Sand is one of the building materials forming the concrete mass. Sand has a type based on quarry sources, namely sea sand, river sand and mountain sand. Sand has different characteristics such as gradations (grain fineness), unit weight, mud content. Based on the SK-SNI 03-2834-1993 standard, sand has a grain size which is classified as very rough, rough, medium, smooth and very smooth. Sand that has a good gradation is separated in the form of a graph as zones 1 to 4. Concrete has good compressive strength but is weak on tensile strength. To increase the tensile strength, fiber can be added. The use of wire fiber is expected to increase the performance of buildings in earthquake-prone areas. In this study the fiber used was metal wire with a length of approximately 2 cm, designed compressive strength of concrete of 25 MPa, with a cylindrical sample diameter of 15cm and a height of 30cm, 3 month old age split tensile strength test was conducted, by using sea and mountain river sand with different zones. The results obtained that the division of the sand zone into rough to fine classification does not provide a significant trend for the tensile strength of the concrete. Mechanically, the addition of wire fibers for Air Lakok sand, Lubuk Kebur river sand and Penanding river sand has decreased the tensile strength. While the sea sand of Selubuk, the river sand of Talang Rasau and the mountain sand has increased tensile strength. Visually, all concrete that is given wire fiber has better ductility, where the concrete does not experience brittle cracks and the elements are still bound to each other.
This research was motivated by the contained SiO2 in zeolite. The purpose of this research was to know the zeolite effect as a substitute of cement in constructing 14 days paving block material which used conventional method toward the compressive strength of paving block. This research used SNI 03-06-1996 in constructing and testing the materials. The material was cube shaped with ±5 cm size which consists of normal paving block and 6 variations with 5 specimens of each variation. Total of specimen were 35. Substitute of zeolite variations used 2,5%, 5%, 7,5%, 10%, 12,5%, and 15% on the weight of cement. The result of compressive strength of normal paving block is 15,64 MPa. The result of compressive strength test had increased in the variation of 2,5% zeolite substitute by 6,28% normal paving block. The result of compressive strength test results showed the greatest decrease in variation of 15% zeolite replacement by 39,05% against normal paving block.
Paving block is used to fill the needs of surface pavement. This research uses waste of sea shell ash and fly ash as cement substitute material in the manufacture of paving blocks. Sea shell ash and fly ash containing calcium oxide (CaO) and silica oxide (SiO) that can replace and strengthen the chemical composition of cement. Variations of replacement much as 2.5%, 5%, 7.5% and 10% compared to normal compressive strength of the paving block (0%). Test specimen numbered 75 samples of rectangular with a length of 20 cm, width 10 cm and a thickness of 6 cm. Manufacture of paving blocks using conventional construction methods. The results of compressive strength testing of the age of 7 days, 14 days and 28 days for any 2 variations on the variations increase to 7.5% and down 10%. The results of the compressive strength largest average variation occurs in the replacement of 7.5% ie at the age of 7 days of 31.19 MPa, aged 14 days amounted to 33.55 MPa and 28 days amounted to 34.74 MPa. The percentage increase was highest compressive strength at 28 days with an increase of 23.19%.
Concrete strength is influenced by several variables, among others by its constituent material, mix design, workmanship, and curing. The objective of concrete curing is to maintain the concrete in certain conditions after the dismantling of the formwork hence the optimization of concrete strength can be achieved close to the designed strength. This study aims to determine the effect of concrete curing on its compressive strength. Designed concrete compressivestrength of 20 MPa with slump values of 60-100 mm to be used. The specimens are cube-shaped with 15 cm dimension. Concrete compressive strength tests were conducted at 28 days and 56 days of concrete age. The types of concrete curing consist of 9 variations, i.e., not treated, water immersed and water sprinkling. Optimum 28 days age of compressive strength of concrete obtained from specimens that immersed in fresh water, which was 31,3 MPa. The concretespecimens that were put outdoor without any curing and treatment generates second highest compressive strength value of 28.6 MPa. The 28 days age of concrete compressive strength values cured with water sprinkling with addition of burlap wrapping are still under the compressive strength of uncured concrete. Significant changes to the strength of cured concrete occurred at age of 56 days and uncured concrete strength decreased up to 19%. The optimum increase occurred in concrete cured with burlap sack wrapping and water sprinkling that was conducted routinely for 3 days by 27,84%. With increasing age (durability) the treated concrete has better strength.
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