A MATHEMATICAL MODEL FOR PREDICTION OF THE STRENGTH OF SANCRETE CEMENT BLOCK

A MATHEMATICAL MODEL FOR PREDICTION OF THE STRENGTH OF SANCRETE CEMENT BLOCK

Abstract

Sandcrete blocks are prismatic units made from lean (sand-cement) mortar mixtures that are the most often used walling materials in Nigeria and other nations. Although the blocks are preferred over other similar walling materials such as bricks and concrete blocks due to the country’s availability of the dominant material (sand) and ease of manufacture, the material is known to have several drawbacks: it has a low compressive strength, which could be a factor in structural failure in buildings. Aside from the compressive strength, little is known about the material’s other strength and permeation qualities. Third, there has been minimal research into the effect of the water-cement ratio, which is known to have a substantial influence on the strength and permeability qualities of cementitious materials. A complete experimental program was devised and carried out in Nigeria on the parameters that influence the material’s strength and permeation capabilities utilizing over ten destructive test methods based on a thorough examination of the literature. More than 1500 sandcrete blocks were manufactured and tested. The literature analysis also revealed a lack of quality control in the Nigerian sandcrete blocks production industry, which accounts for the country’s poor material quality. The experimental results show that with the right constituent materials, manufacturing, and curing processes, it is possible to increase the compressive strength of sandcrete blocks to more than 7.0N/mm2 (the minimum specified by British Standards) with a lean mix of 1:12 cement/sand ratio. The material’s compressive strength was discovered to have a strong link with its other strength qualities and could thus be utilized as the primary criterion for establishing its quality. The addition of quarry dust and coarse aggregate (sharp sand) increased the strength and permeability qualities of the blocks dramatically. Sandcrete was discovered to have a comparatively high permeability when compared to regular concrete. A data base on many strength and permeability qualities has been produced as a result of this study, which can help engineers estimate these values. Finally, recommendations on how to improve the quality of sandcrete blocks throughout the country were provided.

CHAPITRE ONE

INTRODUCTION

1.1.1. Background Information

Sandcrete blocks are the primary masonry unit used in Nigeria, West Africa, and many other developing countries. They are made from a lean mixture of Portland cement, natural sand, and water. Unlike other masonry units used in other civil engineering facilities like as concrete blocks and fire bricks, they are primarily utilized as walling units in the construction of shelter: both as external cladding and for partitions. They are popular in the building industry due to their ease of fabrication and widespread availability of the major constituent material (sand).

Several studies, including the National de Recherche/Development (Sablocrete) (1994) project in France, have recognized sandcrete as a member of a family of concretes that can be employed when environmental and economic constraints prevent the use of coarse aggregate. This project (Sablocrete) in France demonstrated the material’s economic and mechanical advantages, as well as usual uses in public works and construction.

When researching the properties of sandcrete blocks as defined by this study, one encounters a quandary: there is little material in the technical literature on certain properties of sandcrete blocks such as durability, tensile, transverse, and flexural strength, and the value of elastic constants. One solution is to compare sandcrete to some of its closest relatives, such as concrete and mortar. Sandcrete, as a material, can be thought of as a type of zero-slump concrete or mortar. Even though their properties differ at one point, these three materials share numerous similarities. As a result, this paper contains several allusions to concrete and mortar.

Sandcrete blocks are largely manufactured in Nigeria by small-scale manufacturers who, as businesspeople, are motivated by profit and so frequently employ substandard materials and poor techniques in the creation of the blocks. As a result, poor quality blocks with low strength qualities are produced. Whereas Nigerian burnt bricks have compressive strengths ranging from 11.5N/mm2 to 26.0N/mm2, sandcrete blocks only have compressive strengths ranging from 1.45M/mm2 to 3.5N/mm2 (Graham, 1990; Danso, 1994). This issue tends to limit the material’s applicability and could potentially be a major role in the structural failure of structures during earthquakes.

As previously stated, aside from the unit’s compressive strength, very little is known about the block’s other properties, such as the Young’s Modulus, tensile, flexural, and transverse strengths, which are required by structural engineers and other scientists for design computations. The absence of information on the strength qualities of sandcrete blocks allows for much guesswork and approximation, which may be damaging to structural design.

Almost all of the various studies and publications on the material appear to be focused on its strength qualities. There is very little literature on the durability of sandcrete blocks. However, recent reports from throughout the world show that early deterioration of concrete and other cementitious materials is a big issue. For example, it has been stated that considerable sections of national budgets in the United States and Europe have been spent on the maintenance of concrete structures. As a result, the philosophy that a strong concrete is a durable concrete has failed because this is not always true. It can thus be claimed that in order to prevent high maintenance costs for constructions made of concrete and sandcrete blocks, the fundamental masonry units must be both durable and robust.

The water-cement ratio is closely related to the permeability (durability) and strength qualities of cementitious materials. Most experts believe that the water-cement ratio has a significant impact on the durability and strength of these materials, however few sandcrete block researchers have investigated the effect of the water-cement ratio on the attributes of the blocks.