Fresh and hardened properties of self consolidating Portland limestone cement mortars: Effect of high volume limestone powder replaced by cement
Introduction
The largest footprints belong to cement in terms of carbon dioxide release to the atmosphere and also energy consumption. In order to decrease CO2 release to the atmosphere, many experimental studies have been performed on the mineral addition of supplementary materials or limestone powder to Normal Portland Cement. Particularly, limestone powder belonging to technical and economical superiority has been widely used as a replacement material in the production of cement and clinker by being intergrinded with variable amounts. In accordance with ASTM C 150-04, Normal Portland Cement may include up to 5% minor additional constituents for which limestone is one of the most appropriate material since many benefits such as better workability and reduced bleeding could be obtained with it [1]. Both of CEM II/A-L and CEM II/B-L which are also known as Portland Limestone Cement (PLC) composed of 6% to 20% and 21% to 35% grounded limestone, respectively, where CEM II/B-L contain the highest limestone content.
Fresh and hardened properties such as hydration mechanism, compressive strength development, carbonation resistance and microstructure are indispensable parameters for convenient use of PLC. Elgalhud et al. [2] found that factors affecting pore structure sustained unimpaired up to a replacement level of 25% while the pore structure started to deteriorate beyond this replacement level. Bentz et al. [3] reported that early age strength of PLC concrete improved comparing to reference concrete. Parrott [4] and Balayssac et al. [5] reported that concrete carbonation depth increased with the replacement of limestone amount. In addition, mineral addition with larger specific surface area results in lower capillary porosity and therefore increment in compressive strength [6]. Lecomte et al. [7] found that the properties of PLC were affected by grinding and also the use of limestone powder increased matrice sorptivity and altered porosity characteristics.
It was found by several researchers [8], [9] that addition of limestone powder increased both yield stress and plastic viscosity and, thus, this condition induced a decrease in workability while the rest of them reported that incorporation of limestone powder led to a reduction in both yield stress and plastic viscosity [10].
The goal of this experimental study is to investigate and analyze the effect of high volume limestone powder content of up to 35% by weight. In the current article, particularly the test results including the fresh and hardened properties of SCMs with 0%, 15%, 25% and 35% limestone are presented while the fresh and hardened tets results of mortars with LSP are compared to the control mixture with the only PC to evaluate the performance of SCMs having high-volume limestone powder content.
Section snippets
Materials and mixture proportions
In order to produce self-compacting mortars (SCMs), commercially available CEM I 42.5N normal Portland Cement (PC) which satisfy the requirement of ASTM Type I cement with a specific gravity of 3.11 and Limestone Powder (LSP) with a specific gravity of 2.31 were used as cementing materials. Their particle size distributions are represented in Fig. 1. Chemical properties of PC and LSP are given in Table 1. Fine aggregate river sand, whose particle size distribution is given in Fig. 2, with a
Rheological properties
Yield stress is one of the fundamental factors for characterizing rheological properties and also a plastic deformation initiating shear stress. It is the minimum shear stress when the visco-elastic material starts to flow [10]. In the other words, it is the maximum stress under which the viscoelastic material remains at rest and beyond which the material tends to deform [14].
Yield stress values and relevant flow curves for T = 0 min with Bingham approach for self-compacting mortars (SCMs)
Conclusion
Since the performance of clinker or cement could be enhanced by the replacement of cementitious materials, understanding and elucidating performance characteristics of cementitious materials composed of a high volume of replacement material is very important. This paper covers the effect of high volume limestone powder content replaced by cement and focuses on experimental results of fresh and hardened properties of SCMs. Therefore, properties of different SCMs were investigated by workability
Conflict of interest
The authors declare that there is no conflict of interest.
Acknowledgements
The research has been supported by the Scientific Research Projects Committee of Harran University (Project No: HUBAK–12148). Their support is gratefully acknowledged.
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