Portland cement provides strength and durability. Each of the individual ingredients (cement, lime, sand, water, and any modifiers present) contributes to the performance of the mortar. With the diversity of materials available, masonry mortars can be formulated to produce the desired properties for most specific job requirements. The document also limits pigments for coloring to no more than 1 to 10% by weight of cement depending upon the pigment type. 3) limits admixtures to no more than 0.2% chloride ions. Similarly, the Specifications for Masonry Structures (ref. Since chlorides accelerate the corrosion of steel reinforcement and accessories ASTM C1384 stipulates that admixtures add not more than 65 ppm (0.0065%) water-soluble chloride or 90 ppm (0.0090%) acid-soluble chloride by weight of portland cement. Admixtures are functionally classified as bond enhancers, workability enhancers, set accelerators, set retarders, and water repellents. Potability of water is not in itself a consideration, but the water obtained from drinking supply sources is considered suitable for use.Īdmixtures (also sometimes called modifiers or additives) for masonry mortars (ASTM C1384, ref. 4f) must be clean and free of deleterious amounts of acids, alkalis, or organic materials. Water for masonry mortar (ASTM C270, ref. Aggregates which fail these gradation limits may be used, as long as the resulting mortar complies with the property specification requirements of ASTM C270, as shown in Table 2. Gradation limits are established in ASTM C144 for both natural and manufactured sands. It is characterized by sharp, angular shaped particles. Manufactured sand is the product obtained by crushing stone, gravel, or air cooled blast furnace slag. 4c) for mortar consist of either natural or manufactured sand. Air-entrained limes are only permitted in mortars containing nonair-entrained cement.Īggregates (ASTM C144, ref. Types N or NA lime are not typically used in mortar however, they are permitted if shown by test or performance record to not be detrimental to the soundness of the mortar. ASTM C207 limits the amount of unhydrated oxides in Type S or Type SA hydrated limes, assuring the soundness of mortar made using these limes. Slaking of hydrated lime is not required, thus hydrated lime is immediately usable and much more convenient than quicklime. ASTM C207 designates Type N (normal), Type S (special), and air-entraining Type NA and Type SA hydrated limes. 4e) is a dry powder obtained by treating quicklime with enough water to satisfy its chemical affinity for water. Consequently, quicklime is rarely used in mortar. The resultant lime putty must be stored and allowed to hydrate for at least 24 hours before use. Quicklime must be slaked (combined chemically with water) prior to use. 4a) is calcined (burned-decarbonated) limestone, the major constituents of which are calcium oxide (CaO) and magnesium oxide (MgO). Types S or SA (slag cement) may also be used in mortars meeting the property specification requirements of ASTM C270 (Table 2 of this TEK). Types IS, IS-A, IP, IP-A, I(PM), or I(PM)-A blended cements may be used as alternatives to portland cement to produce ASTM C270 compliant mortars. 4g) consist of standard portland cement or air-entrained portland cement (denoted by -A) combined through blending with such materials as blast furnace slag (S), or pozzolan (P & PM) which is usually fly ash. 4j) is a hydraulic cement similar to masonry cement, with the added requirement of a minimum bond strength requirement.īlended hydraulic cements (ASTM C595, ref. In addition, Type N masonry cement can be combined with portland cement or blended hydraulic cement to produce Type S or M mortars. Masonry cements are classified as Type M, Type S, or Type N according to ASTM C270. 4b) is a hydraulic cement consisting of a mixture of portland cement or blended hydraulic cement and plasticizing materials (such as limestone, hydrated or hydraulic lime) together with other materials introduced to influence such properties as setting time, workability, water retention, and durability. Air-entrained portland cements (IA, IIA, and IIIA) may be used as alternatives to each of these types. Types I (normal), II (moderate sulfate resistance), and III (high early strength) are permitted according to ASTM C270 (ref. 4d) is a hydraulic cement (sets and hardens by chemical reaction with water) and is one of the main constituents of mortar. ASTM International maintains national standards for mortars and materials commonly used in mortars, as follows:
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