chemistry book bangla ahsanul kabir pdf compressor

After that, a hyperbolic function and exponential function with multiple variables were used to establish a simulation model of the effects of the DS content and curing time on the compressive strength and surface resistivity of CLSM. The surface resistivity increases with age, and each ratio increases from seven days to 28 days, and the surface resistivity value increases from 9.3% to 20.6%. The test results showed during that the compressive strength on the 28th day, the average desulfurization slag replacement amount increased by 10%, and the compressive strength decreased by 0.9 MPa. In this study, the desulfurization slag used the volume method to replace fine natural aggregates in controllable low-strength materials (CLSM) the desulfurization slag content (DS) and curing time (t) were used as variables to test the compressive strength and surface resistivity of CLSM and simulated a prediction model on the results. This has been finally employed to predict 28 days strength of concrete made with brick aggregates from their 7 days test results. The proposed model has a good potential to predict concrete strength at different age with high accuracy. The mathematical model is developed based on the analysis of stone aggregate concrete data collected from a previous study and is validated with some experimental data of cylinder tests performed in the Concrete laboratory of Bangladesh University of Engineering and Technology (BUET), Dhaka. This is further simplified with a direct correlation of one of the coefficient with concrete strength value. It is found that the constants have the relation of a surface polynomial with the strength of a particular day (7 th day or 14 th day). The model is a simple equation (a rational polynomial) that consists of only two constants and one variable which is the age of concrete in days. This paper presents a simple mathematical model to predict the compressive strength of concrete at 28 day from early age (say 7 days) results.

Though it is quite time consuming to wait 28 days for such tests, it is important to continue the construction work and ensure the quality control process. It is mandatory to test the concrete cylinders at the age of 28 days as per almost all building code requirements.

28 days cylinder strength actually represents the characteristic strength of the concrete. Concrete structures are designed on the basis of 28 days cylinder crushing strength.

Chemistry book bangla ahsanul kabir pdf compressor