Batimix Mortar 741-R8

Description

Pre-packaged BATIMIX Mortar 741-R8 is a unique ready to use floor screed mortar made of blended Type I Portland cement, selected additives, fibers, and carefully graded, aggregates.

Main Purpose

BATIMIX Mortar 741-R8 is used as a floor screed mortar for both interior and exterior elements. Primary applications include industrial floors, high traffic roads, lobbies and waiting rooms of commercial and public buildings, corridors, restaurants, auto showrooms, services centers, factories and warehouse floors, and facilities. It is used to level surfaces before the installation of other flooring products. Tiles can only be laid out on top of screed after full compressive strength development.

Features

BATIMIX Mortar 741-R8 has the following characteristics:

• Easy to use and pump
• Increased resistance against abrasion, wear, impact, and water permeability
• Decreased shrinkage, fissures, and surface cracks
• Significant increase of surface strength and adhesion properties
• Provides a dense surface that resists the penetration of oil, grease, and other liquids

Properties

• Appearance: powder
• Bulk density: around 1.45
• Grain size: 0 to 8 mm
• Yield: approx. 0.022 m³ per bag of 50 kg
• Compressive strength after 28 days (ASTM C 109): 35 MPa
• Flexural strength at 28 days (ASTM C 348): > 8 MPa
• Pull-off strength against concrete at 28 days (EN 1015-12): 0.5 MPa
• Resistance to abrasion at 28 days (EN 12808): 490 mm³

Health and Safety

BATIMIX Mortar 741-R8 contains cement that may harm the eyes and skin. In case of contact, rinse immediately with plenty of water. Wear suitable gloves. For further information, kindly refer to Material Safety Data Sheet.

Directions for Use

1 – Substrate preparation The surface over which BATIMIX Mortar 741-R8 is to be placed must be free of all loose dust, dirt, debris, laitance, oil, cracks and unsound concrete. Any loose or broken piece of concrete must be removed and cracks repaired prior to application. The concrete substrate must be structurally stable prior to application to avoid defects due to substrate movements. It must be at least 3 months old.

The best methods for roughening the surface are shot-blasting, scarifying or milling. The surface texture must have a profile of not less than 5 mms for increased adhesion. Concrete that cannot be properly vacuum-cleaned and textured should be profiled and anchored with mechanical studs to assure an integral bond.

BATIMIX Mortar 741-R8 may be placed monolithically on fresh concrete. Monolithic screeds and toppings are applied at the time when the underlying concrete floor is placed. Screed thickness should hover around 25mm (i.e within the 20 to 40 mm range). In circumstances where the design thickness of a topping has to be increased to more than 40 mm for structural reasons, it should be noted that there will be an increasing risk of loss of adhesion to the base, due to differential shrinkage stresses.

Before laying a monolithic screed, it is important to make sure the humidity in the floor slab is within acceptable limits for this type of flooring and that there is no rising damp. To achieve good adhesion between screed / topping and base concrete, contractors should pay particular attention to the bleeding of fresh concrete. Bleeding causes water to accumulate on the top of the surface of the fresh concrete. The presence of this water layer may impair adhesion unless correctly dealt with in the following manners:

• by immediate placing, applying the screed / topping promptly after the concrete has been compacted leveling it off before bleed water appears. No surface preparation is required in such pacing;
• by delaying placing until bleeding of the concrete has ceased ensuring that bleed water is removed or has evaporated. It should take place within an hour or two after the end of bleeding. The concrete surface should be well prepared, removing latencies by first light brushing with a brush with stiff bristles and then sweeping and vacuum cleaning.

2 – Bonding In case the product is to be placed over existing concrete, proper surface preparation followed by application of a bonding agent are essential to secure good bonding. The bonding agent is brushed into the surface with a soft brush in two layers: the first layer is left to dry to a clear film before the second layer is applied. The floor screed is applied while the bonding agent is still wet.

For the selection and application of a suitable bonding agent, refer to a Holderchem representative and follow the directions of use specified in the product TDS.

In case the screed is to be un-bonded (applied over a layer of polyethylene or PVC sheets) or floating (applied over a layer of thermal insulating material such as expanded polystyrene or polyurethane panels, or sound proofing material), lay down the sheets (PE or PVC), ensuring overlaps of not less than 30 cm and also vertical edges surrounding the screed of about 20 cm. Lay on around 1/3 of the layer thickness polypropylene fiber mesh (1cm x 1cm alkali resistant) or galvanised steel mesh (10 cm x 10 cm) in a way that keeps the screed floating. Fix soft strips of compressible material, such as expanded polystyrene, to separate columns and walls from the screed. Kindly seek engineering consultants advice on minimum screed thickness.

In case the screed is to be a heated screed, (i.e. a floating screed with pipe work elements in plastic or composite materials embedded in a spiral or coil pattern, and inserted above the insulating panels in the direction of the room to be heated), ensure a minimal thickness for better thermal diffusion, albeit not less than 25 mm, inserting metallic reinforcements to achieve strength requirements. For such applications, consult your Holderchem representative who might suggest combining Batimix Mortar 741-R8 with superplasticizing admixtures or the use of alternative Batimix floor screed products.

3 – Product preparation A 50 kg bag of BATIMIX Mortar 741-R8 should be mixed with 4 to 5 liters of clean water, depending on the desired consistency. Do not use water at a rate that will cause cracks, bleeding or segregation. The mixing should be done with a medium-speed mechanical mixer for a minimum of 3 minutes until obtaining a consistent homogenous material. Do not add water to a mix that has started setting.

4 – Application BATIMIX Mortar 741-R8 can be placed by direct discharge, buggy, wheelbarrow, or pump. Working time is approximately 30 minutes at 23ºC.

Tools such as rollers and trowels may be used to assist placement. Typical application depths can vary from 20 to 80 mm. Apply in stages on floor sections preferably of rectangular shape, not exceeding 24 m2, always keeping a wet edge to allow for the pouring of fresh material. It is advisable to leave control joints of 24 m² each. It is recommended joints be sealed with Polyurethane.

5 – Finishing Finish the applied BATIMIX Mortar 741-R8 mortar to the desired texture. It is to be noted that maximum abrasion resistance can be realised with a hard, smooth steel trowel finish. Do not add additional water to the surface during the finishing operations. Wait 30 to 60 days for the screed to be structurally stable before applying a flooring overlay.

6 – Curing Like all cementitious-based systems, BATIMIX Mortar 741-R8 requires curing to ensure durability, minimum cracking, and high performance of the finished product. It is recommended to wet cure the surface with water as soon as possible after placement for 7 days, in a 3 to 5 times a day frequency. Holderchem curing compounds may also be used to avoid fast drying.

Specifications / Compliance with Standards

BATIMIX Mortar 741-R8 exceeds the requirements of ASTM C 387 for Standard specification for packaged, dry, combined materials for mortar and concrete to suit specific product’s application requirements.

Precautions

Try avoiding peak temperatures, direct sunlight and windy conditions to reduce cracks appearing.

Storage

BATIMIX Mortar 741-R8 should be stored in a closed and dry place. Avoid freezing and excessive temperatures. Unopened bags have a shelf life of six months when stored as recommended.

Packages

• 50 kg paper bag
• 25 kg paper bag