Title: Diamond grinding or grooving a concrete pavement? Achieving the 4S s in the 21 st Century. A contractor s experience in Australia

Transcription

1 Title: Diamond grinding or grooving a concrete pavement? Achieving the 4S s in the 21 st Century. A contractor s experience in Australia Dominic O Brien Seovic Civil Engineering Pty Ltd, Sydney dobrien@seovic.com.au Category: Pavement Construction / Maintenance. ABSTRACT: Diamond grinding / grooving (DGAG) of concrete pavements is undertaken for a number of different purposes include improve ride (smoothness), increase skid resistance, quieter pavements (silent) and for concrete road revival (sustainability). This technique was first used in 1965 on a 19 year of section of I-10 in Southern California to eliminate excessive faulting. Since then, DGAG has become a major element of concrete pavement restoration project in the USA. DGAG was introduced in Australia in the early 21 st century. The Company has undertaken diamond grinding / grooving assignments in Australia for the past four years. These assignments were undertaken on new concrete pavements, existing concrete pavements and existing concrete pavement with asphalt overlay removed in New South Wales, Australia. The outcomes of these years of experience show that the DGAG process is a cost effective process in achieving 4S s. This paper presents a brief description of some of the DGAG assignment conducted and a summary of the findings. KEYWORDS: diamond grinding, grooving, concrete, pavement.

2 1. Introduction Over the past six years, an Australian Contractor has undertaken DGAG on various types of new and timeworn concrete pavements on the eastern seaboard of Australia. These concrete pavements include plain concrete pavement (PCP), asphalt overlay plain concrete pavements (AOPCP), continuously reinforced concrete pavement (CRCP) and steel fibre reinforced concrete pavement (SFCP). This paper gives an overview of (DGAG) for a contractor outlook. Figure 2, Eastern Creek Drag Way, Sydney. (Photo courtesy of Seovic Civil Engineering) 2. Background DGAG is a concrete pavement restoration technique (CPR). The primary purposes for this technique can be correct out of tolerance pavement surface levels, improve ride quality, improve pavement surface texture and reduce pavement noise. These purposes are mutually exclusives. Figure 1, Airport Link Tunnel, Brisbane (Photo courtesy of Seovic Civil Engineering Pty Ltd). Existing concrete pavements have suffered from a bad brand image due to the fact they are very mature, are providing a reduced level of services and have been designed to other criteria than today specifications and have been built using old techniques and construction methods. Figure 3, Pacific Highway, NSW. (Photo courtesy of Seovic Civil Engineering Pty Ltd). Typically, DGAG involves removing a thin layer (0-8mm) off the top of the of hardened Portland Cement Concrete (PCC) pavement

3 using an assembly of circular diamond encrusted blades separated at regular and comparatively minor gaps and thereby leaving a longitudinal textured surface with a very slender fins or projections between the saw-cut grooves. (See figures 4, 5 and 6). The result is a smooth level pavement surface with longitudinal texture with desirable friction and quiet pavement characteristic. 3. New diamond grinding and grooving of new pavements (NGCS). Figure 6, Up close view of New Generation Concrete Surfaces. (Photo courtesy of Seovic Civil Engineering) 3. Smoothness Figure 4 Figure 5 (Photo courtesy of Seovic Civil Engineering) MDG is used to achieve corrections to ride characteristics and reestablish of surface coarseness and friction. MDG is usually executed after other CPR procedures. These procedures include full-depth repairs, load transfer restoration, slab stabilization or mud jacking..cpr procedures that occur after grinding are repair joint and crack spalling and resealing joints. DG provides a smooth riding surface that is often as good as or better than new pavement. DGAG equipment is capable of corrective (bump) grinding or continuous grinding depending on the job requirements. DGAG can be sub-divided into three sub sets: 1. Maintenance diamond grinding (MDG) of existing pavements; 2. New diamond grinding (NDG) of new pavements; and

4 quality (a measure of smoothness). These measures are reported in RMS s Annual Report. The RTA manages the gradual and continuous deterioration of road pavement by employing a pavement preservation strategy. A pavement preservation is; 1. Appropriately manages road safety risks; Figure 7. An example of a holiday after grinding. (Photo courtesy of Seovic Civil Engineering) 4. Quietness Conventional DG reduces the thumping noises from concrete slab faulting. Various noise studies show a reduction in road noises after DG. This innovative grinding technique, NGCS, was used on a section of the Hunter Expressway, NSW. It is a two stage technique of grinding and grooving which provides a consistent profile absent of positive or upward texture, resulting in a uniform land profile design with a predominantly negative texture. Studies by RMS shows road noise from NGCS pavement is quieter than stone mastic asphalt. 5. Specifications Road Authorities are placing greater emphasis on tire/pavement noise, smoothness and constructions delays. This has resulted in the ongoing development of tighter smoothness, new noise specifications and development of low noise surface treatments and equipments. The Road and Maritime Services, NSW, (RMS) use two key measures of pavement durability (extent of cracking visible) and ride 2. Results in longer-lasting and smoother pavements; and 3. Minimizes the cost of maintaining the road network over the life of the asset as timely and regular smaller scale interventions reduce the need for more costly and disruptive road rebuilding activities. DGAG was introduced into NSW, as a result of specifications developed by RMS in conjunction with various State Department of Transport Authorities (DOT) in the USA. 6. Ride Quality and Surface Improvement Ride quality measures the undulations in the road and therefore provides an indication of ride comfort experienced by the driver and passenger. Smoother roads also tend to reduce the wear and tear on vehicles and hence minimize road user costs. The ride quality, or longitudinal profile of the road surface, is measured using vehicle mounted laser technology and is measured as IRI and NAASRA. Over the past six years on a numerous assignment in Australia, one pass of DG gives ride quality improvement of greater than 39%.

5 Two passes greater than 50%. Figure 2 give an example of ride quality improvement. Figure 8 Liverpool Road, Ashfield, April Improved road condition is indicated by lower results. carbon savings from using grinding and grooving further research is needed. Modern long life pavements are characterized by low environmental impact, low life-cycle cost and durable high-quality surfaces. Light colored surfaces and rigid structures contribute to tackling of global warming through the positive aspects of albedo and reduced fuel consumption. These turn concrete roads into invaluable assets in terms of sustainability and a benefit for society. Further research is needed in the benefits of cool concrete pavements. 9. Innovation 7. Training / Staff The selection of the appropriate DGAG technique / treatment is dependent on a number of factors. It is the Company s view that a competent qualified workforce makes a fundamental contribution to achieving high quality durable DGAG. This is achieved by using training, 457 work visas, knowledge transfer programs and presentation and develop of training regimes. After purchasing a highway grinder, it was found to have one distinct disadvantage. They are unable to grind up close to any obstructions adjacent to the machine such as kerbs, poles and barriers (see figures 9 and 10) The Contractor is a Board Member of the International Grinding and Grooving Association (IGGA). 8. Sustainability Carbon management is becoming an increasingly important issue for client bodies and highway maintaining authorities are increasingly expected to demonstrate carbon savings on contracts. To illustrate the potential Figure 9 Generally, this is not of particular concern, as highway grinding machines are not primarily designed for urban environments, such as local road. Nominally, however, 650mm is as close as the existing generation of grinding machines can grind to adjacent obstruction. This is due to the straddle-type grinding head

6 centrally mounted to the machine, which is needed to support a heavy-duty grinding drum Figure 10 Great Western Highway, Sydney (Photo courtesy of Seovic Civil Engineering) There accordingly exists a need, in light of the foregoing, for a solution which at least attempts to address these and other problems associated with the existing generations of highway grinding equipment, and their use. In a preferred embodiment, the inventive concept arises from, but is not limited to, a recognition that highway grinding can be performed with far less nominal offset from adjacent obstacles by use of a new grinding attachment that can bolt directly to a highway grinding machine as an accessory, and use an existing main shaft thereof for operation of the grinding attachment. In this embodiment, the grinding drum has minimal support at one end owing to use of a stub axle arrangement to thereby permit grinding to obstacles of the aforementioned type. The invention was designed and manufactured in-house and has a number of patents pending. Figure 11. Edge Grinding under Patent by Australian Contractor. (Photo courtesy of Seovic Civil Engineering) When immovable obstacles are encountered, the existing highway grinders are unable to get sufficiently close the edge of the surface to be grinded or grooved. This necessitates a secondary process, to achieve a consistent result of the grinding surface that is, a result which is truce to grade, and uniform in appearance, with the same longitudinal type line texture. According, the invention provides a grinding attachment comprising: a longitudinally oriented arbor extension for mounting grinding blades and spacers thereon to form a grinding drum, the arbor extension being adapted for engagement and support at one end to a head shaft supplying a source of torque to the arbor extension; a stub axle to engage and support the arbor extension at an opposite end of the arbor; and a mounting assembly to support the stub axle and mount the grinding attachment to a highway grinding machine to drive the head shaft; wherein the grinding drum can thereby operate proximal to obstacles adjacent to a grinding surfaces. Figure 12 shows the completed grinding surface using edge grinding and main grinding together in an urban environment.

7 Figure 14, Sintered metal-bonded diamond blades, diameter varies between 300 mm to 500 mm. (Photo courtesy of Seovic Civil Engineering). Figure 12 Coronation Pde, Enfield, NSW. (Photo courtesy of Seovic Civil Engineering) Diamond Blades Figure 13. Typical DGAS machine layout A highway grinding units has approximately 240 diameter blades. The width of the grinding head is 1.26 metres A diamond blade grinds, rather than cuts, through material. Blades typically have rectangular teeth (segments) which contain diamond crystals embedded throughout the segment for grinding through concrete. The bond is a term used for the softness or hardness of the powder metal being used to form the segments. The powdered metals hold the diamonds in place. The bond controls the rate at which the diamond segments wear down allowing new diamonds to become exposed at the surface to continue grinding with a "sharp" edge. An important step in choosing a blade is to match the bond to the specific material to be cut. Additional factors to consider are the type and power of the equipment to be used and the availability of water. Harder materials need a softer bonded segment to allow for continuous diamond exposure. Softer materials like asphalt or freshly poured concrete can use a harder segment to resist the increased wear that softer, abrasive materials create. In addition, the diamonds' grit (size), toughness, and

8 concentration should also match the nature of the material to be sawed. For example, when hard materials are cut, the diamonds should be smaller. Approximately litres of water are used per minutes to cool the blades. This water is recycled and the fines are removed from the recycled water. cent over 30 years when compared to traditional alternative of restoration by milling and asphalt resheeting. (Legislative Assembly, NSW Parliament, House Business Papers, 1647 Resurfacing of Concrete Roads, Question asked on 6 March 2012 (session 55-1) and published in Questions and Answer Papers No. 7.) 11. Quality Assurance. As a grinding/grooving Contractor generally operates to first party quality assurance schemes. However the intention is to embody grinding/grooving and become registered to ISO Cost Considerations DGAG used to be an expensive operation; however, new, high production equipment as well as improved synthetic diamonds for blades made DGAG, knowledge transfer and improved training has made a more cost competitive option for PCC pavement rehabilitation. Contract prices will be provided by contractors based on an indication of the likely size of the client s programme. Significant reductions in the size of the indicated programme will increase the contractor s overhead costs - and thus the price per square metre of work undertaken - and where appropriate, contracts should make provision for compensating contractors under these circumstances Engineering and economic analysis carried out by RMS has confirmed that surface restoration of concrete roads by diamond grinding will achieve a maintenance costs of up to 26 per 13. Benefits of Diamond Grinding Increasing Road Authorities Specifiers are specifying diamond saw cut surfaces to reduce roughness, reduce noise and increase the friction of their pavements, bridges and runways. In certain situations is it economical, long-lasting, effective and environmentally friendly. Costs are less than a hot asphalt overlay or a thin lift asphaltic concrete treatment. DG ground PCC pavements can provide better fuel economy. Increases and restores surface friction and reduces hydroplaning. It is a challenging time for the Pavement Engineers. Motorists are increasingly demanding safe, smooth, quiet and delay free roadways while funding necessary to meet these demands remains elusive. Diamond saw-cut textures (grooving and grinding) is an additional technique for Pavement Engineers. It is a time proven, cost effective means of providing consistently smooth, quiet and safe textures at a less cost of asphalt overlays. DGAG consists of removing surface irregularities from concrete pavements that are often caused by faulting, offsetting, curling and warping of the slabs. The technology is used

9 for a number of mutually exclusive purposes in pavements; restore smoothness of existing pavements and has also been used to reduce tyre-pavement noise levels and increase pavement friction. In some instances, DGAG has been considered as a possibility to comply with smoothness specifications in newly placed concrete pavement.

10 14. References The International Grooving and Grinding Association (IGGA) is a key source of knowledge on DGGA and documentation is available free of charge at Legislative Assembly, NSW Parliament, House Business Papers, 1647 Resurfacing of Concrete Roads, Question asked on 6 March 2012 (session 55-1) and published in Questions and Answer Papers No. 7. RMS, Specification Guide NR93 Guide to Diamond Grinding of Concrete Pavement RMS, R93, March 2014 RTA, Condition of NSW State Road, update September Acknowledgement The author wishes to acknowledge the advice from RMS, John Seovic (deceased April 2014) and Jason Seovic, Seovic Civil Engineering Pty Ltd.