CHAPTER 1The Problem and Its BackgroundI. IntroductionConcrete is a construction material composed of cement (commonly Portland cement and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravels or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water, and chemical admixtures. Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a stone-like material.Aggregates are the important constituents in concrete. They give body to the concrete, reduce shrinkage and effect economy. Earlier, aggregates were considered as chemically inert materials but now it has been recognized that some of the aggregates are chemically active and also that certain aggregates exhibit chemical bond at the interface of aggregate and paste. The mere fact that the aggregates occupy 70 80% of the volume of concrete, their impact on various characteristics and properties of concrete is undoubtedly considerable. Cement is the only factor made standard component in concrete. Other ingredients namely, water and aggregate are natural materials and can vary to any extent in many of their properties. The depth and range of studies that are required to be made in respect of aggregates to understand their widely varying effects and influence on the properties of concrete cannot be underrated. Cement is an extremely ground material having adhesive and cohesive properties which provide a binding medium for the discrete ingredients. Cement generally represents 12-14% of concrete weight. It plays an active part in the mixture. During the hardening process, it generates shrinkage and heat dissipation phenomena which lead to material crackingThere are many types of concrete available, created by varying the proportions of the main ingredients. By varying the proportions of materials, or by substitution for the cementitious and aggregate phases, the finished product can be tailored to its application with varying strength, density, or chemical and thermal resistance properties. The mix design depends on the type of structure being built, how the concrete will be mixed and delivered, and how it will be placed to form this structure.Water is an essential component of concrete. Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and allows it to flow more freely. Less water in the cement paste will yield a stronger, more durable concrete; more waste will give a more free-flowing concrete with a higher slump.

II. Background of the StudySince water helps to form the strength giving cement gel, the quantity and quality of water is required to be looked into very carefully. It has been discussed enough about the quantity of mixing water but so far the quality of water has not been discussed. In practice, very often great control on properties of cement and aggregate is exercised but the control on the quality of water is often neglected. Since quality of water affects the strength, it is necessary for us to go into the purity and quality of water.Impure water used to make concrete can cause problems when setting or in causing premature failure of the structure. And it has been found (Abram, 1924) that impurity in water samples used in mixing concrete can impair the strength of concrete especially the compressive strength of concrete. In a similar way, water used for curing concrete can impair the strength of the concrete (Smith, 1976). Impurities and deleterious substances which are largely introduced from water used in mixing concrete are likely to interfere with the process of hydration, preventing effective bond between the aggregates and matrix. The impurities sometimes reduce the durability of the aggregate (Neville, 1995).It is significant to determine the suitability of water for mixing concrete. In line with these, the researchers ought to find alternative sources of water for use in concrete production. The assumption that if water is fit to drink it is suitable for making concrete is not always correct (Ullman, 1973). Even though other criteria attempting to ensure the suitability of water for batching fresh concrete require that the water be clean and free from deleterious material, these specifications may not be the best basis for evaluation of the suitability of water as mixing water. Some waters which do not meet these criteria have been found to produce concretes of satisfactory quality (Sandorolini and Franzoni, 2001).Currently there are no special tests developed to determine the suitability of mixing water except comparative tests. Generally, comparative tests require that, if the quality of water is not known, the strength of the concrete made with water in question should be compared with the strength of concrete made with water of known suitability. Both concretes should be made with cement proposed to be used in the construction works. The American Standard ASTM C 94 requires that age of 28 days mortar strengths made with test water to be a minimum of 90% of the strength of concrete made with distilled water. Two criteria should be considered in evaluating the suitability of water used for mixing concrete; one is whether the impurities in the waste water from questionable sources will affect the properties and quality of concrete and the other is the degree of impurity which can be tolerated. This study analyzed the quality of water from different sources. Then, tests were conducted on concrete. Particular attention was focused on rainwater and floodwater, compared to tap water as used in the concrete production.

III. Conceptual Framework of the study

PROCESSINPUTOUTPUT

Cylindrical and Rectangular Concrete Class A Cement, Type 1Pfc = 3000 psiSPECIMEN9 cylindrical samples of 150 mm diameter x 300 mm9 rectangular samples of 150 mm x 150 mm x 550 mmCompressive and Flexural Strength determined

WATERTap WaterFlood WaterRain Water

\

Compressive Strength TestFlexural Strength Test

FEEDBACK

FIGURE 1.1 shows the process used in the study

IV. Research ObjectivesThe main objectives of this research focus on the compressive and flexural strength of concrete with Class A Portland cement, type 1P when water from three different sources were used.a) To differentiate the compressive strength and flexural strength of Class A concrete using different water samples;i. Tap Waterii. Rain Wateriii. Flood Waterb) To check whether the impurities in the waste water from questionable sources will affect the properties and quality of concrete;c) To determine the degree of water impurity which can be tolerated in mixing of concrete, and;d) To test whether the existing mortar mix ratio for Class A cement of 1:2:4 will give minimal difference to compressive and flexural strength given the huge dissimilarity in terms of potability and quality of tap water, rainwater and floodwater;i. In 7 daysii. In 14 daysiii. And in 28 days of curing the concrete samples.

V. Significance of the StudyIn the Philippines and many other countries worldwide, water used in the manufacture of concrete must be potable. At present, it is currently thought that concrete properties are highly influenced by the water type used and its proportion in the concrete mix. Therefore, the identification of the level and nature of contamination in available water sources and their subsequent effect on concrete is becoming an interest.It is all over the news that the Philippines will be experiencing El Nio most probably until the third-quarter of 2016. Given such condition, the use of clean, potable water in concrete mix is undesirable. With such condition, this study is greatly beneficial, a) As it explores new sources of water in terms of their quality and suitability for use in concrete production;b) As it helps in environmental conservation by minimizing the use of clean, potable water in concrete production;c) As it fills the confusion that only clean, potable water is suitable in the concrete production, that with the right cement mix ratio, the compressive and flexural strength of concrete mixed with impure water shows minimal difference as compared to the clean, potable tap water.VI. Scope and LimitationsThe main focus of this study will cover the measurement of the compressive and flexural strength of concrete when water from different sources was used in the mixing of concrete. a) All specimens to be used will be limited up to 18 samples: 9 cylindrical columns (150 mm diameter by 300 mm height) and 9 rectangular beams (150 mm by 150 mm by 550 mm). The specimens will be cured for 7, 14 and 28 days.b) Three (3) water samples will be used for the concrete mix: Tap Water, Rain water and Flood water. c) Class A cement, Type 1P with a design mix ratio of 1:2:4 shall be used.d) Slump test shall be conducted to check the consistency of fresh concrete. A slump height of 6 to 8 inches is tolerable.e) Three (3) cylindrical columns and three (3) rectangular beams will be tested after 7 days, 14 days and 28 days of curing period.f) Quality Control Test (Material Testing) is not required.g) Two (2) types of test shall be conducted: Compressive Strength Test for the cylindrical samples, and Flexural Strength Test for the rectangular samples.

VII. Definition of Termsa) AGGREGATE is a granular material, such as sand, gravel, crushed stone, and iron blast-furnace slag, and when used with cementing medium forms a hydraulic cement concrete or mortar.b) BEAM - a structural member subjected primarily to flexure, but also to some axial loads.c) CEMENTITIOUS MATERIALS are materials as specified in Section 403 of NSCP which have cementing value when used in concrete either by themselves, such as Portland cement, blended hydraulic cements, and expansive cement, or such materials in combination with fly ash, raw or other calcined natural pozzolans, silica fume, and/or ground granulated blast-furnace slag.d) COMPRESSIVE STRENGTH is the capacity of a material to withstand axially directed pushing forces. When the limit of the compressive strength is reached, materials are crushed.e) CONCRETE is a mixture of Portland cement or any other hydraulic cement, fine aggregate, coarse aggregate and water, with or without admixtures.f) CONCRETE, NORMALWEIGHT is concrete containing only aggregate that conforms to ASTM C33.g) CURING is the process in which the concrete is protected from loss of moisture and kept within a reasonable temperature range. This process results in concrete with increased strength and decreased permeability.h) DESTRUCTIVE TESTING tests are carried out to the specimens failure, in order to understand a specimens structural performance or material behavior under different loads.i) FLEXURAL STRENGTH is one measure of the tensile strength of concrete. It is a measure of an unreinforced concrete beam or slab to resist failure in bending.j) HYDRATION a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydratesk) SLUMP TEST is a means of assessing the consistency of fresh concrete. It is used, indirectly, as a means of checking that the correct amount of water has been added to the mix. (The test is carried out in accordance with BS EN 12350-2, Testing fresh concrete. Slump test. This replaces BS 1881: Part 102)