Sand, Cement & Additives

SAND AND CHIPPINGS

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica, usually in the form of quartz.

Aggregates are small rock fragments, 0.08 to 80 mm, of mineral origin. They may be sand, gravel or crushed gravel and mixed with water and cement, are essential for the production of concrete.

Which sand do you need?

  • Building sand is a soft mortar sand for use in bricklaying and pointing where a smooth finish is required.
  • Sharp sand is a washed concreting sand suitable for concrete manufacture when mixed with gravel and cement and for bedding flagstones and block paving.
  • Plastering sand is a washed sand for use both indoors and outdoors for plastering and rendering walls and brickwork.
  • Kiln dried sand is a fine dry silica sand used for filling joints in block paving. The grain size is usually up to 0.5mm.
  • Dried silica sand is a coarse dry silica sand used on sports surfaces. It has a larger sand grain size of up to 3mm.
  • Playpit sand is used in all child play areas, including home sandpits. It is non-staining of children's clothes and safe for their use from 36 months.

 

And chippings?

  • 10mm is suitable for pathways and drives and the production of fine concrete when a smooth finish is required.
  • 20mm, on the other hand, is suitable for pathways and drives and the production of high strength concrete mixes.

CEMENT

Cement is one of the oldest building materials in the world and came into widespread use during the Industrial Revolution. The production process for cement is a mix of traditional chemistry and hi-tech equipment.

Cement is a hydraulic bonding agent which is obtained by heating, then grinding, a mixture of limestone and clay. Most cements are made from clinker and additives and are usually used in the form of a powder. Cement sets when mixed with water. Combined with sand and chippings, it turns into rock-hard concrete or mortar.

At Pentagon, we supply the following quality cements.

  • OPC Cement is ideal for general purpose use in concrete, mortar, render and screed and is compatible for use with a wide range of admixtures and additions.
  • High Strength cement is for use where increased day one strength is required. It is best used for concrete, mortar, render and screed, is beneficial for cold weather working and is ideal for pre-casting.
  • White cement is ideal for general purpose concrete, mortar, render and screed. It incorporates a specially selected additive to entrain air, offers improved workability and enhanced durability to frost when hardened.
  • Lime is for use in Cement / Sand / Lime mortars and offers excellent workability and good water retention.
  • Postfix is used for fence posts, gate posts, pergolas, garden lighting and much much more. Its special formulation is ideal for wooden and metal posts.

ADDITIVES

Additives are the ingredients in concrete other than portland cement, water, and aggregate, supplied in ready-to-use liquid form and are added to the mix immediately before or during mixing. 

Additives are classed according to function. There are five distinct classes of chemical admixtures.

  • Water reducing additives usually reduce the required water content for a concrete mixture by about 5 to 10 percent. Consequently, concrete containing a water reducing additive needs less water to reach a required slump than untreated concrete.
  • Retarding additives, which slow the setting rate of concrete, are used to counteract the accelerating effect of hot weather on concrete setting. High temperatures often cause an increased rate of hardening which makes placing and finishing difficult.
  • Accelerating additives increase the rate of early strength development, reduce the time required for proper curing and protection, and speed up the start of finishing operations. Accelerating additives are especially useful for modifying the properties of concrete in cold weather.
  • Plasticizers reduce water content by 12 to 30 percent and can be added to concrete with a low to normal slump and water cement ratio to make high slump flowing concrete. Flowing concrete is a highly fluid but workable concrete that can be placed with little or no vibration or compaction.
  • Corrosion inhibiting additives fall into the specialty admixture category and are used to slow corrosion of reinforcing steel in concrete. Corrosion inhibitors can be used as a defensive strategy for concrete structures that will be exposed to high concentrations of chloride. 

All our sand, cement and additives are available to collect from our drive-through, shop and back yard in Rue des Pres Trading Estate, St Saviour, or delivered free of charge to any destination islandwide. Pop in, contact us or call us on 01534 888000 for more information.

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