Journal of Materials in Civil Engineering

This paper presents the results of an investigation to study the possibility of developing concrete blocks using waste materials. The blocks were produced from three waste materials: vermiculite and polystyrene beads, which were used as lightweight aggregates with different proportions in the mix, and cement kiln dust (CKD), which was used as a partial replacement for cement. The strength of the three types of blocks and the strength of masonry columns constructed from the blocks were compared with another two types of normal weight concrete blocks with and without high thermal insulation properties. The thermal insulation property of the developed lightweight concrete blocks was also compared. Results showed that lightweight concrete blocks manufactured from polystyrene had lower thermal conductivity than vermiculite and ordinary concrete blocks despite the variation in the density and compressive strength, and that the addition of up to 15% CKD as a cement replacement has a negligible effect on the strength of the block.

During the last two decades, several research efforts have focused on the thermal cracking behavior of asphalt binders. Recently, important low-temperature cracking models have been introduced to include the failure properties and thermovolumetric properties at low temperatures. The main objective of this study is to evaluate selected modified asphalt binders in terms of low-temperature failure and related thermovolumetric properties. The effect of modification on fracture failure properties and related thermovolumetric properties of asphalt binder was determined by laboratory testing. The low-temperature cracking temperatures using the collected laboratory testing data were predicted. The focus of this study is on how commonly used asphalt modifiers affect the failure and thermovolumetric properties for a wide temperature range, in particular at low temperatures. Efforts were also made in this study to put more emphasis on the consideration of strain criterion, the effect of cooling rate, and nonlinearity of the coefficient of thermal contraction of asphalt binders into the prediction of low temperature cracking. The results indicate that modification of asphalt binders can have significant effects on their properties and predicted thermal cracking temperatures. The findings also suggest that in order to have a better understanding of binder behavior, the use of both failure and thermovolumetric properties is necessary.

The addition of lime is an attractive technique when the project requires improvement of the local soil. The treatment of soils with lime finds an application, for instance, in the construction of pavement base layers, in slope protection of earth dams, and as a support layer for shallow foundations. However, there are no dosage methodologies based on rational criteria as exist in the case of the concrete, where the water/cement ratio plays a fundamental role in the assessment of the target strength, and in the case of soil–cement technology, where the voids/cement ratio is shown to be a good parameter for the estimation of unconfined compression strength. This study, therefore, aims to quantify the influence of the amount of lime, the porosity, and the moisture content on the strength of a lime-treated sandy lean clay soil, as well as to evaluate the use of a water/lime ratio and a voids/lime ratio to assess its unconfined compression strength. A number of unconfined compression tests and measurements of matric suction were carried out. The results show that the unconfined compression strength increased linearly with the increase in the lime content as well as with the reduction in porosity of the compacted mixture. The change in moisture content has not presented an obvious effect on the unconfined compression strength of mixtures compacted at the same dry density. It was shown that, for the soil–lime mixture in an unsaturated state (which is usual for compacted fills), the water/lime ratio is not a good parameter for the assessment of unconfined compression strength. In contrast, the voids/lime ratio, defined as the ratio between the porosity of the compacted mixture and the volumetric lime content, is demonstrated to be the most appropriate parameter to assess the unconfined compression strength of the soi-lime mixture studied.

An investigation of carbonation in mortars and methods of measuring the degree of carbonation and pH change is presented. The mortars were manufactured using ordinary portland cement, pulverized fuel ash, ground granulated blast-furnace slag, metakaolin, and microsilica. The mortars were exposed to a carbon dioxide-rich environment (5% $\mathrm{C}{\mathrm{O}}_2$ ) to accelerate carbonation. The resulting carbonation was measured using phenolphthalein indicator and thermogravimetric analysis. The pH of the pore fluid and a powdered sample, extracted from the mortar, was measured to give an accurate indication of the actual pH of the concrete. The pH of the extracted powder mortar sample was found to be similar to the pH of the pore fluid expressed from the mortars. The thermogravimetric analysis suggested two distinct regions of transport of $\mathrm{C}{\mathrm{O}}_2$ within mortar, a surface region where convection was prevalent and a deeper region where diffusion was dominant. The use of microsilica has been shown to decrease the rate of carbonation, while pulverized fuel ash and ground granulated blast-furnace slag have a detrimental effect on carbonation. Metakaolin has little effect on carbonation.

This paper explores the characterization of Kevlar composite materials using Raman spectroscopy. The goal of the research is to develop and understand the Raman spectrum of Kevlar materials to provide a foundation for the development of nondestructive evaluation (NDE) technologies based on the interaction of laser light with the polymer Kevlar. The paper discusses the fundamental aspects of experimental characterization of the spectrum of Kevlar, including the effects of incident wavelength, polarization, and laser power. The effects of environmental exposure of Kevlar materials on certain characteristics of its Raman spectrum are explored. These data may provide a foundation for the development of NDE technologies intended to detect the in situ deterioration of Kevlar materials used for engineering applications that can later be extended to other materials such as carbon fiber composites.