Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
The work presented in this Dissertation involves an effort to broaden sustainable applications (e.g., recycling waste material in concrete, reducing CO2 emissions in cement production) in construction industry. Finely ground brick obtained from demolished masonry was evaluated as a pozzolanic cementitious material in concrete. The hydration characteristics of this material and its effects on cement paste, mortar, and concrete mechanical properties, particularly on alkali-silica reaction deterioration was studied. Ground clay brick (GCB) was produced in the laboratory employing a ball mill. Chemical and physical properties comply with the designated ASTM standard that defines pozzolanic materials. The results of the study on cementitious pastes where cement was replaced by GCB up to 25% showed that the effect on water demand for normal consistency and time of setting was insignificant; the temperature rise during hydration was reduced; and the calcium hydroxide production was decreased. The testing of mechanical properties of concrete containing up to 25% GCB demonstrated that the values were low at early age but higher or comparable at later ages when compared to the control and the resistance to chloride penetration was improved. These results suggested a pozzolanic activity provided by finely ground brick. The results from the accelerated ASR testing of mortar mixtures showed that the expansions were significantly reduced and associated deterioration on the compressive and flexural strengths was limited with the use of GCB. The concrete tests confirmed the mortar testing that the expansion was effectively suppressed and the mechanical properties of a highly alkali-silica reactive mixture could be conserved when cement was replaced by GCB at 15 and 25% loading. Subsequent microstructural study revealed out the quantitatively low gel formation in the presence of GCB and further suggested a modification in gel chemistry by GCB. The reported experimental study demonstarted that GCB shows pozzolanic behavior similar to other conventional materials (e.g., fly ash, calcined clay, or natural pozzolan), and it can be used as a supplementary cementitious material in concrete applications. Use of GCB in concrete can effectively reduce the alkali-silica reaction deterioration in concrete.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
June 1, 2013
Bektas, Fatih, "Use of ground clay brick as a supplementary cementitious material in concrete hydration characteristics, mechanical properties, and ASR durability" (2007). Retrospective Theses and Dissertations. 97.