Assessment of Rational Design of Self-Compacting Concrete Incorporating Fly Ash and Limestone Powder in Terms of Long-Term Durability.

Pavel Reiterman,Martin Keppert,Roman Jaskulski,Ondřej Holčapek,Wojciech Kubissa

doi:10.3390/ma13122863

Abstract

Self-compaction concrete (SCC) is ranked among the main technological innovations of the last decades. Hence, it introduces a suitable possibility for further utilization of supplementary cementitious materials (SCM) in terms of sustainable development. The aim of the work is the assessment of a new approach to binder design, which takes into consideration the activity of the used mineral additive. The proposed approach, which allows a systematic design of a binding system with varied properties of the used mineral additive, was studied on ternary blends consisting of Portland cement (PC), limestone powder and fly ash (FA). The verification was conducted on SCC mixtures in terms of their workability, mechanical properties and the most attention was paid to long-term durability. The long-term durability was assessed on the basis of shrinkage measurement, freeze-thaw resistance and permeability tests including initial surface absorption, chloride migration, water penetration and an accelerated carbonation test, which was compared with the evolution of carbonation front in normal conditions. The durability of studied mixtures was evaluated by using durability loss index, which allow general assessment on the basis of multiple parameters. The carbonation resistance had a dominant importance on the final durability performance of studied mixtures. The experimental program revealed that the proposed design method is reliable only in terms of properties in fresh state and mechanical performance, which were similar with control mixture. Despite suitable results of freeze-thaw resistance and shrinkage, an increasing amount of fly ash in terms of the new design concept led to a fundamental increase of permeability and thus to decay of long-term durability. Acceptable properties were achieved for the lowest dosage of fly ash.

Highlights

Portland cement-based concrete is the most widely used structural material in the world, with an annual production around ten billion metric tons [1]
When limestone filler was replaced by fly ash in one concrete mixture, the results show that FA contributes more to the sealing of the structure of concrete than limestone filler in the case of concrete with the same material parameters; appropriate composition modifications of Self-compaction concrete (SCC) with limestone filler, e.g., reducing the w/c ratio from 0.46 to 0.40, can result in concrete with a clearly lower apparent gas permeability value than FA
The main aim of the program was to take into consideration the reactivity of used FA, as well as the part of used additive resulting in the pozzolanic reaction, and the verification of this approach in terms of complex system of methods relating to the durability

Summary

Introduction

Portland cement-based concrete is the most widely used structural material in the world, with an annual production around ten billion metric tons [1]. A crucial factor in terms of sustainability is the production of Portland cement; it is responsible for 5–7% of global CO2 emissions [2]. Habert [3], the annual production of cement was 2.8 billion tons in 2014. The reduction of the negative impacts of cement production has become a global effort [6,7,8,9]. The more environmentally-friendly nature of such concrete results from the reduction of CO2 emission associated with the production of cement clinker [15] and other factors negatively influencing the sustainability of the building industry

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