ABSTRACT
This research is an investigation into the effects of pulverized burnt brick on selected cement brands used in Nigeria. Pulverized burnt brick obtained from grinding Adamawa burnt brick was used, the burnt brick was established to have the highest pozzalinic activity by Sa’ad(2006). The PBB was reactive at w/c = 0.65, 10% replacement of cement by PBB and 1:6 mortar mix ratio. Test such as specific gravity, setting times, soundness test, oxide composition and compressive strength were conducted. PBB gave the lowest specific gravity of 2.68 while for OPC, cement B gave the highest specific gravity of 3.35 and cement A gave the lowest specific gravity of 3.16. The highest and lowest initial setting times for the blended cement pastes were 206 and 118 minutes for cement E and D which was 98.8% and 78% of the control cement pastes respectively. The highest and lowest final setting times for the blended cement pastes were 257 and 162 minutes for cement C and D which was 107% and 66.94% of the control cement pastes respectively. Control cement pastes did not undergo expansion except for cement A and D. The former and latter underwent expansion of 1mm and 0.5mm respectively while for the blended cement pastes all cement brands underwent expansion of 1mm each except cement C which did not undergo expansion. The brands of cement satisfied the oxide composition for cement as stated in ASTM C150 – 07. The highest and lowest composition of SiO2 (A) was 13.2% and 6.3% for cement A and E while for CaO (A) was 82.63% and 71.66% for cement D and A respectively. The highest and lowest composition of Al2O3 (6% max) was 2.6% and 1% for cement A and D while for Fe2O3 (6% max) was 5.79% and 4.52% for cement E and C respectively. At the end of 90 days of curing, blended mortar cubes made with cement C gave the highest compressive strength of 5.03N/mm2 with the PBB followed by cement E with 3.54N/mm2. The former and latter compressive strengths were 106% and 145% of their control mortar cubes. The experiments indicate cement C to be suitable with the PBB.
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND STUDY
Nigeria is a developing country with annual increasing stock of buildings and infrastructure. The main material used for these indices of development is cement. Ordinary Portland Cement (OPC) is the basic material used for the construction of buildings and infrastructure universally (Salau, 2008). In the National Housing Policy of 1980 in Nigeria, housing problem in Nigeria was described as a ―huge shortfall‖ with concomitant increase in backlog of housing supplies and substandard housing, suffering from overcrowding, lack of utilities and poor environmental conditions. The policy therefore has, as its objective, the provision of housing for all by the year 2000. In the 1987 report of the Nigerian Building and Road Research Institute (NBRRI, 1987), it was estimated that Nigeria would require over twenty (20) million new housing units to achieve the objective of housing for all by the year 2000. Kolawole and Efeovobokan (1990) put the figure at about fifteen (15) million; now the needed housing units had increased tremendously based on the increase in the population within 10 years by about 30%. The increasing demand of housing required, coupled with informal settlements constantly expanding, is underlined by the crucial necessity to research new methods of design and material technologies (UN-Habitat, 2008). Pozzolanic materials as defined by the American Society of Testing Materials (ASTM) specification C618 – 01 are materials that have siliceous or siliceous-aluminous contents which in themselves possess little or no cementitious value, but will, in finely divided form and in the presence of moisture chemically react with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties. The reaction is called pozzolanic reaction and its characteristic feature is that it is initially slow with the result that heat of hydration and strength development will be accordingly slow. The reaction involves the consumption of Ca(OH)2 and not production of Ca(OH)2 thus improving the durability of the cement paste by making the paste dense and impervious (Shetty, 2004). Natural pozzolanas are usually substances of volcanic origin or sedimentary rocks with suitable chemical and mineralogical composition (Lea, 2004). The natural pozzolanas have lost their popularity in view of the availability of more active artificial pozzolanas (Shetty, 2004). Artificial pozzolanas are either calcined clays or byproducts of various industrial and agricultural processes whereby calcination has occurred (Carr, 1995). Others from steel and coal production are pulverized fly ash, electric arc furnace slag, blast furnace slag, silica fume, and others (Anwar et al, 2000). There are various types of pozzolanas depending on their composition. Portland pozzolana is a blend of Portland cement and pure pozzolana such as volcanic ashes or rice-husk ash. Lime pozzolana is a blend of natural pozzolana with lime. Clay pozzolana is a blend of shale or clay with pure pozzolana (Adepegba, 1990). The only difference between Portland and Pozzolana cement is that Pozzolana cement takes about 60 to 90 days depending on composition, to attain the 28 days strength of Ordinary Portland Cement (Salau, 2008). Pozzolanic activity of some selected Pulverized Burnt Brick (PBB) in Nigeria have been studied by Sa’ad (2006), the study established varied activities of the PBB. Investigation into the possible use of PBB and OPC admixture for sandcrete block production was carried out by Bungwon (1996), the study established low cost saving with numerous advantages will be achieved when blended cements (OPC + 20% optimum replacement by PBB) is used to produce sandcrete blocks.
1.2 STATEMENT OF THE PROBLEM
Ordinary Portland cement reacts with water to produce monosulphoaluminate (Ettringite). Ettringite is formed when C3A reacts with gypsum and Ca(OH). Ettringite are long needle-like compounds which are not cementitious, this develops micro cracks in hardened cement paste. Through this micro cracks deleterious compounds can penetrate and cause deterioration.
1.3 JUSTIFICATION FOR THE STUDY
The fundamental property of a pozzolana is its ability to chemically combine with lime (Carr, 1995). Lime is the by-product of OPC when it undergoes hydration in the presence of water and it is also an agent of deterioration in concrete. The pozzolana chemically reacts with lime and forms a binding agent, thus utilizing the agent of deterioration to form a cementitious material. The cementitious material makes the concrete denser and thus improves its strength. The reaction between the pozzolana and lime is affected by the type of pozzolana, w/c ratio, the temperature and the cement type (Balkema, 1992). The pozzolana, w/c ratio and the temperature has been established by Sa’ad (2006). PBB from Adamawa, 0.65 w/c ratio and the experiment was carried out at room temperature. Due to the variation of mineral composition of raw materials used to produce OPC and the geographical location of these materials, there is need to investigate the effect of pozzolana on the brands of cement in Nigeria. Identifying the cement that gives the highest strength with the pozzolana will provide means to produce a more durable concrete that will resist deterioration in hostile and non hostile environment.
1.4 AIM AND OBJECTIVES
1.4.1 Aim
The aim of this research is to determine the effects of pulverized burnt brick on mortar cubes made from the brands of cement used in Nigeria with a view to establishing the cement that gives the highest compressive strength with the PBB.
1.4.2 Objectives
- To assess the effects of PBB on the properties of the cement such as setting time and soundness.
II.To determine the oxide composition of the PBB and the brands of cement.
III.To determine the property of mortars made with the PBB and the selected cement brands such properties as density and compressive strength.
- To identify the cement brand that gives the highest compressive strength with the PBB compared with the control cubes.
1.5 METHODOLOGY
The method adopted for this research is summarized under the following headings
Literature Review
This research was carried out through the review of unpublished research by Sa’ad (2006) and relevant literature in publications, journals unpublished research and other related data.
Experiment
The experiment was carried out in three stages:
In the first stage all relevant materials such as burnt brick from Adamawa, five brands of cement, water and sharp sand were made available in the building department laboratory. The burnt brick from Adamawa was manually grounded using pestle and mortar and sieved using 75µm sieve (No 200) to obtain pulverized burnt brick. The burnt brick was sourced from Adamawa burnt brick factory located at Mubi L.G; cement was purchased from cement dealers in Zaria, Kano and Kaduna. Water and sharp sand were obtained from the department of building laboratory.
In the second stage preliminary tests such as specific gravity of PBB and brands of cement were carried out. Water absorption test of the sharp sand was carried out. Bulk densities of the individual constituents of mortar (brands of cement, sharp sand and PBB) were carried out. The mix for mortar was carried out using 1:6 ratio and 0.65 w/c ratio as established by the research carried out by Sa’ad (2006), absolute volume of the individual constituents for mortar were calculated (See appendix B).
In the third stage the individual materials for mortar were mixed and cast according to the mortar mix in the second stage. OPC replacement level of 0% and 10% was used for each cement brand, three(3) mortar cubes was cast into (70 × 70 × 70) mm mould for every OPC replacement level; a total number of 210 cubes were cast and cured in water in a curing tank.
The following tests were carried out
- Specific gravity test of PBB and brands of cement.
- Setting time tests on the PBB and OPC mixtures. The vicat apparatus was used.
- Soundness tests on the PBB and OPC mixtures. Le Chattelier’s apparatus was used.
- Particle size distribution of the sharp sand. BS test sieve was used.
- Compressive strength of mortar cubes (control and blended cubes). The manual compressive strength machine was used.
- Oxide composition of the PBB and the brands of cement. The Mini Pal PW 4030 X-ray spectrometer was used.
1.6 SCOPE AND LIMITATION
1.6.1 Scope
The research was confined to the use of Pulverized burnt brick from Adamawa and five brands of cement consumed in Nigeria.
1.6.2 Limitation
Only five (5) brands of cement were used, four indigenous cement and one foreign cement was used. Pulverized burnt brick from Adamawa was used. The research will be carried out at room temperature with w/c of 0.65; OPC replacement level of 0% and 10% was used. Ratio of 1:6 was used for mortar mix. Compressive strength test was carried out on the 3rd, 7th, 14th, 21st, 28th, 56th and 90th day only.
