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Development of cement-free concrete using waste material as replacement of cement, with improved thermal properties by adding in the mix low density materials i.e. perlite, aerogel
About
Worldwide there is an ever increasing pressure for countries, governments and companies to become greener and reduce carbon emissions in an attempt to help prevent climate change. Concrete is the most widely used construction material with superior compressive strength, enhanced fire resistance and durability and relatively ‘low cost’. However, the main drawbacks in the use of concrete are related to the use of cement and subsequently the high percentage of carbon dioxide emissions and to the high thermal conductivity properties of concrete and the subsequent high energy consumption of the buildings. One way for reducing the environmental impacts related to the use of concrete is by reducing the amount of cement i.e. replacing cement with waste materials such as Pulverised Fuel Ash (PFA) which is what is done in geopolymer concrete. At the same time one of the most important factors for structures’ energy efficiency is their ability to prevent heat loss which can be achieved by using thermal insulation. The development of a thermal insulated geopolymer concrete can fulfil both the above requirements. With the current study, different cobinations of waste materials such as PFA and demolition construction materials (i.e. bricks) will be used as replacement of cement in the concrete mix design, while partially substation of sand with low density materials such as perlite and aerogel will help in the improvement of thermal properties of the new material.
Key Benefits
With this new thermal insulated geopolymer (cement-free) concrete the environmental impacts related to the use of concrete will be reduced. Concrete is responsible for 5% of annual anthropogenic carbon dioxide (CO2) production. The major contributing factor to CO2 emissions in the concrete industry is cement production, with around 1.1 tonnes of CO2 produced per metric tonne of cement. The majority of CO2 is produced when Calcium Carbonates (CaCO3) are heated at high temperatures in a kiln producing calcium oxides (CaO) and CO2. This CO2 has no further use and is subsequently released into the atmosphere. Replacing cement with waste materials such as PFA (Pulverised Fuel Ash), demolition materials (i.e. bricks), CO2 emissions are reduced on one hand because of the reduction of cement production and on the other hand because of the recycling of this waste material. At the same time, in this new proposed concrete, the partially substitution of the sand with low density materials such as perlite and aerogel, will reduce the thermal conductivity of the concrete and it will give it thermal insulated properties which will improve structures’ energy efficiency.
Applications
In roofs, floors or as external layer to buildings giving thermal insulation and reducing the weight.