Overview Of Studies Related To Cement.docx

Overview of Studies Related to Cement, Fly Ash and PP fibres Modification

Researchers and Title Jayakumar & Sing (2012): Experimental Studies on Treated Sub-base Soil with Fly Ash and Cement for Sustainable Design Recommendations

Mahvash, LópezQuerol, & BahadoriJahromi (2017): Effect of class F fly ash on fine sand compaction through soil stabilization Şenol & Gümüşer, (2014): Effect of Fly Ash and Polypropylene Fibers Content on the Soft Soils

Materials OPC (2%, 4%, 6%) and FA (6%) by dry weight soil sample 3% FA and 3% OPC

Major Findings The trend showed that further OPC increase in mixture increased the MDD value but decrease the value of OMC. As for the CBR test, the soil mixtures were. Non-stabilized mixtures showed the lowest is whereas an addition of 6% OPC is the highest CBR obtained with 11.49%.The mixtures between soil and FA at 6 % produced 9.16% CBR value. Hydraulic conductivity test conducted concluded that the addition of OPC reduces water permeability.

Soil sample, FA (5%, The inclusion of FA and OPC caused an 10%, and 15%), OPC MDD reduction while increasing the value (3%) of OMC.

Fibrillated and multifilament PP fibre (0.5%, 1.0% and 5% by dry weight of soil sample), FA (0.0%, 10.0% and 15.0% by dry weight soil), Jain, Gupta, Khare, PP fibre content of & Dharmadhikari 0.0%, 0.4%, 0.6% (2011): and 0.8% by volume Use of polypropylene of concrete fibre reinforced concrete as a construction material for rigid pavements

The amount of FA into the mixtures decreases the MDD while increasing the OMC. The addition of 0.5% multifilament PP fibres gives maximum percentage increase in CBR after curing for 96 days.

The use of PP fibres reduced the early age shrinkage of concrete. Increasing the volume of PP fibres up to 0.6% increased the modulus of elasticity (MOE) and modulus of rupture (MOR) in concrete. The additions of PP fibres into the mix design induce ductility in plain concrete and increased energy absorption capacity. Optimum dosage of PP fibres in plain concrete mix design is 0.6%.

Olgun (2013): Effects of polypropylene fiber inclusion on the strength and volume change characteristics of cement-fly ash stabilized clay soil

PP fibres (6 mm, 12 mm and 200 mm) added into mixtures with proportion of.25%, 0.5%, 0.75% and 1.0% of total dry weight of mixture, Samples of mixtures containing 4-12% OPC and 10-40% FA

The interaction between PP fibre surface and hydration products is important because the addition of PP fibre caused an increased in tensile strength value. Action of bridging was formed due to additions of PP fibres which controlled the opening and propagation of tension cracks. SEM imaging indicated the formation of cementing gels from the interaction between soil, cement and FA in addition of traces of abrasion formed due to physical interaction of stabilized soil and PP fibre.

Based on the overview of related research above, it is determined that the inclusion of PP fibres and FA into cement stabilized soil and concrete will increase the structural properties of the cement stabilized soil and concrete in terms of UCS, CBR and OMC while increasing the MDD of the mixture. Unfortunately, it is unclear how the inclusion of both FA and PP fibre will affect the performance of cement stabilized road base as there are still a lot to be explored in this field of research. In addition, most of the studies conducted related to the addition of PP fibres and FA in cement stabilized road base was conducted outside of Malaysia. As such, it would be beneficial and interesting to look into the properties of cement stabilized road base with the inclusion of FA and PP fibres in Sarawak.

Review of Methodology There have been numerous published studies that employed structural test methods to analyse and determine the structural properties of modified cement stabilized road base. Unconfined compressive strength (UCS) of cement stabilized road base is proportion to the cement content added into the mixes. It is a common practice to determine the strength of stabilized materials from an unconfined compression test (Ghosh & Subbarao, 2006). Based on the studies mentioned in section 2.2, it is concluded that the addition of OPC and PP fibres increased the UCS of concrete due to the hydration process and the physical bridging effect promoted by the use of PP fibres (Olgun, 2013). The higher the amount of cement added, the higher the UCS values were (Bessa, Aranha, Vasconcelos, Silva, & Bernucci, 2016). However, adding too much cement into the mixture could produce stiffness that would be too high and cause the road base to experience brittle failures. The same study conducted also concludes that the resilient modulus of cement stabilized road base mixed with FA increased in more than 1000% after 7 days of curing process. Thus, combining the right amount of OPC and FA will ensure a high UCS values while not susceptible to brittle failures. Due to the rigidity of cement stabilized road base, the stabilized road base will experience less deflection when load is applied on it. Chai, Oh, & Balasubramaniam (2005) conducted field analysis using falling weight deflectometer (FWD) whereas Trichês & Santos

(2011) used Benkelman beam test to measure the deflection of cement stabilized road base. The results indicated that the deflections found on the pavement segments with cement addition decreased and their rigidity increased after only a few days of curing (Bessa et al., 2016). According to JKR Malaysia (2008), the maximum percentage of OPC that can be added for cement treated base is 5%. As for the addition of FA to replace the amount of OPC in the mix design, Papadakis (1999) recommended 30% as the optimum amount of FA to replace OPC however, later studies conducted by Mahvash et al. (2017) concluded that the optimum percentage is 20%. This contrast in recommendation however, is due to the differences in the maximum percentage of FA set by both researches as Mahvash et al. conducted their studies up to 20% FA content. 0.5% multifilament PP fibres was used by Şenol & Gümüşer (2014) to achieve optimum results whereas Jain et al. (2011) recommended using 0.6% PP fibres in plain concrete. Thus, it can be concluded that the optimum percentage of PP fibres to be added by weight of dry soil is in the between 0.5% and 0.6%. As for the length of PP fibres, Olgun (2013) stated that the optimum length of PP fibre is 12 mm. The California Bearing Ratio (CBR) of base material is an indication of its bearing capacity under traffic loading and is determined as the ratio of the penetration resistance of the base material to that of a standard crushed stone (Thakur & Han, 2015). It has been used by many engineers and researchers to characterize the strength of base materials for road designs. However, its use for pavement design has been limited as the pavement engineers have recently found that the CBR is not a true mechanistic property and suggested that CBR can only be used for guidance of material selection (Bennert & Maher, 2005). Despite that, it still can be used as a measure to determine the bearing capacity of the stabilized road base. In order for cement stabilized road base to obtain its maximum dry density (MDD), sufficient moisture needs to be added to its material so that air is removed from the material and the particles are packed correctly into place to give an MDD. The addition of FA and OPC in existing road base the optimum moisture content (OMC) and MDD of soils because the effects of cation exchange and short-term pozzolanic reactions between lime and the soil results in flocculation and agglomeration of clay particles leading to textural changes that are reflected in the moisture-density relationships (Little & Nair, 2009). Little and Nair also stated that flocculation of clay particles by cement can cause OMC increase and MDD decrease whereas the higher density of cement to soil can result in higher density of the mixes. The higher the MDD, the lower the amount of air void between particles in the road base which results in highly compacted and more durable road base.