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WG EditaSmetonaite CMM

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					INSTITUTE OF ARCHITECTURE AND CONSTRUCTION
    OF KAUNAS UNIVERSITY OF TECHNOLOGY
 THE ACCREDITED LABORATORY OF COMPOSITE AND
              FINISH TECHNOLOGY




              EDITA SMETONAITE


              Eindhoven 13-14 December 2006
 The investigation of the properties of acrylic repair
products when the building is filled with different
mineral fills and offer new sorts of repair materials
that are distinguished by their elasticity, good adhesion
to the base and suitable for the repair of the cracked
constructions and render.
•    The acrylatic binding was prepared which was
    well mixing with cement and the mineral fills of
    various coarseness. Since it was water binding,
    cement in the admixture might hydrate and
    harden. Fine, yet not unground sand and Portland
    cements were used for experiments.
• With the help of the laboratory equipment the extension by
  stretching of the mortar layer and strength of adhesion with
  concrete and strength against stretching have been
  determined. Strength against pressure and bending of the
  samples 4x4x16 cm have also been determined. However,
  such properties may be determined exclusively for the
  mortars having a high degree of saturation with fills. The
  samples were tested after 21 days of hardening under
  ambient conditions. Then some of them were soaked in
  water for 17 days in order to determine their water
  absorption and the coefficient of softening. Other samples
  were soaked for a full year and the rest were periodically
  freezed in the freezing chamber and soaked in the 5% NaCl
  solution a single freezing – soaking cycle was performed
  each day. During the process of hardening the
  spontaneous deformations were determined with the help
  of the clock indicators.
• The mechanical properties of the
  acrilatic binder, of admixtures with
  the mineral fills and portlandcement
  have been determined.
Fig. 1 Mechanical properties of the acrilatic binder and fill
mortars (sand + cement) (1:1): expansion by stretching %;
   strength against stretching Rt, MPa and strength of
             adhesion to concrete Rb, MPa


 %
300




      240
                                                   220
200
                            180                                          MPa
                                     0,9                                 1,0
                                                          0,85



100           0,6
                                            0,45                         0,5
                                                                   0,4

                      0,2



      l       Rt     Rb    l        Rt      Rb   l      Rt      Rb
            1:(1+0)               1:(0,5+0,5)            1:(0+1)
• Fig. 1 displays the test results of the mortar layer
  expansion by stretching, strength against
  stretching and strength of adhesion with
  concrete. It is obvious that the product
  demonstrates high elasticity. Expansion by
  stretching may exceed 200%. On the other hand,
  it shows that with the replacement of the entire
  mineral fill (i. e. fine, yet unground sand), by
  portlandcement, the data changes rather
  inconsiderably, which means that strength
  against stretching and strength of adhesion with
  concrete increased. With the use of the carbonate
  fills instead of sand, the positive results were
  obtained also.
• With the increase of the fill amount in the
  composition of the mortar, the samples
  expansion by stretching decreases. The shaped
  samples, i. e. cubes and prisms get hardened
  which allows for the determination of their
  strength by against bending and against
  pressure. It should be noted that the to some
  extent elasticity of the mortars remains and the
  samples during their stretching or bending do not
  decay immediately.
   Table 1. The impact of the ratio between the acrilatic
     binder and the fills on the properties of the mortars

                        Properties                     Binder: cement   Binder: (cement + sand)   Binder: (cement + sand)
                                                            1:2                 1: (2+2)                  1: (2+6)
Density, kg/m3                                             1790                  1890                      1920
Mechanical strength after 28 days                          16/7.4                16/7.3                    19/9.3
against pressure/ against bending
After 7 days of soaking                                    15/6.8                15/5.1                   13.4/5.5
Deformation during hardening, mm/m                          +0.1                    -                       +0.1
Water absorption, %                                         3.3                   3.0                       4.6
Elasticity (due to the sample’s bend)                      elastic          of low elasticity         of low elasticity
Softening in water                                       0.94/0.92             0.94/0.69                 0.70/0.59
Strength against pressure after 360 days of              14.6/15.3             10.6/11.3                   12/14
soaking/after 300 freezing – heating cycles
Mortar of increased elasticity:                            10/3.8                   -                      12/4.5
Mechanical strength after 28 days
against pressure / against bending
Rg/Rl, MPa
Softening coefficient                                     0.9/0.78                  -                     0.56/0.4
Deformation during, mm/m                                   ~ 0.0                    -                      -0.08
Strength by pressure after 360 days of soaking/after          -                     -                     8.2/10.5
300 freezing – heating cycles
•   Table 1 displays the physical and mechanical properties of the
    mortars with the increased amount of fills. Such mortars
    distinguish by their considerable strength against pressure and
    against bending. They are also water resistant: after 7 days of
    soaking in water the mechanical strength of the samples
    decreased inconsiderably. The values of the coefficient softening
    decrease with the increase of the amount of the fills. The
    mentioned indices get improved with the increase of the
    portlandcement amount in the mortars. Moreover, it has been
    determined that the mortars which were soaked in water for a full
    year demonstrated their subsequent hardening caused by the
    growth of their mechanical strength; therefore they endure the
    cyclical freezing and heating. If after 7 days of soaking the
    mechanical strength decreases to 30 %, so in a full year the
    strength increases to a similar or even higher degree. It is
    interesting to point out that after 300 freezing – heating cycles, the
    strength does not decrease but rather increases and exceeds the
    strength of the soaked samples. It demonstrates the proper
    durability of the mortar.
•   Another good property of such mortars is their non-shrinking during
    hardening. After 28 days of hardening under the ambient conditions, the
    deformation of the samples made only + 0.14 mm/m: practically, they did
    not get deformed
•   On the basis of the obtained results different mortar compositions of
    various purpose were formed and utilized in practice during the repair of
    the cracked concrete constructions, brick masonry and thin render. During
    the repair of the massive concrete or brick constructions, the existing
    cracks were enlarged, deepened (if necessary) and filled with the polymer
    cement mortar of adequate consistence. After hardening the repaired
    areas were finished by the unification of the colours of the repaired and
    surrounding areas.
•   The finish of the facades with the exterior insulating systems and of
    render as well as their repair open an entirely new and unexplored
    problem: here the defects appear due to various temperature and moisture
    deformations and other reasons. For the repair of such surfaces the
    materials of ananalogical composition yet more liquid and resembling the
    putty substance were used. Their hardened layers are elastic, they well
    endure the mechanical effects, including vibration
•   On the basis of acrilate polymers, elastic
    and long durable materials for the repair of
    the cracked constructions and facades were
    composed. Cement included into their
    composition increased water and frost
    resistance of the mortars
•   The composed repair materials were
    successfully used in practice.

				
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posted:12/11/2012
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