Clinker Substitution Benefits Lower CO2 Emissions How Is Solidia

LOW-CLINKER CEMENTS ISustainable alternatives by Dr Vahit Atakan, As CO2 emissions remain one of the key items on cement producers’ Dr Sada Sahu and sustainability agenda, the development of sustainable alternatives to low-

Dr Nick DeCristofaro, clinker cement continues apace. One solution encompasses lower CO2 Solidia Technologies, USA emissions both during and after production, as its resultant concrete cures

via a reaction with gaseous CO2.

ecognising the need to lower both Solidia ConcreteTM hollow core slab being removed its carbon and energy footprints, from the extrusion bed after a 24 hour CO2-cure Rthe cement industry actively participates in the World Business Council for Sustainable Development (WBCSD) Cement Sustainability Initiative (CSI). The WBCSD-CSI has identified four practices that can help reduce the industry’s carbon footprint: 1. improvement of energy efficiency in cement production 2. alternative fuel usage 3. substitution of clinker in the cement 4. carbon capture and storage.

Clinker substitution benefits The cement and concrete industry has emission chemistry, Solidia Cement™ is Solidia Cement is produced using less adapted clinker substitution technologies more sustainable than ordinary Portland limestone and at lower temperatures than

as a strategic approach to meeting its CO2 cement (OPC). Solidia Concrete™ is are necessary for Portland cement. These reduction goals and the conservation of made with Solidia Cement and cures factors translate into an approximately 30

energy and natural resources. Using low- with CO2 instead of water. In addition per cent reduction in the CO2 emissions clinker cements can help: to helping meet CO2 reduction goals, during cement manufacturing, from • save energy Solidia Concrete performs better, is more 816kg/t of OPC clinker to 570kg/t of • cut pollutants durable and cost-effective than traditional Solidia Cement clinker (ca 30 per cent • reduce raw materials consumption concretes, and typically cures in one day. reduction). Other pollutants associated • enable the utilisation of waste products Adaptable to the full range of concrete with cement production, such as mercury, that are otherwise detrimental to the mix specifications, Solidia Cement also has are also reduced by approximately 30 per environment. the ability to save on the consumption of cent. raw materials. Lower CO2 emissions Carbon cure? In recent decades the cement industry How is Solidia cement made? For concretes made with Solidia Cement, has substituted clinker with various Solidia’s patented cement chemistry curing is achieved by a reaction between supplementary cementitious materials and curing processes offer the building the low-lime calcium silicate compounds

(SCMs), such as fly ash, slag, silica fume, materials and construction industries CaSiO3 and Ca3Si2O7, and gaseous CO2 natural pozzolanic materials and fillers the ability to manufacture cement and within a moist environment. Unlike its

such as limestone. Even with these clinker concrete products within existing plants OPC-based counterparts, CO2-cured substitutions, the WBCSD predicts the and using traditional design specifications, Solidia Concrete does not react with water.

CO2 reduction generated by producing with minimal requirements for new On average, 70-80 per cent of the water low-clinker cements will reach only 10 per supply chains and capital investment. used in the Solidia Concrete formulation

cent of the industry’s 2050 CO2 reduction Solidia Cement is composed of a family of can be recovered during the CO2-curing target. ‘green’, low-lime calcium silicate phases process. The remainder of the water To help the cement industry achieve that are similar, but not identical, to the is retained in the concrete and can be its goals of energy conservation chemistry of Portland cement. As a result, recovered if needed.1 and pollutant reduction, USA-based it can be produced in existing cement Solidia Concrete derives its strength ® Solidia Technologies has developed kilns using the same raw materials that from the formation of CaCO3 (calcite) patented processes. Produced with a are used to make OPC, albeit in different and SiO2 (silica gel), as given below in non-hydraulic, lower-energy and lower- proportions. Equations 1 and 2. The overall curing

INTERNATIONAL CEMENT REVIEW FEBRUARY 2015 ©Copyright Tradeship Publications Ltd 2015 LOW-CLINKER CEMENTS

reaction is succinctly written as: 800 Eq 1 H2O CaSiO3 (s) + CO2 (g) → CaCO3 (s) + SiO2 (s). Fuel Eq 2 Savings of H2O Ca3Si2O7 (s) + 3CO2 (g) → CaCO3 (s) + 2SiO2 (s). 550kg CO2/t of CO2 No water is consumed in either reaction. Fuel cement 400 Absorbed The curing reaction is exothermic and in Raw Curing releases -87kJ/mole of heat. The heat Materials Raw

generated during the reaction is dissipated /t of cement Materials 2 by the evaporation of water. The curing

process is controlled by counter diffusion kg CO 0

of CO2 and H2O molecules. Portland Solidia Solidia Cement Cement Concrete The ability of Solidia Cement to avoid and Concrete hydration and cure via a reaction with

gaseous CO2 opens the possibility for -400 the permanent sequestration of CO2 in the cured concrete structure. The curing process described in Equations 1 and 2 enables Solidia Concrete products to Figure 1: CO2 produced from raw materials and fuel for Portland cement (~800kg/t) and Solidia Cement (~550kg/t). The curing reaction in Solidia Concrete consumes CO2 (~300kg/t) to give a sequester between 250-300kg of CO2/t net savings of ~ 550kg/t of Solidia Cement used in the concrete formulation. Depending on the specific ratios of fine and coarse aggregate and improvements in the workability of Solidia production and use of Solidia Cement. Solidia Cement used in the concrete mix, Cement mortars, especially when class F The research demonstrated that waste the final Solidia Concrete part may contain fly ash was used, suggesting a reduction in materials such as fly ash and ground between about 3-7 weight per cent of the overall water demand in the mixtures granulated blast furnace slag can be used

sequestered CO2. thereby allowing for more rapid curing. to replace Solidia Cement by as much as Working with Lafarge as an R&D Solidia Cement can be partially replaced 40 per cent in concrete formulations.2 partner, Solidia has demonstrated that with slag, class F and class C fly ash. The When the ability to replace Solidia Cement standard cement kilns and raw materials amount of replacement depends on the clinker with moderate amounts of fly ash can be used to produce Solidia Cement product and can be as high as 40 weight and blast furnace slag are considered, the

simply by adjusting the relative amounts of per cent. total CO2 savings associated with Solidia the raw materials that are fed into the kiln Cement production and use can be further and operating the kiln at a lower reaction Linking sustainability reduced, resulting in further reduction in temperatures. While this approach does and performance clinker factor. That Solidia Concrete also not completely avoid the decomposition Results of research conducted under Phase performs better, is more durable and cost- of limestone and the high-temperature I of the Small Business Innovation Research effective than traditional concretes, opens

reaction of CaO and SiO2 associated with Program of the US Environmental the potential to added value beyond that Portland cement manufacturing, it reduces Protection Agency confirmed that the of low-clinker cements. Also, depending the amount of limestone decomposed and incorporation of SCMs can further reduce on the product, Solidia Concrete typically energy consumed. In combination with the the carbon footprint associated with the cures in one day, as opposed to the up

capture of 300kg of CO2 during curing, to 28 days required for curing traditional the production and use of 1t of Solidia concretes. The time saving in the curing

Cement will reduce airborne CO2 by process translates into costs saving for the 550kg when compared to the production producers. and use of 1t of OPC (see Figure 1). This new, alternative process offers

This CO2 saving is equivalent to a clinker cement and concrete manufacturers factor of between 0.33-0.39 in a Portland another sustainable and potentially-

cement-based system. profitable route to achieve the IEA’s CO2 Solidia Cement can potentially replace emissions reduction goal. all of the Portland cement currently in ______I use, as it can be made everywhere that Portland cement is made. With the broad References replacement of Portland cement with 1 Water Savings in Concrete Made from Solidia Cement in North America alone, Solidia Cement™, April 2014. 2 airborne CO2 can theoretically be reduced Use of Supplementary Cementitious by 55Mta (1bnt of OPC x 0.55t of CO2). Materials in High Performance, CO2 The inclusion of all the SCMs, namely Sequestering Construction Material, EPA fly ash, bottom ash and slag, led to Red and grey paving stones Extramural Research Contract Number