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Masonry Mortar

Basic Use

CEMEX’s Plastic Cement is specially formulated and manufactured to produce masonry mortar for use in brick, block and stone construction.

Composition and Materials

CEMEX’s Plastic Cement consists of a mixture of Portland Cement and plasticizing materials (such as limestone, hydrated or hydraulic lime) together with other materials introduced to enhance one or more properties. These components are proportioned at the cement plant under controlled conditions to assure product consistency.

Table 1  Physical Properties of Masonry Cements (ASTM C-91)
Masonry Cement Type N S M
Fineness residue on a 45-um (No. 325) sieve max., % 24 24 24
Autoclave expansion max., % 10 10 10
Time of setting
Initial set, min., not less than
Initial set, min., not less than
120
1440
90
1440
90
1440
Compressive strength (avg. of 3 cubes), min.
7 days, MPa (psi)
28 days, MPa (psi)
3.4(500)
8.2(900)
9.0(1300)
14.5(2100)
12.4(1800)
20.0(2900)
Air content, volume %
Min.
Max.
8
21
8
19
8
19
Water rention, flow after suction as % of original flow, min. 70 70 70

Types

CEMEX’s Plastic Cement meets the physical requirements of ASTM C-91 for Type N, S and Type M Masonry Cements for use in preparation of ASTM Specification C-270 Type S, or M mortar, respectively, without any further additions.

Limitations

CEMEX’s Plastic Cement is designed to be mixed with sand and water. The addition of hydrated lime or any other materials to a plastic cement mortar at the job site is not required or recommended.

Plastic Cement is not approved for use in load-bearing structural masonry construction in seismic zones 2, 3 and 4.

Applicable Standards

Related Standards: The following standards are related to the use of CEMEX’s Plastic Cements:

ASTM C-91 Standard Specification for Masonry Cements

ASTM C-144 (Standard Specification for Aggregates for Masonry Mortar)

ASTM C-270 (Standard Specification for Mortar)

ASTM C-780 (Standard Specification for Pre-construction and Construction Evaluation of Mortar for Plain and Reinforced Unit Masonry)

Water

All water should be clean and free from organic material and deleterious amounts of dissolved acids, alkalies and salts.

Physical Properties

CEMEX’s Plastic Cement provides consistent workability, strength and durability (See Table 1).

Durability

Properties of masonry mortar related to its durability include:

  • Drying shrinkage characteristics. Results of laboratory test shown in Figure I indicate that the drying shrinkage of Plastic Cement Mortars is about half that of Portland Cement-Lime Mortars (See Figure I).
  • Resistance to sulfate attack. Plastic Cement Mortars also demonstrate significantly greater sulfate resistance than Portland Cement-Lime Mortars (See Figure II).
  • Water permeance. The properties of Plastic Cement Mortars when combined assure that the designer’s and masons’ needs are met. Laboratory research3 has confirmed the excellent performance of Masonry Cement Mortars in water permeance tests (See Figure III).

Figure I. Drying Shrinkage of Mortars at 28 days
Figure II. Sulfate Expansion of Masonry Mortars
Figure III. Water Absorption of Mortars

Preparation

CEMEX’s Plastic Cement proportioned with sand meeting ASTM C-144, according to Table 2, will produce mortar meeting the requirements of ASTM C-270 under the proportion specifications. Under the property requirements of ASTM C-270, however, cement-to-sand proportions for the job mixed mortar are to be in the range of 1:2¼ to 1:3½, and the mortar must be pre-tested in the laboratory before the job begins.

Machine mixing should be used whenever possible. First, with mixer running, add most of the water and half the sand. Next, add the Plastic Cement and the rest of the sand. After one minute of continuous mixing, slowly add the rest of the water. Mixing should continue for at least three minutes; extending mixing up to five minutes improves mortar.

Application

Good workmanship practices are required for successful application, including proper filling of head and bed joints, careful placement of units, appropriate tooling of the joint, modification of construction procedures and/or schedules to adapt to extreme weather conditions4,5 and proper cleaning procedures.

Masonry joints should be tooled at the same degree of stiffness and moisture. If joints are tooled too early, excess water will be drawn to the surface, producing lighter joints. The joints will appear dark and discolored if tooling is done after stiffening has started.

Hot Weather and Retempering

Mortars exposed to hot winds and full sun will tend to lose workability due to the evaporation of water. Common sense precautions should be taken to protect the mortar such as shading the mixer, wetting mortar boards, covering wheelbarrows and tubs, and balancing mortar production to meet demand.

If it is necessary to restore workability, mortar may be retempered by adding water and remixing. No mortar should be used or retempered beyond 2½ hours after the initial mixing. (ASTM C-270, Section 6.3)

TABLE 2  Plastic Cement Mortar - Proportions by Volume (ASTM C-270)
Mortar Type Portland Cement Cement S Plastic Type M Cement N Sand
S 1/2 - - 1 3 3/8 - 4 1/2
S - 1 - 1 2 1/4 - 3
M 1 - - 1 4 1/2 - 6
M - - 1 - 2 1/4 - 3

Cold Water Precautions

Mortar should be maintained at a minimum temperature of 40° F as prescribed by standard cold weather masonry specifications. Cold weather admixtures should be approved by the architect.

Availability

CEMEX’s Portland Cements can be ordered by contacting at CEMEX Customer Care at:

Customer Care  |   1-800-99-CEMEX

Maintenance

Avoid use of harsh chemical cleaners or strong acid solutions in cleaning masonry.

Technical Services Personnel

CEMEX personnel are available to provide technical assistance by contacting Customer Care at: 1-800-99-CEMEX (1-800-992-3639).

Warranty

CEMEX warrants that the products identified are in accordance with the appropriate current ASTM and Federal Specifications. No one is authorized to make any modifications or addition to this warranty. CEMEX makes no warranty or representation, either expressed or implied, with respect to this product, and disclaims any implied warranty of merchantability or fitness for a particular purpose.

As CEMEX has no control over the other ingredients mixed with this product or the final application, CEMEX does not and cannot warrant the finished work.

In no event shall CEMEX be liable for direct, indirect, special, incidental, or consequential damages arising out of this product, even if advised of the possibility of such damages. In no case shall CEMEX‘s liability exceed the purchase price of this product.

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