Saturday, October 15, 2011: 05:36:37 PM


Mortar Matters

B Joseph describes why focusing on sustainability is important when selecting a dry mix mortar

B Joseph

Decades ago, the introduction of dry-mix mortar technology revolutionised the kinds of raw material used in the construction industry. Ever since, developers around the world have rapidly adopted the use of dry mortar technology in their construction—even more so in the West. One of major drivers for the rapid growth of dry mix mortar at the time was its high efficiency. Another significant advantage of this technology is that the mortar’s production takes place in a dry mix mortar plant by combining all the necessary raw materials such as mineral binders, aggregates, and chemical additives such as cellulose ethers and redispersible polymer powder. The quality of the dry mix mortars can be guaranteed, so that the end-user receives the same consistency and quality every time. Today, the technical and commercial benefits of the dry mix mortars are well understood and appreciated by the construction industry.

A Sustainable Foundation
Infrastructure and the environment are intricately linked. The building industry is a large producer of wastes, and an extensive user of materials and energy. Thus, improvements in construction practice and design throughout the building’s lifecycle can contribute to significant environmental benefits. Globally, buildings contribute to 16 percent of the total water consumption and 40 percent of the energy used every year; close to 70 percent of the sulphur-oxides from fuel combustion are produced through the creation of electricity used to power houses and offices.

Dry mix mortars are among the many different construction materials used in constructing buildings. The impact of dry mix mortars on sustainability has been a topic of discussion and analysis since many decades. The primary impact of dry mix mortar on sustainability can be seen in three distinct areas—durability, quality and efficiency.

The extended durability of this technology can guarantee long-term performance and low maintenance, which is a major consideration for green, efficient buildings since it contributes to energy and cost-savings. Dry mix products can be designed to meet various end-use requirements such as diverse climatic conditions, temperature variations and different substrates, making them an apt choice for variable weather conditions. Additives such as cellulose, ethers such as Walocel cellulose ethers and redispersible polymer powders such as Dow Latex Powder (DLP) can help to enhance the performance of the tile adhesives. Reducing the maintenance cycle has a significant impact on the overall maintenance cost of a building.

Dry mix mortars are primarily manufactured in automated plants that have good process controls. This helps to ensure proper weighing and charging of various raw materials and additives, and guarantees homogeneous mixing. Typically, the process of quality control is carried out for every batch of dry mortar produced. Thus, the quality and consistency of dry mix mortar can be guaranteed, and customers can expect to receive the same quality each time. Since dry mix mortars are modified with polymers and additives, they will provide excellent application properties. This ensures trouble-free installation and excellent finishes, resulting in a higher quality lifestyle.

One of the most important drivers for the surging popularity of dry mix mortar was its very high efficiency. The dry mix mortar can be applied with the help of machines, hence resulting in huge time savings. Further, the enhanced efficiency of the material ensures its optimal usage and also very high productivity. This, in turn, contributes further to time savings that translate into cost savings over time.

The Energy Situation
The function of Exterior Thermal Insulation Composite Systems (ETICS) is to provide thermal insulation for buildings. ETICS containing dry mix mortar are used as building insulation in countries with a cold climate; these systems have also proved to be equally effective heat insulators. In the Middle East, for example, rising energy consumption is a predominant concern and the use of insulation products in a project can have a huge impact on its lifecycle costs.

The Arabian Peninsula is characterised by extreme hot weather conditions, and insulation systems such as ETICS are an ideal energy conservation solution for this region. Table 1 depicts data taken from a study carried out in the Kingdom of Saudi Arabia for buildings made using a dry mix mortar-based ETIC system, as compared to standard houses made from other materials and without insulation.

The base house is built using heavyweight concrete blocks, while the insulated house has an ETIC system that uses Styrofoam boards of 50 mm thickness, and dry mix mortar-based adhesives and base coats.

A Matter of Good Tiling
Cement-based tile adhesive is one of the largest dry mix mortar applications, and also one of the first dry mix applications to be commercialised. Polymer modified thin-bed mortars became popular in the mid-80s due to their excellent application properties and long term durability. The critical properties for tile adhesives are open time, workability, slip resistance and adhesion properties under different conditions.

EN 12004, EN 12002 and its sub norms are the main European norms that apply to cementbased tile adhesives. The norm EN 12004 specifies the values of performance requirements for all ceramic tile adhesives [cementitious (C), dispersion (D) and reaction resin (R) adhesives]. The letters describe one out of three types of adhesive with the following designation:

􀁘 C = Cementitious-based thin-bed adhesives (mortars)

􀁘 D = Dispersion adhesives (mastics)

􀁘 R = Reaction resin adhesives (epoxies and urethanes)

Each type can be divided into two classes with its respective number designation:

􀁘 Normal adhesive 1

􀁘 Improved adhesive 2

This classification is further streamlined as per the adhesives’ additional characteristics. For example, the classes of cementitious tile adhesives according to EN 12004 & EN 12002 are:

􀁘 F = mortar with accelerated setting (which is either fast-setting or fast drying).

This is used only for cementitious mortars)

􀁘 T = mortar with reduced slip

􀁘 E = mortar with extended open time (only for cementitious mortars and dispersion adhesives of class D2)

􀁘 S = deformable mortar (S1) or highly deformable adhesive (S2) This is used only for cementitious adhesives only (EN 12002)

The most important requirements for cement renders are easy workability, low stickiness to the tool, high non-sag properties and crack-free setting. The primary function of plaster is to protect against weathering, chemical or mechanical actions and ensure good adhesion to the substrates. Low water absorption is also a key requirement. Standard laboratory tests for cement spray plaster include: water retention, consistency, air pore content, setting time, compressive strength and water absorption. European norm 998 provides a clear definition and classification for cement renders.

Evaluating ETICs
External Thermal Insulation Composite systems (ETICS) have immense potential in the Middle East due to the region’s rising energy needs. The primary critical customer requirements for ETICS mortars are the adhesive strength of the adhesive mortar and impact resistance of the base-coat mortar. The two main standards that apply to ETICS are:

􀁘 ÖNorm (Austrian Standards Institute Development)

􀁘 ETAG 004 is a European standard compiled by EOTA (European Organisation for Technical Approval)

The ÖNorm (Austrian Norm) 6121 defines requirements for the adhesive mortars, while the ÖNorm (Austrian Norm) 6123 defines requirements for the glass-fibre mesh-reinforced base coat.

The requirements for the adhesive mortar according the ÖNorm are as follows:

􀁘 Measurements according to ÖNorm 6121 (superseded by EN 13499)

􀁘 Pulling mortar probe from EPS substrate requires minimum adhesive strength of 0.1 N/ square mm after 28 days of storage at RT (and 24 hrs water immersions). The impact resistance for base mortar is measured in a similar way for both ETAG 004 and ÖNorm. The requirement is passing 3 Joule impact without any crack formation using the pendulum impact test.

Dry-mix mortars present a great opportunity for the India construction sector to raise its building standards in a sustainable manner. Dry mortars also provide an effective solution to meet the quality and durability requirement for buildings within the country. Due to its high efficiency and higher performance standards, dry mortar technology also provides cost advantages as compared to conventional site-mix mortars.

Mortaring India
As discussed above, many parameters of dry mortar technology determine the sustainability it contributes to a construction project. Many dry mix mortar-based applications are already practiced in India, and applications such as tile adhesive are very well-established. However, one of the major challenges the country faces today is a lack of appropriate norms and standards for dry mortar technology. The role of government bodies is also very critical in creating laws and regulations which ensure that the industry players strictly follow the prescribed standards. The role of different players in the construction industry value chain (suppliers, manufacturers, architects, consultants and contractors) is critical in implementing appropriate norms and standards.

The author is the Technical Development Manager — India, Middle East & Africa for Dow Construction Chemicals

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