The Effect Of Partial Replacement Of Conventional Fine Aggregate (sand) With Lateritic Soil In The Production Of Sandcrete Bricks

2.2  Sandcrete Bricks
Sandcrete bricks are composite material made up of cement, sand and water, moulded into different sizes (Barry 1969). Nigerian Industrial Standard (NIS): 87- 2004) defined sandcrete as a composite material made up of water, cement and sand. It differs from concrete in terms of material composition because of the noninclusion of coarse aggregate in the mix, and from mortar in that the slump is zero. As a matter of fact, sandcrete is often referred to as zero slump concrete. Sandcrete bricks are the most common type of bricks used in modern day construction in Nigeria. The major constituents are water, cement, and sand. The sand, according to the NIS 87: (2004) “Shall be river, crushed or pit sand, clean and sharp and free from loam, dirt, organic or chemical matter of any description.” Their major advantages as compared to the other types of brick are their easy mode of production and the speed of laying them. Their major set back is obviously their poor thermal and hygrometric properties. This can greatly affect their durability especially when they are permanently exposed to the elements. To improve these properties, the walls formed with sandcrete bricks are normally rendered with cement-sand mortar.  Sandcrete bricks are classified as solid.
2.2.1 Constituents of Sandcrete bricks
Sandcrete bricks are traditionally made of a mixture of water, cement and sand
(fine aggregates). Recent practice in sandcrete bricks production often includes the partial replacement of the sand with lateritic soils. This has been found to improve the strength and water absorption properties of the bricks.
2.3  Cement.
Cement plays an indispensable role in concrete production as it is the main material that binds the constituents into a compact whole (Shetty, 2005, Neville, 2011). It is a product resulting from the burning at very high temperatures (1300- 1500oC) of certain proportions of ground calcareous materials such as limestone or chalk and argillaceous materials like clay or shale. The materials fuse into balls called clinker which is allowed to cool. The cooled clinker is then ground with gypsum added to improve its properties. The resulting product is called Ordinary Portland cement (OPC) and is in the form of fine powder which, when mixed with water, forms a paste. Ordinary Portland cement is the most common type of cement used in everyday construction works.  The table below show the major compounds and oxides in a typical Portland cement. Many other types of cement can be produced from OPC by doing any or combinations of the following (i) finer grinding of the clinker, (ii) adding other chemicals such as calcium chloride, (iii) altering the quantities of the oxides or compounds  (iv) blending OPC intimately with Portland blast furnace slag. The other types of cement include: Rapid hardening cement, Sulphate resisting cement, Low heat cement, Extra rapid hardening cement, Portland slag cement to mention but a few.