Note: Descriptions are shown in the official language in which they were submitted.
- 1 - Case 1~7~0240
2~226~7
SPRAY MORTAR
~e invention relates to a sprayable repair mort~Lr compos~on and more par~cularly to
such a composition for use on re~nforoed concrete.
When reinforced concrete is to be repaired, a layer of repa~r mortar, ~pically 30-35mm
~ick, is applied ~ereto, generally by spraying. nle repair mortar should be able to
wi~stand dimer~onal changes in the subsh~te without sulfering damage for a reasonable
period of ~me. A measure of this abili~7 is provided ~y ~e cha~acteris~c crack leng~h.
of the mortar. When a pnsm of the mortar composfflon is su'c~ected to a defle~on te$
using a cen~e point loading apparatus, the prism deflects with increasing load and on
the reverse face of the p~ism from tne loaded face ~ere is fo~ned a re~ion of
microcracks wnich region is characteris~c o~ the par~cular cornposition under test.
Eventual~y ~ese cracks u~ll join to form a major crack and the prism will fail. The
characteris~c aack leng~ may 'oe calculated from a knowledge of the fracture ener~y of
the composition (the area under the characteristic bell shaped curve of shess against
deflechon obtained from the abovementioned deflec~on test), ~e elas~ci~ modulus (E-
modulus) of the composition, and ~e ul~mate centric tens~le streng~ of ~e composiffon.
The greater the cha~aderistic crack leng~, the better perforrrLng the material. The best
materrals have high fracture energy as well as lon~ cnaracteristic crack ]ength."
It has now been fow~d that it is poss~ble to prepare a repair mortar composition w.th
outstanding proper~es as ev~denced by a long characteris~c crack length. The inven~on
therefore provides a mortar composi~on for the repair of concrete surfaces, which
comprises cement and aggregate, the aggregabe having an overall average static modulus
of elastici~y of from 15,00040,000 N/mrn2 `
The sta~c elasticity modulus (usually known as the 'l~-rnoduh~ of the aggrega~e to be
used in the composi~ons of this invention is unusual~ "soft", the hgure for ~e aggregate
in a convenffonal spray mortar being of ~e order of 25,000 to over 60,000 ~/nun2
- 2 - Case 15~0240
~:L226l~7
The E-modulus is commonly measured by means of an ultrasonic testing appa~us; a
~pical exarnple of suoh an apparatus ~s the Steir~mp Type BP 5 ulhasonic test~ (ex
Dr.-In~. G. Steinkamp, Brernen Ge~marly). The E-modulus is the aYerage E-moduhls of
the aggregate; it is pennissible to have an aggregat~ component with an E-modulus in
excess of the upper limit of 40,000 ~ lm2, provided ~at the aggregate comprises
sufflcient a~regate of a lower E-modulus to bring the average within the ~n~e
mentioned hereinabove.
Depending on the field of application, all known types of cement may be used in the
usual quantiffes, Portland cernent being prefe~red.
The "soft" E-modulus ran~e of the a~gregate may be attained by the choice of aggregate
employed and by its use in conjunction w~th nab~al mine~l matenals having a ffbrous
s~ucture. l~e aggregate used is preferably sand in wh~ch the propor~on of sand ha~ng
a high E-modulus is sIr~. In practice, sand ~pes ha~nng a grain size of 4 m~ mæimum
are selected. The sand mi~ture employed should preferab~1 have an average rnodulus of
elas~c~ty of 20,000-30,000 N/m~n2 and in partia~ar should be below 25,000 N/mrn2.
TypicaL~ s~table nat~l fibrous mine~al materlals are lirnestone dust (which rnay be
coarse~ined)"nicro rock dust, micro rock dust fibres or similar ~ibrous matenals. Such
materlals are pre~erably preænt in the compositions of the invention in amounts of 0.
to 2.5% by weight of the total weight of the dry mortar composition.
.. ~ ....
20 The mortar composition of this invention îs prefeTably applied to a subshate by spr~ying,
preferably by the ~y spraying process.
Uthen sprayed as a repair rnortar on to a subsbrate, ~2e mork~ compos~on according
to the inven~on hardens to give a layer with a high f~achlre energy and long
cha~cteristic c~ck length, and ~is manife,ts itself ~n high flexibility, high frost resistance
25 and a low mod~ of elasticity. In cont~st to conventional products which produce
hardened protective layers ui~ a moduh~s of e~astic~ of over 30,000 N/mm2, the
compositions according to the invention may be used to ob~in protective layers v~h a
- 3 - Case 15~0240
212 2 6 ~ I
modulus of elasticity of bolow 25,000 I~/rnm2. Thus, the composi~ons accordin~ to the
invention may be employed whenever it is desired to produce a malleable top layer which
is insensitive towards cracks. The improved ducfflity and the low modulus of elas~city of
the mortar compositions allovJs the reduction and even cornplete elirnination of shrinka~e
reinforcernent. Thus, layers need not be so thick and single-layer application may often
be ernployed.
It has been found that the combination of the fibrous rnatenals ~rnestone dust and rnicro
rock dust fibres with sand as hereinabove desaibed and cernent gives particularly good
results, outstandin~ in the case of the crack test hereinabove described. Especially good
combinations are those in which the weight percentages of limestone dust and micro
rock dust fibres are 1.5 and 0.8-1.5 respec~v~y. If no o~er components are present,
the sand comprises from 77-78% and cement comprises the remainder. 1~ other
components are desued, some adjustmen~; to the Qnd and cement quanffties are
necessary, but such are well within the sl~ll of ~e art.
Other components suitable for use in sprayable mo~ar compositions according to the
invenffon are weD known to the art. These cons~tuents may be added in the usual
proport~ons, depending on the field of use. For example, it is possible to add sllica ~e
or tly ash as a ~qller, or known fibre reinforcement. All cor~uents are rr~xed in ~e dry
state by knowni processes, and fed pneurna~calliy to the spray nozz~e of any dry spraying
machine (e.g. MEYCO Piccola, MEYCO Unica ex Meynadier AG., Winterthur,
Switzerland), where they are n~xed with water and sp~yed. The quantity of water may
~ary depending on condiffons, but may readily be determ~ned in any situation by the
sl~lled worker. Typical water/binder weight ra'dos (where binder naturally includes such
mate~ials as siliica fume or fly ash, where these are present) for a dry spraying operation
are from 0.3-0.6, preferably from 0.4-0.~. An acceleRItor Is norrnally not used. The
application depth may ~ary ~m 12 to 100 mm.
The invention is ~e~ described wi~ reference to tne following non-limi~ng examples
in whii~i all parts are by weight.
- 4 - Case 15~0240
212~6~7
Example 1
Cons~tueni:s modulus of density propor~ons
elas~a~,7 N/mrn2 k~m3 % by wei~ht
cement 18,000 (17,00~21,000) 2000-21~0 20.0
sands 24,000(23,000-83,000) 267~3050 77.7
limestone dust 24,000 2500 1.5
m~cro rock dust 17,000 (crosswise) 2500 0.8
bres 170,000 (leng~wise)
. .
sprayable mortar 22,137 2131 100 -
.
10 The various cons~tuents are mixed in the dry state and water s added at the sp~ay nozle
fn such a rate as to give a ra~o of water/binding agent of 0.4. ~is ra~o is used in ~e
subsequent examples. : ~
.'~ ' ~","'-:
6 '1 7 c~ 15~02~0
amples 2 to 12
Further ex~mples of appropria~e spr~yable morrar rnixes are giv2n in the table, where
~he proportions of the various constituen~; are given in percen~ages by wei~h~ In the
table, "MSM" is n~3cro rock dust, '~SM PF' is rnicro rock d~t ~bres and '~S~' i~5 limestone dust . The limestone dust is coar~ grain (4 mm) materiaL
~ .:
Table
,_ _ _ __ l
Example cernent sandsKSrM MSM ¦ MSM PF ~
_ _ , , .
2 20 77.71.5 0.8
_ _~
3 20 75.5 3 1.~ l : :`
_ ~
~ 20 72 5 3 l
.. . . _ 11 .. ,
~5 74.5 10 0.5 l
6 - 15 75 10 = _ ` ~ ~`
7 . 20 77.7 l.5 1 0.8
8 20 77 2.5 1 0.5 ~ ~
g 20 69.2 10 1 0.8 ~`
77 1.5 1 1.5 ~::
11 20 --~ 77
. _ :
12 20 77 3---- : ~
:`
- 6 - Ca~7e 1540240
~2~7
~ .
The composd$iorLF7 of Examples 1 and 10 are subjected to tes~ng according to the test
me~od RllEM 50-r~lC draft recornrnendation. A cornmercial~available repair mortar
comprising by weigh$ 42% cement, 33% sand (0.1~1.20rnm)7 17% sand (1.2
2.38mrn), 3.4% silica ~ume, 3.3% caldurn o~de, and the remainder mLscellaneous minor
quantiffe~ of adrnixb~res LS subjected to the sal,ne tes~ng procedure. From the tes~ng7 the
charact~ristic crack leng~ are determlned. ~e resul~ are as follow~7: ~ '
Example 1 435nun
Example lû 382mm ",~ '
Cornrnerclal cornposi~on 262mm ~, ' ,
:
::
The crack performances of the composiffons according to the invenffon are conslderably
superior to ~at of ~e commercially~available composi~on.
The composl~ons are sprayed on to a concrete substrate. In subseque~ flexibilits~ testing,
the compositiorls according to ~e invention prove to be superior to the comrnercial
composition in terms of fle70bi~ and durabi~ity. ~ ~
~, ' ',
