However, due to the procedural differences between Specication C and C , the com- pressive strength values resulting from eld sampled mortars are not required nor expected to meet the compressive strength requirements of the property specication of Specication C , nor do they represent the compressive strength of the mortar in the wall.
There is no ASTM method for determining the conformance of a mortar to the property specications of Specication C by testing hardened mortar samples taken from a structure. NOTE 11The results of tests using Test Methods C Annex 4 and C can be compared with Specication C proportion require- ments; however, precision and bias have not been determined for these test methods.
NOTE 12The results of tests done using Test Method C can be compared with the Specication C proportion requirements, however, precision and bias have not been determined for this test method.
NOTE 13Where necessary, testing of a wall or a masonry prism from the wall is generally more desirable than attempting to test individual components. NOTE 14The cost of tests to show initial compliance are typically borne by the seller. The party initiating a change of materials typically bear the cost for recompliance. Unless otherwise specied, the cost of other tests are typically borne as follows: If the results of the tests show that the mortar does not conform to the requirements of the specication, the costs are typically borne by the seller.
If the results of the tests show that the mortar does conform to the requirements of the specication, the costs are typically borne by the purchaser. Keywords 9. The relatively small portion of mortar in masonry signicantly inuences the total performance.
There is no single mortar mix that satises all situations. Only an under- standing of mortar materials and their properties, singly and collectively, will enable selection of a mortar that will perform satisfactorily for each specic endeavor. Mortar inuences the structural properties of the assemblage while adding to its water resistance.
Realistically, mortars differ from con- crete in working consistencies, in methods of placement and in the curing environment. Masonry mortar is commonly used to bind masonry units into a single structural element, while concrete is usually a structural element in itself.
Concrete is usually placed in nonabsorbent metal or wooden forms or otherwise treated so that most of the water will be retained. Mortar is usually placed between absorbent masonry units, and as soon as contact is made the mortar loses water to the units. Compressive strength is a prime consider- ation in concrete, but it is only one of several important factors in mortar. Plastic properties determine a mortars construction suitability, which in turn relate to the properties of the hardened mortar and, hence, of nished structural elements.
Properties of plastic mortars that help determine their construction suitability C 07 5 include workability and water retentivity. Properties of hard- ened mortars that help determine the performance of the nished masonry include bond, durability, elasticity, and com- pressive strength.
For this and other reasons there are no mortar standards wholly based upon performance, thus the continued use of the traditional prescription specication in most situa- tions. Workable mortar can be spread easily with a trowel into the separations and crevices of the masonry unit. Workable mortar also supports the weight of masonry units when placed and facilitates alignment. It adheres to vertical masonry surfaces and readily extrudes from the mortar joints when the mason applies pressure to bring the unit into alignment.
Workability is a combination of several prop- erties, including plasticity, consistency, cohesion, and adhe- sion, which have deed exact laboratory measurement. The mason can best assess workability by observing the response of the mortar to the trowel.
Al- though largely determined by aggregate grading, material proportions and air content, the nal adjustment to workability depends on water content. This can be, and usually is, regulated on the mortar board near the working face of the masonry. The capacity of a masonry mortar to retain satisfactory workability under the inuence of masonry unit suction and evaporation rate depends on the water retentivity and setting characteristics of the mortar.
Good workability is essential for maximum bond with masonry units. Flow after suction is another laboratory property which is determined by the same test, but performed on a mortar sample which has had some water removed by a specic applied vacuum.
Water retention is the ratio of ow after suction to initial ow, expressed in percent. The lower initial ow requirements for laboratory mortars were arbitrarily set because the low ow mortars more closely indicated the mortar compressive strength in the masonry. This is because most masonry units will remove some water from the mortar once contact is made. While there may be some discernible relationship between bond and compressive strength of mortar, the relationship between mortar ow and tensile bond strength is apparent.
For most mortars, and with minor exceptions for all but very low suction masonry units, bond strength increases as ow in- creases to where detectable bleeding begins. Bleeding is dened as migration of free water through the mortar to its surface. This mortar property gives the mason time to place and adjust a masonry unit without the mortar stiffening.
Water retentivity is increased through higher lime or air content, addition of sand nes within allowable gradation limits, or use of water retaining materials. Initial set as measured in the laboratory for cementitious materials indicates extent of hydration or setting characteristics of neat cement pastes.
Too rapid stiffening of the mortar before use is harmful. Mortar in masonry stiffens through loss of water and hardens through normal setting of cement. This transformation may be accel- erated by heat or retarded by cold. A consistent rate of stiffening assists the mason in tooling joints. It is also the most inconstant and unpredictable.
Bond actually has three facets; strength, extent and durability. Because many variables affect bond, it is difficult to devise a single laboratory test for each of these categories that will consistently yield reproducible results and which will approximate construction results. These vari- ables include air content and cohesiveness of mortar, elapsed time between spreading mortar and laying masonry unit, suction of masonry unit, water retentivity of mortar, pressure applied to masonry joint during placement and tooling, texture of masonry units bedded surfaces, and curing conditions.
Test Method C includes provisions for testing the exural bond strength of mortar to full-size hollow masonry units, constructed in a prism. It also contains a crossed brick couplet method for testing direct tensile bond of mortar to solid masonry units.
Loading of the specimens in Test Method C is such that a single joint is tested in tension. Test Method C tests the exural bond strength of hollow and solid units and mortar, constructed in prisms.
Individual joints of the prisms are tested for tensile bond strength. Test Method C is becoming more widely used to test the exural bond strength than the others, due to the large amount of data produced by relatively small amounts of material.
The rst method, for laboratory prepared specimens, is intended to compare bond strengths of mortars C 07 6 using a standard solid concrete masonry unit constructed in a prism. Test Method E provides a method for testing a masonry prism as a simply supported beam to determine exural strength. While individual joints are not loaded in the Test Method E procedure, the resulting strength is deter- mined as the prism behaves in exure.
The exural strength of masonry walls is perhaps best indicated by testing full-scale wall specimens with Test Method E 72 with lateral uniform or point loading applied to the specimen. Research 4,5 on concrete masonry indicates the exural bond strength of concrete masonry walls, using Test Method E 72, may be correlated with results of exural bond strength of concrete masonry prisms, tested in accordance with Test Method C and Test Method E Lack of extent of bond, where severe, may be measured indirectly by testing for relative movement of water through the masonry at the unit-mortar interface, such as prescribed in Test Method E This laboratory test method consists of subjecting a sample wall to a through-the-wall pressure differ- ential and applying water to the high pressure side.
Time, location and rate of leakage must be observed and interpreted. Mortar joints, therefore, are subject to bond failures at lower tensile or shear stress levels. A lack of bond at the interface of mortar and masonry unit may lead to moisture penetration through those areas. Complete and intimate contact between mortar and masonry unit is essential for good bond.
This can best be achieved through use of mortar having proper composition and good workability, and being properly placed. Because of mortar workability, it has been found that Type S mortar generally results with the maximum tensile bond strength that can practically be achieved in the eld. It reects the maximum elongation possible under tensile forces.
Low strength mortars, which have lower moduli of elasticity, exhibit greater plastic ow than their high moduli counterparts at equal paste to aggregate ratios. For this reason, mortars with higher strength than necessary should not be used. Plastic ow or creep will impart exibility to the masonry, permitting slight movement without apparent joint opening.
The accepted laboratory means for measuring compressive strength is to test 2 in. Because the referenced test in this specication is relatively simple, and because it gives consistent, reproducible results, compressive strength is considered a basis for assessing the compatibility of mortar ingredients. Field testing compressive strength of mor- tar is accomplished with Test Method C using either 2 in. Compressive strength should not be the sole criterion for mortar selection.
Bond strength is generally more important, as is good workability and water retentivity, both of which are required for maximum bond. Flexural strength is also important because it measures the ability of a mortar to resist cracking. Mortars should typically be weaker than the masonry units, so that any cracks will occur in the mortar joints where they can more easily be repaired. Retempering is associated with a decrease in mortar compressive strength. The amount of the reduction increases with water addition and time between mixing and retempering.
It is frequently desirable to sacrice some compressive strength of the mortar in favor of improved bond, consequently retempering within reasonable time limits is recommended to improve bond.
The coupling of mortars with certain masonry units, and design without exposure considerations, can lead to unit or mortar durability problems. It is generally conceded that masonry walls, heated on one side, will stand many years before requiring maintenance, an indication of mortars potential longevity.
Parapets, masonry paving, retaining walls, and other masonry exposed to freezing while saturated represent extreme exposures and thus require a more durable mortar. Unless a masonry assemblage is allowed to become nearly saturated, there is little danger of substantial damage due to freezing. Properly entrained air in masonry mortar generally increases its resistance to freeze-thaw damage where extreme exposure such as repeated cycles of freezing and thawing while saturated with water exists.
Air content within the specication limits for mortar, however, may be above the amount required for resistance to freeze-thaw damage. Dura- bility is adversely affected by oversanded or overtempered mortars as well as use of highly absorbent masonry units. Sometimes admixtures are used also. Portland cement con- tributes to strength and durability. Lime, in its hydroxide state, provides workability, water retentivity, and elasticity.
Both portland cement and lime contribute to bond strength. Instead of portland cement-lime combinations, masonry cement or mortar cement is used. Sand acts as a ller and enables the unset mortar to retain its shape and thickness under the weight of subsequent courses of masonry. Water is the mixing agent which gives uidity and causes cement hydration to take place. Portland cement contributes strength to masonry mortar, particularly early strength, which is essential for speed of construction.
Straight portland cement mortars are not used because they lack plasticity, have low water retentivity, and are harsh and less workable than portland cement-lime or masonry cement mor- tars.
Lime mortars carbonate gradually under the inu- ence of carbon dioxide in the air, a process slowed by cold, wet weather. Because of this, complete hardening occurs very slowly over a long period of time.
This allows healing, the recementing of small hairline cracks. This could also cause some leaching, especially at early ages. Successive deposits may eventually ll the cracks. Such autogenous healing will tend to reduce water permeance. This calcium hydroxide performs the same as lime during carbon- ation, solubilizing, and redepositing. Sand acts as an inert ller, providing economy, workability and reduced shrinkage, while inuenc- ing compressive strength.
An increase in sand content increases the setting time of a masonry mortar, but reduces potential cracking due to shrinkage of the mortar joint. The special or standard sand required for certain laboratory mortar tests may produce quite different test results from sand that is used in the construction mortar.
Sands decient in nes produce harsh mortars, while sands with excessive nes produce weak mortars and increase shrinkage. High lime or high air content mortars can carry more sand, even with poorly graded aggregates, and still provide adequate workability. Excess nes in the sand, however, is more common and can result in oversanding, since workability is not substantially affected by such excess.
Mortar properties are not seriously affected by some variation in grading, but quality is improved by more attention to aggregate selection. Often gradation can be easily and sometimes inex- pensively altered by adding ne or coarse sands. Frequently the most feasible method requires proportioning the mortar mix to suit the available sand within permissible aggregate ratio tolerances, rather than requiring sand to meet a particular gradation.
It contrib- utes to workability, hydrates cement, and facilitates carbon- ation of lime. The amount of water needed depends primarily on the ingredients of the mortar. Water should be clean and free from injurious amounts of any substances that may be delete- rious to mortar or metal in the masonry. Usually, potable water is acceptable. Mortars should contain the maximum amount of water consistent with optimum workabil- ity. Mortar should also be retempered to replace water lost by evaporation.
Some chemical additions are essential in the manufacture of basic mortar materials. The inclusion of an additive is also necessary for the production of ready mixed mortars. Undoubtedly there are also some special situations where the use of admixtures may be advantageous when added at the job site mixer.
In general, however, such use of admixtures is not recommended. Careful selection of the mortar mix, use of quality materials, and good practice will usually result in sound masonry. Improprieties cannot be corrected by admixtures, some of which are de- nitely harmful. Admixtures are functionally classied as agents promoting air entrainment, water retentivity, workability, accelerated set, and so on.
Limited data are available regarding the effect of proprietary admixtures on mortar bond, compressive strength, C 07 8 or water permeance of masonry. Field experience indicates that detrimental results have frequently occurred.
Initial set as measured indirectly by testing for relative movement of water through in the laboratory for cementitious materials indicates extent of the masonry at the unit-mortar interface, such as prescribed in hydration or setting characteristics of neat cement pastes.
Too Test Method E This laboratory test method consists of rapid stiffening of the mortar before use is harmful. Time, normal setting of cement. This transformation may be accel- location and rate of leakage must be observed and interpreted.
A consistent rate of X1. Mortar joints, therefore, are subject to bond failures at X1. A lack of bond at the X1. It is also the most penetration through those areas. Complete and intimate contact inconstant and unpredictable. Bond actually has three facets; between mortar and masonry unit is essential for good bond. Because many variables affect This can best be achieved through use of mortar having proper bond, it is difficult to devise a single laboratory test for each of composition and good workability, and being properly placed.
These vari- mortars increase with an increase in cement content. Because ables include air content and cohesiveness of mortar, elapsed of mortar workability, it has been found that Type S mortar time between spreading mortar and laying masonry unit, generally results with the maximum tensile bond strength that suction of masonry unit, water retentivity of mortar, pressure can practically be achieved in the field.
It reflects the maximum X1. Low strength mortars, strength of mortar to masonry units, normal to the mortar which have lower moduli of elasticity, exhibit greater plastic joints.
Test Method C includes provisions for testing the aggregate ratios. For this reason, mortars with higher strength flexural bond strength of mortar to full-size hollow masonry than necessary should not be used. Plastic flow or creep will units, constructed in a prism. It also contains a crossed brick impart flexibility to the masonry, permitting slight movement couplet method for testing direct tensile bond of mortar to solid without apparent joint opening.
Loading of the specimens in Test Method C is such that a single joint is tested in tension. Test Method X1. Individual joints of the prisms are tested for tensile bond strength. Test Method C 4 Thomas, R. The first method, for laboratory pre- Symposium, June Sometimes admixtures are used also. Because the X1. Portland cement con- because it gives consistent, reproducible results, compressive tributes to strength and durability.
Lime, in its hydroxide state, strength is considered a basis for assessing the compatibility of provides workability, water retentivity, and elasticity. Both mortar ingredients. Field testing compressive strength of mor- portland cement and lime contribute to bond strength. Sand acts as a filler and enables the X1.
Water is the mixing agent strength of mortar is overemphasized. Compressive strength which gives fluidity and causes cement hydration to take place. Bond X1. Flexural strength is also important because it measures the ability of a mortar to resist cracking.
Often overlooked is X1. Portland cement will probably be well over twice the value obtained when the contributes strength to masonry mortar, particularly early mortar is tested as a 2 in. Mortars should strength, which is essential for speed of construction.
Straight typically be weaker than the masonry units, so that any cracks portland cement mortars are not used because they lack will occur in the mortar joints where they can more easily be plasticity, have low water retentivity, and are harsh and less repaired.
Retempering is associated with containing portland cement and fines, such as ground limestone a decrease in mortar compressive strength. The amount of the or other materials in various proportions, plus additives such as reduction increases with water addition and time between air entraining and water repellency agents.
It is frequently desirable to sacrifice X1. The Hydrated lime contributes to workability, water retentivity, and coupling of mortars with certain masonry units, and design elasticity. Lime mortars carbonate gradually under the influ- without exposure considerations, can lead to unit or mortar ence of carbon dioxide in the air, a process slowed by cold, wet durability problems.
It is generally conceded that masonry weather. Because of this, complete hardening occurs very walls, heated on one side, will stand many years before slowly over a long period of time. This allows healing, the requiring maintenance, an indication of mortars potential recementing of small hairline cracks.
Parapets, masonry paving, retaining walls, and other X1. This could also cause some leaching, especially at early ages. Successive deposits X1. Such autogenous healing will durability, is subjected to repeated cycles of freezing and tend to reduce water permeance. Unless a masonry assemblage is allowed to become nearly saturated, there is little danger of substantial damage X1.
Properly entrained air in masonry mortar of its weight in calcium hydroxide at complete hydration. This generally increases its resistance to freeze-thaw damage where calcium hydroxide performs the same as lime during extreme exposure such as repeated cycles of freezing and carbonation, solubilizing, and redepositing.
Air content within X1. Dura- constituent of the mortar. Sand acts as an inert filler, providing. An increase in sand content increases entrainment, water retentivity, workability, accelerated set, and the setting time of a masonry mortar, but reduces potential so on. Limited data are available regarding the effect of cracking due to shrinkage of the mortar joint.
The special or proprietary admixtures on mortar bond, compressive strength, standard sand required for certain laboratory mortar tests may or water permeance of masonry. Field experience indicates that produce quite different test results from sand that is used in the detrimental results have frequently occurred. For these reasons, construction mortar. Sands deficient in fines produce harsh mortars, masonry.
High lime or high air content mortars can limits on air content in a field mortar, still continues to create carry more sand, even with poorly graded aggregates, and still controversy.
Most masonry cements, all Type A portland provide adequate workability. Excess fines in the sand, mum as well as maximum levels of air in a laboratory mortar. Mortar stances. At high air levels, a definite inverse selection. Often gradation can be easily and sometimes inex- relationship exists between air content and tensile bond pensively altered by adding fine or coarse sands.
Frequently the strength of mortar as measured in the laboratory. In general, most feasible method requires proportioning the mortar mix to any increase in air content is accompanied by a decrease in suit the available sand within permissible aggregate ratio bond as well as compressive strength. Data on masonry grouts tolerances, rather than requiring sand to meet a particular indicate that lower bond strength between grout and reinforc- gradation.
Most highly air X1. It contrib- entrained mortar systems can utilize higher sand contents utes to workability, hydrates cement, and facilitates carbon- without losing workability, which could be detrimental to the ation of lime.
The amount of water needed depends primarily masonry if excessive sand were used. The use of any mortar on the ingredients of the mortar. Water should be clean and free containing air entraining materials, where resulting levels of air from injurious amounts of any substances that may be delete- are high or unknown, should be based on a knowledge of local rious to mortar or metal in the masonry.
Usually, potable water performance or on laboratory tests of mortar and masonry is acceptable. Water requirement the field is strongly discouraged. Mortars should contain the aggregates or inorganic pigments. Mortar should also be retempered to replace water lost by of the weight of portland cement, with carbon black limited to evaporation. To minimize hardened mortar physically or chemically. The inclusion of an additive is also necessary for the plant or to use preweighed individual packets of coloring production of ready mixed mortars.
Undoubtedly there are also compounds for each batch of mortar, and to mix the mortar in some special situations where the use of admixtures may be batches large enough to permit accurate batching.
Mortar advantageous when added at the job site mixer. In general, mixing procedures should remain constant for color consis- however, such use of admixtures is not recommended. Careful tency. Improprieties cannot be corrected by admixtures, some of which are defi- X1. When the first settlements appeared in North America, a workability loss in the mortar. The use of ready mixed mortar relatively weak product was still being made from lime and is also on the increase.
These are mixtures consisting of sand. The common use of portland cement in mortar began in cementitious materials, aggregates, and admixtures, batched the early part of the twentieth century and led to greatly and mixed at a central location, and delivered to the construc- strengthened mortar, either when portland cement was used tion project with suitable workability characteristics for a alone or in combination with lime. Modern mortar is still made period in excess of h after mixing.
Systems utilizing with from portland cement and hydrated lime, in addition to continuous batching of mortar are also available. At one extreme, a qualification as Types M and S Mortars in this specification.
A wall contain- X1. At the other extreme, a straight lime and any project with the desired performance characteristics are the sand mortar would have low compressive strength and high design, material, procedure and craftsmanship selected and water retention.
A wall containing such a mortar would have used. Between the two compliance with requirements should be appropriate and extremes, various combinations of cement and lime provide a predetermined. Selective pro- soon as the masonry unit and the mortar come into contact. The portions are found in this specification. Microscopic bubbles of en- the mortar and the masonry units, and thus the strength, as well trained air contribute to the ball bearing action and provide a as other properties, of the masonry assemblage.
Freeze-thaw durability of masonry X1. Three types of important external factor which affects the fresh mortar and masonry cement are recognized by Specification C These initiates the development of bond. Masonry units vary widely masonry cements are formulated to produce mortars conform- in initial rate of absorption suction.
It is therefore necessary ing to either the proportion or the property specifications of this that the mortar chosen have properties that will provide specification. Such masonry cements provide the total cemen- compatibility with the properties of the masonry unit being titious material in a single bag to which sand and water are used, as well as environmental conditions that exist during added at the mixer.
A consistent appearance of mortar made construction and the construction practices peculiar to the job. More than X1. A loss of too much water from recognized by Specification C These mortar cements are the mortar can be caused by low water retentivity mortar, high formulated to produce mortar conforming to either the propor- suction masonry units, or dry, windy conditions.
When this tion or property requirements of this specification. Mortar occurs, the mortar is incapable of forming a complete bond cement mortars have attributes similar to those of masonry when the next unit is placed. Where lowering the suction by cement mortars while satisfying air content and bond strength prewetting the units is not proper or possible, the time lapse requirements of Specification C When a very low suction premixed mortars have been made readily available in two masonry unit is used, the unit tends to float and bond is difficult options.
One is a wet, ready mixed combination of hydrated to accomplish. There is no available means of increasing the lime or lime putty, sand, and water delivered to the construc- suction of a low suction masonry unit, and thus the time lapse tion project, and when mixed with cement and additional water between spreading the mortar and placing the unit may have to is ready for use.
The other is dry, packaged mortar mixtures be increased. Special X1. The compressive strength values resulting from field tested mortars do not represent the compressive strength of mortar tested in the laboratory nor that of the mortar in the wall.
Physical properties of field sampled mortar shall not be used to determine compliance to this specification and are not intended as criteria to determine the acceptance of rejection of the mortar. Compliance to this specification is verified by confirming that the materials used are as specified, meet the requirements as given, and added to the mixer in the proper proportions as described.
Note 1: When the property specification is used to qualify masonry mortars, the testing agency performing the test methods should be evaluated in accordance with Practice C These notes and footnotes excluding those in tables and figures shall not be considered as requirements of the standard.
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