Basics of Construction Microbial Biotechnology - Biotechnologies and Biomimetics for Civil Engineering - page 30

2.3 Application of Microbial Biopolymers in Construction
Industry and Geotechnical Engineering
Animal biomaterials such as blood, urine, eggs, milk, lard, and plant biopolymers
such as wood, straw, bark, cactus juice, flour have been used as admixtures from
ancient times to improve properties of mortars and plasters. Straw and cattle dung
were used and are used even at the present time in rural construction as the com-
posite biomaterials to improve construction properties of clay. Probably, the Aztecs
used fermented juice of nopal cactus (Opuntia ficus indica) to improve plasticity
and water absorption capacity of lime mortar and earthen plasters due to the
presence of cellulose fibers, gel polysaccharides, and fermentation products.
Extracts of this nopal cactus and water hyacinth are proposed in our days to enhance
viscosity of cement-based materials (León-Martínez et al. 2014 ; Sathya et al. 2013 ).
The chemical derivates of plant biopolymers, for example carboxymethylcellulose,
carboxymethylcellulose sulfate or such industrial waste as lignosulfonates are often
used as cement and mortar admixtures for set retarding and increase of plasticity of
self-consolidated concrete (Plank 2004 ; Yuan et al. 2013 ).
Chemical and biological admixtures in cement- and gypsum-based materials
are using for dispersing/thikening effects, viscosity enhancement, water retention,
set acceleration and retardation, air-entrainment, defoaming, hydrophobization,
adhesion and film forming (Plank 2003 ) to improve such properties of the material
as plasticity, water retention, adhesion, shrinkage reduction, flow ability, and
stability. The global market of admixtures is estimated at the level of US$15
billions with the share of more than 500 different biological and biodegradable
admixtures about 13 % (Plank 2004 ).
The advantage of microbial admixtures is that the biosynthesis rate of the
microbial biopolymers is significantly higher, by 2-4 orders of magnitude than that
of the plants and these substances can be produced in industrial scale on bio-
technological factories. The major application of microbial biopolymers in con-
struction industry is addition to concrete and dry-mix mortars. The examples of
microbial admixtures that are used in concrete are protein hydrolysates and welan
gum; and in case of dry-mix mortar these admixtures are succinoglycan and
xanthan gum. The market share of microbial biopolymers is expected to increase
because of technological advances and the growing trend to use naturally based or
biodegradable products in building materials (Plank 2004 ; Ramesh et al. 2010 ).
These microbial products of biotechnological industry are mainly viscosity-
enhancing admixtures used to achieve high resistance to segregation of concrete.
Major biotechnological admixtures are shown in Table 2.2 .
Sewage sludge or dewatered dry sewage sludge of municipal wastewater
treatment plants, are used in the cement and concrete industry (Mun 2007 ; Fytili
and Zabaniotou 2008 ). It is mainly biomass of anaerobic Bacteria and Archaea
performing acidogenic and methanogenic fermentations. This material contains
various biopolymers, such as linear and branched polysaccharides, globular pro-
teins and rRNA, and linear chains of DNA and mRNA. Our experiments with