2 LA TECNOLOGÍA
2.5 Análisis de las principales BPMS
2.5.2 Intalio BPMS Community Edition
N. Sivalingarao1, V. Bhasker Desai2 and B.L.P. Swami3
1Research Scholar and Technical Assistant, Grade-I, 2Professor Department of Civil Engineering, JNTU College of Engineering, Ananthapur
3Professor, Co-ordinator, Research & Consultancy, Department of Civil Engineering, Vasavi College of Engineering, Hyderabad.
Email: 1[email protected], 2[email protected]
ABSTRACT
Light weight aggregate concrete mixes can be used for high rise civil engineering structures, heavy constructions like bridges, dams etc. In this present investigation, mix design for M20 concrete with natural granite stone aggregate, local river sand as a fine aggregate and Ultra Tech OPC 43 grade cement as a binding material is carried out. The normal aggregate has been replaced upto a maximum of 100 percent by naturally available pumice aggregate by volume and the binding material cement is replaced with silica fume in various proportions of 5%, 8%, 10%, 15% and 20% by weight.
As part of the durability studies, the temperature effect on strength is studied and the acid resistance studies on the various light weight concrete mixes are conducted in the present investigation. Specimens of light weight concrete are tested with and without silica fume to find out the influence of silica fume.
Keywords— Light weight concrete, Pumice stone, Condensed Silica Fume, Temperature exposure, Acid resistance.
INTRODUCTION
Brick bats or cinder or emery stone or pumice are the innovative light weight materials used in the construction sector. Some sources of those are brick or steel manufacturing units. Some of them are being used by many engineers as a filler material in construction industry for different civil works. Emery stone is a waste material from granite polishing units and pumice stone is a naturally occurring volcanic based light weight aggregate.
Advantages of Light Weight Concrete
There are many advantages of having low density. It helps in the reduction of dead load, increases the progress of building and lowers the haulage and handling costs.
The use of light weight concrete has made it possible to proceed with the construction of tall and heavy structures on soils with low bearing capacities. In framed structures if floors and walls are made up of light weight concrete, it would result in considerable economy. Another most important characteristic of light weight concrete is its relatively low thermal-conductivity.
Structural Light Weight Concrete
Structural light weight aggregate concretes are considered as alternatives to concretes made with dense natural aggregates because of the relatively high strength to unit weight ratio that can be achieved.
Physical Properties of Various Light Weight Aggregates
Light weight aggregates are available from different sources and mostly as waste materials. Brick bats, cinder, emery stone, pumice etc., are easily available. Cintered fly ash aggregates are manufactured. Table.1 gives the physical properties of various light weight aggregated.
Brief Review of Previous Work
J.B. Newman(1) has reported other reasons for choosing light weight concrete as a construction material. It is becoming increasingly important as more attention is being paid to energy conservation and to the use of waste materials to replace exhaustible natural sources. For example, the thermal resistance of such materials increases with the decreasing density and this ensures considerable energy saving.
Brown BJ, Skinner M(7) reported that Pumice aggregates combined with Portland cement and water produce a light weight thermal and sound insulating, fire-resistant light weight concrete for roof decks, light weight floor fills, insulating structural floor decks, curtain wall system, masonry blocks and a variety of other permanent insulating applications.
Details of the Present Study
The present experimental investigation aims at the determination of strength and durability of light weight
Durability Studies on Pumice Light Weight Aggregate Concrete with and without Silica Fume
pumice aggregate concrete with and without silica fume.
The study includes the preparation of various concrete mixes varying the proportions of light weight aggregates in the total aggregate from 0 to 100 percent. Condensed Silica Fume (CSF) is used as replacement to Ordinary Portland Cement (OPC) in various percentages from 0 to 20. The specimens prepared are tested for compressive strength at room temperature and after exposing to elevated temperature (100˚C). The specimens are also subjected to chemical resistance tests.
EXPERIMENTAL INVESTIGATION
The details of experimental investigation conducted on pumice light weight concrete mixes are given as follows.
Description of Constituent Materials
The main constituents used for the specimens are (1) Normal coarse aggregates (Granite) (2) Medium light weight aggregate (Pumice stone) (3) Fine aggregate (sand) (4) Cement (OPC), (5) CSF, (6) Acids, (7) Water and (8) Superplasticizer (SP-430).
a) Cement— Ultra Tech ordinary Portland cement (OPC) of 43 grade conforming to ISI standards is used for the entire experimental investigation.
b) Fine aggregate— The locally available natural river sand is procured and is found to be conforming to grading of zone-1. The physical properties are tested as per the standards.
c) Conventional Natural Aggregate (Granite)—
Machine crushed granite aggregate of 20mm nominal size confirming to IS 383-1970 consisting of 20mm maximum size of aggregates has been obtained from the local quarry. The physical properties are tested as per the standards.
d) Pumice Stone Aggregate (PSA)— Pumice stone aggregate is available as densified lava near the volcanic rocks. It is porous and light in weight and is available from some of the states in Western India. In the present investigation, broken pumice aggregate of 20mm nominal size are employed. Figs. 1 and 2 show
the conventional granite aggregate (CGA) and the pumice stone aggregate (PSA). Table.1 gives the properties of different light weight aggregates including pumice.
e) Condensed Silica Fume (CSF)— Condensed silica fume is an industrial waste bi-product available from ferro silicon industries. In the present investigation, it was obtained from M/s. V.B. Ferro Alloy’s Ltd., Rudraram, Near Hyderabad-(A.P).
f) Water— Potable water has been used in this experimental program for mixing and curing.
g) Superplasticizer— Superplasticizer (SP-430) of M/s.
Fosrock India Ltd., has been used to maintain more or less medium workability throughout the experimental investigation.
h) Acids— Diluted acids H2SO4, Hcl and Na2SO4 with 5% concentration were employed for acid resistance tests.
Combinations of Light Weight Aggregates and Admixture
To start with mix design has been conducted for M20 concrete making use of IS method of mix design using normal constituents of concrete. In the course of investigation, normal granite aggregate has been replaced by 0%, 20%, 40%, 60%, 80%, 100% of light weight aggregate namely pumice. In the present investigation, OPC has been replaced by a mineral admixture (silica fume) in equal proportions in size percentages i.e. 0, 5, 8, 10, 15, 20 by weight for the study of various properties.
Mixing, Casting and Curing
All the ingredients were mixed in a pan mixer and cube specimens of size (100mm x 100mm x 100mm) were cast.
Workability was maintained at medium level by adding small dosages of superplasticizer. After 24 hrs. of air drying, demoulding was carried out and the specimens were cured till the age of 28 days and tested. Standard procedures were adopted for mixing and casting.
Table 1: Physical Properties of Various Light Weight Aggregates
S. No. Name of the test conducted Brick Bats Cinder Emery Pumice
Proceedings of the National Conference on Advances in Civil Engineering and Infrastructure Development Sufficient member of cube specimens were prepared for
conducting all the tests on various combinations.
Testing
The details of tests carried out are as follows.
Compressive Strength at Room Temperature
Average compressive strength was found at room temperature by testing the specimens in a standard compression testing machine by following standard procedure for all the combinations of composites considered in the present investigation.
Compressive Strength after Exposure to 100˚C
Sufficient number of specimens of various combinations were exposed to 100˚C in an oven for 24 hrs. taken out, cooled and tested for compressive strength.
Chemical Resistance
Sufficient number of specimens were exposed to acids by immersing them in 5% solutions of H2SO4, Hcl and Na2SO4 over periods ranging from 28 to 180 days. After the required exposure period, the specimens were taken out, cleaned, dried and the weight loss was determined accurately.
Fig. 1: Conventional Granite Aggregate
Fig. 2: Pumice Stone Aggregate
RESULTS AND DISCUSSION Tables and Graphs
Tables 2 and 3 give the results of compressive strength with and without CSF at room as well as 100˚C temperatures. Tables 4 and 5 give the results for 0%
CGA with 100% PSA and 60% CGA with 40% PSA respectively. CSF is included in both cases. Tables 6 and 7 give the details of weight losses of specimens exposed to H2 SO4, Hcl and Na2SO4 over different periods from 28 to 180 days. Various combinations of CGA with PSA are considered. Tables 8, 9, 10 and 11 give the weight losses for 60% CGA with 40% PSA combination with various percentages of CSF. Compressive strength is plotted against CSF percentage for various combinations at room temperature in fig.3 and at 100˚C in fig.4.
Temperature Studies
Compressive Strength of Silica Fume Pumice Concrete at Elevated Temperature
The compressive strength results of specimens with the various percentage replacements of natural aggregate by pumice subjected to an elevated temperature of 100˚C for 24 hours (after 28 days of curing in water) are presented in Table. Upto 40% replacement of natural aggregate by pumice the target mean strength is achieved and the compressive strength is observed to be 27.60 N/mm2 and the percentage increase of strength at elevated temperature with respect to that at room temperature is 16.31%. After 40% replacement for the higher percentage replacement however design strength is assured.
Compressive strength is observed to be higher at an elevated temperature when compared to compressive strength at room temperature. The optimum percentage of silica fume is around 10% for all percentages of pumice added.
In addition the compressive strengths for the specimens exposed to elevated temperature with all percentages of pumice added in this study are found to be higher than those at room temperature. This shows that the pumice concrete can with stand higher temperature.
Acid Resistance of Silica Fume Pumice Concrete Specimens of concrete cured for 28 days in normal water are then immersed in three chemical solutions (H2SO4, Hcl and Na2SO4) at 5% concentration for 7 days, 28 days, 90 days and 180 days. All the specimens with various basic replacements of pumice are tested for percentage of weight loss and the results are calculated and tabulated.
a) Na2SO4 — The results of the specimens exposed to 5%
concentration of Na2SO4 indicate that there is very less percentage of weight loss for the specimens exposed to 7 days, 28 days, 90 days and 180 days of immersion in base. Hence, the pumice is observed to be much resistant towards nitrates and sulphates. It
Durability Studies on Pumice Light Weight Aggregate Concrete with and without Silica Fume may be observed that more or less there is an increase
in percentage weight loss from 0% to 100%
replacement of natural aggregate by pumice. The weight loss marginally increases upto 20% pumice concrete (80% natural aggregate) and afterwards it gets decreased. Afterwards increased percentage of pumice resists the attack of Na2SO4.
b) Hcl— There is no much difference of weight between normal specimen and specimens when they are dipped in 5% concentrated solution of Hcl after exposure for 7 days, 28 days, 90 days and 180 days immersion in acid like Hcl. It may be observed that there is an increase in percentage weight loss for each replacement from 7 days of curing to 180 days of curing. For 100% natural aggregate weight loss is minimum. This shows the good resistance of pumice concrete to Hcl attack.
c) H2SO4 — The results of specimens exposed to 5%
concentration of H2SO4 indicate that pumice have poor resistance for sulphate attack. Here the specimens are found to loose their shapes. From the studies, it is also seen that with the increase in pumice percentage the percentage weight of loss for any curing period increases. This shows that the pumice concrete has least resistance to H2SO4 attack.
Normal Aggregate Replaced by 40% Pumice
a) With 0% Silica Fume in all Acids— It may be observed that the loss of weight is more w.r. to H2SO4
which ranges from 3.5 to 19.39 percent as when compared to the Hcl and Na2SO4, where as in Hcl immersion the loss of weight ranges from 3.18 to 3.72 percent. The loss of weight with respect to Na2SO4 is 3.2 to 3.49. This is observed to be very less compared to the H2SO4 and Hcl acid attacks.
b) Na2SO4 (with silica fume)— It can be understood that percentage loss of weight with respect to 8% addition of silica fume and with respect to any immersion fume is observed to be minimum when compared with that for other percentages of silica fume. Hence, for this combination of (60% NA + 40% P), 8% silica fume addition is the best/optimum percentage.
c) Hcl (with silica fume)— It can be understood that percentage loss of weight with respect to 8% addition of silica fume with respect to any immersion period is minimum. Besides as the immersion period is increased from 28 days to 180 days, the increase in percentage loss with respect to 8% addition of silica fume is observed to be minimum when compared with that for other percentages of silica fume. Hence for
this combination of (60% NA+40% P), 8% silica fume addition is the best/optimum percentage.
d) H2SO4 (with silica fume)— It can be understood that percentage loss of weight with respect to 5% addition of silica fume with respect to any immersion period is minimum. Besides as the immersion period is increased from 28 days to 180 days, the increase in percentage loss with respect to 5% addition of silica fume is observed to be minimum when compared with that for other percentages of silica fume. Hence for this combination of (60% NA + 40% P), 5% silica fume addition is the best/optimum percentage.
Table 2: Compressive Strength for Replacement of CGA with PSA at Room Temperature and 100˚C without CSF
S.
Table 3: Compressive Strength for Replacement of 100%
CGA: 0% PSA at Room Temperature and 100˚C with CSF
S.
Table 4: Compressive Strength for Replacement of 0%
CGA: 100% PSA at Room Temperature and 100˚C
S.
Proceedings of the National Conference on Advances in Civil Engineering and Infrastructure Development Table 5: Compressive Strength for Replacement of 60%
CGA: 40% PSA at Room Temperature and 100˚C
S.
Table 6: Weight Loss of Specimens for Replacement of CGA with PSC for Different Immersion periods in H2SO4
S. Table 7: Weight Loss of Specimens for Replacement of CGA
with PSC for Different Immersion periods in Hcl
S. Table 8: Weight Loss of Specimens for Replacement of CGA
with PSA for Different Immersion periods in Na2SO4
S. Different Percentages of Silica Fume
S. Table 10: Durability of 60% CGA: 40% PSA in Hclwith
Different Percentages of Silica Fume
S.
Different Percentages of Silica Fume
S.
Fig. 3: Typical Variation of Compressive Strength Vs.
Percentage Replacement of Pumice at Room temperature
Durability Studies on Pumice Light Weight Aggregate Concrete with and without Silica Fume
Fig. 4: Typical Variation of Compressive Strength Vs.
Percentage Replacement of Pumice at Room Temperature and 100˚C
CONCLUSIONS
1. From the limited temperature studies conducted in this investigation at 100˚C for 24 hours exposure, the compressive strengths increase with percentage replacement of cement by CSF similar to that at room temperature.
2. Comparing the corresponding strengths at room and elevated temperatures, the compressive strengths are found to be higher for the specimens subjected to higher temperature upto 100˚C.
1. From acid resistance studies conducted in this investigation it is again observed that pumice concretes are better resistant to Hcl and Na2SO4
attacks.
2. Finally it is concluded that the presence of CSF used as part replacement of cement contributed to improve the durability of light weight pumice concrete.
REFERENCES
[1] J.B. Newman, T.W. Bremner, the Testing of Structural Light Weight Concrete, the Concrete Society, the Construction press, Lancaster, UK, 1980, pp. 152-172.
[2] Kornev NA, Kramar VG, Kudryavtsev AA. Design peculiarities of pre-stressed supporting constructions from concretes on porous aggregates. Lancester, London, New York, UK: The Concrete Society, the Construction Press;
1980 pp. 141-52.
[3] H. Bomhard, light weight concrete structures, potentialities, limits and realities, the Concrete Society, the Construction Press, Lancaster, UK, 1980, pp. 227-290.
[4] Abeles PW, Bardhan-Roy BK Pre-stressed concrete designer’s hand book. In: Cement and Concrete Association. Wexham Springs: A View point publication;
1981.
[5] P. Morabito, measurement of thermal properties of different concretes, high temp., high press 21(1) (1989) 51-59.
[6] B.J. Brown, Report on concrete mix design for structural concrete using Yali Pumice Coarse and Fine Aggregates report no. 89/3408E/3379, STATS Scotland, East Kilbride, Scotland, UK, 1990.
[7] Brown BJ, Skinner M report on concrete mix design for light weight masonry units using Yali Pumice Coarse and Fine Aggregates. Report no. 89/3408D/2923, STATS Scotland Ltd., East Kilbride, Scotland, UK; 1990.
[8] Light weight concrete provides efficient thermal and sound insulation in buildings.
Proceedings of the National Conference on Advances in Civil Engineering and Infrastructure Development (ACEID-2014), Vasavi College of Engineering, Hyderabad, A.P. 6 - 7 February, 2014. pp.124-129.