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Title: The consequences of the dewatering of freshly-mixed wet mortars by the capillary suction of brick masonry
Author: Al-Defai, Nidhal
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2013
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The main water transport properties of clay brick are critically examined in respect of suction and water content. An experimental investigation is carried out to compare the sorptivity and vacuum saturation porosity with suction and “porosity” tests in the standards. The water retaining ability (desorptivity) of freshly mixed hydraulic lime and cement mortars is examined and the effect of hydraulicity, pozzolanic and non-pozzolanic additive materials, binder particle size and the chemistry of mix water on the water retentivity of these mortars are investigated. The inter-relationship of substrate (brick) suction and desorptivity of freshly mixed wet lime and cement mortar are investigated. It is shown that the initial setting time of dewatered freshly-mixed mortars is reduced by a factor of up to 80% and the final setting time is reduced by a factor of 60%. The extent of this reduction depends on hydraulicity. For the cured mortars, following dewatering in the wet state, the compressive and flexural strengths are increased by about 40% for cement mortar and by more than 3 times for lime mortar. The sorptivity of hardened cement and lime mortars is reduced by 80%. These results have implications for the British and European standards where mortars are cast in impermeable steel moulds in which dewatering cannot occur prior to setting. The accuracy of the methodology of the American Petroleum Institute (API) pressure cell technique for testing the water retaining ability of fresh mortars was critically examined. An experimental investigation was carried out in two parts, first by changing the controlled variables of the experimental set up. Second the consequences for the results obtained were evaluated. Experimental verification is undertaken of the fundamental Sharp Front equation S=(2KΨf)^(1/2) which describes the inter-relationship of capillary pressure, sorptivity, porosity and hydraulic conductivity.
Supervisor: Wilson, Moira Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Dewatering, freshly-mixed mortar, brick masonry, capillary pressure, cement, lime