Hashim Abdul Razak | University of Malaya, Malaysia (original) (raw)

Papers by Hashim Abdul Razak

Cement and Concrete Research, 2005

The concept of efficiency can be used for comparing the relative performance of various pozzolans... more The concept of efficiency can be used for comparing the relative performance of various pozzolans when incorporated into concrete. In this paper, an alternative approach for the evaluation of efficiency factor k of a pozzolanic material has been introduced. The method, developed following Abram's strength-W/C ratio rule, calculates efficiency in terms of relative strength and cementitious materials content. The advantage of this method is that only two mixtures are required to determine the k factor of a specific mixture. A laboratory investigation on silica fume (SF) and metakaolin (MK) concrete found that the computed efficiency factors varied with pozzolan type, replacement level and age. At 28 days, the k values ranged from 1.6 to 2.3 for MK and 2.1 to 3.1 for SF mixtures, while at 180 days, the k values varied from 1.8 to 4.0 for MK and 2.4 to 3.3 for SF mixtures. Generally, the k factors increased with age but declined with higher pozzolanic content. It was also observed that change in W/CM ratio from 0.33 to 0.27 did not significantly affect the resultant efficiency factors. © 2004 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S000888460400242X
http://ac.els-cdn.com/S000888460400242X/1-s2.0-S000888460400242X-main.pdf?_tid=bd7a69b8-7820-11e3-868e-00000aacb360&acdnat=1389156956_b3c258306027f97b5631be2a0618449f

Advanced Science Letters, 2012

For deep-water oil and gas exploration, spar platform is considered to be the most economic and s... more For deep-water oil and gas exploration, spar platform is considered to be the most economic and suitable floating offshore structure. Analysis of spar platform is complex due to various nonlinearities such as geometric, variable submergence, varying pretention, etc. The Finite Element Method (FEM) is an important technique to deal with this type of analysis. However, FEM is computationally very expensive and highly time-consuming process. Artificial Neural Network (ANNs) can provide meaningful solutions and can process information in extremely rapid mode ensuring high accuracy of prediction. This paper presents dynamic response prediction of spar mooring line using ANN. FEM-based time domain response of spar platform such as surge, heave and pitch is trained by ANN. Mooring line top tension is predicted after 7200 sec (2 hours) of wave loading. The response obtained using ANN is validated by conventional FEM analysis. Results show that ANN approach is found to be very efficient and it significantly reduces the time for predicting long response time histories. Thus ANN approach is recommended for efficient designing of floating structures. © 2012 American Scientific Publishers. All rights reserved.

www.ingentaconnect.com/content/asp/asl/2012/00000014/00000001/art00033
http://www.ingentaconnect.com/content/asp/asl/2012/00000014/00000001/art00033?token=0055134ed587e2a46762c6b795d76766c25443a2b5f7b673f7b2f267738703375686f492388928b81ab5d

12th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC12, 2011

The effects of far distant earthquakes felt in regions with low and moderate seismicity has incre... more The effects of far distant earthquakes felt in regions with low and moderate seismicity has increased markedly over the last decade. Henceforth fragility curves in this study are to indicate whether buildings are safe to enter or not after an earthquake event occurring more than 300km away. The probability of light, moderate and severe damage states occurring on two and four storey reinforced concrete buildings up to a peak ground acceleration of 0.2g were predicted. The building models were constructed using finite element software based on eight node brick elements with three degrees of freedom at each node. The analysis was carried out using a dynamic response spectrum to calculate the peak inter-storey drift ratios. For the development of fragility curves, the results were collated following a log-normal mean distribution. The results showed that light damage is likely to occur with a probability of over 10% within a 50 year period, while the existing record is unlikely to cause structural damage. The fragility curves were comparable to those for RC moment resisting frames obtained by (Rossetto and Elnashai 2003) at a lower drift limit, with approximately 2% of inter-storey drift ratio.

http://www.sciencedirect.com/science/article/pii/S1877705811013531

Construction and Building Materials, 2012

In this investigation 12 mortar mixes including three groups were prepared using binder contents ... more In this investigation 12 mortar mixes including three groups were prepared using binder contents 380 and 500 kg/m 3. All the specimens were cured after casting and demoulding in curing regimes, i.e. at room temperature (ac) and in water (wc). The highest strength was obtained for cement-slag mortars 380-wc at later ages as 80 MPa. For all groups of mortars, there could rarely be strength loss at later ages. It was observed that in duration of 3-7 days, wc is the optimum for all groups of mortars with exception of cement mortar 500 and slag mortar 500. In duration of 28-90 days, wc is also the optimum for three groups of mortars with exception of cement mortar 500. It was revealed that an exponential relationship exists between the strengths obtained in air and water curing conditions for each group of mortar, i.e. with and without using ground granulated blast furnace slag. It was proved that higher strengths could be obtained using lower binders' contents for cement and cement-slag mortars provided the specimens were cured in water. This is a new finding having importance from economic and environmental viewpoints; meaning that for producing higher strengths it is not a necessity to use more binders. It was found that increase in level of cement and slag makes the mortars more sensitive to air curing conditions. © 2012 Elsevier Ltd. All rights reserved.

www.sciencedirect.com/science/article/pii/S0950061811007355
http://ac.els-cdn.com/S0950061811007355/1-s2.0-S0950061811007355-main.pdf?_tid=26025898-7820-11e3-9063-00000aacb35d&acdnat=1389156702_b93082424e6b2ed0826f2509178dce76

Construction and Building Materials, Jan 1, 2011

This paper compares three methods for activation of OPC-slag mortars (OSM): (1) prolonged grindin... more This paper compares three methods for activation of OPC-slag mortars (OSM): (1) prolonged grinding of binders (mechanical method), (2) elevated temperature curing of mortars (thermal method), and (3) use of chemical activators such as NaOH, KOH, and Na2SiO3, 9.35H2O (chemical method). The proper reactivity of OSM was evaluated using a mixture of 50% OPC and 50% slag. Early and ultimate strengths were compared. All three activation methods accelerated both the slag reaction and strength development rates. However, the chemical method did not show a significant effect on the ultimate strength, while thermal activation increased the early strength by 3 days. Mechanical activation increased the early strengths of the mortar significantly, but about 6% strength loss occurred in the ultimate strength. Although, the application of mechanical and thermal activation methods needs extra equipment and energy, due to more significant of strength improvement; based on current test results, it can be said that mechanical activation is the most efficient and feasible method for the activation of OSMs. © 2010 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0950061810003090
http://ac.els-cdn.com/S0950061810003090/1-s2.0-S0950061810003090-main.pdf?_tid=1f70136c-7820-11e3-8df9-00000aacb362&acdnat=1389156691_598fed59ba988ef24a61b55479cb6ea7

Materials & Design, Feb 1, 2011

Activation methods and curing regimes have crucial effects on the strength of mortars and concret... more Activation methods and curing regimes have crucial effects on the strength of mortars and concretes. The objective of this investigation is to examine the early and later compressive strength of activated ordinary Portland cement (OPC)-ground granulated blast-furnace slag (GGBFS) mortars and identify the most effective activation technique. The methods of activation used were thermal, mechanical and thermal-mechanical combined. Two curing regimes were adopted and five groups of mortars were prepared. It was observed that OPC-GGBFS mortars have greater sensitivity to OPC mortars against the curing regimes. However, the study revealed that there was no particular activation method which when used gave the best results for both early and later strengths and did not cause strength loss. It also proved that the most effective activation method for early strength is a combination of both the thermal and mechanical, while for later strengths, none of the activation methods was recommended. © 2010 Elsevier Ltd.

http://www.sciencedirect.com/science/article/pii/S026130691000525X
http://ac.els-cdn.com/S026130691000525X/1-s2.0-S026130691000525X-main.pdf?_tid=1229bb4a-7820-11e3-8e47-00000aacb361&acdnat=1389156669_c78b476f13a6d3bb40a13b23d78b741e

Construction and Building Materials, Apr 1, 2011

Curing techniques and curing duration have crucial effects on the strength and other mechanical p... more Curing techniques and curing duration have crucial effects on the strength and other mechanical properties of mortars. Proper curing can protect against moisture loss from fresh mixes. The objective of this experimental work is to examine the compressive strength of ordinary Portland cement mortars (OMs) under various curing regimes and cement fineness. Six different curing methods including water, air, water heated, oven heated, air-water, and water-air were applied to the specimens and also six groups of mortars were used. The results showed that the highest and lowest compressive strengths are attributed to the specimens of OPC mortar water cured using grounded OPC for duration of 6 h (OM-G6-wc) and OPC mortar air cured under room temperature with oven heated after demoulding of the specimens at 60 °C for duration of 20 h (OM-OH-ac), respectively. The maximum levels obtained of compressive strengths at 7, 28, and 90 days are 57.5, 70.3, and 76.0 MPa, respectively. © 2010 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0950061810005738
http://ac.els-cdn.com/S0950061810005738/1-s2.0-S0950061810005738-main.pdf?_tid=09f98766-7820-11e3-9d0a-00000aacb35f&acdnat=1389156655_7805547d3ec55afc3716f2e77b5b146c

Construction and Building Materials, Oct 1, 2010

Although the use of slag has many benefits, its low hydration at early stages causes the strength... more Although the use of slag has many benefits, its low hydration at early stages causes the strength to be low. Hence, the uses of slag are restricted, even before it needs to be activated. In this investigation, a chemical method was used to activate the ordinary Portland cement-slag mortars (OSM). 37 OSM were used, 4 of them as control. All mix designs were made by W/B = 0.33, S/B = 2.25, and with 0%, 30%, 40%, 50%, and 60% levels of slag. The activators; sodium hydroxide, potassium hydroxide, and sodium silicate have been used. Whenever the activators were used alone, the highest effect was obtained by sodium silicate and the lowest for sodium hydroxide. It was determined that the effects of the combined activators are better than that of an individual one. It was observed that strength loss for some mixes, at long ages, is determined by some factors, such as level of slag used, type and dosage of alkali activators, and curing regimes. © 2010 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0950061810001261
http://ac.els-cdn.com/S0950061810001261/1-s2.0-S0950061810001261-main.pdf?_tid=037aee7a-7820-11e3-91fd-00000aab0f26&acdnat=1389156644_0a6299272577efa3436bc0823103770b

Asian Journal of Civil Engineering, 2010

The use of high strength concrete (HSC) has been studied for many years in developed and developi... more The use of high strength concrete (HSC) has been studied for many years in developed and developing countries. Although, HSC has a few disadvantages, it has many advantages. The concrete with compressive strength (CS) levels in the range of 50 to100 MPa, is called HSC. The most important property of HSC is 28-day CS as a criterion. Sometimes due to time limitations and construction project problems, estimation of 28-day CS based on 7-day CS can be useful. Based on many experimental tests and analysis of the results, three sets of equations are determined with ANN and Regression techniques are compared and the best is recommended. © 2009 by DotNetNuke Corporation.

www.bhrc.ac.ir/portal/Portals/2/pdf/asian%20jornal/APRIL%202010/Sajedi-5.pdf

Materials & Design, 2010

Thirty one mix proportions of ordinary Portland cement (OPC)-slag mortars (OSM) used to study the... more Thirty one mix proportions of ordinary Portland cement (OPC)-slag mortars (OSM) used to study the effects of temperature on early and ultimate strengths. Three levels of slag (0%, 40%, and 50%) and different temperatures were used; it was found that 50% is the optimum level and 60°C with 20. h duration is also optimum. The maximum strengths obtained of optimum mortar, at 3 and 7. days, for specimens cured in the air, are 55.00 and 62.00. MPa, respectively. These strength levels are 64.50% and 66.50% greater than those without heating. The results show for 0 and 2. h heating time, the strength of specimens cured in the water are greater than those cured in the air, but for 4-26. h, this statement is reversed. This is a novelty, is very important in the precast industry and has many advantages for arid regions to overcome curing of concrete structures. © 2010 Elsevier Ltd.

http://www.sciencedirect.com/science/article/pii/S0261306910002220
http://ac.els-cdn.com/S0261306910002220/1-s2.0-S0261306910002220-main.pdf?_tid=4b495f20-7820-11e3-8de5-00000aacb361&acdnat=1389156764_49f8a0a270b4c08c72a8f2afdc01e44d

DOI 10.1016/j.cemconres.2004.05.040, Apr 1, 2005

A mathematical model is presented for estimating compressive strength of high-strength concrete i... more A mathematical model is presented for estimating compressive strength of high-strength concrete incorporating pozzolanic materials, based on the strength of a control ordinary Portland cement (OPC) concrete made with similar mixture characteristics and curing history. In this study, metakaolin (MK) and silica fume (SF) were used as cement replacement materials at 5%, 10%, and 15% by mass. Water/cementitious materials (w/cm) ratios varied from 0.27 to 0.33, and strength testing was conducted up to an age of 180 days. It was found that the strength of a pozzolanic mixture could be related to the strength of its equivalent control by a linear function. Key parameters involved in the model are the pozzolanic and dilution factors, which can be correlated to the pozzolan content in the mixture. The study concludes that the accuracy of the model increases with concrete age. At ages 28 days and above, 97% of the estimated strengths are within ±5% of the actual value. © 2004 Elsevier Ltd. All rights reserved.

www.sciencedirect.com/science/article/pii/S0008884604002431
http://ac.els-cdn.com/S0008884604002431/1-s2.0-S0008884604002431-main.pdf?_tid=e31e0e6e-781f-11e3-a67d-00000aacb361&acdnat=1389156590_3902df83d3e76ecf10573f064c38f96f

Proceedings of the International Modal Analysis Conference - IMAC, 2001

This paper describes the detection and identification of cracking severity in a reinforced concre... more This paper describes the detection and identification of cracking severity in a reinforced concrete beam using modal data. Experimental modal test was performed on the beam before and after application of load of increasing intensity to induce a single crack at a fixed location. Modal parameters extracted were categorised into two groups, namely local response parameter (mode shape data) and global response parameters. Localised changes such as cracking reduce the stiffness of the structure, and therefore caused a localised change in the discrete function of the mode shape. From a previous research, Laplacian Operator was initially proposed. However, when applied to a non-homogeneous and composite material such as reinforced concrete, the operator was too sensitive and did not yield meaningful results. Hence, a simplified Laplacian operator was suggested. In this investigation, it was found that global response such as natural frequency is a good indicator to detect the occurrence of the deterioration in the structure. However, the local response data such as mode shape was required to detect the defect location accurately and a simplified Laplacian operator worked quite successfully. Furthermore, it was observed that the higher frequency modes tend to detect the occurrence of cracking in the earlier stages.

http://www.sem.org/Proceedings/ConferencePapers-Paper.cfm?ConfPapersPaperID=26695

Materials & Design, Sep 1, 2011

Thirty-eight mix proportions of ordinary Portland cement-slag mortars (OSMs) were used to study t... more Thirty-eight mix proportions of ordinary Portland cement-slag mortars (OSMs) were used to study the effects of temperature and relative humidity on strength. Three levels of slag (0%, 40%, and 50%) and different temperatures were used; the 50% level and heat curing of 60 °C for duration of 20. h were found to be the optimum. The optimum mortar's strength at 3 and 7. days for the specimens cured in air were 55.0 and 62.0. MPa, respectively. The results show that for durations of 4-26. h, the strength of specimens cured in air is greater than those cured in water. This is a novelty with major advantages in arid areas. It was proved that more ettringite production at early ages resulted in higher early strengths. Comparison of curing regimes with different temperatures and the same relative humidity or different relative humidity and the same temperatures showed that higher strengths are attributed to higher temperatures and lower relative humidity, respectively. © 2011 Elsevier Ltd.

http://www.sciencedirect.com/science/article/pii/S0261306911003074
http://ac.els-cdn.com/S0261306911003074/1-s2.0-S0261306911003074-main.pdf?_tid=cf7886fa-781f-11e3-aff7-00000aacb362&acdnat=1389156557_dee611520f2b3bdf24a0177163ea4af3

Arabian Journal for Science and Engineering, Oct 1, 2010

This paper reports the details of investigations carried out to study the performance of industri... more This paper reports the details of investigations carried out to study the performance of industrial waste incineration bottom ash and refined kaolin to produce controlled low-strength material (CLSM). CLSM mixes were designed with varying amounts of incineration bottom ash, refined kaolin, and cement. Water content was adjusted to get sufficient flowability. Tests for density, stiffening time, bleed, settlement, sorptivity, water absorption, moisture content, California bearing ratio, initial surface absorption, and compressive strength were carried out on the CLSM mixtures. Study for corrosivity and leaching of heavy metals and salts on the bleed and leachate were also performed. The compressive strength of CLSM tested ranged from 0.36 to 4.40 MPa. CBR values ranged from 10 to 46 and ISAT values at 1 hour from 0.56 to 4.76 ml/m2/s. None of the heavy metals tested exceeded the threshold limits in leachate. Addition of kaolin controls the compressive strength development, and reduces initial surface absorption, California bearing ratio, and water absorption values. It is shown that the incineration bottom ash, along with refined kaolin, can be successfully employed in CLSM, thereby contributing to sustainability in civil engineering practice.

ajse.kfupm.edu.sa/articles/352B%20p.05.pdf

Journal of Hazardous Materials, Dec 30, 2009

Controlled low-strength material (CLSM) is slurry made by mixing sand, cement, ash, and water. It... more Controlled low-strength material (CLSM) is slurry made by mixing sand, cement, ash, and water. It is primarily used as a replacement for soil and structural fillings. This paper presents the findings of a preliminary investigation carried out on the performance of industrial waste incineration bottom ash as CLSM. CLSM mixes were designed using industrial waste incineration bottom ash, and cement. Tests for density, setting time, bleed, and compressive strength on cubes under various curing conditions, corrosivity, and leaching of heavy metals and salts were carried out on the CLSM mixtures, and the results discussed. Compressive strength for the designed CLSM mixtures ranged from 0.1 to 1.7 MPa. It is shown that the variations in curing conditions have less influence on the compressive strength of CLSM at high values of water to cement ratio (w/c), but low values of w/c influences the strength of CLSM. The CLSM produced does not exhibit corrosive characters as evidenced by pH. Leaching of heavy metals and salts is higher in bleed than in leachate collected from hardened CLSM. Cement reduces the leaching of Boron in bleed. It is concluded that there is good potential for the use of industrial waste incineration bottom ash in CLSM. © 2009 Elsevier B.V. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0304389409011893
http://ac.els-cdn.com/S0304389409011893/1-s2.0-S0304389409011893-main.pdf?_tid=be4739c6-781f-11e3-9f12-00000aab0f6b&acdnat=1389156528_7d710042bbe701383e9f7279f1e70f17

British Ceramic Transactions, Aug 1, 2002

Lightweight clay bricks were produced using a chemical cellulation technique from a residual soil... more Lightweight clay bricks were produced using a chemical cellulation technique from a residual soil of high clay content, mostly non-crystalling. The cellulation technique introduces cells into the material during the mixing stage as a result of the chemical reaction between aluminium powder and quicklime, which liberates hydrogen gas. The technique also requires the use of sodium silicate to achieve a proper cellulated structure. The mechanisms of reaction of the abovementioned chemicals with each other as well as with the raw material were investigated. Engineering properties of the fired product, namely compressive strength, bulk density, water absorption, and volumetric shrinkage, were determined and compared with solid bricks prepared in the laboratory. Based on the results of the study, a mechanism for the cellulation process, though complex, is postulated. The process is a combination of chemical reaction between the chemical additives used and the response of the soil to the chemicals or to the reaction products. The study also reveals the possibility of producing lightweight clay bricks, mostly of loadbearing performance, using the residual soil.

http://www.maneyonline.com/doi/abs/10.1179/096797802225003352

Mechanics of Advanced Materials and Structures, Jun 1, 2013

This article attempts to explain the effect of composite action in reinforced concrete (RC) eleme... more This article attempts to explain the effect of composite action in reinforced concrete (RC) elements on the natural frequencies. Natural frequencies are governed by the relationship between the physical properties of RC elements and its composite action. The softening of concrete in tension, compression, and pre- and post-yielding steel behavior are considered. The bonding action between steel and concrete under loading and unloading conditions is also taken into account. The assumption of the increase in stiffness of RC elements in tension due to bond action is investigated by tests on two RC beams. Both static and modal testing were carried out after inducing different levels of damage in the beams. Results show the validity of the assumption made due to composite action. Mode 1 can be an indicator for bond action behavior and for predicting the yield state of steel in the RC beams. Mode 2 behavior is governed by the amount of steel reinforcement, where for maximum steel ratio it will be affected by concrete softening, while for minimum steel ratio it will be affected by both concrete softening and bond action. Modes 3 and higher can be indicators for concrete softening. © 2013 Copyright Taylor and Francis Group, LLC.

www.tandfonline.com/doi/abs/10.1080/15376494.2011.627636
http://www.tandfonline.com/doi/pdf/10.1080/15376494.2011.627636

Building and Environment, Jan 1, 2004

The weatherability of PTFE- and PVC-coated fabrics under tropical climate was evaluated based on ... more The weatherability of PTFE- and PVC-coated fabrics under tropical climate was evaluated based on outdoor exposure test for a period of 2 years. This study is confined to the examination of the surface characteristics of 10 different types of fabric which include dirt repellency, discolouration and coating condition. The results indicate that the dirt repellency of PTFE-coated fabrics is generally more superior. However, the surface treatment for some of the PVC-coated fabrics, do provide excellent dirt repellency as well. Morphological examinations using the scanning electron microscope revealed that cracking and peeling of the coating were more evident on the PVC-coated as compared to the PTFE-coated fabrics. The hot and humid conditions prevalent in a tropical environment were very conducive for the growth of fungi, which adhered on the surface of some of the PVC-coated fabrics. Generally the degree of surface degradation on all the fabrics was more severe due to the much harsher tropical climate in comparison with other exposure tests conducted in the past. © 2003 Elsevier Ltd. All rights reserved.

www.sciencedirect.com/science/article/pii/S0360132303001586
http://ac.els-cdn.com/S0360132303001586/1-s2.0-S0360132303001586-main.pdf?_tid=68dc113c-781f-11e3-8ead-00000aab0f6b&acdnat=1389156385_2e118ad95309b4cec2c4f107a09dd05a

Engineering Structures, 2001

An experimental investigation to study the effect of general corrosion on the modal parameters of... more An experimental investigation to study the effect of general corrosion on the modal parameters of reinforced concrete beams was conducted. The full scale beams were subjected to reinforcement corrosion until an appreciable amount of steel corrosion damage was introduced. The states of damage in the test beams were assessed through measurement of crack width and spalling. Modal tests were performed on the test beams after corrosion damage and the modal parameters extracted were compared against that from a control beam. The results obtained showed changes in the modal parameters especially natural frequencies and damping ratio. The trend in the measured natural frequencies was sensitive to the deterioration state of the beams. Changes in modal damping ratio for the transfer function method and the normal mode method were also observed. However, the changes were inconsistent with the changes in natural frequencies, as concluded by previous researchers, but a trend was obsedved which was rather mode dependent. Furthermore, the load carrying capacity of the beams was determined through static load test and the results were correlated with the state of corrosion damage and changes in the modal parameters. This investigation provides further insight on the use of modal parameters to detect damage in structural concrete elements which can be useful for structural appraisal and assessment purposes when applied to full scale structures. © 2001 Elsevier Science Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S0141029601000050
http://ac.els-cdn.com/S0141029601000050/1-s2.0-S0141029601000050-main.pdf?_tid=6f59f448-781f-11e3-8709-00000aacb35d&acdnat=1389156395_fe9cc521987889353e8edfd6467acda4