ACI 2007 Concrete Projects Competition Winners

 

1st Place:
 Designing and Analyzing a New Shrinking Reducing Admixture for Concrete
Author:
 Michael J. Loy  
Advisor:
 Rosa Hemphill
Abstract:
 Concrete is the most widely used building material in the world. The challenge for construction engineers is to design durable concrete, which does not crack. While chemical air-entraining admixtures (AEA) are added to concrete to reduce cracking from the freeze/thaw process, AEA increase shrinkage which results in cracking, thus prompting the addition of shrinking-reducing admixtures (SRA), which have an effect on concrete properties. The goal of this project was to design a new, effective, non-toxic RA superior at reducing shrinkage because of its low surface tension. A dipropylene glycol-based SRA was formulated by the student, mixed with AEA into concrete, then analyzed against two established SRA-AEA combinations for effects on rate of shrinkage, compressive strength, air void quality and air content. Surface tension, slump and unit weight tests were also conducted. Results indicated that lower surface tension correlated to lower rates of shrinkage by retaining water in the capillaries thus reducing drying shrinkage. Based upon promising results of the student-SRA, future study should analyze the chemical composition and reactions of dipropylene glycol-SRA, without AEA, to reformulate the admixture composition for optimal results.
 
  
2nd Place:
 Rapid Setting Composite Concrete for Blast Protection  
Author:
 Cadets Dan Long, Chip Heidt and Mark Hogan
Advisor:
 Lieutenant Colonel Karl F. Meyer