Revision of Australian Standard AS Rock and Aggregate for Engineering Purposes Part 1 Concrete Aggregates

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1 Revision of Australian Standard AS Rock and Aggregate for Engineering Purposes Part 1 Concrete Aggregates Peter Clarke 1 and Vute Sirivivatnanon 2 1 Consultant, Chair Standards Committee CE12 2 Professor of Concrete Engineering, University of Technology, Sydney Abstract: The current edition of the Australian Standard for concrete aggregates, AS was published in The normal revision of the standard at 10years was delayed for a variety of reasons and the final consensus document is expected to be published late in 2013 or early This revision of the document includes a basic specification requirement to minimize the potential for Alkali Aggregate Reaction (AAR) and has considered and specified the requirements for manufactured sands. In the Committee work between 2011 and present, development of the new standard has involved and required extensive revision of sampling procedures for aggregate (AS and AS ) and publication of three new test procedures. Specification for manufactured sand required assessment of the quality of the fines in the sand grading. In turn this was best achieved by determining the Methylene Blue Value (MBV) of the sand and this test was evaluated and published. The specification of AAR required the publication of an accelerated mortar bar test (AMBT) and a concrete prism test (CPT). Although in part a prescriptive standard, AS is now including some performance concepts which should allow for greater cooperation between the aggregate producer and the concrete producer in developing concrete mixes that best utilize local materials in the production of pre-mixed concrete. Keywords: Concrete aggregate, specification, Methylene Blue, AAR. 1. Background Technical Committee CE12 is responsible for the aggregate test procedures published in the Australian Standard series AS 1141 Sampling and Testing Aggregates. Currently this group of methods numbers 57 test procedures covering sampling, dimensional properties, strength and durability tests, tests for contaminants, tests for chemical stability, mineralogical properties and special tests for slag materials. The Committee also administers the Australian Standards for rock and aggregate. Currently seven general aggregate standards are available in the AS 2758 series Aggregate and rock for engineering purposes Part1 of the series covers Concrete aggregates Committee CE12 was formed in the early 1970 s and commenced its work in adapting the then specification for concrete aggregates, A77, which included a series of appendices of test procedures. Much of the specification and the test methods in that document were developed from the concrete work and testing controlled by the Snowy Mountains Authority dating from the post war construction of the 1950 s but Australian Standards for concrete aggregate date back to 1934 and standard AS A24. Over the years the scope and complexity of the recommended specifications for the materials and test methods have increased and today the two series of documents represent a very significant part of the technical requirements of Australian quarry production testing and specification. Organizations represented on the current committee included those associated with the supply of materials or the production of concrete, along with representatives of specifiers, organizations representing testing authorities and research authorities. 2. CE 12 Work Project Between approximately 2008 and 2010, Standards Australia developed and implemented its new Business Model to address the significant demand for Australian Standards and the huge number of active projects that were beyond the capacity and funding of the organization. The Business model has established a process of multiple pathways to the development of Australian Standards. Common to all these pathways is the requirement that proposals to develop or revise Australian Standards must be accompanied by a Net Benefit Analysis. This analysis allows Standards Australia s Project Management 1

2 Group to allocate Standards Australia s resources based on Return on Investment to the Australian community as a whole. Towards the end of 2010 the Cement Concrete and Aggregates Association (CCAA) submitted a proposal to Standards Australia for a collaborative project to advance the work of Standards Committee CE 12. The proposal was evaluated by a Nett Benefit Analysis that cited economic, environmental benefits and correction of market failure as the principal reasons for the acceptance of the project. Economically, the Building and Construction segment of the Australian economy represented approximately $A102 billion in or 7.7% of GDP. Pre-mixed concrete and quarry products underpin this significant sector of the Australian economy as a major supplier. In the same year, premixed concrete suppliers produced approximately 24mill m 3 of concrete and contributed between 5 and 7 billion dollars to the economy. In supplying the concrete industry and other civil engineering projects, Australia s 2200 quarries employed some 18,000 persons and contributed a further $A1.7billion to the Australian GDP. Of the 130million tonnes of quarry product, approximately 43million tonnes would have been used in pre-mixed concrete. Most hard rock quarries produce between 30 and 35% of the quarry raw feed as a fines product less than 5mm in size. Although much of this material can be utilized, the past history of quarries had seen much of this material disposed of as waste or a low cost by-product. At the same time, sources of natural fine sands have become constrained through environmental legislation which has prevented recovery of sands from rivers and beaches. The quarrying industry has been working over the past twenty years to develop and encourage the use of quarry fines as an alternative to natural fine sands. Sufficient information is now available to publish an Australian Standard specification for this material which improves the sustainability of quarry reserves while taking some environmental pressure off more traditional sources. Finally, the proposal for the project of work for CE12, recognized damage to some concrete structures in Australia as a result of Alkali Aggregate Reactivity. These failures are the result of swelling pressures developed in the concrete caused by expansive gel formed from the reaction of silica minerals in the aggregate and alkali hydroxides in the cement. The reaction, and its consequences has been known since the 1940 s and was first identified in Australia in the 1950 s. Research work in Australia and overseas since the 1980 s has resulted in both testing methods that identify the potential for AAR and control measures that can be specified to prevent the damage evident in damaged structures. The CCAA proposal was accepted by Standards Australia and work commenced on the project on 30 th June Changes in Sampling - AS and AS Australian Standard AS Sampling Aggregates is concerned with the sampling of aggregate and sand products of nominal size 63mm or less. It is applicable to all products from rail ballast through to sands and quarry fines. The procedures are referenced in the AS 1289 series Method of testing soils for engineering purposes and some of the procedures may be used for sampling at construction sites in addition to the common application of sampling at quarry sites. Although many of the procedures have not been altered from previous editions, this edition of the standard has introduced some significant changes as follows: The gradual introduction of statistical specifications and controls is recognized in the definitions. The intention of the sampling is to achieve random sampling in most instances as this best suits statistical analysis. The standard allows for plant based mechanical samplers for the first time. Requirements are detailed in the Standard for the calibration of these devices and the sampling scheme or other documentation should describe the use of the mechanical sampler. Sampling schemes are recognized as a key element of quality schemes and the standard now requires that sampling is documented. A minimum requirement for the documentation is given in the method and it is expected that this documentation will result in greater traceability of results. Mechanical, rotary splitters are recognized as suitable devices for preparing representative samples from large bulk samples. 2

3 The sampling technique of costeaning has been included in the method, particularly for those quarries that operate on a campaign strategy without the benefit of on-site testing during the process of building large product stockpiles. An informative appendix has been added to the document that discusses terminology, material segregation, the purpose and principles of sampling and the use and requirement of sampling schemes. Methods for sampling quarry products with maximum size greater than 75mm are addressed in Australian Standard AS Sampling Rock spalls and boulders. This method was revised in the project but required little change. The method deals with sampling larger rock pieces such as boulders, armourstone and gabion stone. Because sampling of boulders is a technique used in the assessment of quarry reserves, the method briefly addresses the procedures used by VicRoads for quarry assessment. The methods for sampling and storage of drill core, which were a part of the previous edition of the standard, have been withdrawn. The method lacked the detail necessary for good practice and, as most drilling programmes are unique to the deposit investigated, it is difficult to write standardized procedures. The Committee believes that good practice is best left under the control of the supervising geologist. Both sampling Standards are designed to deliver representative samples for testing. Samples taken by staff of accredited laboratories following these methods, supported by the documentation of the sampling schemes will result in data traceable from the supply source to the product application. 4. Manufactured sands- The Methylene Blue Value AS The introduction of Manufactured Sands, defined as a purpose produced quarry fines material intended as a substitute for natural sand, as a part of the concrete mix has resulted in the need for additional standard requirements for this form of fine aggregate. Unlike sands from river or beach sources, quarry fines have not been shaped or sorted by natural processes. Many plants processing sands from rivers or beaches will use wet processing where the fines will be washed as part of the processing. By contrast manufactured sands are likely to be dry processed. As a consequence there is a greater likelihood that the manufactured sand will have a grading with a much higher proportion of material passing the 75micron size and that a proportion of these fines may be reactive or deleterious in concrete. In turn these properties of the fine aggregate will affect the water demand of the concrete mix. Table 1 Test properties of the eight selected manufactured sand samples Sizing Test Results Flow Cone Results Durability Results Calculation Sample Mass passing 75 µm (%) Mass less than 2 µm (%) Clay & Silt AS Voids (%) Flow Time (secs) MBV Sodium Sulphate Loss (%) Deg Factor (Fines) Sand Equiv MBV X % passing 75 µm D S L N G L S T

4 Water Demand l/cu m Water Demand l/cu m Between 2004 and 2007, CCAA conducted an investigation into the aggregate properties of 21 commercially available manufactured sands from across Australia (1). A second investigation tested 8 of these 21 sands in mortar mixes and reported the investigation in November 2008 (2). The physical properties of the 8 selected sands, which covered the range of properties of the sands in the first investigation, are given in Table 1 From the results of these two investigations CCAA published the Guide to the Specification and Use of Manufactured Sand in Concrete in November 2008 (3) and recommended the findings to the Standards Committee for the revision of the Concrete Aggregate standard. The Guide and the reports are available at the CCAA website The investigations showed that the Methylene Blue Value (MBV) of the passing 75 micron fines was not sufficient to indicate the effect of manufactured sand on the performance in mortar. MBV is indicative of the activity of the fines, but it is a standardized value; it determines the activity in terms of adsorption of the Methylene Blue dye per gram of sample. The effect of the fines on performance is determined by both the activity of the fines and the quantity of fines present. The investigation recommended using the multiple of the MBV and the percentage passing the 75micron sieve as the best indicator of the effect of the fines on the performance of the concrete mortar. The 8 samples of manufactured sands were tested in mortars in blends with a single sized, rounded, clean quartz sand with the blend between 20% and 100% of the manufactured sand. Figure1 shows that for blends with low concentrations of manufactured sand, the water demand of the mortar was related to the void content of the aggregate but for mortars produced from the manufactured sand, the water demand correlated with the multiple of the MBV and the percentage passing the 75µm size. The CE12 committee later defined this multiple as the Deleterious Fines Index (DFI) It was still necessary to standardize a test procedure for the MBV. The dye test is used in many different formats both in Australia and world-wide so much so that the Australian Standard provides a number of warnings concerning some of the differences in tests that may still report a result as a Methylene Blue Value. The most common variants of the test either use different concentrations of the dye in solution or use different gradings of the fines (upper size 425µm or 2.36mm) or use crushed sample to determine the clay activity of the rock fabric rather than testing the fines. Much use has been made of Methylene Blue dye adsorption in the identification and evaluation of expansive clays within rock material intended for the production of coarse aggregate. This type of test usually commences with a washed, dry aggregate which is then crushed and ground to liberate clays within the rock fabric. The dye test is conducted on this material and is indicative of the clay content, particularly expansive clays that may eventually lead to deterioration of rock particles. On occasions these tests may be identified as a Methylene Blue Test or a Methylene Blue Value. It must be understood that this style of test is not related to the Australian Standard under discussion. The Australian Standard is a measure of the reactivity of the fines in sand or crushed product as it is delivered to the concrete production plant. The reactivity will immediately affect the production of concrete by affecting the water demand of the mix. The Australian Standard does not deal with any future expansive potential of the rock fragments. The Standard specifically warns against any crushing or grinding of rock particles to produce sample material for testing R² = R² = Voids % NZS 3111 Lab 1 Lab 2 Linear (Lab 1) Linear (Lab 2) R² = R² = MBV X 75micron Lab 1 Lab 2 Linear (Lab 1) Linear (Lab 2) (a) Blends using 20% Manufactured Sand (b) Fine Aggregate 100% Manufactured sand Figure 1 Mortar water demand dependant on aggregate voids and DFI 4

5 5. Alkali Aggregate reactivity- The Accelerated Mortar Bar Test (AMBT) AS The potential for certain silicate minerals to react with hydroxide ions in the pore solution of concrete and to then combine with alkali metal ions to form expansive gels in combination with water was first recognized by Stanton in the 1940 s (4). The reaction was described as Alkali Silica reactivity (ASR) and, along with a similar process in carbonate rocks was given the more general title of Alkali Aggregate Reactivity (AAR). ASR was first recognized by Vivian in Australia in the 1950 s. Chemical and mortar bar expansion tests to assess potential AAR were in use in Australia by 1974 and were available in the AS1141 series of methods as methods 38 and 39. However the methods were proven to be ineffective or misleading in assessing slowly reacting aggregates and by the mid 1990 s they were withdrawn from Australian Standards although comparable methods are still included in ASTM Standards. Research in Australia in the 1980s (5) and 1990s, at CSIRO and then at ARRB, conducted by Dr A Shayan developed a method and limits for an accelerated test using the mortar bars described in the withdrawn AS 1141 method 38. The Australian developed method was published and specified by two State Road authorities as test methods RMS T363 and Vic Roads RC from the mid 1990s A similar test, originating in South Africa in the 1980 s was modified and published as ASTM C1260 and gained fairly wide support internationally. By 2011, when a suitable method for an Australian standard method for the Accelerated Mortar Bar Test was considered, the CE12 committee was faced with a difficult compromise. Standards Australia encourages the use and recognition of International Standards where possible and use of the ASTM method for the Mortar bar test makes it somewhat easier to use the extensive overseas research into AAR if test data is comparable. However, State Roads authorities that had used the Australian developed procedure were reluctant to change methods and to perhaps abandon twenty years of accumulated data. Some limited research also suggested that the classification limits and the time period for the procedure described in ASTM were inappropriate for some Australian rock types The consensus reached by the committee was to accept the basic parameters of the ASTM method so that the Australian Standard specifies the moulding and curing requirements used by ASTM C1260. The standard also uses the fixed water/cement ratio of 0.47 of the ASTM method rather than the using the flow table as specified in the NSW and VicRoads methods. However, because of the research that drew attention to limitations in the ASTM classification and to avoid any compromise of the existing data base, the Australian Standard has extended the measurement period to 21days and has accepted a classification limit of 0.1% expansion as the identification of reactive aggregate. This approach is similar to that adopted by Western Australia s Main Roads Department in The classification of aggregate distinguishes between aggregates that react slowly to the effects of the alkali hydroxide and those aggregates that react in a time period that may indicate a faster reaction in the field. This is determined by classifying the aggregate by its expansion at two time periods as given in Table 2 Table 2 AGGREGATE REACTIVITY CLASSIFICATION Mortar bar expansion (E), % Specimens in 1 mol/l NaOH at 80 C 10 days 21 days Classification E < 0.10* Non-reactive E 0.10* Reactive E < 0.10* 0.10* E < 0.30 Slowly reactive 5

6 Percent Expansion * The limit of E for natural fine aggregates is 0.15% To date, there has been very little data generated in Australia to quantify the precision of this (or for that matter, many other) test method. As with many civil engineering test methods it is possible to obtain different results from different laboratories, even when testing split samples to the same standard test method. The best data available in Australia at this time, and especially now that the Australian Standard follows the same general procedure as ASTM 1260, is to consider the precision statement of the ASTM method, which states for Multi-Laboratory Precision It has been found that the average multilaboratory coefficient of variation for materials with an average expansion greater than 0.1% at 14 days is 15.2%. Therefore the results of two properly conducted tests in different laboratories on the same sample of aggregate should not vary by more than 43% of the mean expansion The issue is illustrated in Figure 2 following. In this construction, the mean data is very close to the classification limit and an aggregate with these, not unreasonable, results would be classified as slowly reactive However if we plot the upper and lower limits of the acceptable precision range (43% of the mean around the mean) then the figure demonstrates the possibility of one laboratory classifying the aggregate as reactive while a second laboratory could classify the same sample as non-reactive Mean data Days Lab 1 Lab 2 6 Figure 2 Construction of data to illustrate the impact of AMBT Precision on Classification This situation is only an issue for aggregates that plot close to the classification limit but it represented a point of concern for the Committee. As a consequence, the Committee introduced a number of control measures on those conditions of the test that were identified as most likely to cause variation in test results. The test conditions were not altered in the Australian Standard so it and the ASTM method remain identical in the required exposure environment of the mortar bars. But the Australian Standard requires the testing laboratory to monitor solution concentration and temperature very closely during the period of testing. Allowable departures from the standard test conditions are specified and beyond those departures, the test must be abandoned and the sample re-tested. It is hoped that these additions to the method will improve multi-laboratory precision in Australia. Once the test procedure is well established in a number of Australian laboratories then it would be useful for both the Authorities and Industry to conduct an inter-laboratory testing programme aimed at establishing Australian precision data. 6. Alkali Aggregate reactivity- The Concrete Prism Test (CPT) AS A Concrete Prism Test was developed in Australia through the early to mid 1980s and is published as RMS T364 or VicRoads RC The method is different to the test developed in the late1980s in Canada for testing siliceous aggregates. This Canadian test was later adopted in America as ASTM C1293 and this method has gained some world-wide use, mainly in the Americas and in Asia. RILEM 3 Determination of potential alkali reactivity of aggregates- method for aggregate combinations using concrete prisms is the method most likely to be used in Europe.

7 Although all three methods accelerate the reaction by storing concrete prisms over water to achieve a 100% RH and increase the storage temperature to 38 C there are differences in each procedure as follows: 7 The Australian developed test uses 5.8kg/m 3 of alkali in the concrete mix and takes an expansion of 0.03% at 52 weeks as the criterion for reactive aggregate ASTM C1293 uses 5.25kg/m 3 alkali in the mix and take an expansion of 0.04% expansion at 52 weeks as the criterion RILEM 3 uses 5.5kg/m 3 alkali in the mix and takes as expansion of 0.04% expansion at 52 weeks as the criterion for reactive aggregate but recognizes that some field reactive aggregates may not reach this expansion at 52weeks and therefore allows the test to be extended for these aggregates Faced with similar issues to those in the standardization of the AMBT, the CE12 committee took the decision to standardize on a concrete mix using 5.25kg/m 3 of alkali in the mix but adopted the lower expansion limit of 0.03% at 52 weeks as the criterion for defining reactive aggregate. Some Australian interlaboratory testing had shown that the difference in alkali levels between 5.25kg/m 3 and 5.8kg/m 3 did not appear to make much difference in the measured expansion of split samples measured at 52 weeks or the difference measured in any one laboratory was significantly less than the interlaboratory precision variation for either method. However, this conclusion is still controversial. As for the AMBT, there was very little Interlaboratory data available in Australia to determine the precision of the test and so the best data became that quoted by ASTM 1293 for multi laboratory precision For average expansion greater than 0.014%, the multi-laboratory coefficient of variation of a single test result (mean measurement of three prisms) for average expansion greater than 0.014% has been found to be 23% (CSA A A-M90). Therefore, results of two properly conducted tests in different laboratories on the same aggregate should not differ from each other by more than 65% of their average, nineteen times out of twenty. As one example, this precision (or lack thereof) could mean that for an aggregate with a mean expansion of 0.03% at 52weeks (i.e. just on the Australian criterion for reactive aggregate) one laboratory could report a result of 0.04% (i.e. just on the ASTM criterion for reactive aggregate) while a second laboratory could report a result of 0.02% or well within the range of non-reactive aggregate. And yet both laboratories have produced results from properly conducted tests The committee accepted the test as the best available, but, as with the AMBT, the committee introduced a number of controls to the ASTM procedure to attempt to reduce the variation between laboratories. Since drafts of the Australian Standard became available in late 2012, a number of laboratories have been using the method to determine if there is any improvement in the inter-laboratory precision. 7. Concrete Aggregates AS Changes to the Standard Australian Standard AS was first published in 1985 with a second edition in Since the middle 1970 s, the standard for concrete aggregate has recognized the variations in testing and specification practiced in the different States and has provided a range of testing choices to accommodate this variation. The standard has always recognized that the components of a concrete mix may be sourced from multiple aggregate suppliers and may come from multiple sources. Therefore the properties and values specified have always applied to individual aggregates and not to the combination of materials incorporated in the concrete mix. This edition of the standard has addressed the introduction of manufactured sands as a necessary consequence of environmental changes that have reduced the availability of natural sands. Natural sands will continue to be needed, both as a fine aggregate where suitable manufactured sands are not available, but more importantly as part of a blend with the crushed fine aggregate. These blends now mean that many concrete mixes will comprise combinations of at least 4 aggregates and these blends might be produced in any combination to suit the local resources, the local concrete plants, and the economics of supply. The possible wide range of blend combinations suggested that it was no longer appropriate to specify grading envelopes. Further manufactured sand components that might be blended economically in small proportions and might therefore be considered a suitable aggregate might prove adverse to a concrete mix if used in significant quantities in the mix.

8 Finally, this edition of the standard has, once suitable tests were agreed, addressed the specification of aggregate to minimize the potential for Alkali Aggregate reactivity in concrete. 7.1 The recommendation for Mix design It has always been the case that although individual aggregates may comply with the requirements of the standard, there was no guarantee that any particular combination of aggregates would produce workable or specification compliant concrete. The preface to the 1998 edition of the standard addressed this matter with respect to specified grading envelopes when it stated It should be noted that compliance with the grading requirements given in Tables 1 and 3 will not necessarily ensure the production of workable concrete in all mix proportions. The determination of mix proportions should be related to the actual nature and gradings of the aggregates to be used. The introduction of manufactured sands and the effect that they can have on the concrete mix water demand combined with the removal of specified grading envelopes means that there is a greater probability of aggregate combinations producing unworkable mixes or mixes that do not achieve design parameters. AS 2758 is concerned with the supply of aggregate for a variety of purposes. The standard is not intended to enter into the area of concrete design and yet the Committee felt that it was necessary to make the point as strongly as possible that not all combinations of complying aggregate would produce good concrete. Thus the introductory paragraph of the standard, describing the Scope of the document now includes a strong note that recommends the use of trial mixes as the final determinant of mix combinations of complying aggregates. A note in an Australian Standard is not obligatory and clearly this note is intended for the concrete producer not the supplier of the aggregate who is obligated to comply with the requirements of the standard when it is called up in contract documents. 7.2 Removal of specified grading envelopes Except for special applications, most concrete mix designers seek to combine coarse and fine aggregates into a continuous grading curve that is designed to minimize void space in the aggregate skeleton, which it turn reduces the water demand of the mix and reduces the amount of cement paste required to fill voids. The ideal fine aggregate grading assists in filling voids and provides workability to the mix. But fine aggregate must be minimized to the point that it does not prevent the formation of a continuous network of coarse particles that carries the stresses applied to the hardened concrete. These requirements have led to the specification of idealized grading curves for both coarse and fine aggregates and to the specification of gradings for single sized aggregate products that can be combined to achieve the continuous grading curves. For many years AS has specified one set of these grading envelopes but it has become increasingly apparent that a multitude of aggregate gradings can be combined to produce suitable continuous gradings to achieve the basic technical requirements of the concrete mix. Aggregate producers, in co-operation with local concrete plants, will, and should be encouraged to adjust gradings to suit the production peculiarities of the quarry plant, to produce product that suits the local transport capabilities and that suits the storage and plant capabilities of the concrete plants serviced by quarry. In this edition of the standard, specified grading envelopes have been deleted on the assumption that either a local supply agreement, specifying gradings suitable for the local market, will exist or will be established. Alternatively, for special project or major contract work, aggregate gradings will be specified in those documents. To aid in this process, and in lieu of local information being available, the gradings specified in the 1998 document have been moved to an informative appendix. What was considered of far greater importance was that once a supply agreement was established, both the quarry producer and the concrete producer had an interest and responsibility to ensure that the product gradings remained consistent. The deviation limits on grading are retained from the previous editions of the standard, with the observation in a note that some projects will require lesser deviation ranges. The specification requirement is that the aggregate grading comply with the deviation limits and those limits are stated as a maximum allowable at any time in a supply contract. The aggregate producer is required to advise the concrete producer of deviations outside the limits given in the standard. 8

9 7.3 Requirements for Manufactured sand Manufactured sands are specified as individual components, based on the data from the CCAA investigation into manufactured sands that were already being used commercially. However commercial use included materials that were being used in blends with natural sands in proportions as low as 15% of the blend. Where it is expected that a material will be blended and that the properties of the blend will be improved by the natural sand then it is appropriate to specify a limit on the parameter that allows a proportion of manufactured sand to be used. Hence the limit for the Percent passing 75µm for manufactured sand is set at 20% but a material with this proportion of fines would create such a high water demand that a concrete mix would become uneconomic and would probably be prone to both dusting and shrinkage cracking. The proportion of the manufactured sand capable of use would need to be established by trial mixes, but is unlikely to be greater than 50%. A similar argument applies to the specification limit of 150 for the Deleterious Fines Index. In most cases DFI s higher than about are unlikely to be used without blending but the higher limit is set to allow the use of some proportion of material. Those properties that affect durability of the fine aggregate have been made more stringent than those applying to natural fine aggregates. Manufactured sands are not exposed to natural processes that tend to remove non durable particles. Finer particles that are not durable must be restricted or eliminated from the total aggregate to prevent the possibility of non-durable particles at the surface of the concrete, deteriorating in the life of the structure. The Degradation factor (fines) has been set at 60 for manufactured sand and the sodium sulphate loss is set at 6% for all exposure classifications. At the time of preparing the standard the Committee was not convinced of the application of any particular test procedure or any appropriate limit to assess the resistance of manufactured sands to surface abrasion. No appropriate limits or a method of test could be set for assessing the skid resistance of the fine material. This led to a note under clause that requires a specifying authority to address these issues if they are of importance in the authority s project. In particular specifications for flat work subjected to high abrasions such as warehouse floors or concrete road pavements requiring resistance to both abrasion and polishing may need to have special provisions outside the current scope of AS Recent research in Australia (6) and the U.S. (7) has found that a sand (natural or manufactured sand) with a Micro-Deval loss limit of 15-20% can be successfully used to provide good skid resistance to concrete pavements. This approach has been adopted in the newly revised RMS QA Specification R83 Concrete Pavement Base. (August 2013.) 7.4 requirements for control of Alkali Aggregate reactivity The test methods for AAR produce a classification of reactivity of the tested aggregate. AS takes this classification and provides a basic specification for the aggregate that requires: 1. That aggregate used in concrete in an environment conducive to supporting AAR must be assessed for its potential reactivity by or one or both of the Australian Standard methods. 2. Aggregate classified as non-reactive by either or both methods may be used in concrete without the need of mitigative measures to control AAR. 3. Aggregate classified as slowly reactive or reactive by either method can only be used with mitigative measures. 4. The method and specification for testing aggregate blends shall be addressed in the project supply agreement. The producer of the blended aggregate is responsible for the testing of an aggregate blend. 5. The aggregate producer is responsible for testing his aggregate products and for suppling documentation that provides the aggregate classification. As acceptable mitigative measures vary in the States and the determination and specification of mitigative measures are beyond the scope of this aggregate standard, AS cannot go further in specifying the control of AAR. 9

10 Unlike a number of overseas specifications, that see the AMBT as a fast screening test while the CPT is a better indicator of field performance, the Australian Standard at this time does not recognise any hierarchy in the tests. The CPT has not been used extensively in Australia, it has been used mainly in research and in the investigation of failures and in the only extensive Interlaboratory exercise conducted to date, the repeatability of the test is at least as bad, if not worse than that reported in ASTM standards. Until these issues are resolved in Australian practice, the CPT cannot be relied upon as the defining test procedure for potential Alkali Aggregate reactivity in the Australian Standard. The standard includes a note on the precision of the test methods that recommends that aggregate classification should not rely on single test results. As has already been demonstrated above, with the precision of these tests it is entirely possible to obtain different aggregate classifications from two different laboratories even when the laboratories are using split samples and this outcome is more likely for materials with results close to the classification limit. To reduce the possibility of false negative (i.e. an aggregate classified as non-reactive when in fact it should have been classified as reactive ) the note recommends that a history of results over a period of time be considered to avoid the serious potential consequence of aggregates being used without mitigative measures. 8. Conclusion The revision of AS2758.1, the standard for concrete aggregate, the development of new test methods and the revision of the sampling test methods has achieved the following for the production of pre-mixed concrete in Australia. New and less labor-intensive methods for sampling at quarries and for splitting samples are introduced. Quarry sampling moves closer to supporting statistically based specifications and sampling schemes are better able to provide sample traceability from production to application by requiring minimal documentation. The effects of manufactured sand on concrete mortars have been researched with suitable test procedures developed for the specification of this fine aggregate. Specification requirements for the individual components of manufactured sands and manufactured sand blends have been included in AS for the first time. However, appropriate tests for determining the abrasion resistance and skid resistance of manufactured sand had not been evaluated and were not available for inclusion in the standard at this time. New Australian standard test methods were developed for determining the potential for aggregates to react with alkali hydroxides in the concrete and these methods made use of Australian research to establish suitable aggregate classifications. A basic requirement for the reporting and control of AAR was included in the standard. The standard has moved closer to becoming performance based with the removal of specified grading envelopes. This allows for more localized supply agreements that should lead to greater sustainability in the Industry. However the consequent need for confirmation of concrete mix designs with trial mixes and the need for consistency of supply is emphasized. 9. Acknowledgements The work and involvement of all representatives on the CE12 Standards Australia Committee is acknowledged in the development of these methods and standard. In particular the research and contributions of Dr A Shayan to the work of the committee on AAR is acknowledged. The research and contributions of the representatives of CCAA on manufactured sand is also acknowledged. 10. References (1) CCAA Research Report (2007) Manufactured sand-national test methods and specification values (2) CCAA Research Report (2008) Manufactured sand- Abrasion resistance and effect of manufactured sand on concrete mortar (3) CCAA technical Guide T60 (2008) Guide to the specification and use of manufactured sand in Concrete (4) Stanton, TE, Expansion of concrete through reaction between cement and aggregates, Proceedings, American Society of Civil Engineers, 1940,pp

11 (5) Shayan, A., Diggins, R.G., Ivanusec, I. & Westgate, P.L. 1988, Accelerated testing of some Australian and overseas aggregates for alkali-aggregate reactivity, Cement and Concrete Research, 18, pp (6) CCAA Research Report. Effect of Manufactured Sand on Surface Properties of Concrete Pavements Stage II Skid & Abrasion Resistance of Concrete with Manufactured Sand. (7) Fowler, D.W., and Rached, M.M., Evaluation of the Polish Resistance of Fine Aggregates in PCC Pavements, submitted and accepted for publication in TRB. 11