CHAPTER 3 MATERIALS AND MIX PROPORTIONING

Transcription

1 33 CHAPTER 3 MATERIALS AND MIX PROPORTIONING 3.1 GENERAL The mix design for self-compacting concrete warrants thorough knowledge of properties of materials used. In this chapter, the properties of the materials used for the preparation of self-compacting concrete are discussed. The mix proportioning is also discussed in this chapter for M20, M30 & M40 grade concrete with steel slag as partial replacement for coarse aggregate. 3.2 MATERIALS Cement Ordinary Portland cement 43 grade conforming to IS: and ASTM type III (C150 95) was used in this work. The cement was tested as per IS: and IS: and the results obtained are given in Tables 3.1 and 3.2.

2 34 Table 3.1 Physical properties of OPC 43 grade cement Properties Results Requirements as per IS: Fineness (m 2 / kg) 310 Minimum 225 Specific gravity Initial setting time (Min) 120 Minimum 30 Final setting time (Min) 180 Maximum 600 Soundness (mm) 1.20 Maximum 10 Standard consistency (%) Table 3.2 Chemical composition of OPC 43 grade cement Compound Result (%) Requirements as per IS: CaO SiO Al2O Fe 2 O K2O MgO Na 2 O P2O SO Cl 0.05 Maximum 0.1 Loss on ignition 1.15 Maximum 4% Insoluble residue 0.42 Maximum 3%

3 Fine Aggregate Natural river sand with fractions passing through 4.75 mm sieve and retained on 600 micron sieve was used as fine aggregate. The fine aggregate was tested as per IS: and the results are given in Table 3.3. Table 3.3 Physical properties of fine aggregate Properties Results Specific gravity 2.52 Fineness modulus 2.77 Bulk density (kg/m 3 ) 1680 Water absorption (%) 0.70 Free moisture content (%) 0.07 Figure 3.1 Particle size distribution curve for fine aggregate Sieve analysis test for fine aggregate is conducted and the results are shown in Table 3.4 and grain size distribution curve is also given in Figure 3.1.

4 36 Table 3.4 Sieve analysis of fine aggregate IS Sieve size % Passing IS Recommended limit 4.75 mm mm mm Micron m Micron m Micron m Coarse Aggregate Crushed granite stone aggregates of mm size were used in this work. The coarse aggregates were tested as per IS: and the results are given in Table 3.5. Table 3.5 Physical properties of coarse aggregate Sl. Properties Results IS Recommended limit No. 1 Specific gravity Bulk density (kg/m 3 ) Aggregate impact value Aggregate crushing value Fineness modulus Water absorption (%) 0.18 < 0.5% 7 Flakiness index % 6 7 for 20 mm aggregate for mixed aggregate Sieve analysis test for coarse aggregate is conducted and results are shown in Table 3.6. The grain size distribution curves for coarse aggregate and steel slag are given in Figure 3.3.

5 37 Table 3.6 Sieve analysis of coarse aggregate IS Sieve size % Passing IS Recommended limit mm mm mm Steel Slag Steel slag from Agni Steels Pvt. Ltd., Ingur, Perundurai, Tamil Nadu, India was used in this work. Physical and chemical composition of steel slag are given in Table 3.7 and 3.9 respectively. The results of sieve analysis of steel slag is given in Table 3.10 and Figure 3.3. Table 3.7 Physical properties of steel slag Sl. No. Test particulars Results 1 Specific gravity Bulk density (kg/m 3 ) Aggregate impact value Aggregate crushing value Water absorption (%) 2.50 The important compounds in the steel slag are dicalcium silicate, tricalcium silicate, tricalcium aluminate, dicalcium ferrite, merwinite, oxides of Iron and free lime and magnesia. The chemical composition of steel slag was determined by Le Chatlier method.

6 38 Table 3.8 Specific gravity of combined coarse aggregate and steel slag Slag Coarse Aggregate Specific Gravity 0% 100% % 90% % 80% % 70% % 60% % 50% % 40% % 30% % 20% % 10% % 0% 2.48 Table 3.9 Chemical composition of steel slag Compound Composition (%) Requirements (%) as per ACI 233 R-03 CaO to 45 SiO to 42 Fe 2 O to 0.50 MgO to 15 Al 2 O to 16 P2O SO Table 3.10 Sieve analysis of steel slag IS Sieve size % Passing IS Recommended limit mm mm mm

7 39 The angularity number of the natural coarse aggregates and slag aggregates were determined as per IS: 2386 (Part-I) The values of angularity number for natural aggregates and slag aggregates were obtained as 4 and 7 respectively. Therefore, the slag aggregates are more angular than the natural aggregates Scanning Electron Microscopy Analysis Figure 3.2 SEM Images of steel slag The following details were observed from the SEM images of steel slag at 2500, 6000, and magnifications. The SEM images of steel slag are given in Figure Length of major axis = 1.92 Micro meter 2. Length of minor axis = 0.58 Micro meter 3. Elongation = Area of the particle = 1.05 Sqr. Microns 5. Perimeter = 4.82 Microns 6. Roundness = 0.55 From these, it is inferred that the particles are elongated.

8 40 Sieve Analysis for steel slag Sieve analysis was carried out for the combination of coarse aggregate and coarse slag as per IS It is represented in the following Figure 3.3 and the specific gravity of combined coarse aggregate and steel slag is shown in Table 3.8. Figure 3.3 Comparison between coarse aggregate and coarse slag particle size distribution Flyash Fly Ash from Mettur Thermal Power Plant was used in this work. The fly ash was tested and physical and chemical properties are presented in Tables 3.11 and 3.12 respectively.

9 41 Table 3.11 Physical properties of fly ash Sl. No. 1 Test particulars Specific Surface area (cm 2 /gm) Results 2 Specific gravity Bulk density (kg/m 3 ) to Physical Form Powder Form Table 3.12 Chemical composition of flyash Compound % By Weight SiO % Al 2 O % Fe 2 O % CaO % Na 2 O % MgO % K 2 O % Moisture % Superplasticizer (Conplast SP 430) Superplasiticizer conplast SP 430 was used in this work. Conplast SP 430 is a chemical based on sulphonated naphthalene polymers. This superplasticizer complies with IS: , BS: 5073 Part 3 and ASTMC 494. The properties of the superplasticizers given by the manufacturer are given in Table 3.13.

10 42 Type Table 3.13 Properties of superplasticizer (Conplast SP 430) Properties Specific gravity Results Sulphonated naphthalene formaldehyde condensate to at 30o C Chloride content Nil as per IS: 456 and BS: 5075 Recommended dosage Approximate additional air entrainment Solids content 40% Compatibility Workability Cohesion Litres per 100 kg of cement 1% at normal dosages All types of cement except high alumina cement Produce high workable flowing concrete mix without segregation and requires no compaction. Minimizing segregation and improving surface finish Compressive strength Early strength up to 40 to 50 % Durability Increase in density and impermeability Determination of Dosage of Super Plasticizer The solid content of SP (Conplast 430) given by the manufacturer is 40%. The marsh cone test was conducted on various combination of cementing materials with w/b of The optimum dosage of SP for cement with fly ash was found to be 1.72% by weight of total binder whereas for cement alone and cement with fly ash the optimum dosage was found to be 1.30%. According to the marsh cone test results, for the combinations of mineral admixtures, the optimum dosage of SP was found to be 1.72% of the total binder content for meeting the SCC requirements (JSCE) as referred by Nan Su et al. (2001) specified in Table The marsh cone test results of various replacement levels of mineral admixtures with cement are shown in Figure. 3.4.

11 43 Figure 3.4 Optimum dosage of superplasticizer Water Water is the most important ingredient next to the cement in the concrete making process. Locally available potable tap water was used in this work. 3.3 MIX PROPORTIONING Mix design for this work has been arrived at as per the specification given in IS , IS , IS for aggregates, IS for cement and EFNARC In this investigation, three grades of concrete, namely M20, M30 & M40 were tested with steel slag as partial replacement for coarse aggregate. The replacement was done at an increment of 10 %. The entrapped air was taken as 2%. The dosage of superplasticizer (Conplast SP 430) was

12 44 fixed at 1.75% of total binder content as per marsh cone test and the requirements of self-compacting concrete as laid down by Japanese Society of Civil Engineering (JSCE). The mix proportions for M20, M30 & M40 are given in Tables 3.14, 3.15 and 3.16 respectively. These properties are represented in Pie charts in Figure 3.5 to Figure Table 3.14 Mix proportion for M20 grade SCC Mix Designation % of Replacemen t of CA by Steel Sag Water (lit.) Ceme nt (kg) Fly Ash (kg) Fine Aggregate (kg) Coarse Aggregate Natural aggregate 20 SCC SCC SCC SCC SCC SCC SCC SCC SCC SCC SCC Slag

13 45 Figure 3.5 Mix proportion for SCC M20 Grade Figure 3.6 Mix proportion for SCC M20 grade with 10% steel slag as coarse aggregate

14 46 Figure 3.7 Mix proportion for SCC M20 grade with 20% steel slag as coarse aggregate Figure 3.8 Mix proportion for SCC M20 grade with 30% steel slag as coarse aggregate

15 47 Figure 3.9 Mix proportion for SCC M20 grade with 40% steel slag as coarse aggregate Figure 3.10 Mix proportion for SCC M20 grade with 50% steel slag as coarse aggregate

16 48 Figure 3.11 Mix proportion for SCC M20 grade with 60% steel slag as coarse aggregate Figure 3.12 Mix proportion for SCC M20 grade with 70% steel slag as coarse aggregate

17 49 Figure 3.13 Mix proportion for SCC M20 grade with 80% steel slag as coarse aggregate Figure 3.14 Mix proportion for SCC M20 grade with 90% steel slag as coarse aggregate

18 50 Figure 3.15 Mix proportion for SCC M20 grade with 100% steel slag as coarse aggregate Table 3.15 Mix proportion for M30 grade SCC Mix Designation % of Replacem ent of CA by Steel Sag Water (lit.) Cement (kg) Fly Ash (kg) Fine Aggregate (kg) Coarse Aggregate Natural aggregate 30 SCC SCC SCC SCC SCC SCC SCC SCC SCC SCC SCC Slag

19 51 Figure 3.16 Mix proportion for SCC M30 grade Figure 3.17 Mix proportion for SCC M30 Grade with 10% Steel slag as Coarse aggregate

20 52 Figure 3.18 Mix proportion for SCC M30 Grade with 20% Steel slag as Coarse aggregate Figure 3.19 Mix proportion for SCC M30 Grade with 30% Steel slag as Coarse aggregate

21 53 Figure 3.20 Mix proportion for SCC M30 Grade with 40% Steel slag as Coarse aggregate Figure 3.21 Mix proportion for SCC M30 Grade with 50% Steel slag as Coarse aggregate

22 54 Figure 3.22 Mix proportion for SCC M30 Grade with 60% Steel slag as Coarse aggregate Figure 3.23 Mix proportion for SCC M30 Grade with 70% Steel slag as Coarse aggregate

23 55 Figure 3.24 Mix proportion for SCC M30 Grade with 80% Steel slag as Coarse aggregate Figure 3.25 Mix proportion for SCC M30 Grade with 90% Steel slag as Coarse aggregate

24 56 Figure 3.26 Mix proportion for SCC M30 Grade with 100% Steel slag as Coarse aggregate Table 3.16 Mix proportion for M40 grade SCC Mix Designation % of Replace ment of CA by Steel Sag Water (lit.) Cement (kg) Fly Ash (kg) Fine Aggreg ate (kg) Coarse Aggregate Natural aggregate 40 SCC SCC SCC SCC SCC SCC SCC SCC SCC SCC SCC Slag

25 57 Figure 3.27 Mix proportion for SCC M40 Grade Figure 3.28 Mix proportion for SCC M40 Grade with 10% Steel slag as Coarse aggregate

26 58 Figure 3.29 (a) Mix proportion for SCC M40 Grade with 20% Steel slag as Coarse aggregate Figure 3.29 (b) Mix proportion for SCC M40 Grade with 30% Steel slag as Coarse aggregate

27 59 Figure 3.30 (a) Mix proportion for SCC M40 Grade with 40% Steel slag as Coarse aggregate Figure 3.30 (b) Mix proportion for SCC M40 Grade with 50% Steel slag as Coarse aggregate

28 60 Figure 3.31 (a) Mix proportion for SCC M40 Grade with 60% Steel slag as Coarse aggregate Figure 3.31 (b) Mix proportion for SCC M40 Grade with 70% Steel slag as Coarse aggregate

29 61 Figure 3.32 (a) Mix proportion for SCC M40 Grade with 80% Steel slag as Coarse aggregate Figure 3.32 (b) Mix proportion for SCC M40 Grade with 90% Steel slag as Coarse aggregate

30 62 Figure 3.33 Mix proportion for SCC M40 Grade with 100% Steel slag as Coarse aggregate 3.4 CASTING OF SPECIMENS All the specimens were cast in steel moulds. The concrete was mixed using dipping type mixture machine in laboratory. First, aggregates were put in the mixture machine and cement and fly ash were added next. Then water mixed with designated dosage of superplasticizer was added. The mixture was allowed to rotate in a mixture machine for thorough mixing. The specimens were cast by pouring the concrete mix in specimen moulds without vibration. The specimens were de-moulded and cured in a water tank for 28 days. 3.5 SUMMARY The mix proportions for M20, M30 & M40 SCC were arrived by replacing coarse aggregate with steel slag from 0 to 100% with the increment of 10%.