Abstract
The durability of eco-efficient, clinker reduced concrete is a key factor of its performance. In the presented study, different durability indicators of a newly developed eco-concrete composition (ECO) are tested versus standard normal concrete as reference (REF). The tested durability indicators are open porosity, water penetration depth, rate of water absorption by capillarity and two different methods of measuring air permeability (PermeaTORR AC device versus Testing bubble counter). The ECO mix and in particular its cementitious matrix is designed by a combined filler concept substituting Portland cement partially by properly selected limestone fillers of different grain sizes. The approach is based on a combination of particle packing optimization techniques and the reduction of water demand for certain flowability of the paste. Cement content is below the limits of traditional standards while w/c-ratio exceed such limits. While the performance of the eco-concrete in terms of workability and strength is at least equivalent to the standard mix, ecological impact indicators as global warming potential and embodied energy are substantially improved. Durability indicators overall show nearly equivalent performance of ECO and REF. In detail, the resulting air permeability coefficient tested with a bubble counter differs significantly from the coefficient tested by PermeaTORR.
Highlights
In times of climate change increasing attention must be directed to greenhouse gas emissions and embodied energy of the most used construction material worldwide – normal concrete [1], [2]
Previous studies on ecological concrete [6] and ultra‐high performance concrete (UHPC) [10] showed that a physical filler effect can be achieved by a size ratio of smaller particles to larger particles dMF/d(larger particle) ≤ 0.33 with an optimum reached at a ratio ⋍ 0.1
In this study eco‐concrete (ECO) and in particular its paste was designed by a combined filler concept with the aim of optimizing its performance in respect to functionality, environmental impact and durability
Summary
In times of climate change increasing attention must be directed to greenhouse gas emissions (kg CO2‐equ., global warming potential, GWP) and embodied energy (or total primary energy, PEt) of the most used construction material worldwide – normal concrete [1], [2]. This paper specifies durability parameters tested on standard concrete (REF) as a reference and a newly developed eco‐concrete (ECO) and attempts to evaluate their equivalent performance. The following properties of powder materials are crucial for a functional and environmental performance optimization of the paste, cementitious matrix respectively [9]: (i) particle size distribution (PSD) including average particle diameter d50 (ii) packing density and (iii) water demand to reach the desired flowability associated with specific surface area (SSA) as well as (iv) environmental indicators (GWP and PEt, see Table 2 and chapter 3.3).
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