roller.

In-situ cement stabilisation is common for pavement rehabilitation and can be used for new pavements using imported granular materials. However, additional coarse aggregate and cement may be needed to allow for breakdown of aggregates.

Laboratory testing of the hoed material is recommended to ensure that the cement stabilised material achieves the required strength.

Plant Mix

Plant mix is produced either by continuous feed mixing or in a pugmill at static mixing plants. Electronic weighing systems and automated batching improve control over the mix proportions of aggregates, binders, water and additives.

Plant mix provides tighter control of batch quantities than in-situ mixing, meaning it’s more suitable for new modified base course layers.

Plant mix needs to be placed within two hours of manufacture.

Cement and water can be blended with the aggregate on site or at a separate processing plant.

In-situ concrete stabilisation: mixing cement and water in place.

The Transfund New Zealand Pavement Evaluation Manual is the approved framework for economic calculation of the merits of road works. The list of areas associated with the calculation which affect measures of concrete pavements and the competing flexible pavement options include:

• Discount rate, analysis period and initial cost
• Future pavement maintenance assumptions
• Pavement rigidity effects and surface texture on rolling resistance and fuel consumption
• Tyre/surface noise generation
• Carbon dioxide emissions
• Travel time savings during maintenance activities and early completion

1. Jointed Plain Concrete Pavement (JPCP) contains enough joints to control the location of all natural cracks. Jointed plain pavements do not contain any steel reinforcement. However, there may be smooth steel bars at transverse joints and deformed steel bars at longitudinal joints.
2. Jointed Reinforced Concrete Pavement (JRCP) contains steel mesh reinforcement. In jointed reinforced concrete pavements, designers increase the joint spacing purposely, and include reinforcing steel to hold together intermediate cracks in each slab.
3. Continuously Reinforced Concrete Pavement (CRCP) does not require any transverse joints. Transverse cracks are expected and CRCP pavements are designed with enough steel to hold cracks together tightly. Determining an appropriate spacing between the cracks is part of the design process for this type of pavement.

1. Slip Form Paving: produced by a machine that rides on treads over the area to be paved.
   Fresh concrete is deposited in front of the paving machine which then spreads, shapes, consolidates, screeds, and float finishes the concrete in one continuous operation.
2. Fixed Form Paving: produced by stationary metal forms are set and aligned on a solid foundation and staked rigidly. Final preparation and shaping of the subgrade or sub base is completed after the forms are set.
   Forms are cleaned and oiled to ensure they release from the concrete after hardening. Once concrete is deposited near its final position on the subgrade, spreading is completed. The spreading machine is followed by one or more machines that shape, consolidate, and float finish the concrete.