Innovations in Civil Engineering for Society and the Environment

Proceedings of The 4th International Conference of Euro Asia Civil Engineering Forum 2013 (EACEF 2013), National University of Singapore, 26-27 June 201

THE INFLUENCE OF COMPACTION METHODS ON THE PROPERTIES OF HOLLOW CONCRETE BRICKS UTILIZING FLY ASH AND BOTTOM ASH

This study focuses on the maximal use of industrial waste from burning coal, i.e. fly ash and bottom ash, in making hollow concrete bricks (HCB). Fly ash (FA) and bottom ash (BA) obtained from East Java, Indonesia, is incorporated to partly replace the use of Portland cement and natural sand. The purposes of the study are to determine the appropriate mix proportion incorporating the maximal use of waste products and to evaluate the effectiveness of three compaction methods, i.e. Manual, Vibration with load and Static compaction. This study is part of an effort to produce environmentally friendly construction materials for sustainable development. The optimum composition of the mixtures was found to be the use of 31% FA of the total binder and 24% BA of the total filler, with the filler-to-binder ratio of 8.6 by mass. Among the three compaction methods studied, it was found that the maximum compressive strength of 66.9 kg/cm2 was achieved when applying the Vibration-with-load compaction method with 3 layers, 7 second vibration period and 40 kg block weight. This compressive strength satisfies the requirement for Grade II concrete brick in accordance to Indonesian National Standard SNI 03-0349-1989. The water absorption of HCB produced from all the mixes was found small, less than 15%, satisfies the requirement of maximum water absorption in accordance to the standard

Studies of fly ash-based geopolymer concrete

The use of Portland cement in concrete construction is under critical review due to high amount of carbon dioxide gas released to the atmosphere during the production of cement. In recent years, attempts to increase the utilization of fly ash to partially replace the use of Portland cement in concrete are gathering momentum. Most of this by-product material is currently dumped in landfills, creating a threat to the environment. Geopolymer concrete is a ‘new’ material that does not need the presence of Portland cement as a binder. Instead, the source of materials such as fly ash, that are rich in Silicon (Si) and Aluminium (Al), are activated by alkaline liquids to produce the binder. Hence concrete with no Portland cement. This thesis reports the details of development of the process of making fly ash-based geopolymer concrete. Due to the lack of knowledge and know-how of making of fly ashbased geopolymer concrete in the published literature, this study adopted a rigorous trial and error process to develop the technology of making, and to identify the salient parameters affecting the properties of fresh and hardened concrete. As far as possible, the technology that is currently in use to manufacture and testing of ordinary Portland cement concrete were used. Fly ash was chosen as the basic material to be activated by the geopolimerization process to be the concrete binder, to totally replace the use of Portland cement. The binder is the only difference to the ordinary Portland cement concrete. To activate the Silicon and Aluminium content in fly ash, a combination of sodium hydroxide solution and sodium silicate solution was used. Manufacturing process comprising material preparation, mixing, placing, compaction and curing is reported in the thesis.Napthalene-based superplasticiser was found to be ii useful to improve the workability of fresh fly ash-based geopolymer concrete, as well as the addition of extra water. The main parameters affecting the compressive strength of hardened fly ash-based geopolymer concrete are the curing temperature and curing time, the molar H2O-to-Na2O ratio, and mixing time. Fresh fly ash-based geopolymer concrete has been able to remain workable up to at least 120 minutes without any sign of setting and without any degradation in the compressive strength. Providing a rest period for fresh concrete after casting before the start of curing up to five days increased the compressive strength of hardened concrete. The elastic properties of hardened fly ash-based geopolymer concrete, i,e. the modulus of elasticity, the Poisson’s ratio, and the indirect tensile strength, are similar to those of ordinary Portland cement concrete. The stress-strain relations of fly ash-based geopolymer concrete fit well with the expression developed for ordinary Portland cement concrete

Processed bottom ash for replacing fine aggregate in making high-volume fly ash concrete

Bottom ash is a coal plant by-product that is abundant and underutilized. There is the potential use of bottom ash as a fine aggregate replacement in concrete mixtures; however, the problems of water absorption and uniformity of quality of the material need to be overcome first. In this study, bottom ash was treated by sieve separation and pounding to smaller particle size for use as a sand substitute. The physical and chemical characteristics of bottom ash were tested after treatment including water absorption, sieve analysis, and fineness modulus. High volume fly ash (HVFA) mortar specimens were made and the compressive strength and flowability test using bottom ash after treatment are compared with that of the sand specimen. Low water to cementitious ratio was used to ensure higher strength from the cementitious paste and superplasticizer demand was determined for each treatment. The result showed that bottom ash can be used as fine aggregate replacement material. Sieve separation of the bottom ash could produce 75% of the compressive strength compared with the control sand specimen, whereas pounded bottom ash could have up to 96% of the compressive strength of the control specimen. A 28-day compressive strength of 45 MPa was achievable with 100% replacement of fine aggregate with bottom ash

Experimental Study on the Use of Natural zeolites as Partial Replacement for Cement in Concrete

Study on the use of natural zeolite as partial replacement for cement in concrete has been carried out in China and in other countries since early 1980. However, very few information has been reported in Indonesia on this subject, although the availability of the natural zeolite in the country is abundant. So far, natural zeolite is only utilized in the agricultural sector. In this research, natural zeolite has been used to partially substitute the ordinary Portland cement (OPC) in concrete. The presence of silicon dioxide in natural zeolite was expected to increase the concrete strength through reaction with the calcium hydroxide from the hydration of OPC. However, results from the investigation revealed that the compressive strength, the tensile splitting strength and the modulus of elasticity of concrete containing natural zeolite decreased with the increase of natural zeolites content

A Preliminary Study on Cracking Tendency of Cement Paste Incorporating High Calcium Fly Ash

Fly ash is a waste material from burning coal that can be used to reduce the amount of cement in making concrete and to improve the characteristics of concrete. Besides being able to improve the flowability of fresh concrete, fly ash can also serve to reduce cracking of concrete. But in certain cases, cement paste incorporating fly ash type C (high calcium fly ash) experiences cracks, right after being released from formwork. The purpose of this study were to investigate the causes of cracking of cement paste incorporating fly ash type C, the influence of fly ash variations, and the countermeasures. The evaluation conducted for this experiment were based on visual inspection and compressive strength test of cement paste at 28 days. Test specimens were made in the form of cement paste with fly ash content of 50%, by mass. Fly ash used was of type C taken from three different batches from one source; with fly ash type F from three different sources used for control specimens. Superplasticizer, silica fume, and calcium carbonate were used as additives to evaluate their effect in mitigating cracks. The results show that the use of fly ash type C may cause cracks on the surface of hardened paste. Fly ash content, especially CaO and MgO, are the key factors affecting the cracks tendency on the surface of cement paste, due to expansion. Superplasticizer and silica fume can be used to mitigate cracks of cement paste

The Impact of Using Fly Ash, Silica Fume and Calcium Carbonate on the Workability and Compressive Strength of Mortar

AbstractPozzolanic materials and calcium carbonate can be used to partially replace the use of cement in making mortar or concrete without altering the rheological properties of the fresh mixture. This study focuses on the use of fly ash in the range of 0-30%, silica fume 0-10% and calcium carbonate 0-15% of the cement content, by mass. The workability of the fresh mortar was evaluated and the compressive strength of hardened mortar were measured at the ages of 7, 14, 28 and 56 days. Test results show that increasing partial replacement of cement with fly ash increased the workability and compressive strength of mortar. The use of silica fume reduces the workability of the fresh mortar, and thus requires the addition of superplasticizer to improve the workability. Finer particle size of calcium carbonate also increase workability. The addition of calcium carbonate resulted in higher early strength, whereas the Strength Activity Index (SAI) values slightly reduced with age