The ASTM standard presumes that the proportions developed in the laboratory to meet the property requirements will result in satisfactory performance in the field. It should be understood that the property requirements of ASTM C 270 are for laboratory specimens and are not for field quality control. If project specifications do not indicate which has been selected, the proportion specifications govern, unless data qualifying the mortar under the property specification are presented to and accepted by the specifier. Either the proportion specifications or the property specifications should be selected, not both. Under the property specifications, in addition to meeting the individual product standards, mortar materials mixed in the laboratory using job site proportions must meet certain property requirements. No physical requirements are placed on the mortar itself. Under the proportion specifications, mortar ingredients must meet indicated product standards and be volumetrically proportioned within limits.

Type O is a low-strength mortar that is sometimes used for interior masonry or repointing.ĪSTM C 270 provides two alternatives for specifying mortars: proportion specifications and property specifications. Type M is a high-strength mortar that may be considered for load bearing or demanding freeze-thaw applications. It also provides increased resistance to freeze-thaw deterioration. Type S mortar is used in structural load-bearing applications and for exterior applications at or below grade. It is commonly used in interior walls, above-grade exterior walls under normal loading conditions, and in veneers. Type N mortar is a general-purpose mortar that provides good workability and serviceability. Mason contractors and specifiers need to understand the provisions of that specification and available options.ĪSTM C 270 defines four different types of mortars intended to address the variety of needs stemming from different masonry applications. Project specifications should reference ASTM C 270, the Standard Specification for Mortar for Unit Masonry. Mortar TypesASTM Standard Specifications provide a means for specifiers to identify acceptable materials and products without limiting those items to specific brands or manufacturers. No single mortar property defines mortar quality.No one mortar type will rate the highest in all areas of performance.

No one mortar type is best for all applications.

However, a balanced perspective is needed in the selection process. The relative influence different team members have on mortar selection varies from project to project. The owner/builder wants a completed project, delivered on time and within budget, which will serve his needs. The engineer focuses on the structural implications of mortar selection, the architect looks at appearance, and the mason contractor expects a workable product to facilitate productivity. provide required structural performance, andĬonsideration to each of these areas of performance needs to be given in the selection of mortar type and mortar materials.ĭifferent members of the design and construction team have different perspectives on the relative importance of these areas of performance.contribute to the serviceability of masonry,.Underlying Principles and IssuesMortar is used to lay brick, block, or stone units.

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