Sand for Mortars

Although most sand used for mortars is naturally occurring siliceous sand, crushing hard rocks such as dense limestones produces fines which, if correctly processed are suitable for use as building sands. 

Limestone sand is generally produced by wet screening, although dry screening is also used. In wet systems, hydrocyclones may be used to separate sand from finer particles. 

The main factors affecting the quality of a sand used for mortar are  

The crushing strength must be adequate for the duty, but this is not an issue for sands produced from dense limestones. 

Most countries have their own specifications for sand used in mortars. In Europe, work is well in hand to produce a standard (see section 8.8.1). In the UK, the relevant standards are BS 1199 (for plastering and rendering mortars) [8.13] and BS 1200 (for masonry mortars) [8.14]. Sands for floor screeds are specified in BS 882 [8.2] and in BS 1199 [8.13]. 

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In many countries, the largest market segment for the sale of limestone is as an aggregate in the construction and building industry. The major uses are in concrete and roadstone (both bound and unbound). Other applications include sand for mortar, rip rap, armourstone for sea defence works, land fill, filter media, pebble dash and roofing gravel. Finely divided limestone is used as an inexpensive filler for asphalt concrete. 

BS 1199 Specifications for building sands from natural sources — sands for mortars for plastering and rendering , 1986. 

Silicates of natural origin and synthetic manufacture have been used as raw materials for centuries for example, silicate glass for windows and household utensils, sand for mortar (cement), mica as an insulating material, montmorillonite as a lubricant during boring, asbestos as a thermally stable insulating material, glass wool in insulation, etc. 

All the apparatus, chemicals, etc. should be available in the laboratory and be efficiently accommodated and stored. Suitable office furniture also forms part of the equipmentto be provided. Fig. 1 is presented as a suggestion of what a modern laboratory building should comprise and how its internal layout may be. The individual work rooms should be of ample size and preferably all be on the same floor - the ground floor, if possible. If this is impracticable for architectural reasons, the rooms in question should at least be conveniently accessible from all parts of the cement works. Cellars or basements should not be used as laboratory space, but may be used for the storage of certain bulky materials or equipment (e.g., standard sand for mortar tests, empty receptacles and moulds, comparison specimens which have to be kept for some time, etc.) and may also accommodate the heating installation. 

Hydraulic limes (84) may be used for mortar, stucco, or the scratch coat for plaster. They harden slowly under water, whereas high calcium limes, after slaking with water, harden in air to form the carbonate but not under water at ordinary temperatures. However, at elevated temperatures achieved with steam curing, lime—silica sand mixtures do react to produce durable products such as sand—lime bricks. 

Sample 19 was divided in two, since the upper layer of plaster in this room is visibly different from the layer lying beneath The first 4 mm of plaster consists of a white, brittle, hard material (sand-poor lime plaster), while the layer underneath consists of an ochre-colored, sand-rich lime plaster. The separation was not completely successful parts of the sand-rich mortar remain in Sample 19a. The analysis for iron, which might possibly have been even lower in the presence of complete separation, confirms the assumption that the upper layer is an iron-poor lime plaster. This explains the deficient formation of blue spots of pigment on the surface of the plaster in this room, since there is too little iron available for the formation of pigment. Nevertheless, even the upper layer of plaster exhibits quite high cyanide values. This shows that the layer of plaster was not applied after termination of the disinfestation actions. 

Hydraulically setting cements were first developed by the Greeks and Romans [B.69]. It was found that, after the addition of volcanic ash (pozzolana) to the slaked lime and sand, a mortar was obtained that possessed superior strength. This was discovered by the Greeks (700-600 BC) and later passed on to the Romans (150 BC) who called it Caementum. It was used, for example, for the construction of the Colosseum in Rome. 

The binder can be calcium lime, dolomitic lime, a hydraulic lime, a lime-cement mix, or cement. When calcium lime, or Type S dolomitic lime is mixed with sand to produce a sand-lime mortar, its initial role is that of a void filler. It subsequently causes the mortar to harden slowly, as a result of carbonation of the calcium hydroxide (N.B. when the term lime is used in connection with mortars, it refers to fully slaked lime with a low expansion potential. This includes Type S dolomitic times, which are widely used for mortars in the USA). 

C, and in a non-oxidizing atmosphere, B4C is the hardest compound known up to now. B4C is thus used for wear-resistant parts and inserts for mortars and ball mills, wear plates, sand blasting nozzles, dressing tools for grinding wheels, lightweight armor plates for helicopters, tanks, and in composites of glass fiber-reinforced plastics as bullet-proof protection for personnel. 

Ymyl chloride-aaylic acid copolymer and epoxy resin latices and a phenol formaldehyde resin solution were used to modify sand-cement mortars at room tanperature. The compression strength increased with an increase in the latex/resin concentration and with the addition of calcium chloride or calcium carbonate and a superplasticiser. Tensile and flexural strengths also increased with polymer incorporation. The porosity of the modified mortars decreased with the addition of resin. The percentage of water absorption and acid solubility decreased for the latex/resin modified samples. 21 refs. INDIA... 

Acid-resisting Cement. The principal types are as follows 1. Silicate an inert filler bonded with silica gel that has been precipitated in situ from Na- or K- silicate in the presence of Na2SiFg, or from silicon ester. 2. Rubber Latex essentially cement sand mixes impregnated with rubber. 3. Synthetic Resin with an inert filler. 4. Sulphur Cements usually with sand as filler. 5. Bituminous Cements. ASTM specifications for these materials are listed in Vol 4-05 of the Annual Book of ASTM Standards, and number some 25, including specifications for mortars and grouts. 

Geotextile systems utilize a high-strength synthetic fabric as a form for casting large units by filling with sand or mortar. Within these geotextile systems a distinction... 

It was ascertained, by careful measurement, that the void spaces, in 1 bulk of sand No. 1, taken from the middle of the heap, amounted to 0.33 the cementing paste, whatever it may be, should not be less therefore, than one-third the bulk of this sand. Taking one bulk of cement A, measured in powder from the cask, and a little compacted by striking the sides of the vessel, water was added till the consistence was proper for mortar 0-35 of water was required to do this, and the bulk of the stiff cement paste was 0.625. To obtain, at this rate, an amount of cement paste equal to the voids (0.33) in the sand, will require, therefore, 0.528 cement in powder, and 0.185 of water, or... 

In mixing the ingredients for mortar, the lime is first spread on a platform and wet by sprinkling with water, which causes it to give off a great deal of heat and vapor, and fall into a powder. The sand is then applied, and the whole brought with water to a consistent paste. 

Make a sample from a larger mix a drawback with this may be that it is difficult to take out small representative samples, both concerning the water content and the sand content (for mortars), and it might be difficult to know how much cement there is in the sample, especially if the sample shows segregation. Quantitative measurements are thus difficult in such cases, but qualitative ones (for example, to determine retardation - see in the following) are still possible. Nevertheless, if it is possible to take a homogeneous sample out of the mix, it is possible to perform quantitative measurements. 

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