The name itself explains the behaviour of the concrete which can self contact and settles itself into the mould. in general we use to add admixtures like mobility admixtures to ease flow of concrete aggregate along with the cement

since concrete is occupied the bulk using category of the world. self healing concrete is a living concrete which can move by self in to the deeper cracks and can heal itself.
  • crack information is a typical phenomenon related to durability
  • percolation of cracks may lead to leakage problems, causing deterioration of the concrete matrix or corrosion of embedded steel reinforcement.

WHAT IS BIO CONCRETE


  • it is a special type of concrete invented by a group of microbiology researchers under the head of henk jonkers
  • bio concrete is also called as BACTERIAL CONCRETE or self healing concrete.
  • it is specially made to increase the life span and durability of concrete structure by the self healing action of that concrete

SPECIALITY OF BIO CONCRETE

there are two special characteristics present in bio concrete

  1. the special bacteria that can resist the alkalinity and the mechanical stress of concrete
  2. the chemical precursor to activate the bacteria.

BACTERIA USED


  • Most of the bacteria belongs to genus bacillus are fulfilling the required criteria discussed above. some of the list of bacteria are B.pseudofirmus, B.cohni, b.filla, b.pasteurii..etc
  • the suitable chemical precursor found to be most suitable is calcium lactate Ca(C3H5O2)2

MECHANISM

  • the cracks are formed on the surface of concrete due to many reasons like shrinkage, inadequate water for hydration...etc.
  • the water is deliberately forced in to the crack and precursor is activated.
ca(c3h5o2)2 + 7o2  --> caco3 + 5co2 + 5h2o
co2 + ca(oh)2   --> caco3 + h2o


  • the activated precursor intern induces the bacteria to react with that precursor  and form a base of calcium carbonate called as lime stone, the chemical equation is given above

APPLICATION OF HEALING AGENT

  1. BY DIRECT APPLICATION 
          The bacteria and the chemical precursor (calcium lactate) are added by directly while making              the concrete.                                                                                  

      2. ENCAPSULATION LWA
         a) the part of the coarse aggregate is replaced by the light weight aggregate(LWA),which is                    impregnated with twice the calcium lactate solution and the spores of bacteria.
         b) After impregnation the clay particles with 6% healing agents and the concrete is made.

EVALUATION


  • the concrete properties should not be negatively affected by the addition of a healing agent to the concrete mixture.
  • a large amount of bacteria and certain mineral precursor compounds like calcium lactate do substantially influence concrete compressive and tensile strengh.
  • when the healing agent is added , Optimization of healing agent is necessary so that it wont affect the characteristics of the concrete 

APPLICATIONS

  • the spore would be crushed by small holes 
  • no strong spores were detected in a 135-day old specimen, implying the majority of spores in the cured cement mixture were available  for less than 4 months