Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

C Ince,S Derogar,T M Michelitsch

doi:10.3989/mc.2015.05214

Abstract

The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs) on water transport kinetics and mechanical properties of hydrated lime (CL90) and Portland cement (PC) mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often are the main barriers to the use of hydrated lime in construction practice. The results show that transfer sorptivity and time to dewater freshly-mixed hydrated lime mortars can be modified when binder is partially replaced with SCMs. Compressive strength of CL90 mortars is increased systematically with the increased replacement levels of SCMs and the results are supported with the microstructural images. The ability to modify the water transport kinetics and mechanical properties allows compatibility between the mortar and the substrate unit in masonry construction.

Highlights

In masonry construction, mortars, renders and plasters are applied in the freshly-mixed wet state as thin layers to absorbent substrates such as brick, stone and concrete block and they are dewatered by varying amounts by these substrates prior to setting
Strong water retaining ability of CL90 mortars is destroyed when fly ash (FA) and ground granulated blast furnace slag (GGBS) are used as partial replacement materials
Experimental measurements of the parameters such as initial and final volume fraction of water contents were extremely challenging considering that those measurements had to be done at the freshly mixed state of hydrated lime and cement mortars

Summary

Introduction

Mortars, renders and plasters are applied in the freshly-mixed wet state as thin layers to absorbent substrates such as brick, stone and concrete block and they are dewatered by varying amounts by these substrates prior to setting. For the practically important case of jointing mortars applied in 10 mm layers to a typical facing brick, 40–60% of the original mix water is lost (2) It was previously reported in (3) that the loss of mix water during dewatering of freshly mixed mortars when in contact with a dry absorbent substrate results in an increase in strength compared to non-dewatered mortars. It is well known that porosity plays a significant role in determining the mechanical properties of hardened mortars It was reported in (3) that the increase in the hydraulicity of the binders results in a decrease in porosity that contributes in the development of mortar strength

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Conclusion