Ahmad Rifa’i

Characterization and Effective Utilization of Volcanic Ash for Soil Improvement

Volcanic ash becomes environmental important issues as waste material if it is not effectively reduced or reused. In engineering practice, utilization of volcanic ash as substitution material is limited. Indonesia has a large road on soft soil and volcanic ash. The objectives of this paper are focused to study the characterization, classification and utilization of volcanic ash as soil stabilization material which give benefit in engineering practice and also be environmental friendly material. Engineering properties, mineral composition and soil mixture characteristics involve physical and mechanical properties are discussed. Result shows that the effect of addition of volcanic ash after curing time 14 days can improve the engineering properties of soft soil, decrease liquid limit, change curve of grain size distribution, increase bearing capacity, and decrease swelling potential. The soil-volcanic ash mixture with 35% of volcanic ash and 5% of lime is obtained as optimum mixture design. This result is still early stage and need further study.

Behavior of Expansive Clay of Ngawi Region (East Java) Under Water Content Variation

The key in developing a strategy for management of non-revenue water (NRW) is to gain a better understanding of the reasons for NRW and the factors which influence its components. The components of NRW can be determined by conducting a water balance analysis. The International Water Association (IWA) provides a water balance calculation that gives guidance to estimate how much is lost as leakage from the network (physical losses), and how much is due to non physical losses. Further, IWA has established the Infrastructure Leakage Index (ILI), a performance indicator for comparisons of leakage management in water supply systems. This paper introduces ILI and reasons why it is a more appropriate approach to use than the percentage of system input volume.This paper reviews the applicability of nine selected expressions in determining the equivalent value of the Manning coefficient of roughness. For this purpose, a prismatic 4m-long and 0.05m-wide trapezoidal-shape channel was constructed, namely the homogeneous channel and the composite channel. The homogeneous channel had the same surface lining, whereas the composite channel had two different surface linings. Four different lining materials were considered: plaster, small, medium, and large-sized aggregates. The homogeneous channel showed a reliable Manning coefficient prediction, provided that a uniform flow was achieved. The roughness of the composite channel can be predicted accurately by the nine expressions; the average was 0.96, with standard deviation of 11.13%. Out of the nine expressions, the expression that considers wet-perimeter as its main parameter showed the best estimate. The error was about 2% with standard deviation of 5.15%. This can be actually traced back to the limited width of the test channel, thereby increasing the role of wet perimeter.This paper presents an experimental and analytical research conducted to study the in-plane behavior of reinforced concrete (R/C) frames in-filled with lightweight materials. The tests were performed on two single bay, single story in-filled frame specimens with 1⁄2 scale models. One of the test specimens was in-filled with lightweight materials, i.e. autoclaved aerated concrete (AAC) blocks, and the other, used as the comparison, was in-filled with clay brick materials. The loading used in the tests was in the form of cyclic in-plane lateral loads, simulating earthquake forces. Behavior of the frame structures was evaluated through the observed strength and deformation characteristics, the measured hysteretic energy dissipation capacity and the measured ductility. The experimental results show that the R/C frame in-filled with AAC blocks exhibited better performance under in-plane lateral loads than that in-filled with conventional clay bricks. In the analytical work, the performance of some analytical models available in the literature was evaluated in simulating the experimental results

Utilization of Coal Ash As Recycling Material Options in View Point of Geoenvironment

Disposed coal ash is result from the residual of coal refinery processes and become environmentalimportant issues. Coal ash consists of bottom ash and fly ash. The number of coal ash production is abundant, and can be considered as waste material if it is not effectively reused or recycled for other application. In engineering practice, utilization of fly ash as additive materials is limited and in small quantity while the disposal of fly ash is quite high. The major aim of this paper is to stress the characterization, classification and utilization of coal ash as recycling structural material in view point of geoenvironment. Also, to prove of coal ash contribution in geotechnical engineering, give benefit in engineering practice and also become as part of engineering material that is environmental friendly. Material characteristics involve physical, mechanical, mineral composition and chemical properties, including environmental aspect by laboratory tests are presented. Uniaxial test, CBR test, sulphate resistance test and leaching test of heavy metal contents of coal ash as recycling structural material were also conducted to ensure environmentally acceptable based on Indonesian standard SNI. Fly ash is grouped in F class. Based on SNI-03-2460-1991, fly ash sample is available as additive material in concrete. Mix design of coal ash paving block is conducted toward several mixes, different volumes of coal ash and cement to grasp optimum utilization of coal ash and qualify minimum standard requirement of Indonesian standard SNI 03-0691-1996. Coal ash paving block with quality B, i.e. has compression strength 200 kg/cm2 can be mixed with fly ash adding 30% maximum as additive, or use of 50% fly ash as substitution with cement content is kept or using fly ash 30% and bottom ash 40%. Coal ash paving block samples resist to sulphate. Effect of addition of fly ash, bottom ash and lime on physical and mechanical properties can improve the index properties of soft soil sub grade layer, increases bearing capacity, as well as decreases swelling potential. Coal ash-soil mixture contains some heavy metals, but concentration values is still under boundary threshold of government act PP No. 20, 1990 about criteria of water quality in group D.