ABSTRACT
The spate of building collapse in Nigeria has put in the front burner the need to investigate the quality of sandcrete blocks used in building construction. Collapse and heavy cracks are the frequent features of many building in Uyo capital city of Akwa Ibom State, Nigeria. There are many causes for collapse of building; one of which is weak and poor quality walling units, for example hollow sandcrete blocks. Therefore, this research work assessed the compressive strength and water absorption qualities of hollow sandcrete blocks produced in Uyo capital city of Akwa Ibom State, Nigeria. Three types of investigation, namely; literature review, field survey and laboratory experimentation procedures were used for the method. A total number of one hundred and eight (108) hollow sandcrete blocks were randomly collected. Twelve (12) blocks sampled from each of the nine (9) local government area of Uyo Capital City. Blocks sampled collected were tested at the age of 28days for their compressive strength and water absorption being two major characteristic requirement specified by Nigerian industrial standard for sandcrete blocks for testing and verifying the quality of sandcrete blocks, apart from the appearance and dimension. Structure interview was conducted at each factory with some of the factory staff to elicit further information on their production. All the tests were carried out in the soil laboratory, department of civil engineering, ministry of works Uyo, Akwa Ibom State, Nigeria. Test results shows that, there was no appreciable difference in water absorption values of the produced at the nine industrial sites. However, the water absorption values obtained are not higher than 12% specification. The average means of compressive strength of nine inches blocks (machine production) is 2.01N/mm2 and the manual production is 1.78N/mm2. However, for six inches blocks, the average means of compressive strength are 1.80N/mm2 and 1.69N/mm2 for the machine and manual productions respectively. This is far below the 2.5 N/mm2 recommended by Nigerian Industrial Standard (NIS) for non-load bearing walls and 3.45n/mm2 for load bearing walls. The result shows that, the blocks produced in Uyo, both machine and manual productions do not meet the minimum requirements by NIS, therefore it cannot be used for the construction of building. The study revealed that, poor quality control, poor selection of constituent materials, poor control of mix ratio and inadequate curing period by the producers contributed to the negative results obtained. It is recommended that workshop should be organized periodically to enlighten the block producers in the locality.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Contents vi
List of Tables viii
List of Figures ix
Abstract x
CHAPTER 1: INTRODUCTION
1.1 Background of Study 1
1.2 Statement of Problem 3
1.3 Objective of Study 4
1.4 Significance of Study 4
1.5 Scope of Study 5
CHAPTER 2: LITERATURE REVIEW
2.1 Sandcrete Blocks 6
2.2 Quality of Sandcrete Blocks 8
2.3 Standardization and Regulation of Quality 9
2.4 Standard Requirements 10
2.5 Standard Enforcements 12
2.6 Factors Affecting Quality of Sandcrete Blocks 13
2.7 Block Producers 14
CHAPTER 3: MATERIALS AND METHODS
3.1 Materials 15
3.1.1 Cement 15
3.1.2 Aggregates (sand) 15
3.1.3 Water 16
3.1.4 Manufacturing process of sandcrete blocks 16
3.2. Methods 17
3.2.1 Water absorption test 18
3.2.2 Compressive strength 19
CHAPTER 4: RESULTS AND DISCUSSIONS
4.1 Materials Utilized 22
4.1.1 Fine aggregate 22
4.1.2 Cement 22
4.1.3 Water 24
4.1.4 Test on raw materials 24
4.2 Method Employed in Production 25
4.2.1 Batching method 25
4.2.2 Mix ratio 25
4.2.3 Method of mixing 25
4.2.4 Method of molding 25
4.2.5 Addition of water 26
4.2.6 Curing method and duration 26
4.3 Water Absorption Test Results 29
4.4 Compressive Strength Test results 32
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusions 36
5.2 Recommendations 36
Reference 38
LIST OF TABLES
PAGE
4.1: Block factories and numbers of block specimens collected. 23
4.2: Proportions of fine aggregate and mix ratio. 24
4.3a: Results of water absorption test on block specimens (6 inches) 27
4.3b: Results of water absorption test on block specimens (9 inches) 28
4.4a: Results of compressive strength test on block specimens (6 inches) 31
4.4b: Results of compressive strength test on block specimens (9 inches) 32
LISTS OF FIGURES
1.1: Sandcrete Block specimens 7
4.1: Sources of water used by sampled factories. 24
4.2: Percentage of mix ratio used by sampled factories. 26
4.3a: Mean Values for Water Absorption of all 6 inches block. 30
4.3b: Mean Values for Water Absorption of all 9 inches block. 30
4.4a: Mean compressive strength values of all 6 inches block. 33
4.4b: Mean compressive strength values of all 9 inches block. 34
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
Building failures have resulted in loss of lives as well as assets in Nigeria (Odeyemi, 2012). In some cases, even though the building has not totally collapsed, the aesthetics value is lost to cracks and others defect. The concern for sudden building failure in Nigeria requests that materials used for construction of buildings meet minimum requirements. Housing is a necessity of man and the ambition of people to have right to a decent shelter is necessary. Sandcrete block is a composite substance having the makeup of cement, sand and water, can be moulded into diverse sizes. (Ajagbe, 2013). Self-supporting walls and building structures having load bearing and non-load bearing sandcrete blocks are typical in Nigeria due to their effortlessness of construction and their affordability.
Over 90% of physical infrastructures in Nigeria are usually constructed using blocks made from sandcrete (Baiden and Tuuli, 2004). This has made sandcrete blocks a precise essential material in building construction. It has gained extensive usage in Nigeria, Ghana, and many other African nations as load carrying and non-load carrying walling units (Ko, 2011).
For an extensive period in Nigeria, sandcrete blocks are mass-produced in several parts of the country without any orientation to suit local building specifications or features of a good quality work (Oyekan and Kamiyo, 2011). In the year 2000, an endeavor was made to enhance the finest materials and production practice, the Standard Organization of Nigeria (SON) established a reference article which recommended the least possible requirements and usage of different categories of sandcrete blocks (NIS 87:2000 series).
Amongst the objectives of the developed NIS article are to ensure that all block mas-producers meet a minimum indicated standard, as well as to exercise control over the quality of blocks produced by these manufacturers. It has been years since the introduction of the standards, yet variations in quality still exists in the quality of sandcrete blocks being mass-produced by these manufacturers. In relation to the NIS article coincidental and transferrable variations are two influences recognized to be the cause inconsistencies in the sandcrete blocks quality. Chance/coincidental variations in quality happen as a consequence of environmental effects for instance temperature, radiation, noise etc. The effects of coincidental variations are usually unnoticed. Transferrable/assignable variations on the other hand are variation that can be accredited to raw materials, machine, man and technique. It is in contradiction of these assignable causes of variations that this study would evaluate the quality of sandcrete blocks mass-produced in Uyo, Akwa Ibom State.
In practice, normal technical knowhow, suppliers, tools, machines and all required infrastructures are necessary to start manufacturing blocks either for private or commercial purposes. (Okoli et al., 2008) was of the opinion that asides the producers and entrepreneurs who manufacture blocks strictly for business purposes, a reasonable number of contractors and individuals also make blocks for use on their projects. Such contractors and clients employ block makers, equip them by providing all necessary materials and logistics needed for the production of the blocks required for their building or infrastructural projects, with the major goal being the reduction of production cost and make certain the quality. Sandcrete blocks can either be solid or hollow rectangular types with 450mm x 225mm x 225mm and 450mm x 150mm x 225mm being the most common sizes (Tunde, 2015). (Anosike and Oyebade, 2012) testified that the NIS identified two categories of blocks, category A blocks are load bearing and category B blocks are non–load bearing. Both of them can either be solid or hollow. Building factories in Nigeria habitually produce two cell hollow sandcrete blocks (Eze, 2005). There is an empty space from upper to lowest parts of the hollow sandcrete blocks occupying about one third of the volume of the blocks while solid sandcrete block has no empty space in it. Sandcrete blocks are comparatively cheap when likened to other construction materials. They provide an outstanding resistance to impairment devoid of the additional cost of protection devices. Sandcrete blocks are not susceptible to rust, decay, or neither do they serve as a place of abode for destructive insects as other building materials possibly can. They do not comprise of environmentally harmful material (Odeyemi, 2012). The minimum sandcrete compressive strength stated in the Nigeria Industrial Standard, NIS 87:2000 ranges between 2.5N/mm2 to 3.45N/mm2 for non-load carrying and load carrying walls respectively. This strength of sandcrete blocks can be greatly influenced by the production method, mix ratio, compaction method, duration of curing, sizes of blocks and the properties of constituent materials.
1.2 STATEMENT OF PROBLEM
The elementary component of sandcrete blocks are water, fine aggregate and cement. The proportions of these components affect properties of blocks; sure properties are compressive strength, curing, durability, workability and shrinkage.
Cement is the major component of sandcrete block used in building construction in Nigeria. Most popularly used type of cement in Nigeria is ordinary Portland cement (OPC) whose price is on the increase due to inflation and cost of its production materials. The continued increase in price of cement discourages Nigerians from embarking on construction of housing unit. This high rate of cement result in producing low quality of sandcrete blocks in Nigeria.
1.3 OBJECTIVE OF STUDY
i. To assess the compressive Strength of sandcrete blocks produced in Uyo, Akwa Ibom State, in accordance with NIS standard specifications.
ii. To compare the compressive strengths of sandcrete blocks of machine production and manual production.
iii. To investigate among block manufacturers, the level of conformance to NIS standard specifications.
iv. To evaluate the production process employed in the production of sandcrete blocks.
v. To assess the level of quality of the materials used in the production of sandcrete blocks in comparison to NIS standards.
vi. To make recommendations.
1.4 SIGNIFICANCE OF STUDY
On realization of the objectives of this work, it is expected that the low or poor production of sandcrete blocks using in building houses and general construction in Uyo will be reduced. Strength characteristic of sandcrete hollow blocks produced using manual and machine mould will be compare to encourage sandcrete block manufacturers and researchers on the use of appropriate methods and materials in producing high quality blocks in accordance with NIS standard specification.
1.5 SCOPE OF STUDY
The scope of this study is based on assessments of strength characteristic of hollow sandcrete blocks produced in Uyo Akwa Ibom state. 450x225x225mm and 450x150x225mm sandcrete blocks specimens was tested for compressive strength to compare the strength with standard specified by Nigerian industrial standard.
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