Mechanical Properties of Volcanic Ash Based Concrete

Transcription

1 Proceedings of International Seminar on Applied Technology, Science, and Arts (3 rd 224 Mechanical Properties of Volcanic Ash Based Concrete JANUARTI JAYA EKAPUTRI, TRIWULAN, PUJO AJI, AND AHMAD BAIHAQI Department of Civil Engineering, Faculty of Civil Engineering and Planning Institut Teknologi Sepuluh Nopember, Surabaya, 6111, Indonesia. Abstract This paper presents the results of investigation to assess the suitability of using volcanic ash obtained from Mount Bromo as a cement replacement material to produce normal concrete. Tests were conducted on concrete mixtures replacing to % by mass of ordinary portland cement (OPC) by volcanic ash. The performance of volcanic ash concrete mixtures was evaluated by conducting comprehensive series of tests on fresh and hardened properties. The mechanical properties were assessed by compressive strength, while microstructure properties were investigated by setting time, hydration temperature, autogeneous shrinkage and porositys tests. Concrete with volcanic ash showed better properties compared to concrete with 1%, 2% and % volcanic ash. It was attributed to the refinement of pore structure, and pozzolanic action of. Development of non-expensive and environmentally friendly concrete with volcanic ash with acceptable strength is extremely helpful for the sustainable development and rehabilitation of volcanic disaster areas around the world. Keywords volcanic ash, concrete, compressive strength, Mount Bromo I. INTRODUCTION T he search for alternative binders or cement replacement materials has continued in the last three decades and from the economical, technological and ecological points of view, cement replacement materials play an undisputed role in the construction industry. Comprehensive research has been carried out in the past on the use of fly ash (FA), pulverized-fuel ash (PFA), blast furnace slag, rice husk ash, silica fume, etc., as cement replacement materials. Small amounts of inert fillers have always been acceptable as cement replacement. If the fillers have pozzolanic properties, they impart not only technical advantages to the resulting concrete but also enable larger quantities of cement replacement to be achieved. Volcanic ash (), volcanic pumice (VP), PFA and FA are pozzolanic materials because of their reaction with lime (calcium hydroxide) that is liberated during the hydration of cement. Amorphous silica present in the pozzolanic materials combines with lime and forms cementitious materials. These materials can also improve the durability of concrete and the rate of gain in strength and burnt oil shale are common in regions where these materials are available. Volcanic materials such as are found abundantly in volcanic areas around the world and finding new and improved ways to build with such materials is becoming widespread. New sources of volcanic materials are being produced steadily. Recently the eruption of Mount Bromo in the last 21 volcanoes emitted large quantities of such materials. Physical and chemical properties of a volcanic ash could be referenced with ASTM C618-3, a Standard Specification for Fly Ash and Raw or Calcinated Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete. The meaningful use of volcanic materials can, not only transform them into natural resources to produce low cost construction materials but also lead to sustainable development. Development of nonexpensive and environmentally friendly based concrete with acceptable strength and durability characteristics can be extremely helpful in the development and rehabilitation of volcanic disaster areas around. II. FUNDAMENTAL THEORY Volcanic activities are common in Indonesia and due to frequent volcanic eruption, volcanic debris such as is found abundantly. The 21 Merapi volcano eruption that occurred in Yogyakarta was the most destructive one, which completely devastated the province and created an environmental disaster. Comprehensive research had been conducted over the last few years on the use of and pumice in cement and concrete production. Research suggested the manufacture of blended PC (Portland volcanic ash cement) with maximum replacement of up to 2% [3]. Hossain in 23 [1] studied the effect of partial replacement of cement with volcanic ash () on the compressive strength of cement mortar. Percentage

2 Proceedings of International Seminar on Applied Technology, Science, and Arts (3 rd 2 replacement varied from to 5%. Tests were conducted up to the age of 28 days. Based on the results, he concluded that compressive strength decreased with the increase in content as shown in Table 1. The finely divided silica (6%) in can combine with calcium hydroxide (liberated by the hydrating PC) in the presence of water to form stable compounds such as calcium silicates, which have cementitious properties. Such pozzolanic action of contributed to the enhancement of strength and long-term durability although the reduction of strength in blended cement due to cement replacement by was not compensated [1]. Mix details TABLE I EFFECT OF ON THE PROPERTIES OF CEMENT AND MORTAR Normal Consistency Setting Time (hours) Initial Final Compressive Strength of Mortar (MPa) 1 day 3 days 7 days 28 days Hossain (23) III. METHODS Materials and Chemical Composition of The used in this investigation was collected from Mount Bromo, East Java Province. It is one of the most active volcano in Indonesia. Raw, collected from the source was dried and sieved to remove larger particles and other debris. It has a specific gravity of The cement used was locally manufactured ordinary Portland cement (OPC) conforming to ASTM Type I. The Portland cement has a specific gravity of 3.5. The fine and coarse aggregates were local natural river sand and 2 mm maximum size crushed limestone, respectively and analyzed with ASTM C [8] for aggregates. Chemical properties of Bromo are compared with those of the chemical composition of Mount Merapi in Table II. The seems to satisfy most of the criteria of Class N fly ash as per ASTM C [7]. TABLE II CHEMICAL COMPOSITION BY XRF (%) Chemical Compound (%) Bromo Merapi Type N Fly Ash ASTM C-618 Silica (SiO 2 ) 39.6% 76.% - Alumina (Al 2 O 3 ) 1.% 2.97% - Iron oxide (Fe 2 O 3 ) 26.5% 5.68% - SiO 2 + Al 2 O 3 + Fe 2 O % 84.9% 7% (min) Calcium oxide (CaO) 11.9% 4.48% - Magnesia (MgO) 1% 4.82% - Sulfur trioxide (SO 3 ) 1%.12% 4 (max) Sodium oxide (Na 2 ) % - LOI 1% 2.99% 1% Mix Proportion of Concrete Specimens The mix proportions of HPC mixtures are presented in Table III. HPC mixtures were designed to provide a minimum 28-day compressive strength of 3 MPa with water to binder ratio was kept constant at.51 for all mixtures. was introduced as cement replacement and its proportions were varied from to % by mass. Control mixes incorporating OPC were also prepared for comparison purposes. The numeric in mix designations represents the percentage of by mass. TABLE III MIX PROPORTION OF CONCRETE SPECIMEN Fine Coarse Code content (% ) OPC Water Agg Agg C- % C-1 1% C C-2 2% C- % Test Specimens, Curing Conditions and Testing Details Comprehensive series of tests on fresh, mechanical, and micro-structural properties of concretes such as slump, compressive strength, setting time, hydration temperature and autogeneous shrinkage were carried out. Compressive strength test was performed on

3 Proceedings of International Seminar on Applied Technology, Science, and Arts (3 rd mm cylinders at an age of 28 days as per ASTM C-39 [9]. Three specimens were tested for each test at each age and mean values were reported. The specimens were removed from the moulds after 24 h of casting. Hydration temperature test was performed for the paste specimens with water content confirming from normal consistency test. A thermocouple was located in the center of specimen and connected to data logger for recording the temperature. Autogeneous shrinkage test was conducted for 1 2-mm cylinders specimens to measure the strain of mortar just after casting. The specimens were cast for each mix proportion. A special strain gauge for cementitious material was inserted to the center of each specimen inside the mould and linked to data logger for recording the strain [4,5]. The strain obtain from this test was then connected to mortar compressive test at the corresponding time. TABLE IV MIX PROPORTION OF MORTAR SPECIMEN content OPC Water (% ) Fine Agg Code M- % M-1 1% M M-2 2% M- % Typically, autogenous deformation was measured simultaneously on two nominally identical specimens, and the average result was reported. Mix proportion of mortar for compression and shrinkage test is listed in Table IV as per ASTM C-19-2 [1]. IV. EXPERIMENTAL RESULTS Effect on normal consistency and setting time of cement The variation of normal consistency with different percentage of is presented in Fig. 1. The normal consistency is increased by 9.79% for when the content varied from to %. The increase in normal consistency is due to the reduction of cementitious binder in the fresh mixture with the increase of content. On the other hand, specific gravity of is less than that of cement, which resulted in the larger volume of compared to the volume of cement replaced as the replacement was made by mass. As a result, the overall volume was increased needing more water to form a paste of same consistency for different % of in the mixture w/c Volcanic Ash Content (%) Fig. 1. Effect of on normal concistency The variation of setting times with the percentage of is also presented in Fig. 2..The trend shows an increase in both setting times with the increase of content. Initial setting and final setting time is increased by 63% when content is increased from % to %. This is reasonable as the increase of content reduces the cement content in the mixture and also decreases the surface area of the cement. As a result, the hydration process slows down causing setting time to increase. This result has a good agreement with the research conducted by Hossain [1]. In his observation, the initial setting time increased by 9% where the increase in final setting time was 58% with the increase in content from to 5%. The slow hydration means low rate of heat development as shown in Fig 3. Internal temperature of OPC specimen shows the highest as in comparison to specimens. The variation of internal temperature shown by each specimen indicates the different hydration process at early ages. Higher content shows lower hydration temperature. However, replacement 1% of OPC gives less effect on rate of heat. This is of great importance in mass concrete construction, for which volcanic ash cement can be mostly used, besides other general use.

4 Proceedings of International Seminar on Applied Technology, Science, and Arts (3 rd 227 Setting Time (Hour). Temperature ( C) % 5% 1% 2% % Volcano Ash(%) Fig. 2. Effect of on setting time Fig. 3. Effect of on temperature of hydration Effect on compressive strength The variation in the compressive strength is shown in Fig. 4. The compressive strength is found to decrease with an increase of content. This is reasonable due to the reduction of cement content in the mix with the increase of content. The finely divided silica (39.6%) in can combine with calcium hydroxide (liberated by the hydrating PC) in the presence of water [1] to form stable compounds such as calcium silicates, which have cementitious properties. Such pozzolanic action of contributes to the enhancement of strength. Different pore structures in the matrix due to different hydration mechanism are subjected by variation of content. This different mechanism causes the value vary in strength development. It can be seen in Fig 5 that the strength is reduced by 24% (28 days), when content varies from to %. The reduction in strength with the increase of content up to 5% can reach about a half of OPC concrete strength at 28 days [1]. Initial Setting Final Setting % 1% 2% % % Reduction in Compressive Strength Age (Hour) f'c (MPa) % 1% 2% % Age (Day) Fig. 4. Effect of on compressive strength Volcanic Ash Content (%) Fig. 5. Effect of on compressive strength reduction (%) 3 days 7 days 14 days 21 days 28 days Effect on autogeneous shrinkage Autogeneous shrinkage-time curve from mortar specimens with composition listed in Table 4 in Fig 6. As predicted, specimens made with OPC exhibit shrinkage larger than those specimens made with. This deformation occurs due to selfdesiccation at early ages in specimens contain more OPC than others. The effect is more obvious for specimen containing %. The autogeneous shrinkage of 1% and mortars were higher than those of 2% and %. It indicates that content in cement decreases shrinkage of

5 Proceedings of International Seminar on Applied Technology, Science, and Arts (3 rd 228 specimens. When some part of cement is replaced by pozzolanic material, the autogeneous shrinkage decreases. The effect of content of about is sufficient. The decrease of autogeneous shrinkage in mortar containing is generally believed due to coarser particles size of as compared to those of cement [5,6]. It indicates the advantage of application in concrete in mass production. Tazawa and Miyazawa [2] reported that this effect was caused by the increased contact angle between the solid phase and pore water in early ages od hydration. 14days, and 28days. A linear relation is expressed by all specimens. The slopes presented by the shrinkage-fc' relation at cement specimens are different from the slope of OPC specimens. The steeper slope of slag cement specimens indicates their different pore size as a consequence of finer cement size particles involved in hydration process at early ages. Surprisingly, when 1% cement weight is replaced with, the slope is still the same as those of OPC specimens. The more capillary space is occupied with the hydration products, the higher compressive strength will be achieved. This can also explain the different strength given by each specimen at the same age [5]. At the later ages, gradually the progression of the hydration process generates finer gel pores developing continuously. In case of cement, OPC replaced with 1% of has lower strength but higher shrinkage resulting in a line parallel to that at OPC mortar line Effect on slump The slump values of concrete are presented in Fig 8. Air content ranged between 2.6% and 3.2%. Generally air content of the HPCs increased with the increase of content. All the mixtures were produced at a slump that ranged between 7 and 9 mm. No segregation or excessive bleeding was observed during mixing and casting. 37 Fig. 6. Effect of on autogeneous shrinkage % Shrinkage (micron) 45 1% 4 % 3 % M- M % M-2 1 M- 5 f'c (MPa) fc` (MPa) % content (%) 1% 27 % Slump (mm) Fig. 8. Slump and compressive strength relation at fresh concrete Fig. 7. Autogeneous shrinkage and compressive strength relation at mortar Fig 7 shows a relation between compressive strength and shrinkage at the age of 3days, 7days, V. CONCLUSIONS The results suggest that the normal consistency and setting time of PC are affected by the replacement of cement by. Manufacture of concrete is possible with maximum replacement of up to %. A possible use of this concrete will be

6 Proceedings of International Seminar on Applied Technology, Science, and Arts (3 rd 229 in mass concrete construction due to lower heat of hydration, higher setting time and less shrinkage compared to OPC. Application of concrete in Indonesia should be one of idea in concrete innovation if they meet the requirement of the specific job, including strength, micro-properties and durability. The latter has not been discussed in this paper. However, the beneficial effects of concrete on the long-term durability of concrete are reported [3]. A campaign in the form of poster, pamphlet and advertisements is conducted to market the blended cements and to build consumer confidence. Cheaper and environmentally friendly concrete has to be conducted in the rehabilitation projects of volcanic areas of Indonesia. VI. REFERENCES Periodicals: Hossain, Khandaker M. Anwar (23). Blended cement using volcanic ash and pumice. C(ement and Concrete Research, 33, Tazawa, Eichi and Miyazawa, Shingo (1995). Influence of Cement and Admixture on Autogeneous Shrinkage of Cement Paste, Cement and Concrete Research,, 2, Books: Siddique, Rafat (28). Waste Materials and By-Products in Concrete. Springer. Ekaputri, J. J., Ishida T., Maekawa, K. (29). Autogeneous Shrinkage of Mortars Made with Different Types of Slag Cement. JCI Annual Conference, 32. Dissertations: Ekaputri, J. J., "Thermo-Hygro Stability of Solidified Pozzolans in Aqueous Medium," Ph.D. dissertation, Dept. Civil. Eng., the Univ. of Tokyo, Japan, 21. Baihaqi, Ahmad, The Use of Volcanic Ash as an Innovative Development Composite Concrete Material with f'c of 3 MPa, Bachelor Thesis (in Indonesian), ITS Surabaya, 211 Standards: ASTM C618-3, Standard Specification for Fly Ash and Raw or Calcinated Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete, 23 ASTM C 136-1, Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates, 23 ASTM C39-1 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, 23. ASTM C19-2S Compressive Strength of Hydraulic Cement Mortars, 23