28707 Demonstrate Knowledge of Mix Design Fundamentals and Treatment Selection for Slurry

Explanatory notes

1Assessment against this unit standard must be based on the fundamental principles of treatment selectionin the following references:

RNZ 9806, Specification for Slurry Surfacings, RNZ 9806: June 2010, Roading NewZealand, available at ;

ISSA A105 Recommended Performance Guideline for Emulsified Asphalt Slurry Seal A105 (Revised February 2010) International Slurry Surfacing Association available at ;

ISSA A143Recommended Performance Guideline For Micro Surfacing A143(Revised February 2010),International Slurry Surfacing Association available at

2Definitions

Job Mix Formula is the combined aggregate particle size distribution andtotal bitumen content that falls within the SME and produces a mix that complies withspecified volumetric and mechanical criteria.

Slurry surfacingis the generic term for a mix of asphalt emulsion binder, crushed aggregate, and stabilising filler. A development of slurry using a polymer modified binder and selected aggregates is known as micro surfacing.

SME stands for Specified Mix Envelope or the asphaltic concrete particle size distribution and effective bitumen content limits, which are set out in Section 5 of NZTA Specification M10Specification for Dense Graded and Stone Mastic Asphaltsavailable at

Outcomes and evidence requirements

Outcome 1

Demonstrate knowledge of mix design fundamentals for slurry surfacings.

Evidence requirements

1.1Slurry and micro surfacings are defined and their components are described in accordance with RNZ 9806.

Rangebinder content, mineral aggregates, fillers, potable water, additives, modifiers, sand equivalent.

1.2Performance requirements for slurry and micro surfacing design aredescribed in accordance with RNZ 9806.

Rangewet track abrasion, wet striping, wet cohesion, binder content, gradation.

1.3Slurry and micro surfacing design is explained in terms of factors that affect the performance of these surfacings.

Rangegrading, aggregate moisture content, residual binder content, application depth, mix and set times, climatic conditions, time of day, weather, wind speed, humidity.

1.4A slurry surfacing Job Mix Formulais described in terms of what it contains and why.

Rangerecipe, emulsion content, cement content, aggregate content, moisture content, dope content.

Outcome 2

Demonstrate knowledge of treatment selection for slurry surfacings.

Evidence requirements

2.1Treatment selection for slurry surfacings is explained in terms of determining the condition and composition of the existing surface.

Rangedetermination from – records, site visit;

surface conditions – deflections, cracks, flushing, skid resistance requirements, traffic stresses, traffic times, tack coat, rolling, surface shape.

2.2Treatment selection for slurry surfacings is explained in terms ofselecting appropriate systems for different situations and specific requirements.

Rangesystems – slurry, micro surfacing, cape seal, rut filling;

situations – traffic stress, cracking, deflections, traffic loading, rutting, flushing, polishing, unravelling;

specific requirements – texture, skid resistance, colour, noise level.

Status information and last date for assessment for superseded versions

This CMR can be accessed at

Please note

Providers must be granted consent to assess against standards (accredited) by NZQA, before they can report credits from assessment against unit standards or deliver courses of study leading to that assessment.

Industry Training Organisations must be granted consent to assess against standards by NZQA before they can register credits from assessment against unit standards.

Providers and Industry Training Organisations, which have been granted consent and which are assessing against unit standards must engage with the moderation system that applies to those standards.

Requirements for consent to assess and an outline of the moderation system that applies to this standard are outlined in the Consent and Moderation Requirements (CMRs). The CMR also includes useful information about special requirements for organisations wishing to develop education and training programmes, such as minimum qualifications for tutors and assessors, and special resource requirements.

Comments on this unit standard

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