An Experimental Study on Effect of Palm – Shell Waste Additive to Cement Strenght Enhancement

Enhancing the cement strength through attaching chemical additive has been popular to meet the required condition for a particular well-cementing job. However, due to a low oil-price phenomenon, pouring and additive should be reconsidered because it can raise the cost and make the project become uneconomic. Another additive material in nanocomposite form will be introduced through this experimental study. The nanocomposite material consist of silica nanoparticle, known as “Nanosilica” and a palm-shell-waste, which is abundant in Indonesia. Before making a nanocomposite, the palm-shell should be burned to obtain a charcoal form, ground and sieved to attain a uniform size.   The study focuses on the two parameters, compressive strength and shear bond strength, which can reflect the strength of the cement. These values are obtained by performing a biaxial loading test to the cement sample. Various samples with different concentration of nanocomposite should be prepared and following the mixing, drying, and hardening process before the loading test is carried out. The result from the test shows a positive indication for compressive strength and shear bond strength values, according to the representative well cementing standards. Increasing the nanocomposite concentration on the cement will increase these values. Furthermore, an investigation on the temperature effect confirms that the sample with 700oC burning temperature have highest compressive-strength and shear-bond-strength values. This is a potential opportunity utilizing a waste-based material to produce another product with higher economic value.


Int r oduct i on
The cement strength issue is a common problem in the oil-w ell cem enting operation. The strength can be reflected from its Compressive strength (CS) and Shear-bond Strength (SBS) values, w hich is appropriate to the proper standard. (Rubiandini et al., 2005) In oil and gas industry, these values should refer to the Ameri can Petroleum Institution standard (Institut, 2002). CS defines as the ability of cement to w ithstand the horizontal force such as formation and casi ng pressure w hile SBS describes the capacity of the cement in resisting the vertical force such from the casing string w eight. (Palmer, 1990) Enhancing the slurry w ith chemical additives is a solution to keep our design consistent w ith t he required condition. (Rubiandini et al., 2005) Enhancement of pozzolanic material and other supportive material into the slurry has successfully increased the cement strength. (Siregar, n.d.) According to ASTM C618-93, material w hich contains silicon oxide, iron oxide, and aluminium oxide more than 70% can be utilized as an additive material. (Al-Dahlaki, 2007) Other engineered particle such as silica, iron oxide, and aluminium oxide nanoparticle can raise up the cement strength and reducing the filtration loss phenomenon (Ershadi et al., 2011) This experimental study uses nanocomposite additive, a combination of Nanosilica and palm -oil shell, w hich is commonly found in Indonesia. Palm -oil trees flourish in almost over 33 million acres, w here 70% of this plantation site lies in Sumatera. An abundant source of palm -oil, w hich is nearly 17.3 ton per year, leads to other w aste product such as liquid w aste, (Palm Oil M ill Effluent, POM E), fibres, and shell. (Dirjenbun, 2015) One ton of Palm -oil w ill dispose 700 kg POM E and 190 kg of fibres and shell. (Haryanti A., Norsam si,Sholiha P.S.F., 2014). The shell from the palm -oil-fruit contains silica (Worathanakul et al., 2009). M oreover, another w ork by (Bae, 2016) has yielded an optimum concentration for nanocomposite additive, w here CS and SBS reach its maximum values for sample w ith 3w t% nanocomposite additive.
The Effect of heating temperature has been observed (Hadiguna, 2016). Experiment by using palm -shell carbon additive have show n the optimum heating temperature is 700 o C. How ever, the optimal temperature for a sam ple w ith nanocomposite temperature is not studied yet. The objective of this paper is to investigate the effect of the heating temperature to cement strength.

M at er i al
The CS and SBS values can be obtained by performing the tri-axial test. The sam ple should be prepared carefully to keep the quality of the recorded data. A class G cement pow der from PT Holcim has been purchased. Class G cement is applicable in the w ell cementing environment (Falode et al., 2013). Furthermore, nanosilica from Aldrich Company, w here t he physical properties are listed in the table 1, is procured. One of the Palm -Oil Company in Indonesia, CV Berkat Jaya, located in Sampit, Kalimantan has supported us by providing the shell from the palmoil fruit. The shell w as ground and sieved to obtain the uniform size (200 mesh). The shells in pow dery form, is then heat ed by using the oven furnace. To see t he effect of heating temperature, six shells sam ple w ill be roasted w ith different temperature, from 500 o C to 900 o C w ith 100 o C escalation to obtain its charcoal form, know n as Palm Shell Carbon (PSC). Six cement sam ples w ill be prepared based on the table 3. Water should be kept in turbulent condition by maintaining a high speed propelled mixer in constant condition (1200 + 500 RPM ). It is important because the cem ent and the palm -oil shell should mixed completely. After the cement pow der and the palm -oil are decanted into the mixing container, the mixer speed w ill be increased to the 4000 + 200 RPM for 15 m inutes. Cement suspension is then placed into the mold and dried for 24 hours at 140 o F. After sam ple totally dried, a sam ple is taken out and then positioned in the hydraulic press apparatus. A certain am ount of hydraulic force w ill burdened to the sam ple until the crack w as generated and t he rock rupture. The load w as recorded as maximum load and CS and SBS values can be calculated by using this parameter. The procedure w ill be repeated for other sam ple w ith different heating temperature of PSC. The struct ure and the crystal content of the sam ple w ill be identified by using X-Ray Diffraction (XRD) and Scanning Electron M icroscope (SEM ) apparatus.

Result s and Di scussi on
The effect of heating temperature on CS and SBS values is depicted in Fig 1 and 2 respectively. According to the API standard, the CS and SBS values are acceptable and can be implemented in the field condition. The positive trend has been illustrated in the Fig 1, w here the CS value increases up to more than 1400 psi for sam ple w ith 700 o C heating temperature, compared to the sam ple w ith 500 o C heating temperature. How ever, the greater CS value is not established for the sam ple w ith higher heating temperature. Similar thing occurred in the SBS plot in Fig 2, w here the highest SBS value w as recorded for the sam ple w ith 700 o C heating temperature. Fig 1 and 2 clearly expresses that CS and SBS values w ill improve if the heating temperature of the PSC higher. Performing the heating process w ith higher temperature w ill trigger the charcoal purification process, yield to the increment of PSC-active-carbon-content up to 90%. M ore carbon active improve the bonding quality of the cement, resulting higher CS and SBS value. How ever, the active carbon w ill decrease after the heating temperature exceeds 700 0 C. This due to the presence of hydrogen gas, w hich can lessen t he bonding quality of the cement.  Fig 3.b. Furthermore, sam ple w ith higher heating temperature has greater crystal content (82.2% compares to 62.5%). Sam ple w ith greater crystal content tend to strengthen the interparticle bonding, resulting a high strength concrete. Result from The SEM have indicated the PSC temperature has effective covered more pore space in the cement sam ple. It is clearly show n in Fig 4.a and 4.b, w here the sam ple w ithout PSC (Fig 4.b) has w ider void space (darker area) w hen w e compare to the sam ple w ith PSC (Fig 4.a). Hence, the presence of the PSC material, combined w ith Nanosilica can plug more pore, resulting a more compact structure of cement.

Conclussi on
An experimental study has been accomplished to investigate the effect PSC heating temperature to the cement strength in t he oil-w ell cementing job, w hich are described from the CS and SBS Value of the cement. The object of the experiment is a cement concrete, w hich is enriched w ith the nanocomposite additive. The nanocomposite comprises of Nanosilica and PSC, a w aste material from the palm -oil mill. Result from the tri -axial loading test conclude that the more heating temperature of the PSC, t he higher CS and SBS value w ill be acquired. An optimum heating temperature, w hich yield the highest CS and SBS value, is obtained for a sample w ith 700 o C heating temperature PSC. M oreover, result from the XRD and SEM result confirm that PSC has a potential opportunity to be a product w ith a higher economic value.