59 CHAPTER 3 PROPERTIES OF MATERIALS Concrete is made up of cement, fine aggregate (sand), coarse aggregate (stone chips) and water. It is important to know the properties of constituent materials, as they impart strength and durability to the concrete. This chapter deals with the study of properties of various materials such as cement, sand, quarry dust, coarse aggregate, water, steel bar, plasticizer, mineral admixtures and inhibitors that were used in this experimental investigation. 3.1 CEMENT Of all the materials that influence the behaviour of concrete, cement is the most important constituent, because it is used to bind sand and aggregate and it resists atmospheric action. In this study, OPC of 43grade conforming to IS :8112-1989 was used for casting of the specimens. The required quantity was procured as single batch, stored in airtight bags and used for the experimental programme. The chemical composition details as furnished by the supplier and the physical properties determined in the laboratory are given in Tables 3.1
60 Tables 3.1 Properties of cement Dalmia 43 grade OPC S.No particulars Result A Chemical composition Requirement as per IS :8112-1989 1 Silicon-di-oxide (SiO 2 ) 19.62 % 17-25% 2 Aluminium oxide (Al 2 O 3 ) 5.62 % 3-8% 3 Iron oxide (Fe 2 O 3 ) 5.33 % 0.5 6% 4 Calcium oxide(lime) Cao 61.24 % 60 67% 5 Sulphur-tri-oxide(SO 3 ) 2.60 % 1.3 3% 6 Magnesia (MgO) 0.88 % Max.6% 7 Loss on ignition 2.06 % Max.5% B Physical properties 1 Normal consistency 33% 2 Initial setting time 38 minutes Min 30 minutes 3 Final setting time 270minutes Max.600 minutes 4 Fineness (m 2 /kg) 300.6 Min 225 m 2 /kg Compressive strength 5 3 days 25.3N/mm 2 Min 23N/mm 2 7days 36.4N/mm 2 Min 33N/mm 2 28days 46.6N/mm 2 Min 43N/mm 2
61 3.2 AGGREGATES Aggregates are the major ingredients of concrete. They constitute 70-75% of the total volume; provide a rigid skeleton structure for concrete, and act as economical space fillers. The aggregates form the main matrix of the concrete. The aggregate particles are glued together by the cement and water paste. With cement and water the entire matrix binds together into a solid mass called concrete. Aggregates influence the properties of concrete such as water requirement, cohesiveness and workability of the concrete in plastic stage, while they influence strength, density, durability, permeability, surface finish and colour in hardened stage. It is therefore significantly important to investigate the various properties of aggregates. Aggregates are generally inert and broadly divided into two categories, i.e. fine and coarse, depending on their size. Aggregates with grain size below 4.75mm are termed fine aggregates and above 4.75mm are termed as coarse aggregates. I.S.383-1963 defines the requirement of aggregates. 3.2.1 Gradation of Aggregates Gradation refers to the particle size distribution of aggregates. Grading is a very important property of aggregate used for making concrete, in view of its packing of particles, resulting in the reduction of voids. This in turn influences the water demand and cement content of concrete. Grading is described in terms of the cumulative percentages of weights passing a particular IS sieve. IS 383-1970 specifies four ranges or zones for fine aggregate grading. Table 3.2 gives the range of percentage passing for each zone.
62 Table 3.2 Grading limits for fine aggregate as per IS: 383-1970 IS sieve size Grading zone I Percentage passing (%) Grading zone II Grading zone III Grading zone IV 10 mm 100 100 100 100 4.75 mm 90-100 90-100 90-100 95-100 2.36 mm 60-95 75-100 85-100 95-100 1.18 mm 30-70 55-90 75-100 90-100 600 m 15-34 35-59 60-79 80-100 300 m 5-20 8-30 12-40 15-50 150 m 0-10 0-10 0-10 0-15 Zone I sand is the coarsest and Zone IV is the finest whereas sand in Zone II and Zone III are moderate. It is recommended that fine aggregates conforming to grading zone II or Zone III can be used in reinforced concrete 3.2.1.1 Sieve analysis of river sand Sieve analysis was performed for the river sand used for the investigation. The weights of particles retained in the various sieves are tabulated below. Table 3.3 Grading of river sand Percentage passing I.S sieve IS requirement for size As per test Zone II 10mm 100 100 4.75mm 98.57 90-100 2.36mm 83.46 75-100 1.18mm 58.67 55-90 600 42.46 33-59 300 29.48 8-30 150 17.78 0-20 75 8.19 Max 15 Remark Falling in zone II
63 3.2.1.2 Sieve Analysis of quarry dust Sieve analysis was performed for the quarry dust sample utilized for the investigation. The quantities of sieved particles retained in the various sieves arranged in descending order were weighed and tabulated below. Table 3.4 Grading of quarry sand I.S sieve size As per test Percentage passing IS requirement for Zone II 10mm 100 100 4.75mm 100 90-100 2.36mm 98.9 75-100 1.18mm 75.8 55-90 600 41.6 33-59 300 15.9 8-30 150 18.8 0-20 75 10.09 Max 15 Remark Falling in zone II 3.2.2 Specific Gravity Specific gravity refers to the relative (as compared to water) density of a unit volume of aggregate. Specific gravity of the aggregate generally is indication of its quality. A low specific gravity may indicate high porosity and therefore poor durability and low strength. The range of specific gravity for aggregates is generally between 2.4 and 2.9 Specific gravity of sand = Dry weight of sand Weight of equal volume of water
64 G = (W 2 W 1) (W 4- W 1)-( W 3- W 2) where, W 1 - weight of empty pycnometer in gms W 2 - weight of pycnometer + dry sand in gms W 3 - weight of pycnometer + sand + water in gms W 4 - weight of pycnometer + water in gms The values of specific gravity determined are given in Table 3.6. Table 3.5 Specific gravity of aggregates Aggregates Specific gravity River sand 2.507 Quarry dust 2.688 Coarse aggregate 2.703 3.2.3 Fineness Modulus Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 4.75mm to 150 microns and dividing the sum by an arbitrary number 100. The larger the value, the coarser is the material. Fine aggregate is classified as coarse sand, medium sand and fine sand based on the fineness modulus (IS 2386 - PART III 1963) as shown in Table 3.6.
65 Table 3.6 Fineness of aggregates Sl.No. Fineness Modulus Nature of sand 1 2.2 2.6 Fine sand 2 2.6 2.9 Medium sand 3 2.9 3.2 Coarse sand Sand having a fineness modulus more than 3.2 will be unsuitable for making satisfactory concrete. The fineness modulus values obtained for sand, quarry dust and coarse aggregate are given in Tables 3.7 to 3.9. Table 3.7 Fineness modulus of sand S. No. I.S. sieve size Weight retained (gm) Cumulative weight retained (gm) Cumulative percentage of wt. retained 1 4.75mm 0 0 0 2 2.36mm 11 11 1.1 3 1.18mm 231 242 24.2 4 600 342 584 58.4 5 300 257 841 84.1 6 150 157 998 99.8 7 Pan 2 1000 100 Total= 267.6 Fineness modulus of sand = 267.6/100 = 2.676
66 Table 3.8 Fineness modulus of quarry dust I.S. sieve Weight Cumulative weight Cumulative S. No. percentage of size retained (gm) retained (gm) wt. retained 1 4.75mm 0 0 0 2 2.36mm 88 88 8.8 3 1.18mm 176 264 26.4 4 600 243 505 50.5 5 300 342 847 84.7 6 150 150 999 99.9 7 Pan 1 1000 100 Total = 270.7 Fineness modulus of quarry dust = 270.7/100 = 2.707 Table 3.9 Fineness modulus of coarse aggregate S. No I.S. sieve size Weight retained (gms) Cumulative weight retained (gms) Cumulative percentage of wt. retained 1 40mm 0 - - 2 20mm 1721 1721 34.42 3 10mm 3238 4959 99.18 4 4.75mm 41 5000 100 5 2.36mm 0-100 6 1.18mm 0-100 7 Pan 0-100 Total = 433.6 Fineness modulus of coarse aggregate =433.6/100 = 4.336
67 3.3 WATER Water is the next most important ingredient after cement for making concrete. It is also the least expensive. Careless use of water can lead to poor quality concrete. The purpose of water in concrete is threefold. (1) It distributes the cement evenly (2) It reacts with cement chemically and produces calcium silicate hydrate (CSH) gel. (3) It provides workability, i.e., it lubricates the mix. Potable water was used for casting concrete specimens. The water was free from oils, acids, alkalis and has a water soluble chloride content of 160 mg/lit. As per IS 456:2000, the permissible limit for chloride is 500 mg/lit for reinforced concrete, hence the amount of chloride present in the water utilized for the investigation is less than the permissible limit. 3.4 STEEL High yield strength cold twisted deformed bar of Fe 415 grade conforming to IS 1786 has been used. Its mechanical properties are: Yield strength of 476 N/mm 2, Ultimate tensile strength of 584 N/mm 2 and Percentage of elongation on 30cm gauge length is 13%. 3.5 PLASTICIZER Requirement of right workability is the essence of good concrete. A plasticizer is defined as an admixture added to wet concrete mix to impart adequate workability properties. These plasticizers can help the difficult conditions for obtaining higher workability without using excess of water.
68 Because every increase of 0.01 in the water cement ratio decreases the strength by 1-1.5 N/mm 2. To maintain a slump of 60mm in quarry dust concrete without increasing water cement ratio, a plasticizer namely ROFF SUPER PLAST 320 has been used. ROFF SUPER PLAST 320 dramatically increases the workability of concrete mixes by its powerful deflocculating and dispersing effect on the cement particles. This increase in workability can be utilized to produce high workability concrete. Field trials were conducted to determine the optimum addition rate of the plasticizer ROFF SUPER PLAST 320. A dosage of 100 ml for 50 kg of cement is determined as an optimal value to obtain required slump. 3.6 MINERAL ADMIXTURES Mineral admixtures are finely divided siliceous materials which are added to mixtures in relatively large quantities. The mineral admixtures used in this study are fly ash and ground granulated blast furnace slag (GGBFS). The chemical composition given by the supplier is reproduced below. Table 3.10 Chemical composition of fly ash Element Percentage Silica 54.92 Alumina 23.04 Calcium oxide 3.84 Magnesium oxide 2.82 Iron 6.62 Phosphorous 0.3 Alkali Metals oxide 2.7 Sulphur 0.76 Magnesium 2.82 Loss of ignition 2.88
69 Table 3.11 Chemical composition of GGBFS Constituents Percentage contents CaO 30-47 SiO 2 30-48 Al 2 O 3 15-25 Fe 2 O 3 15-25 MgO 4.0-17.0 MnO 2 1.0-5.0 Glass 85-98 Specific gravity 2.9 3.7 INHIBITORS The organic and inorganic inhibitors used in this study were i) Triethanolamine(TEA) - N(CH 2 CH 2 OH) 3 ii) Diethanolamine(DEA)- HN(CH 2 CH 2 OH) 2 iii) Diethylamine-CH 3 CH 2 NHCH 2 CH 3 iv) Calcium nitrite- Ca(NO 2 ) 2 v) Calcium nitrate-ca(no 3 ) 2 vi) Sodium nitrate-nano 3 Figure 3.1 Corrosion inhibitors