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This thesis reports the details and results of an experimental study into the effect of porosity on the thermal conductivity of lightweight and normal-weight concretes. The concretes were made from either Pellite, limestone or quartzitic coarse aggregates, with or without air-entraining agent. Their density varied from 1550 to 2350 kg/m3 and their porosity from 10 to 39 per cent. The thermal conductivity of all the concretes was measured in accordance with B.S. 874: 1988, using a plain hot-plate technique and the total porosity and pore size distribution of each mix were determined using vacuum saturation and Mercury Intrusion Porosimetry. Micromorphological changes were additionally assesed by: a) using thermal analysis methods to monitor lime and non-evaporable water content of mortars and also to monitor the carbonation process by quantitative evaluation on mortar samples. b) assessment of the depth of carbonation on concrete cubes. c) using Scanning Electron Microscopy on coarse aggregates and mortar samples. For characterization purposes, the experimental programme also involved studying the properties of fresh concrete, such as workability and air content and other engineering properties of hardened concretes, such as compressive strength. The results obtained from the individual tests were statistically analysed using a standard `Statistical Analysis System' (SAS) package. This enabled detailed examination of the relationship between the different properties to be assessed. Resulting from this, a model was developed which enabled the thermal cocductivity of a concrete to be estimated knowing its dry density, total porosity and median pore diameter. The findings of this investigation confirm that in general, the thermal conductivity of concretes are directly related to density and inversely related to porosity and pore diameter and that density and total porosity have the highest coefficient of correlation respectively.

Nineteen red tropical soils from the States of Paraiba and Pernambuco which are located in the North East of Brazil were treated with high calcium lime, they reacted showing a wide range of variation of maximum unconfined compressive strengths with - 4.5% or 6.0% lime generally required to produce maximum strength. The reaction between the soil and lime is mainly a diffusion controlled process. Most of the reaction takes place within five to seven days and the reaction within this period obeys Jander's diffusion equation for solid state reactions. Based on the constant rate of reaction obtained from this equation and on the quantity of the reactive components of the soil, an activity index, Ai, is proposed and its validity tested against the unconfined compressive strength of the soil-lime system. A valid statistical correlation is presented linking Ai value with the empirical reactivity parameter of Thompson. Identification of the types of the reaction products by x-ray diffraction which is greatly aided by the use of a semiautomated computer search program reveals that the soils form cementitious reaction products varying from dense and close textured calcium silicates of the tobermorite-like type through alumino-silicates to calcium alumino-ferri-silicates with relatively larger voids when the soils are treated with lime and cured for two years at 22°C. The increase in strength of the soil-lime system not only depends on the volume of the reaction products but also on their types and purity. Other constituents of the soil-lime system affect the strength to varying degrees. While the increase in the amount of unreacted material at the expense of cementitious reaction products is not desirable, an amount of unreacted material is essential for other engineering requirements other than strength to be satisfied. Unlike other cemented composites, the strength of the soil-lime system is not related to the overall porosity of the system.

Silicafume (SF) has been used as a partial replacement for cement in concrete and experiments have been carried out to measure the durability of the mixes. The SF mixes were made with 20% SF replacement of cement and waterlcement (wlc) ratios of 0.3 and 0.46. Three different curing conditions were used to simulate different site conditions and tests were carried out at 3,28 and 90 days after casting. The following properties were measuredfor the two SF mixes and the two control (OPC) mixes for each of the ages and curing conditions: corrosion rate of embedded steel by linear polarisation, electrical resistivity, carbonation depth, water vapour permeability, chloride permeability, oxygen permeability and porosity from helium and mercury intrusion. Samples were also investigated by thermogravimetric analysis. The resulting data matrix was analysed by using the method of analysis of variance to quantify the effect of the SF on the properties tested and their sensitivity to age and curing. It was also analysed by multiple regression to identify major effects of one property on another. It was concluded that SF will reduce the corrosion rate and that the major contributing factor is the substantial increase in resistivity that the SF causes. This increase in resistivity was found to be highly sensitive to cold curing in the short term but this effect was not permanent. The cause of the increase in resistivity is believed to be the depletion of calcium hydroxide which is caused by the pozzolanic activity of the SF. The analysis also indicated that the SF reduces the porosity in the .01-.15)1m size range and that this has a major influence on the durability.

A stable slow setting cationic emulsion has been developed, suitable to coat dense graded mixtures high in fine aggregate content, in particular gap graded rolled asphalt type and dense graded macadam mixtures. The slow setting emulsion, NH-10, is the outcome of an investigation into five different formulations using two surfactants, two adhesive agents and a water shading compound. The rheological studies of the NH-10 emulsion have shown that it possesses a thixotropic behaviour. The thixotropic behaviour has been justified by the "complex flow" coefficient, a technique proposed by Traxler for bitumens. The viscosity of the emulsion is greatly influenced by the amount of binder and level of temperature. The hardness of binder does not change appreciably the viscosity value of the emulsion. The highly stable mildly cationic emulsion has been used to prepare two types of dense bituminous mixtures containing limestone aggregate, river sand and limestone filler, blended in appropriate proportions. The study presents information regarding the properties of two dense graded bituminous mixtures i. e. a gap graded "Cold Rolled Asphalt" (C. R. A. ) and a continuously graded "Dense Emulsion Macadam" (D. E. Mc). A design procedure based on a modified Marshall method and the evaluation of permeability and creep stiffness is proposed as a laboratory method for the design of the bituminous mixtures developed. The evaluation of permeability and creep stiffness is carried out with equipment designed and developed specially for this investigation.

Researchers over the years have demonstrated the need for the determination of the nature and fundamental properties of soils as an approach to the understanding of engineering behaviour. This has teen shown to be particularly true in the case of tropical soils. This thesis approaches the analyses of engineering behaviour from a standpoint of the study of the intrinsic properties. The mineralogy, chemistry, structure and strength behaviour of three concretionary red soils from Paraiba State in North-East Brazil, have been determined. The mineralogy- of the red soils were determined using X-ray analysis, differential thermal analysis and thermogravimetric techniques. The microstructure of the red soils has been examined with the optical and scanning electron microscopes. The strength behaviour of compacted specimens was examined in the oedometer, direct shear and triaxial machines. A phenomenon of breakdown of soil particles under stress is isolated. The influence of the phenomenon on the strength behaviour is demonstrated. The soil elements and properties responsible for the phenomenon are discussed.