nonshrink hydraulic cement mortars and grouts_tcm45-346372

8/21/2019 Nonshrink Hydraulic Cement Mortars and Grouts_tcm45-346372

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If your job is one of those listed in the accompanyingb ox, the chances are you could ve ry well use a non-shrink hydraulic cement product to accomplish it. Thiscould be one of the following:

a patching mortar or concre t e

a grout or anchoring cement

a fiber-containing patching mortar or concre t e

D o nt assume, howe ve r, that eve ry available material issuitable for eve ry job listed in its category. Check with

the manufacture r. Most manufacturers have a pro d u c tline that includes from 2 to 8 or more separa t e, special-i zed nonshrink materi a l s. These have been form u l a t e d

with va rious job conditions and re q u i rements in mindand the manufacturer can recommend the pro d u c tmost suitable for your re q u i re m e n t s.

The materials to be discussed in this article are basedmainly on portland cement but they contain expansion-causing agents and sometimes other modifiers. The pur-pose of the expansive agent is to make the product swe l lenough to assure tight contact and good bond with the

Nonshr ink hydr aulic cementmor tar s and gr outsA broad spectrum of highly useful materials

Patching mortars and concretes

Re p a i ri n g :p a vements and ru n w a y ss i d e w a l k s, curbs and guttersb ridge decks

Applying we a r- resistant toppings

Caulking joints

Re p a i ri n g :h o n e yc o m b i n g

c racks and spallsc o n s t ruction faults

Filling holes left by tie wire s

Re p a i ring stucco

Making watertight seals around penetra t i o n s

Making rigid joints watert i g h t

Stopping leaks

Making underwater re p a i r s

Re p a i ring concrete pipe

Patching precast concre t e

Grouts and anchoring cem ents

Providing fill and support on the foundations for:m a c h i n e ry base platescolumn base platesb e a ring or rocker plates for bri d g e sc rane ra i l s

A n c h o ring in concre t e :b o l t s, dowels or ro d srailings and posts

c e ramic fixture s

Pa t c h i n g :h o l e sc ra c k s, spalls and pits in floors

Re s u rfacing floors

Bedding precast units

Grouting junctures of precast units

Sealing between concrete pipe units

Setting tile

Repointing mortar joints and stru c t u ral cra c k s

Sealing around penetra t i o n s

Filling and sealing post-tensioning cable ducts

Fibrous patc hing mort ars and concret es

Uses such as those above but uses that must resist im-pact loads or high dynamic stre s s

Su rfacing or re p a i ring heavy-duty traffic are a s p a rk-ing decks, bri d g e s, industrial floors

Applying a waterproof traffic topping on new slabs

Making column-beam joints for antiseismic stru c t u ra lm e m b e r s

As a substitute for re i n f o rcement in highly stre s s e ds t ru c t u ral elements that might otherwise need multi-d i rectional re i n f o rc e m e n t

Lining tunnels in ro c k

Wa t e r p roofing and re p a i ring water-holding stru c t u re s

APPLICATIONS OF NONSHRINK CEMENTITIOUS REPAIR PRODUCTS


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s u r rounding materials but not to swell so much that itd i s rupts them. Ma t e rials not discussed in this article arep roducts based pri m a rily on epoxy and other syntheticm a t e ri a l s, or on magnesium phosphate cements.

Whether the job is large or small, it will most likely bebest to purchase the nonshrink material in standardpackages rather than in bulk. Huge bulk purchases havebeen made, and they can be arranged with some manu-f a c t u re r s, but even for big jobs bulk quantities may notbe particularly convenient. Pro p o rtioning with standardpackages is simple: all the user needs to do is mix the

package contents with the recommended amount of wa-

ter or the recommended amount of water and aggre g a t e.Not only are bulk materials likely to be harder to batcha c c u ra t e l y, but they also may tend to lose uniformity ins t o ra g e, particularly if they contain metallic part i c l e s,which segregate re a d i l y.

Patc hing mort ars and concretes

Most of these products contain components thatcause the mortar or concrete to expand after it has hard-

ened. (Usually this is accomplished by compounds thatreact with one another to produce ettri n g i t e, a minera lthat takes up much more space t han the salts fro mwhich it was formed.) The expansion is intended to ove r-come or compensate for the expected drying shri n k a g eand to maintain a tight bond to the material with whichit is in contact. Ge n e ra l l y, provision must be made to re-s t rain the expansion. This causes compre s s i ve stress tobe built up within the mortar or concre t e. Then, when itu n d e rgoes subsequent drying, the loss of moisture sim-ply re l i e ves the compre s s i ve stress instead of causings h ri n k a g e. The amount of potential expansion va ri e sover a wide ra n g e, depending on the particular pro d u c t

(Table 1). Co n s e q u e n t l y, depending on the applicationand the product chosen, the re s t rained expansion andthe drying shrinkage are likely to be only approx i m a t e l ye q u a l .

Another type of repair material in this category ob-tains its expansion through release of air from its speciala g g re g a t e. This occurs only while the material is in theplastic condition, causing the repair material to expandand establish intimate contact with the surrounding ma-t e rials before it hard e n s, thus completely filling thespace and promoting good bond.

Each of the pro p e rties of the available products spansa considerable ra n g e, as shown in Table 1. Thus users

can achieve a va riety of re s u l t s, depending on the pro p-

Fractured concret e such as this can be repaired wit hpackaged nonshrink mort ars. Manufacturers formulatethese products for specific kinds of applicati ons,incorporating c arefully graded aggregate in t heir mixes.

a Some products also available in pails or cans as small as 12 pounds.b One manufacturer claims 2300 psi at 1 hour for one of the companys products.c This value, the only one found among the sources available, is for a repair material whose compressive strength at 28 days is 11,600 psi.

TABLE 1. CHARACTERISTICS OF NONSHRINK PATCHING M ORTARS AND CONCRETESBASED ON HYDRAULIC CEMENTS.

Pro p e rt y Ra n g e Ty p i c a l

Bag size, pounds 30 to 100a

5 5

Yield, cubic feet per bag 0.41 to 0.59 0 . 5 0

Expansion at 28 days, perc e n t 0.01 to 0.10 0 . 0 5

Early compre s s i ve strength (24 hours), psib

810 to 3900 3 0 0 0

Co m p re s s i ve strength at 28 days, psi 5000 to 11,600 7 0 0 0Fl e x u ral strength at 28 days, psi Up to 1330

Modulus of elasticity at 28 days, psi 4 , 3 0 0 , 0 0 0c

Bond strength to concrete at 28 days, psi 5 0 0c

Resistance to fre ezing and thawing, durability factor, perc e n t 69 to 90


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e rties of the products they choose. Some contain hardm i n e ral aggregate for wear resistance and others containmalleable iron powder for resistance to both wear andimpact. Ex t remely short setting times (as short as 5 min-utes) are available in some pro d u c t s. Some are said tobe more resistant than portland cement mortars andc o n c retes to acids and to certain other chemicals. Ma n-u f a c t u rers can supply litera t u re describing these pro p e r-t i e s. The litera t u re also makes recommendations aboutthe amount of water (or water and aggregate) needed toa c h i e ve the re q u i red workability and about the best

techniques to use for a particular application.The lines of some companies include a patching ma-

t e rial that has a composition much like their re g u l a rn o n s h rink mortars and grouts but also has some latexthat imparts trowelability and makes it possible to feath-e redge a patch. Such materials are not re p resented inTable 1 but they are available from a few of the samem a n u f a c t u re r s.

Grouts and anchoring c ements

Many grouts and anchoring cements are basically thesame kinds of materials as the patching mortars andc o n c re t e s m a t e rials based on portland cement which

d e ri ve their expansion from the formation of ettri n g i t eor from the release of air from the aggregate into theplastic mix. There is another system that gets its actionf rom releasing gas into the plastic mix, in this case thegas is generated by the reaction of fine aluminum pow-der in the grout with the cement alkalies. This is one ofthe oldest ways of obtaining expansion in grouts and an-c h o ring cements but the system is seldom used todaybecause of difficulty in controlling the amount of expan-

sion. Still another system, also ve ry old, is one that de-pends on iron powder and an agent that ox i d i zes thei ron, causing it to expand by a controlled amount. Thereaction causes staining, so this kind of product is for usew h e re color doesnt matter.

The ranges of some of the pro p e rties of grouts and an-c h o ring cements are given in Table 2. The data showp ro p e rties in broad outline and do not give any pictureof how the va rious pro p e rties would be re p resented inany particular product one might select. For these de-tails it is necessary to consult with the specific pro d u c e r

or study the pro d u c e rs litera t u re.

TABLE 2. CHARACTERISTICS OF NONSHRINK GROUTS AND ANCHORING CEMENTS.(BOTH NONMETALLIC AND M ETALLIC M ATERIALS INCLUDED.

ALL MATERIALS BASED ON HYDRAULIC CEMENTS.)

Pro p e rt y Ra n g e Ty p i c a l

Bag size, pounds 30 to 108a 5 0

Yield, cubic feet per bag 0.35 to 1.0 b

Fl ow, seconds 21 to 152

Expansion at 28 days, perc e n t 0.02 to 0.40 c

Early compre s s i ve strength (24 hours), psi d 1500 to 10,500 5 5 0 0

Co m p re s s i ve strength at 28 days, psi 4800 to 13,950 8 0 0 0

Fl e x u ral strength at 28 days, psi 800 to 1500

Bond stress on re i n f o rcing bars at failure in pulloutat 28 days, psi 750 to 4080e 1 5 0 0

a Some products also available in pails or cans as small as 5p o u n d s

b Highly variable because of many bag sizes.c Expansions vary widely. Many are between 0.03 and 0.07 per-

cent; many others between 0.10 and 0.40 percent.

d One manufacturer claims 7500 psi at 1 hour fo r one of thecompanys products.

e Data were obtained on grouts with a broad range of strengthsand tests were made with various rebar sizes, hole diametersand lengths of embedment.

This deck is being repaired with a fiber-reinforced nonshrinkmortar. The manufacturer advocates applying it inthicknesses not to exceed 34 inch.


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Some manufacturers also claim special pro p e rties forone or another of their pro d u c t s, such as stable fluidityover a considerable period of time, higher than norm a lresistance to penetration of chlori d e s, above - n o rmal re-sistance to fatigue, and capability of shielding against ra-d i a t i o n .

Some grouts are promoted for use in grouting post-tensioning cables. Where these cables run long distancesve rt i c a l l y, special water- re t e n t i ve grouts that re s i s t

bleeding have been advocated (CONCRETE CO N-S T RUCTION, Ja n u a ry 1984, pages 47 to 51).

Fibrous patc hing mort ars and concret es

At least two nonshrink mortars on the market containsteel fibers. These are for use where high impacts t rength, great ductility after cracking, and high flexura ls t rength are needed. One product is said to be part i c u-larly useful on old concrete or masonry because it doesnot disjoin; it is also said to impart watertightness andsome resistance to sulfates and aggre s s i ve water. Ap p a r-ently the premixed material does not cause the work a-bility problem sometimes experienced with stra i g h t

steel fibers when they we re introduced a number ofyears ago. Co m p re s s i ve strengths of 13,750 to almost16,000 psi at 28 days have b een re p o rted and flexura ls t rengths of 3300 to 3750 psi. Impact resistance is ve ryhigh. The product is supplied in 55-pound bags.

Another product is supplied in only 17.6-pound pack-ages so it can be mixed on the job at the rate of one pack-

age to one bag of a locally available portland cement and140 pounds of sand. This saves the cost of shipping thep o rtland cement and the sand a long distance. Thisblended material contains glass and polymer fibers plussome chemical pro d u c t s. Co m p re s s i ve strengths are saidto range from 6000 to 8000 psi and flexural stre n g t h sf rom 1500 to 1900 psi. High impact strength is claimed,and the product is said to show no weight loss after 300c ycles of fre ezing and thawing. It is also said to be chem-

ically resistant to solve n t s, fuels, strong alkalies andc h l o ride salt solutions.One use for which this material is promoted is as a

topping for parking decks or pave m e n t s. It is said to becapable of spanning cracks up to l3 2 - i n c h w i d e. Wherec racks are larg e r, a re i n f o rcing mesh is laid over the cra c kand anchored along its edges before applying the top-ping. As with all the other materials described here, fullp ro c e d u ral details are available from the manufacture r.

To obtain proprietary information on nonshrink patchingmortars and concretes, consult the Concrete Source-Book or the Buyers Guide in the December issue of

CONCRETE CONSTRUCTION. In either place look underthe category Patching compounds.

For information on nonshrink grouts and anchoring ce-ments look in the same references under Grouts,metallic; Grouts, nonmetallic; and Grouts, non-shrink.

PUBLICATION #C840893Co py right 1984, The Ab e rdeen Gro u p

All rights re s e rve d

nonshrink hydraulic cement mortars and grouts_tcm45-346372

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