EFFECT OF RICE HUSK ASH ON CONCRETE PRODUCED WITH SAW DUST ASH

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Concrete is the most mainstream building material in the world. Concrete is known to be the most wide spread fundamental material because of its quality to take care of various geometrical configurations. It is a collection of cement, fine and coarse aggregates and water. Over three hundred million tons of manufacturing wastes are being process problems of discarding, health menaces and aesthetic difficulties. The global utilization of cement is too high because of its extensive importance in concrete (Oluremi, 2014). Over five billion tons of cement is manufactured in the world each year. However, the cement production is gradually consuming the limestone reserves worldwide and also characterized by high energy consumption. River sand has been the most widespread choice for the fine aggregate element of concrete in the past, but excess exploitation of the resource has led to environmental concerns, the exhausting of protectable river sand resources and an associated price increase in the cost of the material. Thus, there is the need for the pursuit of materials locally as alternative materials for the construction of workable but low-cost buildings in both rural and urban areas (Al-Dulaijan, et al., 2002).

Construction industries are under pressure to pinpoint alternative materials to replace the ever growing demand for sand and cement. On the other hand, the advantages of use of by products or aggregates acquired as discarded materials are obvious in the aspects of lessening environmental load and waste controlling cost, reducing production cost as well as enhancing of concrete. To overcome the pressure of demand for natural acceptable aggregate and cement, scientists and specialists in the construction businesses have recognized some alternative materials such as fly ash, slag, limestone-powder, siliceous resources, sawdust ash and rice husk ash.

Concrete is taken as the most extensively used man made building material and studies show that it will continue to be so in the next millennia to come. Round the world yearly concrete utilized is about five billion tons, enough for close to one ton for every individual each year, at about the volume of 400 liters per individual. Such usefulness of concrete is due to the fact that from the collective constituents, namely, cement, aggregate and water, it is imaginable to adapt the properties of concrete so as to meet the demands of any specific situation (Kamran, 2013). The progresses in concrete technology has created opportunities for the advancement in the  use of the locally available materials by cautious mix proportioning and appropriate workmanship, so as to give rise to a concrete meeting the performance requirements. Scientists, Engineers and Technologists are thus in constant lookout for materials which can serve as alternatives for the regular materials or which have those properties as would support its usage for new designs and innovations. Concretes using substitute materials fall under the initial category. The raw materials for the production of cement and aggregates are basically limitless, since almost all of earth’s crust can be consumed, if related costs and energy requirements can be conformed with. This course of achievement cannot be taken as there are other limitations that merit closer examination. One question is therefore asked: Is the recycling of waste products into a new building material whose binder ability is not Portland cement and whose aggregates may not be organic is a viable headway? Perhaps the response is confirmatory since planned utilization of waste products importantly helps to maintain balance ecologically.

In this research, cement was in part substituted with sawdust including rice husk ash as 5%, 10% 15% and 20% and 25% by weight. Concrete specimens were verified for slump test, compressive strength, durability (water absorption) and light weight nature for diverse rice husk ash plus sawdust ash percentages. The results obtained were matched with those of regular M-25 concrete mixture and it was realized that maximum improvement in compressive strength happened for the concrete mix having 5% say dust plus rice husk ash by mass of cement. Slumps test was performed on the fresh concrete and compressive strength test on toughened concrete. The concrete cubes were tested at the ages of 3, 7,14,28,56 and 90 days. The results showed that sawdust ash including rice husk ash is good pozzolan with combined SiO2, A12O3 and Fe2O3 of 73.07%. The slump decreased as the sawdust ash including the rice husk ash content amplified. The compressive strength reduced with increasing sawdust ash including rice husk ash replacement. The compressive strength of concrete added with sawdust ash including rice husk ash was lesser at initial stages but improved significantly after 28 days. It was concluded 15% sawdust ash including rice husk ash substitution is satisfactory to enjoy maximum benefit of strength. This work summarized the behavior of concrete involving incomplete substitution of cement by sawdust ash including rice husk ash as 0%, 5%, 10%, 15%, 20%, and 25% by weight which may help to reduce the disposal problems of sawdust ash including rice husk ash, and also enhance properties of concrete.

This work is focused on the effect of Rice husk ash (RHA) plus sawdust ash (SDA) on the strength of concrete by incomplete replacement of cement.

The objective of this work includes the following:

The use of rice husk ash including sawdust ash as in part replacement for cement in concrete can be determined by carrying out test on the coarse aggregate (granite), fine aggregate (sharp sand) rice husk ash, sawdust ash, cement and the concrete cubes. The test include 

Sieve Analysis: The test is performed to ascertain the percentage difference in diverse grain particles enclosed within a soil. The mechanical or sieve analysis is performed to determine with certainty the distribution of the rougher, larger-sized elements, and the hydrometer process is used to ascertain with a level of certainty the distribution of the smoother and smaller particles.

Specific Gravity Test: This test is performed to establish the precise gravity of soil with the aid of a pycnometer. Specific gravity is the ratio of the weight per unit value of a certain volume of soil at a specified temperature to the weight per unit of the same volume of gas-free distilled water at a specified temperature.

Slump Test: This test is used to establish the workability of the concrete.

Compressive Strength Test:  This is used to evaluate the strength of the concrete. 

Grain-size analysis, which is amongst the oldest of soil tests, is used in soils classification and as part of the qualifications of soil for airstrips, infrastructures, earth dams, and other soil-realizable construction. The typical grain-size analysis test was used to establish the relative quantities of altered grain sizes as they are scattered among certain size range, which is denoted as particle-size or grain-size distribution.

This is accomplished in two steps:

The specific gravity of a soil is utilized in the segmented relationship of water, air, and solids in a specified volume of the soil. Specific gravity is a test that provides us with the ratio of the weight per unit volume of soil at a specified temperature to the weight of similar volume of gas-free distilled water at a stated temperature. 

Compressive strength test of concrete was performed to know if the concreting was done properly or not. It gives us the idea about all the characteristics of concrete.

Nigeria is rich in timber and production of rice. The production of cement for construction is now expensive because of the high demand for erection of structures and aggregates and sudden depreciation of the country’s economy. This had escalated the cost erection of structures and maintenance. Therefore alternative pozzolan other than cement has to be sought for to encourage engineering activities within the country. Some of the pozzolanic materials are costly while some are not easily accessible.

In carrying out this work, we hope that the rice husk ash and the sawdust ash could be useful material instead of a nuisance to the environment.