ICE - Institution of Civil Engineers - Virtual Library

Although several warm-mix asphalt projects have been explored in the USA, Europe, and some countries in Asia, there is a need for the research to evaluate the applicability of warm-mix asphalt in Thailand. In this study, the fundamental properties of bitumen modified with one of the commonly used additives (Sasobit, a long-chain aliphatic hydrocarbon (LCAH)) were evaluated. The properties evaluated included the viscosity, rheological properties, rutting, and fatigue resistance. In addition, the compactability of the mixtures was also investigated to determine whether they could reach the desired density at lower temperatures. It was found that the LCAH modification improved the workability and the fundamental properties of bitumen as shown in better rutting and fatigue resistance, and also in higher complex shear modulus. The measurement of the compactability showed that less energy was required to compact the LCAH-modified asphalt mixtures to the desired density even at 20–40°C below compaction temperature. The mixtures modified with the LCAH had greater resistance to densification under traffic or higher potential to resist permanent deformation. The LCAH had no effect, however, on the resistance of asphalt mixtures to moisture damage, but the reduction of mixing and compaction temperatures could have a detrimental effect on the moisture sensitivity.

This study investigated the effect of wheat straw ash (WSA) on the performance of concrete in response to thermal cycling, which was evaluated by measuring the compressive strength and electrical resistivity and by visual inspection of cracks in the concrete specimens. Three levels of WSA replacement—5, 10 and 15% by weight of sand—were utilised. The other experimental parameters investigated in the study were: aggregate type (volcanic tuff and crushed basalt), water-to-cement ratio (w/c; 0·5 and 0·7) and air entrainment (non-air-entrained and air-entrained). After an initial moist curing period of 90 days, the concrete specimens were subjected to thermal cycling over the range 30–150°C for a period of 24 h using an electric furnace. The results of the study showed that thermal cycling of WSA concrete induced many cracks that were dispersed over the surface of the specimens. The WSA concrete was found to be more resistant to the effects of thermal cycling in comparison with plain concrete and furthermore, the performance of WSA concrete in response to thermal cycling improved with increasing WSA content. WSA concrete containing tuff aggregate showed more resistance to thermal cycling than that containing basalt aggregate. In response to thermal cycling the WSA concrete at a w/c ratio of 0·5 was observed to show better performance in comparison with WSA concrete at a w/c ratio of 0·7. The air-entrained WSA concrete showed a greater improvement in response to thermal cycling in comparison with non-air-entrained WSA concrete.

This paper assesses the effectiveness and effects of a water repellent (sodium methylsiliconate in aqueous solution) on crystallisation in stone and brick masonry materials. The salt crystallisation method adopted in this study is based on capillary rise, concentration by evaporation and consequent crystallisation and prevention of efflorescence by surface treatment. The results confirm that cryptoflorescence (salt growth within pores) is considerably more damaging than efflorescence (salt growth on surfaces). They also provide strong evidence that treatment with sodium methylsiliconate can have a harmful effect on masonry materials and may promote their decay by suppressing the capillary transport of water and salt solution to the surface, thus forcing the formation of cryptoflorescence.

This paper describes the factors influencing the reactivity of quicklime; namely the chemical composition of the raw material, the calcination and decrepitation processes to manufacture calcium oxide (CaO) and the slaking rate of lime in water. The water composition was also investigated. It was found that the presence of impurities, the tendency to decrepitate and overburning of the lime during calcination dramatically decreased its reactivity. Furthermore, the water chemistry has an important influence on the slaking rate of lime: the presence of chloride in the slaking water increases the hydration rate whereas sulfate and magnesium ions decrease this rate and delay the slaking process.

The minimum cement content requirement given in codes of practice over the years to ensure durability of concrete is being increasingly questioned. Of all the durability problems related to concrete structures, corrosion of reinforcing steel is the single most prevalent deteriorating process. This paper describes a study undertaken to determine the influence of variation in cement (binder) content at fixed water/cement ratio on carbonation- and chloride-induced reinforcement corrosion. Cement (binder) content was varied above and below the limits given in current European standards in the tests. The fines content (particles < 75 μm) of some cement-reduced mixes was maintained with the inclusion of a limestone filler as part of the sand content. The results indicate that cement reduction below the given minimum cement contents in current standards has insignificant influence on the overall carbonation-induced reinforcement corrosion process. Moreover, cement content has very little influence on the overall chloride-induced reinforcement corrosion process except the possible better performance of cement-reduced concrete with filler. It is suggested that the attention traditionally given to minimum cement content in determining reinforcement corrosion resistance may be disproportionate to the effective influence of this parameter.