Journal of Materials in Civil Engineering

The fly ash produced from thermal power plants (TPP) is disposed of in the form of slurry into ash ponds, lagoons, or dykes. Fly ash slurry, after undergoing sedimentation and consolidation processes under its own self-weight, exhibits a different engineering behavior than those compacted after dewatering. Literature review indicated no studies are available on the engineering behavior of sedimented fly ash beds/deposits, which is impeding the recycling efforts of the sedimented fly ash beds/deposits. This paper presents test results from laboratory studies conducted on sedimented fly ash deposits prepared by simulating both natural sedimentation and consolidation processes in a prototype environment. A series of compressibility, consolidation and collapse tests were then conducted on specimens collected from the sediment deposits. Test results revealed that the sedimented fly ash material exhibits a pseudoover consolidation effect including a moderate collapsible behavior and an increased compressibility at applied stresses. Collapse potential of the materials ranged between 0.5 and 1%, indicating a metastable fabric of these materials formed in the sedimentation process. Potential engineering behavioral issues related to recycling efforts of fly ash beds are mentioned.

A general relationship between cumulative pore volume and pore sizes as measured through mercury intrusion porosimetry (MIP) and BSE image analysis technique is presented in this paper. From the results of the MIP study conducted on hardened cement paste, cement silica fume paste, cement silica fume sand mortar, brick, soil cement, and concrete, it is observed that a general relationship exists between applied pressure and intruded volume of mercury. This relationship closely follows the MMF (Morgan, Mercer and Flodin) model. The general relationship between pore sizes and intrusion volume in MIP is then derived from this relationship using Washburn’s equation. A similar model is also observed to describe the relationship between cumulative volume and pore sizes obtained through BSE image analysis. The variations of the parameters namely median pore radius and dispersion coefficient (a measure of the spread of pore sizes), with silica fume content, ratio of water-to cementitious material and age are then discussed to demonstrate the utility of the model.

Two lateral-loading inelastic tests on a real masonry-infilled reinforced concrete (RC) building are presented. The first test has been carried out on the original building. Extensive damage to both masonry panels and RC elements (columns and staircase structure) has been produced, with out-of-plane collapse of almost all the walls parallel to the loading direction. The second test has been carried out on the repaired building. Namely, perimeter masonry panels were completely rebuilt and also strengthened by placing fiber-reinforced polymer (FRP) rods into the mortar bed joints of masonry. Extensive damage was produced also during this second test. Test results are discussed and compared to each other. Besides, the ability of current analytical methods in predicting the shear strength of both unreinforced and FRP-reinforced masonry panels is investigated. Eventually, simple analytical models are proposed for the lateral response of the whole building, including also contribution from the staircase structure.

The preferred management option for the municipal solid waste bottom ash (MSW-BA) around the world is utilization rather than landfilling, but the current environmental quality criteria for bottom ash to be utilized in bulk quantities are rather strict. The purpose of this paper is to analyze the physical and environmental properties of asphalt mixtures containing different amounts of MSW-BA used as an aggregate substitute. The Marshall mix design method, water sensitivity, and wheel track rutting tests were conducted on MSW-BA asphalt mixtures to evaluate the engineering properties of the mix. Leach tests were performed to measure the concentration of heavy metals. The MSW-BA asphalt mixture had relatively lower rutting resistance when compared with the conventional one. The results of the water sensitivity test showed that the MSW-BA asphalt mixtures had a lower tensile strength ratio compared with the conventional asphalt mixtures. It is recommended that the use of the MSW-BA ash in asphalt concrete mixtures be limited to be 20% ash, by total weight of the mix, in binder or base course and 10% in surface mix to ensure satisfactory pavement performance. The test results obtained from the toxicity characteristic leaching procedure testing indicated that, after being mixed with asphalt binder, the concentration of heavy metals and the levels of toxicity were significantly reduced. The concentrations of MSW-BA all along were below regulation limits.

A field and laboratory study was carried out to study the effect of pressure and temperature on the compaction of asphalt pavements. Density, temperature, number of passes, and type of roller were recorded in the field at four different paving projects in Wisconsin, with binder and mixture samples obtained from each project. Compaction in the field occurred at temperatures that ranged from 125 to $60°\mathrm{C}$ . Densification was achieved only for temperatures above the $70–80°\mathrm{C}$ range. Roller contact pressures were estimated between 300 and $700\mathrm{kPa}$ during the compaction process. Laboratory compaction was performed with Superpave gyratory compactor using the field compaction temperatures and contact pressures. The lab compaction results confirmed that below a certain temperature limit densification decreased significantly. Binder testing was performed to determine the binder viscosities in the full range of field compaction temperatures observed. The upper limit of viscosity for significant reduction in densification was estimated to be $50\mathrm{Pa}\mathrm{s}$ . A procedure for identifying the lowest temperature at which acceptable densification rate can be achieved is proposed based on testing using the dynamic shear rheometer. The determination of the lower temperature limit for compaction is an important task that is absent in the current specifications.

Recycled concrete use is necessary in order to decrease the environmental impact of the construction industry. Coarse aggregates from crushed concrete may lead to relatively high porosity in the resultant concrete. For this reason, recycled concrete may seem detrimental to the durability of reinforced concrete structures, particularly when they are exposed to marine environments. The objective of this paper is to analyze the influence of coarse aggregates from concrete on the chloride penetration rate and binding capacity of concrete under marine exposure. Concrete specimens were molded and exposed to a natural marine atmosphere. After exposure periods of 6, 12, and 18 months, ingress profiles of total and water soluble chlorides were measured. Results indicate that recycled aggregate incorporation causes two opposed effects on concrete: It increases its chloride penetration rate and chloride binding capacity. Therefore, water soluble chloride contents in conventional and recycled concrete series have similar values.