Bioinspired Concrete - Biotechnologies and Biomimetics for Civil Engineering - page 301

356

300

205

0

Ordinary Liquid &

40% Cement

-157

100%
Cement

-300

-471

100%
Aggregate

-600

-900

-1134

-1,200

TOTAL

Formulation

Fig. 13.3 GHG analyses of different concrete formulations where traditional components are
replaced by novel carbon-reducing carbon sequestered limestone components. The formulations
are based on a generic ''moderate-strength'' mix design that includes, per m 3 concrete, 356 kg

cement, 178 kg water and 1,880 kg aggregate (848 kg fine, 1,032 kg coarse)

twenty-first century we cannot simply assess the situation from the similar view-
point as the nineteenth and twentieth century. Considering the civil engineered
world around us is a core component to an overall sustainable future. Reducing
cement production by offsetting cement needs in concrete, using concrete as a sink
to receive captured carbon materials are solutions leading to a direction that can
solve our challenges of today and tomorrow.
Below we see the green house gas (GHG) analysis for ordinary concrete as
compared to advanced mix designs that not only reduce the amount of carbon per
yard of ordinarily mix designed concrete compared to low cement mix designs as
well as synthetic limestone inclusive mix designs (Fig. 13.3 ).
A green house gas analysis of kilograms of carbon dioxide per cubic meter
(kg CO 2 /m 3 ) concrete in Fig. 13.1 exemplifies that replacement of traditional
components in a concrete formulation by novel, carbon-reducing components, can
lead to a significant reduction in the kg CO 2 /m 3 concrete. If we consider that an
average of 927 kg of CO 2 is emitted for every 1,000 kg of OPC produced in
the U.S., depending on fuel type, raw ingredients and the energy efficiency of the
cement plant (Source: ''Concrete CO 2 Fact Sheet'', National Ready-Mix Concrete
Association, Feb 2012, based on the most recent survey of Portland Cement
Association members), an ordinary moderate-strength mix design has 356 kg CO 2 /
m 3 concrete; this also assumes no CO 2 contributions from the water and aggregate
components of the concrete mix design. If, for example, a carbon-reducing liquid
that contains 5 % by weight CO 2 is used as a complete water replacement, the
kg CO 2 /m 3 concrete is reduced by 9 kg CO 2 . When the carbon-reducing liquid is
used in combination with a 40 % replacement of OPC by interground limestone, the
kg CO 2 /m 3 concrete is reduced to a mere 205 kg CO 2 /m 3 (from 356 kg CO 2 /m 3 ).