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Research Report 011 Emulsified bituminous materials in road maintenance and construction: a survey of current New Zealand practice

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

Bitumen emulsions are now being used in almost every application in which hot, cut-back or fluxed bitumen binders are used. A survey of current practice in New Zealand for road maintenance and construction from 1987 to 1991 is recorded. Experience ranges from using bitumen emulsion for maintenance, tack coat, sealing, and slurry applications for State Highways, City streets and Council roads, and in Transit New Zealand regions. Binder performance of bitumen in general is discussed, with particluar reference to the effects of heat, oxidation, cutter and luxing stocks, and emulsification. Acceptance criteria for bitumen emulsions are specified in terms of stability, curing characteristics, and resistance to stripping. The summary provides volumes of bitumen used annually in New Zealand, applications used for bituminous emulsions, comparison of costs of hot bitumen with those of bitumen emulsions, as well as lists of benefits and limitations of bitumen emulsions.

Research Report 307 Fatigue design criteria for low noise surfaces on New Zealand roads

Published: | Category: Activity management , CAPTIF , Research programme , Research & reports | Audience: General

Internationally low noise porous asphalts are typically laid on top of structural asphalt layers. In New Zealand structural asphalt is generally prohibitively expensive and porous asphalt is used directly on chipseal-surfaced unbound granular pavements. Two accelerated pavement tests were undertaken at the Canterbury Accelerated Pavement Testing Indoor Facility (CAPTIF) in 2004–2005. The first test was to develop a horizontal tensile strain versus fatigue life curve and establish a relationship between basecourse surface curvature and fatigue life. The second test evaluated the extension of fatigue life by short trafficking before surfacing rather than using enhanced binders in porous asphalt. The outcomes of the project suggest that the Austroads Rehabilitation Design Guide is very conservative in predicting fatigue and that deformation leads to surface failure before fatigue of the pavement occurs. Pavements to be sealed with low noise surfaces could tolerate more deflection if initial trafficking was undertaken.

Research Report 634 Effect of road seal type on resistance to traffic stresses

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

This report details research carried out from 2016 to 2017 as the preparatory stage of a larger programme to understand how chipseals may be improved to withstand increases in horizontal shear forces imposed by traffic loadings. The research aimed to develop an understanding of mechanisms and factors that lead to chip loss resulting from surface shear stresses, and to develop a methodology for testing seal performance under realistic but controlled laboratory conditions. The report commences with a literature review to collate and examine existing data and experience on seal selection and chip loss processes from New Zealand and overseas. Physical mechanisms, site and vehicle factors that contribute to seal damage are also investigated. Finally, an experimental test method and plan is developed to quantitatively compare and evaluate the effect of seal and binder type on overall seal performance in the laboratory, but under realistic loading and temperature conditions.