Browsing by Author "Abeyruwan, H"

Now showing 1 - 3 of 3

item: Conference-Full-text
Characterization of self compacting concrete in terms of bingham constants
(2013-12-01) Karunarathna, HMGU; Abeyruwan, H; Gunasoma, HHM; Situge, SDJMT
The purpose of this experimental work is to determine the domain of the Bingham constants within which a concrete mix possesses self-compactability. Flow characteristics or the rheological characteristics of concrete were expressed by using the Bingham model. Yield shear stress and the plastic viscosity are the two flow properties included in the Bingham model. A range of the combinations of yield shear stress and plastic viscosity was identified within which the concrete is likely to be self-compactable. To determine the self-compactability of a concrete three index properties were determined by experiments. Those three properties are the filling ability, passing ability and the segregation resistance. To measure the filling ability, slump flow by Abram’s cone, T50cm slump flow time and V funnel test were used. To measure the passing ability, J ring test was used. V funnel at T5min test was used to test the resistance to segregation. Self-compactability was judged by comparing the results with the acceptable regions given in the EFNARC publications. Yield shear stress and the plastic viscosity were calculated by using the rotational speed and the applied torque on the concrete which were measured by a coaxial type cohesiometer. The analysis of data by statistical procedures led to the charts showing variations of the workability indices with the water powder ratio and the superplasticizer dosage for different water cement ratios. Those charts are useful when proportioning self-compacting concrete mixes.
item: Conference-Full-text
Selection of proper mode for pavement rehabilitation – a challenge for engineers
(2013-11-12) Wijekoon, S; Abeyruwan, H; Wickramasinghe, V
The Government of Sri Lanka is investing heavily on infrastructure development which is the gateway to the economic development of the country. Accordingly, a significant number of national, provincial and rural road projects have been implemented. Designs for most of these road projects are done according to the international standards. There are a number of techniques available to rehabilitate or upgrade pavements and the intended benefits cannot be reaped unless a judicious technique is followed. This paper covers an example of an estimating design equivalent standard axles and a comparison of two common surfacing techniques, viz., thin bituminous surfacing and thin asphalt surfacing. Pavement structure is analysed using mechanistic method. The significance of mechanistic method over empirical approach is highlighted. The fallacy of the belief that the design life of pavement increases monotonically with the thickness of asphalt layer is revealed. The analysis leads to the selection of suitable pavement structure.
item: Conference-Full-text
Yield shear stress of cementitious mortar for self-compacting concrete
Dharmarathne, SBKD; Samarakoon, SMCJB; Edirisinghe, END; Abeyruwan, H
Abstract: Self-Compacting Concrete (SCC) is extensively used in modern constructions as it consolidates under its own weight without requiring any other compactive effort, whilst maintaining homogeneity. SCC is a thick suspension, and its rheology can be characterized by Bingham model, in terms of yield shear stress (τy) and plastic viscosity (μ).The main objective of this study is to explore variation of consistence of the mortar fraction, in terms of τy, when high-range water-reducing admixtures (HRWR), fly-ash and river sand are present in mortar. As SCC is a suspension of coarse aggregates in mortar, the research focuses on τy of grout and mortar. In this study, τy of pastes that contain different quantities of HRWR, fly-ash and sand was measured. Combined effects of the constituents on τy were observed for two common w/c ratios using concentric rheometer and mini slump cone with the view to determine the optimum compositions. Results suggest to maintain HRWR and fly-ash contents around 1.0L/100 kg, and 25%-30% by mass of cement, respectively, and sand content below 40% by the total volume of the mix. Moreover, the study validates an analytical model derived to evaluate τy by using slump spread diameter and also develops and empirical formula linking τy to the slump spread diameter of cement paste. The findings pave way to use mini slump test as simple tool to judge the adequacy of the consistence of mortar and grout in proportioning of SCC, minimizing the repetitive trials.