Geotechnical Engineering Properties of Peat, Stabilized with a Combination of Fly Ash and Well Graded Sand

Abstract

Abstract:Peat has several unfavourable characteristics such as low bearing capacity, high compressibility, high content of natural water and difficulty of access and thus is not suitable for Civil Engineering constructions. One of the widely used techniques for its improvement is its chemical stabilization through the addition of chemical admixtures such as ordinary Portland cement, lime, fly ash, natural fillers etc. This research was focused on stabilizing peat using low Ca fly ash (ASTM Class F) combined with well graded sand. An experimentally based approach was followed to analyse the stabilization of peat samples with different proportions of fly ash (10, 20 and 30 % by weight) and 125 kg/m 3 of well graded sand. With the increase in the fly ash content, the Maximum Dry Density (MDD) increased while the Optimum Moisture Content (OMC) decreased. The Unconfined Compressive Strength (UCS) increased with the addition of fly ash up to 10 % by weight and thereafter it began to reduce as more and more fly ash was added. The UCS increase with curing period for all of the stabilized samples. Rowe cell test results showed that there was an improvement in the compressibility of peat after stabilization. On the whole, it was found that the geotechnical engineering properties of peat can be improved by stabilizing it using fly ash and well graded sand.

Compressibility Behaviour of Peat Reinforced with Single and Multiple Deep Soil Mixing (DSM) Columns

“…Index properties of raw peat are tabulated in Table 2. Based on the index properties, this peat is classified as amorphous peat [15].…”

“…Due to the presence of peat-fly ash mixed columns in the P-MC sample, a pozzolanic reaction is induced between fly ash and water molecules in the peat. Pozzolanic reaction produces a stiff matrix in peat molecules and increases the packing of peat molecules [6,10,15]. Due to the close packing of peat soil, rate of drainage reduces, leading to a reduction in permeability value.…”

“…(a) P It can be seen from Table 6 that Cc value of raw peat reduces significantly when it is stabilized with fly ash. Addition of fly ash to peat promotes pozzolanic reaction as water from the peat is extracted for pozzolanic reaction producing a stiff matrix [6,10,15]. In addition, P-MC sample showed the lowest values among all the three samples indicating higher effectiveness of P-MC in reducing the compressibility compared to P-SC sample.…”

“…Peat is formed from the accumulation of partially decomposed and disintegrated plant in certain type of ecosystem in which water is abundant [9]. It possesses unfavourable characteristics such as low strength, low bearing capacity, medium to low permeability, high compressibility, high water holding capacity and high rate of creep [9,15]. Peat covers about 5-8% of earth's surface and two-thirds of the total world coverage of peat is in South East Asia [9].…”

“…Peat covers about 5-8% of earth's surface and two-thirds of the total world coverage of peat is in South East Asia [9]. Peat covers approximately 2.4 million ha of land area in Malaysia [13] while 25000 ha of land is covered by peat in Sri Lanka [15]. As the coverage of peat is quite extensive and the available land space is limited, peat land should be used for construction to meet the demand for land.…”