Presentation on theme: "Alkali-Silica Reaction: “The Cancer of Concrete”"— Presentation transcript:
1 Alkali-Silica Reaction: “The Cancer of Concrete” Courtney Collins . Jason Ideker . Gayle Willis . Jessica Hurst
2 Outline What is ASR and why is it important? How does ASR work? How can ASR damage be prevented?
3 What is ASR?Alkali Silica Reaction (ASR)Alkalis+Reactive SilicaMoistureASR Gel which expandsConcrete cracking
4 Concrete failure due to ASR AASHTO Innovative Highway TechnologiesAASHTO Innovative Highway TechnologiesAASHTO Innovative Highway TechnologiesGeorgia Tech School of CEE - Courtney Collins
5 Why is it important to study ASR? Concrete qualityLoss of strength, stiffness, impermeabilityPremature failure of concrete structuresEconomic/Environmental impactsASR lowers concrete lifetimeLess reactive aggregates often expensive or difficult to findCement production creates 7% of the world’sCO2 emissions (a greenhouse gas).
6 Case Study: Parker Dam, California Alkali-Aggregate Reactions in Hydroelectric Plants and Dams:Hydroelectric dam built in 1938180 mm of arch deflection due to alkali silica gel expansionCracking and gel flow in concrete
7 Case Study: I-85 - Atlanta, Georgia Possible ASR damage on concrete retaining wall - picture taken 1/2002
8 How does ASR work? What we know: What we don’t know: Which reactants involved and their sourcesHow alkali-silica gel is createdASR prevention can be achieved by using low alkali cement and non-reactive aggregateAdditives such as lithium compounds and pozzolanic material help prevent ASR damageWhat we don’t know:Mechanism of gel expansionLithium: it’s mechanism of inhibition, which compounds work best, how much of each compound is needed to prevent expansion
25 Alkalis + Reactive Silica + Moisture How to prevent ASR damageAlkalis + Reactive Silica + MoistureASR GelAvoid high alkali content:use low alkali portland cementreplace cement with pozzolanic admixturesAvoid reactive aggregate (amorphous silica)Control access to waterUse lithium additives prior to placement of concrete or as a treatment in already existing concrete