Studi Penggunaan Bahan Aditif Dan Variasi Dosis Accelerator Terhadap Perkerasan Beton Yang Dipercepat (Studi Kasus Mutu Beton K-300)

Penelitian ini bertujuan untuk mengetahui hasil pengujian kuat tekan awal beton kombinasi sikafume (mineral additive) dan variasi dosis penggunaan accelerator (chemical admixture). Penelitian ini menggunakan metode eksperimental. Adapun prosedur penelitian dimulai dengan studi literatur, dilanjutkan dengan persiapan material, pemeriksaan sifat fisis agregat, perencanaan campuran beton (concrete mix design), pembuatan dan perawatan benda uji, serta pengujian benda uji berupa pengujian slump dan pengujian kuat tekan serta analisis data. Berdasarkan hasil dan pembahasan penelitian terkait dengan nilai kuat tekan beton, maupun bentuk atau workability dan waktu perkerasan adalah sebagai berikut: 1) hasil uji kuat tekan beton kombinasi sikafume dengan variasi dosis penggunaan accelerator 1:2 memiliki nilai kuat tekan rata-rata sebesar 26,823 Mpa dan 31,280 Mpa untuk umur pengujian 24 dan 72 jam; 2) hasil uji kuat tekan beton kombinasi sikafume dengan variasi dosis penggunaan accelerator 1:3,5 memiliki nilai kuat tekan rata-rata sebesar 24,913 Mpa dan 30,643 Mpa untuk umur pengujian 24 dan 72 jam; 3) hasil uji kuat tekan beton kombinasi sikafume dengan variasi dosis penggunaan accelerator 1:5 memiliki nilai kuat tekan rata-rata sebesar 23,640 Mpa dan 30,325 Mpa untuk umur pengujian 24 dan 72 jam; 4) nilai slump yang diperoleh pada setiap variasi benda uji lebih besar dari yang direncanakan dalam mix design, yaitu nilai slump yang diperoleh termasuk katagori slump runtuh; dan 5) kombinasi sikafume dan variasi dosis accelerator dapat mempercepat waktu perkerasan dengan nilai kuat tekan rata-rata di atas 24,90 Mpa atau K-300 dalam waktu 24 dan 72 jam

Uji Eksperimental Penggunaan Zat Additif Mastersure 1007 Terhadap Workobility Dan Waktu Ikat Beton

Penggunaan bahan tambah pada beton merupakan suatu inovasi yang dapat berkembang sesuai kebutuhan dalam penggunaan beton pada pekerjaan kontruksi. Penggunaan bahan tambah ditujukan untuk mengubah ataupun memperbaiki sifat beton agar sesuai dengan kebutuhan dan pekerjaan tertentu seperti mempercepat dan memperlambat pengikatan dan mempermudah pekerjaan (workability). Untuk mengatasi permasalahan dilapangan jarak tempuh yang jauh yang mampu memperlambat waktu ikat semen dapat digunakan Jenis bahan tambah yang digunakan bersifat kimiawi (chemical admixture), dalam hal ini bahan tambah (admixture) MasterSure® 1007 Tipe G, yang mana kandungan Retarder lebih dominan daripada Superplasticiser. Tujuan penelitian ini untuk mengetahui pengaruh penambahan MasterSure® 1007 dalam campuran beton terhadap nilai slump dan waktu ikat beton. Metode penelitian yang digunakan merupakan metode eksperimental, dengan cara membuat benda uji (sampel). Benda uji yang menggunakan bahan tambah MasterSure® 1007 sebesar 0,8%, 0,9%, 1%, 1,1%, 1,2%, 1,3% dan 1,4% dari berat semen sesuai dengan Job Mix Design. Pengujian pada penelitian adalah penggujian Slump Test dan Penetration Test. Hasil penelitian menunjukkan bahwa pada variasi penambahan MasterSure 1007 dari dosis terkecil yaitu 0,8% sampai dosis terbesar yaitu 1,4% rata-rata mempunyai nilai slump optimum pada umur 3 jam pengecoran. Pada umur 4 jam pengecoran dapat dilihat bahwa semua variasi mengalami penurunan slump dikarenakan reaksi retarder pada zat additif MasterSure 1007 sudah mulai habis. Hal ini menyebabkan zat additif MasterSure 1007 yang memiliki kandungan superplasticizer mulai bekerja sehingga mempercepat hidrasi semen pada beton. Hasil penetrasi test didapatkan pada variasi Beton normal, 0,8%, sampai 1,4% masing-masing yaitu waktu pengikatan awal dari 75menit;150 lbs/in2, 360menit;120lbs/in2, 360 menit;170lbs/in2, 420menit;160lbs/in2, 540menit;120lbs/in2,720 menit;120lbs/in2 dan pengikatan akhir dan pengikatan akhir masing-masing 150 menit; 700lbs/in2, 540 menit; 700lbs/in2, 600 menit; 700lbs/in2, 720 menit; 700lbs/in2, 840 menit;700;bs/in2,1080 menit ; 700lbs/in2

An experimental study on production of high strength non-shrink grout containing fly ash

Cement-based grouts are widely used thanks to its outstanding features such as high workability, non-separation, non-bleeding, easy to fulfill small gaps with complex shapes. This paper descrcibes the first phase of a series of laboratory experiments that examined the ability of production of self - levelling mortar at the University of Transport and Communications. The Portland cement-based grout incorporated superplasticizer, fly ash, fine aggregate, water along with expansion agent to match as closed as possible the given high strength non-shrink grout. The experimental study focused on the performance of non-shrink grouts regarding the flowability, expansion and bleeding, strengths and drying shrinkage of the test grout mixtures. The high range water reducer (HRWR) at dosage of 1% by weight of cement was used as a flowability modifying chemical admixture to prevent water segregation and leads to an increase in compressive strength. The parameter tests consist of water-cement ratios, and fixed dosages of superplasticizer and expansive agent. To examine the flowability of grout mortars, the flow cone test was applied. The flow cone test result indicated that there were three proportional of grouts that can meet the requirement of fluidity. The compressive strength of specimens was tested according to ASTM C349-14. It was concluded that the compositions of grouts at a water-cement ratio of from 0.29 to 0.33 have compressive strengths greater than 60 MPa. The tested specimens using the expansive agent with the dosage recommended by the manufacturer meet the non-shrinkage requirement of a grout. The experimental results have demonstrated the ability of production of high strength non-shrink grouts.

Comparative Analysis on the Micropore and Microstructure Characteristics of Concrete under Insulated Formwork

During concrete construction in winter, the concrete performance is generally improved by adding a chemical admixture or providing protection using tents and hot-air blowers. However, long-term strength or safety accidents may occur due to the installation and removal of the tents. This study considered insulated gang forms to improve formwork methods. In this regard, the microstructure and micropore characteristics of concrete were investigated experimentally to examine the insulated gang form effect on the physical and mechanical properties of concrete. The micropore characteristics were investigated through scanning electron microscopy. The results confirm that applying insulated gangs improves workability and safety without adding chemical admixture. Moreover, the application of insulated gang forms reduces the use of tents and hot-air blowers. Therefore, insulated gangs provide excellent initial quality to the concrete.

Investigations on Improving the Compressive Strength of Sand Column with Cement Grout and Chemical Admixture

Grouting is one of the most commonly adopted technique for soil improvement and strengthening. Adding super plasticizers, accelerators, antifreezes, air entraining agent improves the performance of the cement grout. The performance of the grout while injecting in the sand column mainly depends on its fluidity property. Keeping it in mind about the water cement ratio, the strength of the sand column is studied in two sets of experiments one by sand column with cement grout only and another set by sand column with cement grout added with super plasticizers by varying the water cement ratios. Strength parameters like angle of internal friction and cohesion were obtained be direct shear test and unconfined compressive strength test on the specimens by varying the water content. An increase of 15.2kPa to 60.33 kPa was observed in the cohesion value for specimens with 10% water content and 13.8 kpa to 47.2kPa cohesion value observed in the specimens with 20% water content. The angle of internal friction was decreased from 360 to 160 for 10% water content whereas 300 to 100 for 20% water content. A series of experiments were conducted on the sand column grouted with cement and for different water cement ratios as 1.5, 2.0 and 2.5. Another set of experiments were repeated by adding 2%super plasticizer Sulphonated Melamine Formaldehyde (SMF). The experiment results revealed that at lower water cement ratio higher value of compressive strength was observed. It was also observed that the strength increases with curing period.

Effect of Electrically Precipitated Fly Ash(EPFA) On Fresh and Hardened Properties of High Strength Self- Compacting Concrete

Concrete is the most common heterogeneous material in the construction industry. Admixtures have gained wide use in modern constructions, which are having congested reinforcement with ambitious casting conditions. For such applications, self-compacting concrete (SCC) is the only special concrete, which can have high cohesiveness and fluidity. This paper shows the study on the fresh properties, compressive, flexural and split tensile strength in addition to RCPT, sorptivity of SCC with partially replaced electrically precipitated fly ash (EPFA) from 0 to 30% at 5% interval in cement and polycarboxylate ether-based superplasticizer as a chemical admixture. Compared the results with conventional SCC mix the fresh concrete performance was studied through the measurement of passing ability, filling ability and flowing ability by using L-Box, U-Box, V-Funnel and slump flow. The results showed that 20% EPFA as partial replacement to SCC gives better results than the conventional concrete, thereby leading to economical profits as well as ecological benefits.

The Effect of Various Polynaphthalene Sulfonate Based Superplasticizers on the Workability of Reactive Powder Concrete

A superplasticizer is a type of chemical admixture used to alter the workability (viscosity) of fresh concrete. The workability of fresh concrete is often of particular importance when the water-to-cement (w/c) ratio is low and a particular workability is desired. Reactive Powder Concrete (RPC) is a high-strength concrete formulated to provide compressive strengths exceeding 130MPa and made of primarily powders. RPC materials typically have a very low w/c, which requires the use of a chemical admixture in order to make the material workable for placing, handling and consolidating. Superplasticizer are commonly used for this purpose. Superplasticizers are developed from different formulations, the most common being Polynaphthalene Sulfonate (PNS), Polymelamine Sulfonate (PMS) and Polycarboxylate Ether (PCE). This study investigates the impact of various PNS based superplasticizers on the compressive strength and rheological performance of a RPC mixture. Six different types of PNS based superplasticizers were used; three of various compositional strengths (high, medium, low range) from a local provider, and three of the same compositional strengths (high, medium, low) from a leading manufacturer. Specific properties assessed were the superplasticizers viscosity, concrete workability through the mortar-spread test, concrete rheology, and 7, 14, and 28 day RPC compressive strengths. Two mixtures were produced with two w/cm (0.20 and 0.15), which would subsequently increase the amount of superplasticizer needed, from 34.7L/m3 to 44.5L/m3. The results show that the name brand high range composition produced the overall highest spread, lowest viscosity, and a highest compressive strength at all ages tested. However, the local provider outperformed the name brand in the mid and low range compositions. Additionally, the rheology test also demonstrated that the name brand high range, and RPC produced with the name brand high range, had a lower viscosity at all angular speeds than the others tested.