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To date, alkali-silica reactivity (ASR) has been identified in a number of highway concrete structures. However, there is very limited data on the occurrence of ASR in airfield pavements, such as runways, taxiways, and aprons, although damage to concrete due to ASR can jeopardize the safety and functionality of the airfield pavement. A study was undertaken to develop a protocol for ASR distress rating analysis in airfields. It includes both field evaluation and laboratory investigation. Two candidate US airports with known pavement cracking were selected for this purpose. The effectiveness of field detection kits was assessed. One of the primary tasks was to distinguish distress due to ASR from other forms of distress. Complimentary to this, the contribution of ASR towards total damage was assessed. Field inspection was followed by collection of cores from strategic locations for laboratory investigation, which included microstructural identification of ASR gel, and reactive aggregates, characterization of distress features, and estimation of damage. Finally, a distress rating scheme was developed for airfield pavements. The study reiterates the importance of proper inspection, followed by detailed laboratory investigation to assess ASR-related damage to airfield pavements.

Wick action is defined as the transport of water (together with any dissolved salts) through a concrete element from a face in contact with water to a drying face. This study investigated the depth of chloride penetration in a range of concrete types exposed to salt water with and without wick action. Concretes containing normal portland cement (NPC) only, silica fume and ground granulated blast-furnace slag (GGBS) were tested. Initial moisture content and cementitious type were found to influence water and chloride transport. The relative performance of the various concrete types is discussed together with possible reasons for the observations and implications for in-situ performance.

Chloride induced reinforcement corrosion represents an enormous problem world-wide. The exposure conditions for concrete structures in the Persian Gulf area constitute one of the most aggressive climatic environments in the world. In this region, interaction between concrete and environment controls material performance and has resulted in premature deterioration and low durability of concrete structures and is of major concern. This paper reports experience from in-situ investigations on the effects of differ- ent dosages of silica fume and also a surface coating system applied to concrete decks in Persian Gulf area. The specimens were kept in various placement conditions: fully submerged zone, tidal zone, atmospheric zone, underground zone and laboratory conditions. The focus is placed on the abilitv to prevent chloride ingress. Moreover, the test results have been compared to numerical results obtained, using Life-365 model proposed by Thomas and Bentz.

This paper presents the results of an investigation undenaken to develop addi- tional data on the chemical and mechanical properties on porous concrete. When immersed in seawater for a period of 360 days, the compressive strength of porous concrete decreased by about 15 to 20% compared with standard curing, due to the leaching of free lime. Abrasion resistance of porous concrete in water showed a slightly lower value compared with that of normal concrete. The dynamic modulus of elasticity shows a steep rise during early periods up to 7 days. This tendency became more noticeable when the binder-voids ratio was decreased. The resistance of porous concrete to freezing and thawing is considered to be low, because porous concrete has continuous voids into which water can permeate during freezing and thawing. Increasing the binder per unit volume of porous concrete increases its durability.

One of the major concerns during application of cementitious grouts inside his- toric masonry is the possible presence of gypsum, which may lead to the creation of ettringite and the subsequent damage of the masonry. The design conccpt ofthe presented hydraulic grouts is based on the reduction ofthe portland cement content to the 30%-wt of the total hinder mass, in favour of appropriately proportioned mixtures of hydrated lime and natural and artificial (silica fume) pozzolans. The behaviour of the system lime-pozzolan-ponland cement in the presence of gypsum is investigated. A series of mortar specimens are made, in which a part of the sand is replaced by gypsum. The various grouts are used as hinders. The evolution of the length change and the modulus of elasticity are followed for 730 days. A very big expansion is recorded in the Iime-natural pozzolan-portland cement mortars, which may be considered as non-sulfate resistant. On the contrary, the substitution of a part of the natural pozzolan (10%-wt of the pozzolan) by an equal in weight amount of silica fume leads to a drastic reduction of the recorded expansions.