Strength Evaluations for Treated peat with Cement and Polypropylene Fibres using CBR Tests
Peat or organic soils are those types of soils that contain a significant amount of organic material derived from plants or animals. Although peat deposits create obvious topographic features such as swamp and bogs, others are buried underground, having been covered with inorganic alluvial soils. These often are difficult to detect and are the source of differential settlements when subjected to loads from civil engineering projects. This article describes a laboratory study on treating peat using ordinary Portland cement (OPC) as binding agent and polypropylene fibers as additive. Due to high initial water content of peat, the usual moist curing technique used to cure the treated peat samples is not used and air curing method is used instead. Beside routine laboratory tests on plain peat, strength evaluation test on the treated peat samples with cement and fibres used in the research was California bearing ratio (CBR). Air curing period used was 90 days for the CBR (soaked and un-soaked) test samples. Various amounts of cements ( 15, 30 and 50%) as well as 0.15% of fibres were used to treat plain peat samples. The result of CBR tests show significant strength improvement of stabilized peat through curing period. Also as the cement amounts increase, treated samples gain more strength, while polypropylene fibers when added to the treated peat with cement not only give more strength values, rather contribute a considerable amount of uniformity and intactness to the cement treated peat
Reinforced Stone Columns in Weak Deposits: Laboratory Model Study
This paper investigates the performance of stone columns in a weak deposit such as peat. It evaluates the effects of reinforcing stone columns by jacketing with a tubular wire mesh and bridging reinforcement with a metal rod and a concrete plug. A series of plate loading tests was conducted on isolated stone columns installed in a soil bed consisting of a peat layer sandwiched between two layers of sand. The load–displacement characteristics of footings supported by stone columns were investigated by applying load to a circular plate supported on: (a) untreated soil; (b) soil treated with stone columns; and (c) soil treated with stone columns reinforced with the above reinforcing techniques. The work has shown that the settlement characteristics of the soil can be improved by installing stone columns and that a significant enhancement in the load–settlement response is achieved when the columns are reinforced by the various methods.
HRTEM study of orthorhombic zirconia in MgO-PSZ
High-resolution transmission electron microscopy (HRTEM) was used to study the phase of orthorhombic ZrO2 formed in magnesia partially stabilized zirconia (MgO-PSZ) during HRTEM specimen preparation. Based on the three reported crystal structures of orthorhombic ZrO2, with the space groups Pbcm, Pbc21 and Pbca, here it is shown that orthorhombic ZrO2 formed in MgO-PSZ has the Pbcm structure.