Mortars with an extended board life were successfully developed in Germany from 1970 to 1973. Since that time, they have been successfully used in Switzerland, Ireland, Austria, Spain, France, Italy and Canada. In 1982, they have started being used in the United States.
Unlike conventional mortars, which are prepared at the job site and batched by volume, extended life mortars are prepared in manufacturing plants and batched by mass weight, or by volume.
Extended life mortars are delivered to the job site at consistencies ready to use. Usually, they are delivered in ready-mix trucks or in containers. They are stored in containers at the job site in a protective manner that minimizes moisture loss resulting from evaporation and protected from freezing in cold weather. No other materials or admixtures are added at the job. The mortars contain set regulators, which are retarding-type admixtures that control the initial hydration period of the cement. These allow the mortars to remain plastic and workable for a period, which is generally 24 to 36 hours. At any time during this period, when mortars are used, suction by the masonry units will occur and the initial set will take place in a normal manner. The early strengths that develop are satisfactory for the walls to be constructed at a normal rate and for the mortars to retain enough water to ensure long- term strength development. Often the walls are loaded at approximately the same time as with conventional mortars and current masonry practices followed. However, when in doubt, it is recommended that prism tests be conducted in order to ensure the best results. Measures of bond strength, compressive strength, and water permeance can be equal to or better than those of conventional mortars.
Selection criteria
Mortar properties that generally influence the selection process include bond strength, water leakage, durability, compressive strength, drying shrinkage, uniformity, appearance, color, workability, availability, ease of use, cost, board life, and yield.
Mortar properties related to wall performances tend to be more important to architects while workability is an important consideration to contractors. When selecting mortar types, architects generally consider the following:
- Compressive strength.
- Interior or exterior use.
- Building code requirements.
- Compatibility of the mortar with masonry units.
- Mortar structures (load-bearing or non-load bearing, with or without reinforcements).
Testing
Extended Life Mortars are normally designed in accordance with ASTM C1142 Standard Specification for Extended Life Mortar for Unit Masonry. This specification essentially adopts the test method ASTM C780 for evaluating mortar properties.
Property specification requirements
When sampled and tested in accordance with ASTM C 1142, the mortar shall comply with the appropriate sections of the table below:
| Mortar Types | Average (A) Compressive Min. Strength Min (MPa) | Water Max. Retention % | Air Content (B) % |
|---|---|---|---|
| RM | 17.2 | 78 | 18 |
| RS | 12.4 | 75 | 18 |
| RN | 5.2 | 75 | 18 |
| RO | 2.4 | 75 | 18 |
(A) 28 days old from the day of casting cubes.
(B) when structural reinforcement is incorporated in the mix.
Tests for compressive strengths are averages of at least three specimens from one batch.
Ordering information
The purchaser must specify the mortar type to be used (RM, RS, RN, RO), the time period during which the mortar remains workable, and the desired mortar consistency.
The purchase order or contract may list the mortar ingredients desired and may state a list of optional data, in addition to the performance requirements.
Materials specifications
Extended Life Mortars are made of materials, which specifications must conform to the following:
- Cementitious Materials:
- Portland Cement types, I, II, or III ASTM specification C 150.
- Masonry Cement types M, S or N ASTM Specification C 91.
- Hydrated Lime ASTM specifications C 207 Type S.
- Aggregates: these must conform to ASTM specification C 144.
- Water: It must be clean, free of oils, acids, alkalis, salts, organic materials or other substances that may be deleterious to mortar or corrosive to metals in masonry.
- Admixtures: The admixtures used at the production plant shall not cause nor accelerate the corrosion of metals in contact with the mortar. It is important to ensure that the admixtures used have no adverse effect on the long term strengths, durability, or appearance on any of the mortar, material or components in contact with the mortar, or assemblage of which the mortar forms a part of.
The admixture, which controls the setting-time, may be altered when needed to maintain a similar time of set to adjust to seasonal temperature changes.
The established proportions for extended life mortars should not be changed for a particular job nor materials with different physical characteristics utilized before checking that under the new conditions the requirements of ASTM C 1142 are met.
A mortar of higher strength shall not be used as a substitute indiscriminately when a mortar type of anticipated lower strength is specified.
Field practice
A mortar that has stiffened due to water loss from evaporation shall not be tempered, by adding water to restore the required consistency, more than once during its working life.
Storage at the site
The mortar shall be protected from freezing and evaporation.
Batch ticket information
The delivery ticket provided by the manufacturer of the mortar to the purchaser shall clearly show the following information:
- Name of the extended life mortar manufacturer and batch plant as well as trade names of the admixtures used.
- A Serial number of tickets.
- Date and time the mortar was produced.
- Truck or vehicle delivery number.
- Name of the purchaser.
- Specific designation of the job (name and location).
- The specific type of mortar ordered and delivered.
- Amount of mortar delivered (in cubic meters).
- A field for the signature or initials of the purchaser’s representative.
Statement of Responsibility: The information and application advice contained in this document are based on the present state of scientific and practical knowledge of Holderchem SAL. It is provided with no warranty, implied or otherwise, as to its completeness or accuracy. Since methods and conditions of application and use are beyond the control of Holderchem, HOLDERCHEM MAKES NO WARRANTIES, IMPLIED OR OTHERWISE, AS TO THE MERCHANTABILITY OR FITNESS FOR ORDINARY OR PARTICULAR PURPOSES OF ITS PRODUCTS AND EXCLUDES THE SAME. Holderchem warrants that its products shall be of sound materials and workmanship. As products are applied, handled and stored in manners and site conditions over which Holderchem has no control, Holderchem's liability in respect of any material which can be proven defective shall be limited to the replacement of such defective material or reimbursement of its cost at Holderchem's option. Holderchem shall not be liable for any consequential or incidental damage or loss arising out of the use of its products. Important Note: Holderchem shall have the right to modify product specification sheets at any time without previous notice. Buyers should always refer to the most recent data sheets, copies of which can be supplied upon request. The sale of products mentioned in this literature shall be subject to Holderchem's General Conditions of Sale Delivery and Payment.
Holderchem R&D seeks to develop solutions to meet construction challenges by bringing to market innovative products and systems, which offer benefits across the complete life cycle of buildings and other constructions. The aim is to supply customers with high-performance products to help them achieve better productivity, lower overall costs, and achieve extended service life and functionality. Research also aims at developing the Holderchem range of Batimix® products with a particular focus on polymer emulsions, polymer-inorganic interactions, and product applications.