Ian Sims

Quality and durability of stone for construction

Abstract The use of natural stone materials in construction is now experiencing a marked revival particularly for external claddings. In contrast with most other construction materials, there are few British Standard tests for natural stone or Standard specifications defining the minimum quality requirements for various purposes. The Code of Practice for cladding is inadequate in these respects. The range of test methods provided by ASTM and the complementary series of Standard specifications covering the major stone families are summarized but none of these directly address durability. Selected quality assessment procedures from German, Italian and other European practices and a number of different approaches to the evaluation of durability of stone are critically reviewed. The crucial importance of representative samples in such evaluations is recognized but the aspects of source selection and sampling are not discussed in detail.

RILEM Recommendations for the Prevention of Damage by Alkali-Aggregate Reactions in New Concrete Structures

This book contains the full set of RILEM Recommendations which have been produced to enable engineers, specifiers and testing houses to design and produce concrete which will not suffer damage arising from alkali reactions in the concrete. There are five recommended test methods for aggregates (designated AAR-1 to AAR-5), and an overall recommendation which describes how these should be used to enable a comprehensive aggregate assessment (AAR-0). Additionally, there are two Recommended International Specifications for concrete (AAR-7.1 & 7.2) and a Preliminary International Specification for dams and other hydro structures (AAR-7.3), which describe how the aggregate assessment can be combined with other measures in the design of the concrete to produce a concrete with a minimised risk of developing damage from alkali-aggregate reactions

Petrographic Atlas: Characterisation of Aggregates Regarding Potential Reactivity to Alkalis

This RILEM AAR 1.2 Atlas is complementary to the petrographic method described in RILEM AAR 1.1. It is designed and intended to assist in the identification of alkali-reactive rock types in concrete aggregate by thin-section petrography. Additional issues include: optical thin-section petrography conforming to RILEM AAR 1.1 is considered the prime assessment method for aggregate materials, being effective regarding cost and time. Unequivocal identification of minerals in very-fine grained rock types may however require use of supplementary methods. the atlas adheres to internationally adopted schemes for rock classification and nomenclature, as recommended in AAR 1.1. Thus, rock types are classified as igneous, sedimentary or metamorphic based upon mineral content, microstructure and texture/fabric. in addition, the atlas identifies known alkali-reactive silica types in each rock type presented. It also identifies consistent coincidence between certain lithologies and silica types; however, it refrains from attributing alkali-reactivity to a specific silica property or quality. operator skill and experience remain essential for reliable assessment by thin-section petrography. aggregate materials must be classified according to local criteria, based on regional experiences with ASR-damaged field structures and geology. Access to additional data may be relevant for the assessment of imported materials. mere application of rock nomenclature does not provide any sort of warranty to the development of deleterious alkali-reaction. Such may result in either rejection of a suitable aggregate material, thus wasting a valuable resource, or acceptance of an unsuitable material leading to concrete damage, both of which are undesirable

RILEM Recommended Test Method: AAR-4.1—Detection of Potential Alkali-Reactivity—60 °C Test Method for Aggregate Combinations Using Concrete Prisms

This is a method developed by RILEM in the light of the results of an international trial. This trial showed that the method can reliably differentiate reactive and non-reactive combinations for a range of aggregate compositions from around the world.

Alkali–silica reactivity of some common rock types. A global petrographic atlas

The correct identification of potentially alkali–silica reactive aggregates is important for the prevention of alkali–silica reaction (ASR) in concrete. Although a number of standards for assessment of concrete aggregate by petrography are available, distinction of potentially deleterious from innocuous rock types can be problematic. The application of geological nomenclature alone is insufficient, as the geological history and hence mineralogical texture of a given rock type may strongly influence its performance in concrete. One of the goals of RILEM TC 219-ACS is to develop a worldwide photo atlas as a guide for petrographers in the identification of the mineral compositions and textures that are characteristic of alkali-reactive rocks. The atlas is based on micrographs of rock types recognized as potentially deleterious by field performance and/or laboratory expansion testing. It is intended to serve as an independent reference work and aims to unify rock terminology so as to improve the petrographic characterization of aggregates. The mission of RILEM, the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (Réunion Internationale des Laboratoires et Experts des Matériaux), is to advance scientific knowledge in the field of construction. Its Technical Committee TC 219-ACS focuses on alkali reactions and their effects on concrete.

Sand, gravel and crushed rock aggregates for construction purposes

1. Introduction Engineering geology has traditionally been concerned more with interaction between the engineering structure and its geological environment than with the performance of rock aggregates in the structure itself. In recognition of this imbalance, the Engineering Group of the Geological Society established a Working Party in 1978 to compile a reasonably comprehensive document covering the most important aspects of natural and crushed rock aggregates used for construction purposes. The objectives of the Working Party are set out in detail in Section 1 of the Working Party Report, which is being published by the Geological Society in separate book form. The membership of the Working Party, under the Chairmanship of Professor Peter Fookes, reflected a broad range of expertise and consisted of experienced individuals involved with construction materials, including producers, specifiers, users and researchers. The Working Party members are listed at the end of this summary. The first complete draft of the Report was submitted for open discussion at a one-day session of the 17th Annual Regional Meeting of the Engineering Group in 1981 at Bangor. A great number of suggestions arising from the open discussion have been considered in the preparation of the final Working Party Report; additional advice has been obtained from a considerable body of corresponding members and professional organizations. The Working Party Report contains a full list of acknowledgments. The Report was written for a wide audience and is intended to provide basic information on subjects that are new to the reader as well as serving

A procedure for assessing compositional uniformity of sand and gravel aggregates for concrete

Abstract Modern assessments of the suitability of aggregates for concrete frequently include the petrographical examination of a single set of samples taken from stockpiles at a particular time. This study has shown that a structured petrographical study (SPS) carried out over a period of production gives a more reliable representation of the aggregate composition and can also be used to provide reassurance about the probable future uniformity of the material. Two flint-dominated sand and gravel sources in regular operation were selected: one sea-dredged and the other land-based. Sets of processed coarse and fine aggregate samples were taken monthly during a year of continuous exploitation and supply. The samples were each subjected to quantitative petrographical examination in accordance with the draft British Standard procedure. The results have been evaluated and indicate for these samples a higher degree of compositional uniformity over a period of production than might have been anticipated from a preliminary geological consideration of the source deposits. In both cases, the main constituents repetitively occurred, but the relative proportions varied within limits. In this single comparison of one sea-dredged source with one land-based source, the sea-dredged aggregate was marginally the less variable material. The practical application of SPS is illustrated with regard to the control of flint or chert content in aggregate combinations.

RILEM Recommended Test Method: AAR-5—Detection of Potential Alkali-Reactivity—Rapid Preliminary Screening Test for Carbonate Aggregates

The accelerated mortar-bar test (AAR-2) has been widely and successfully used as a screening test to identify aggregates that are potentially alkali-reactive. However there are some aggregates that, though alkali-reactive according to both field experience and concrete prism test results, do not show as such in the mortar-bar test.

RILEM Recommended Test Method: AAR-2—Detection of Potential Alkali-Reactivity—Accelerated Mortar-Bar Test Method for Aggregates

This draft method was originally prepared by RILEM TC 106-AAR (Alkali-Aggregate Reaction—Accelerated Tests) as TC 106-2, and has been revised by RILEM TC 191-ARP

RILEM Recommended Test Method:AAR-1.1—Detection of Potential Alkali-Reactivity—Part 1: Petrographic Examination Method

Petrographic analysis should always be the first step in the assessment of the potential alkali- reactivity of concrete aggregates as stated in RILEM AAR-0 (Outline guide to the use of RILEM methods in assessments of aggregates for potential alkali-reactivity).