Generally, peat has recognize as organic soilhigh that has high natural moisture content content due to its naturalwater-holding capacity. The high natural water holding capacity of peat soil isdue to the structure of soil that have characterized by organic coarseparticles (known as fiber) which can hold a considerable amount of water sincethe soil fibers are very loose and hollow (Bujang and Kazemian 2011). From theresult from table 1, the value of natural moisture content at burnt peat areahas ranged between 354 to 709 %, as suggested by Huat and B. K. (2004) thatmoisture content range values of peat soil of West Malaysia is between 200 to700%.
In geotechnical engineering aspect, organic soils with organic contentthat greater than 75% are known as ‘peats’ (Bujang, 2004). From the result, allof the burnt peat soil samples contain more than 75% of organic matter withless than 25% of ash content. Normally, the volume of peat samples were higherin wet condition and started to decrease when it getting dried and shrunk. Itcan be seen from figure 9, the percentage of shrinkage limit getting higherwith the increasing of moisture content of burnt peat soil. With addition ofOrdinary Portland Cement (binder) and mineral soil (filler), it might fill theair void of grain particles; thus the tendency of stabilized burnt peat can bereduced. Abu Bakar (2008) studied the properties of stabilized peat (Banting peats)with and without the addition of sand concluded that the shrinkage ofstabilized without sand was reduced with the increase of admixture content andcuring time.
From the result (table 1 and figure 9), the linear shrinkage wassignificantly reduced by the addition of admixture and curing period ofstabilized peat with addition of mineral soil filler particles. InUnconfined Compressive Strength (UCS) test, there is no radial stress acted tothe sample (?=0) which is theaxial load is increasing rapidly until the samples of soil tend to fail untilit cannot support any additional load. The pore water cannot drain anymore fromthe soil since the loading acted quickly and making the soil sample is sheared ata constant volume. As indicated by Kalantari andHuat (2008), the most guideline of utilizing the Air Curing Technique to settlepeat is the natural moisture content of peat soil sample has ranged between 198to 417%. From the result, the value of UCS strength increased with addition ofnatural moisture content of peat sampling but the strength started to decreasewhen the value of moisture content surpassed 425% in intersect line 1. The UCSstrength value seem to be a slower rate of strength gain after 14 days ofcuring. The highest value of UCS value recorded at point BP-2 with 412.
17 kPawhich has 425.34% of moisture contentindicates the optimum content of water needed to gain the maximum UCS strength of burnt peat samples. Water content capacity isthe most important properties in determination of peat soil. It can be seenfrom the result at table 1, whereas the lowest value of UCS strength recordedat BPL-2-4 (intersect line 2) with 121.48 kPa and BP-6 (intersect line 1) withvalue of 149.
59 kPa, which has the lowest and the highest value of naturalmoisture content; BPL-2-4 (205.56%) and BP-6 (709.805) respectively. This isindicate that moisture content give the big impact to the strength of burntpeat stabilization. According to Chen and Wang (2006), the large amount oforganic matter present in peat soil allow peat to hold a large water rentationcapacity; resulting a high natural moisture content and will caused the organicparticles to adsorb to the surface of the cement and also to the surfaces ofsolid mineral particles.
This will prevent the hydration process of cementproduct and inhibiting hydration reaction between solid soil particles and thehydration product; thus affected the increment of the strength of peat-cementadmixture. As the air curing time for the stabilized peat samples wasincreased, the moisture content decreased, thus weight of ratio Water/Weight ofCement (W/C) was reduced, and as a result the stabilized peat samples werehardened and gaining significant strength (Behzad and Bujang, 2008).