AGE AND COMPRESSIVE STRENGTH OF CONCRETE FROM VARIOUS BRANDS OF PORTLAND COMPOSITE CEMENT (PCC )

. Recently it is provided in the construction market several types of cement such as OPC (Ordinary Portland Cement), White Cement and most recently is PCC (Portland Composite Cement). The composition of PCC cement ’ s raw materials is Clinker, gypsum and additive materials. Additive materials used are limestone, fly ash and Trass. Unlike OPC type which does not use Fly Ash and Trass additives, in PCC it is used additives like Fly Ash and Trass where there is SiO2 compound that can increase the compressive strength. The research was carried out at the Laboratory of Civil Engineering Department of the Bali State Polytechnic using a cylindrical test object with size 15x30 cm of 20 pieces for each concrete age with a compressive strength of 25 MPa plan, tested at the age of 3, 7, 14, 21, 28, 56, and 90 days following PBI'71. The concrete strength of the concrete characteristics of the plan was achieved at the age of 56 days, with the value of the compressive characteristic of the plan reached at age 56 days with consecutive values of 25.82, 27.67, 26.80, 31.20 MPa and 28.81 MPa for Tonasa, Holcim, Bosowa, Merah Putih, and Tiga Roda cements. This value is greater than the value of compressive strength targeted based on the calculation of job mix design, in which it is 25 MPa. Conversion of Age and Compressive Strength Characteristics for the 5 (five) brands of PCC cement.


INTRODUCTION 1.1 Background
In public market, it is very difficult to get Portland type I (OPC) cement. The currently outstanding types are PPC (portland pozollan cement) and PCC (portland composite cement). This type of cement is currently used as an adhesive in a mixture of concrete. In the ready mix business there is also a tight competition, so in order to be able to exist they substitute cement with fly ash to get more competitive price.
Problems arised at the time of the testing of cube and cylinder test objects; that is the testing of concrete samples in various ages. The test data are often obtained at the ages 3, 7, 14 that the compressive strength of the concrete in accordance with the planned compressive strength is even greater. However, the 28-day sample test often results in a smaller value than the quality of the plan. To determine the value of compressive strength in the test at age less than 28 days converted with the coefficient of age and compressive strength quoted from PBI 71. Cube test object used in PBI 71 comes from cement of type I. Because of the controversy, the author wants to find out why such problems can happen.

Problems of the Study
The problems of this research are as follows: a. At what age is the planned compressive strength of the concrete achieved? b. What is the conversion rate of the compressive strength characteristic achievement in the variation of age for the concrete of the adhesives from several PCC cement brands?

Specific Aims of the Research
The expected objective of this research is to get an answer about the achievement of concrete compressive strength value in the age variation for some PCC cement brands. The value is to become a new reference in the construction industry which still uses the age conversion and concrete compressive strength value of type I cement adhesive.

METHOD 2.1 Materials
This research uses mixed concrete materials consisting of water, adhesives and fine aggregates. The provisions of each of these materials are described as follows.
The water used for mixing the concrete is taken from the existing water channel of the water supply company in the Materials Laboratory of the Civil Engineering Department of the Bali State Polytechnic. For hydraulic adhesive, a mixture of 5 PCC cement brands, among others: Tonasa, Holcim, Bosowa, Merah Putih, and Tiga Roda.
For fine aggregates, it is used natural sand derived from Karangasem in which the grain arrangement is designed to meet the gradations of zone 2 according to SNI 03-2834-2000. Coarse aggregate in the form of crushed stone with the provisions of the grain arrangement is designed to meet the gradation for the maximum grain size of 20 mm in accordance with SNI 03-2834-2000.
It was made 14 kinds of concrete with ratio in weight unit between adhesive material: fine aggregate: coarse aggregate equal to 1.00: 1,93: 2,67, with adhesive water factor = 0,52. The comparison of this mixture was obtained from the calculation of concrete mix design with f'c = 25 MPa. Types of concrete treatment are given in Table 1.  3  TGR 3  7  TGR 7  14  TGR 14  21  TGR 21  28  TGR 28  56  TGR 56  90 TGR 90

Research Method
The implementation of the research is divided into several stages: preparation, manufacture of test specimens, specimen treatments, data collection and data analysis.
Preparatory steps include the preparation of tools, inspection of materials including the making of the implementation schedule. Equipment used such as mixer, cylinder mold 30 mm x 150 mm, vibrating machine, place of care and press test equipment. The feasibility of carrying out the research condition is checked.
Examination of the material concerning the examination of the characteristics of the basic materials used in the study such as specific gravity, unit weight, the design of fine aggregate gradation and coarse aggregate which will be used in any mixture and others.
Mixing of materials is done by using mixing machine 'Mixer' by following the standard procedure. In this study, un-mixed aggregates were prepared under SSD conditions. The number of specimens prepared according to the age of the test and the number of specimens per test.
Power measurements were performed at ages of 3, 7, 14, 21, 28, 56 and 90 days using each 20 (twenty) cylinders 30 mm x 150 mm for each type of cement and test life. Thus the required test piece for each treatment is 140 (one hundred and forty) pieces, so the total of 30 mm x 150 mm total cylinders made entirely is 280 (two hundred and eighty) pieces. The specimens were left in the mold for 24 hours and then opened from the mold for further maintenance. Treatment is carried out by placing test specimens in a room protected from direct sunlight up to the time specified for testing: 3, 7, 14, 21, 28, 56 and 90 days.
The test is done at the material laboratory of Civil Engineering Department of Bali State Polytechnic. The data collected are crushed loads for compressive strength. All of it is obtained from the test results of the cylindrical test object in accordance with the specified test age. Before testing the specimens were weighed and measured on the sides. From the information of compressive strength values, produced for each group of specimens and each subsequent age of testing, it is done an analysis to obtain the age and strength relationship of concrete made with mixed adhesive of PCC and PPC and concrete with Cement Type I adhesive.
For the purposes of drawing conclusions, the discussion involving the tested parameters and related theories in the literature is carried out. To facilitate an understanding of the discussion, the test results will be displayed in the form of tables and curves.

Examination of Concrete Materials
The results of inspection of materials obtained from laboratory experiments shall be in accordance with the requirements of the concrete-forming material specified in the applicable concrete guidelines. This data will then be used in calculating the concrete mix design. a. Fine aggregates From the results of sand examination in the laboratory, sand data obtained as follows: (more data can be seen in appendix A-1) 1) Density of sand in state of SSD = 2.56 water absorption = 4.69% and volume weight 1,578 gr / cc 2) Gradation of fine aggregate designed according to SNI 03-2834-2000 goes into the gradation of zone 2 (Figure 4.1) with the fineness modulus (Fm) = 2.79. 3) Sandblood content = 1.44%, which means that sand is eligible for concrete mixtures according to SNI 03-4142-1996 that fine aggregates for concrete mixtures should not contain more than 5% sludge against dry weight.
b. Coarse aggregates From the examination of crushed stone in the laboratory, it is obtained data as follows: (more data can be seen in Appendix A-2) 1) Weight of the crushed stone is in state of SSD = 2.32 water absorption = 3.93% and weight of volume 1.210 gr / cc 2) Gradation of coarse aggregate is designed according to SNI 03-2834-2000 with grain diameter of 20 mm (Figure 4.2), from this gradation it is obtained the fineness modulus = 6.55.
3) The level of crushed stone slurry obtained from the examination results is 0.3%. This value indicates that the crushed stone is eligible for the concrete mixture. In accordance with SNI 03-4142-1996, the crushed stone shall not contain more than 1% sludge. 4) The wear resistance is 35.56% which means that in accordance with the requirements of SNI 03-2417-1991, coarse aggregates shall not lose weight more than 50% when using a Los Angeles worn machine.
c. Cement PCC cement is used in this study. The examination of the cement includes the volume, and from the examination it was found that the average cement volume was 1,235 g / cm3.

Results of Concrete Examination a. Value of slump
The slump value test is intended to determine the degree of viscosity of the concrete mix which can further illustrate the workability of the concrete mixture. The slump test results obtained can be seen in the following table 3.1 below.