Part I of this report is a synthesis of knowledge of mechanisms of damage to concrete by alkali-silica reactivity. The details of the alkali silica reaction are discussed, and it is noted that the process is complicated by the effects of drying and growth of shrinkage cracks in exposed surfaces. The presence of chloride salts accelerates alkali-silica reactions. Formation of Friedel's salt and other complex chloride containing salts complicates test results. Part II of the report identifies 10 specific gaps in knowledege of alkali-silica reactions in concrete that limit the ability to control these reactions or to predict performance of concrete with reactive aggregates. These involve rapid and reliable test methods; moisture conditions in highway structures; effects of salts, role of sulfate reactions accompanying expansions caused by reactivity; measurement of aggregate reactivities; effect of restraint on kinetics; mechanisms by which pozzolans prevent expansion; test methods and specifications for pozzolans; and inhibition of reactivity by chemical agents.

Alkali-silica reactivity: an overview of research

Alkali silica and pozzolanic reactions in concrete. Part 1: Interpretation of published results and an hypothesis concerning the mechanism

29Si MAS NMR spectroscopic investigation of alkali silica reaction product gels

The influence of alkali–silica reaction (ASR) gel composition on its hydrophilic properties and free swelling in contact with water vapor

### Concrete in the built environment

The word “concrete ” is derived from the Latin concretus (compact, condensed), representing a conjunction of con (together) and the past participle of cresco (to grow; compare: crescendo ). Thus, concrete could be liberally translated as ‘grown solid together,’ alluding to the consolidation of a particulate aggregate material with a cement binder of some sort. Concrete containing aggregate has been used in construction by the ancient Greek and Romans, possibly as a further development of clay initially used by the Assyrians and Babylonians as a binder, later superseded by burnt lime and gypsum by the Egyptians.

As a construction material, concrete allows architects and engineers to design a structure with only minimal constraints to its form. A complicated shape requiring great effort to chisel out from a piece of stone can simply be poured in a mold and reproduced as often as desired, also ex situ . Both the invention of Ordinary Portland Cement (OPC), first patented by British bricklayer Joseph Aspdin in 1824, and of reinforced concrete first patented by Parisian gardener Joseph Monier in 1867 (for making durable flower pots), contributed to the development of mechanically stronger concrete allowing yet slimmer and taller structures to be built. Today, concrete is the most popular building and construction material with an annual production volume exceeding 7.5 km3, or about 20 billion tonne. Concrete is the prime ingredient in the world’s largest and most prominent structures and landmark edifices, including hydropower dams (e.g., Three Gorges Dam, Yichang/CN; also see Charlwood and Solymar 1995), coastal defense works (e.g., Delta Works/NL), telecommunication (e.g., CN Tower, Toronto/CA), office skyscrapers (e.g., Burj Khalifa, Dubai/UAE), theatres (e.g., Opera House, Sydney/AU), hotels and casinos (e.g., Marina Bay Area, Singapore/SG), nuclear power plants, oil and gas drilling and productions rigs (e.g., Sakhalin/RU), sea ports and harbors (e.g., …

W.A. Gutteridge

Papers

Some chemical and physical properties of beltane opal rock and its gelatinous alkali silica reaction product