Mixing Time & Strength of Concrete

This book is about the Relationship between Mixing Time and Compressive Strength of Concrete. It involves the study of variations of compressive strength of concrete with mixing time at different ages like 7, 14 and 28 days. For this purpose three mixes, 1:2:4, 1:2:4 with plasticizer and 1:4:8, having total 90 cubes of 4 inch (30 cubes for each Batch) were cast having different mixing times varying from 3 minutes to 5 minutes with the difference in mixing time interval of 30 seconds. The cubes were placed under normal conditions for the purpose of curing and testing. The testing was done on Denison Compression Testing Machine. The failure load was worked out and then the compressive strength of concrete was calculated in 'Psi' by dividing the failure load by cross-sectional area of the concrete cube. Graphs displaying the variations of strength of concrete with different mixing time intervals were plotted for all the three mixes and from these graphs, the conclusions were drawn. It was observed that the compressive strength of concrete increases with increase in mixing time but with the increase in mixing time after a certain time of mixing, the concrete strength tends to decline. The time at which the strength of concrete is maximum, is the optimum time for which the concrete should be mixed thoroughly to achieve maximum strength. This time was found out to be between 4 minutes to 4.5 minutes for different mixes used in the experiment. Thus we may conclude from this research work that concrete should be mixed for at least 4 minutes but not more than 4.5 minutes to achieve maximum compressive strength.
About the Author: Sajjad Qaiser received his M.Sc. and B.Sc. in Civil Engineering in years 2009 and 2017 respectively from University of Engineering & Technology Lahore, Pakistan which is a top ranked technical institution among public sector universities in the country. Mr. Qaiser has an outstanding academic career having ranked himself among the top 5 students of his undergrad class. He is a registered professional member of many national and international organizations including Pakistan Engineering Council (PEC), America Society of Civil Engineers (ASCE) and Engineer's Australia (EA). His areas of research interest lie in concrete technology - materials & structures. Sajjad Qaiser possesses more than (8) years of field experience as Civil Engineer, Structural Design Engineer and Estimation Engineer. The areas of engineering explored during his brief journey include design of steel structures including pre-engineered and light gauge structures, structural design of transmission lines and substations, residential & office buildings and hydropower engineering. He is currently performing duties as a Senior Engineer (Structures) on multi-billion dollar project having net worth of 420 Billion USD. Dr. Raja Rizwan Hussain is associate Professor at the Center of Excellence for Concrete Research and Testing (CoE-CRT), Civil Engineering Department at the College of Engineering, King Saud University, Riyadh, Saudi Arabia. He received his M.Sc. and Ph.D. in Civil Engineering from the University of Tokyo, Japan; for his performance in the latter, he was ranked as Outstanding and awarded the Best Research Thesis prize and medal by the University of Tokyo. He completed his Ph.D in a record short period of just 2 years from a university ranked among Top 20 in the world. He has authored over 200 publications and has been a recipient of several awards, prizes, and distinctions throughout his research and academic career. His research interests lie in corrosion of steel reinforced concrete.