Pengaruh Variasi Nilai Fas Pada Beton Dengan Metode Pracampur (Premixed) Terhadap Kuat Tekan Beton F’c 20 Mpa

Concrete is the primary material used in construction and must have consistent quality. In practice, improper water addition during mixing often changes the Water-Cement Ratio (WCR), resulting in a reduction in concrete compressive strength. This study aimed to design a 50 kg packaged premixed concrete mixture with a target compressive strength of f’c 20 MPa, determine the optimum water requirement, and analyze the effect of WCR variations on the workability and compressive strength of concrete as a reference for the use of packaged concrete in the field. The research employed a laboratory experimental method with water addition variations of 0% (normal), +5%, +10%, and +15%. The specimens were cylindrical with a diameter of 15 cm and a height of 30 cm, while slump and compressive strength tests were conducted at curing ages of 7, 14, and 28 days. The results showed that increasing the water content increased the slump value but decreased the compressive strength of concrete. At 28 days, the compressive strengths were 23.80 MPa for the normal mixture, 21.04 MPa for +5%, 19.53 MPa for +10%, and 17.30 MPa for +15%. The normal mixture and the +5% variation met the target compressive strength of f’c 20 MPa, whereas the +10% and +15% variations did not. It can be concluded that WCR variations significantly affect the workability and compressive strength of premixed concrete, with the optimum mixture achieved under normal conditions and a maximum allowable water addition tolerance of 5%.