Papers by Mohammed Maslehuddin
Journal of Materials Research and Technology
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As reported in the January issue of Concrete, the Sixth International Conference on Deterioration... more As reported in the January issue of Concrete, the Sixth International Conference on Deterioration and Repair of Reinforced in the Arabian Gulf was held in Bahrain in November 2000. An award of US$10,000 was offered for the best submitted and presented paper. From 55 papers, no clear winner could be established. The prize was shared between Laith Haboubi for his paper Extending boundaries of concrete repair - an electrochemical approach to cost-effective durability, and this present paper from the King Fahd University of Petroleum and Minerals, Saudi Arabia, which has also been trimmed for space.
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This paper reports an experimental investigation conducted to evaluate the durability performance... more This paper reports an experimental investigation conducted to evaluate the durability performance of concrete mixtures prepared utilizing blends of Type I Portland cement (OPC) and natural pozzolans (NPs) obtained from three different sources in Saudi Arabia. The control concrete mixture containing OPC alone as the binder and three concrete mixtures incorporating NPs were prepared keeping water/ binder ratio of 0.4 (by weight), binder content of 370 kg/m3, and fine/total aggregate ratio of 0.38 (by weight) invariant. The compressive strength and durability properties that included depth of water penetration, depth of carbonation, chloride diffusion coefficient, and resistance to reinforcement corrosion and sulfate attack were determined. Results of this study indicate that at all ages, the compressive strength of NP-admixed concrete mixtures was slightly less than that of the concrete containing OPC alone. However, the concrete mixtures containing NP exhibited lower depth of water p...
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This study investigated the effect of alkaline activators - NaOHaq (NH) (NH: 0-16 M) and Na2SiO3a... more This study investigated the effect of alkaline activators - NaOHaq (NH) (NH: 0-16 M) and Na2SiO3aq (NS) (NS/NH: 0-3.5) in the synthesis of silico-manganese fume (SMF) and ground blast furnace slag (BFS) blended alkali-activated mortar (AASB). The use of individual activator was ineffective in producing AASB of sufficient fresh and hardened properties, compared to the synergy of both activators. This may be attributed to incomplete dissolution and condensation of oligomers required for gelation of the binder. An inverse relationship was noted among the fresh properties and the NH concentration or NS/NH ratio. This was influenced by the dissolution and condensation of silicate monomers under polymerization process. The maximum 28-day strength of ~45 MPa, setting time of 60 min and flow of 182 mm was obtained with the use of combined activators (10M-NH and NS/NH=2.5). The combined activators at NS/10M-NH=2.5 constituted SiO2/Na2O, H2O/Na2O and H2O/SiO2 molar ratio of 1.61, 17.33 and 10...
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Journal of Building Engineering
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Construction and Building Materials
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Materials
This present study evaluates the effect of silica modulus (Ms) and curing temperature on strength... more This present study evaluates the effect of silica modulus (Ms) and curing temperature on strengths and the microstructures of binary blended alkali-activated volcanic ash and limestone powder mortar. Mortar samples were prepared using mass ratio of combined Na2SiO3(aq)/10 M NaOH(aq) of 0.5 to 1.5 at an interval of 0.25, corresponding to Ms of 0.52, 0.72, 0.89, 1.05 and 1.18, respectively, and sole 10 M NaOH(aq). Samples were then subjected to ambient room temperature, and the oven-cured temperature was maintained from 45 to 90 °C at an interval of 15 °C for 24 h. The maximum achievable 28-day strength was 27 MPa at Ms value of 0.89 cured at 75 °C. Samples synthesised with the sole 10 M NaOH(aq) activator resulted in a binder with a low 28-day compressive strength (15 MPa) compared to combined usage of Na2SiO3(aq)/10 M NaOH(aq) activators. Results further revealed that curing at low temperatures (25 °C to 45 °C) does not favour strength development, whereas higher curing temperature ...
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Materials
This paper presents the outcome of work conducted to develop models for the prediction of compres... more This paper presents the outcome of work conducted to develop models for the prediction of compressive strength (CS) of alkali-activated limestone powder and natural pozzolan mortar (AALNM) using hybrid genetic algorithm (GA) and support vector regression (SVR) algorithm, for the first time. The developed hybrid GA-SVR-CS1, GA-SVR-CS3, and GA-SVR-CS14 models are capable of estimating the one-day, three-day, and 14-day compressive strength, respectively, of AALNM up to 96.64%, 90.84%, and 93.40% degree of accuracy as measured on the basis of correlation coefficient between the measured and estimated values for a set of data that is excluded from training and testing phase of the model development. The developed hybrid GA-SVR-CS28E model estimates the 28-days compressive strength of AALNM using the 14-days strength, it performs better than hybrid GA-SVR-CS28C model, hybrid GA-SVR-CS28B model, hybrid GA-SVR-CS28A model, and hybrid GA-SVR-CS28D model that respectively estimates the 28-da...
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European Journal of Environmental and Civil Engineering
Different treatment strategies have been explored in a quest to improve the properties of recycle... more Different treatment strategies have been explored in a quest to improve the properties of recycled aggregate concrete (RAC). The improvement strategies are directed towards the removal of residual ...
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Construction and Building Materials
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Measurement, 2020
Corrosion initiation time of embedded steel is an important service life parameter, which depends... more Corrosion initiation time of embedded steel is an important service life parameter, which depends on concrete material make-up, exposure environment, and duration of exposure. Early and accurate determination of corrosion initiation time will aid in designing durable reinforced concrete, saves cost and time. This study leveraged on the power of ensemble machine learning by combining the performances of different models in estimating the corrosion initiation time of steel embedded in self compacted concrete using corrosion potential measurement. The concrete specimens were prepared with limestone powder as supplementary addition to Portland cement and was exposed to 5% sodium chloride in accordance with the requirements of ASTM C876-15 for 8 months. During the exposure, corrosion potential of the embedded steel was measured, and the recorded datasets were used in training five different machine learning models. With cement, limestone powder, coarse aggregate, fine aggregate, water an...
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Structural Concrete
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Journal of Sustainable Cement-Based Materials
The strength, pore structure, morphology and mineralogical composition of hydration products of n... more The strength, pore structure, morphology and mineralogical composition of hydration products of natural pozzolan (NP) and nanosilica (nSiO2) based alkali activated binder (AAB) were examined. It was noted that AAB without nSiO2 was relatively porous with the presence of micro-, meso- and macro-level pores. In contrast, as the proportion of nSiO2 increased in the mixture, the pore structure started to refine with a reduction in the pore volume due to transformation of source material to polymeric compound, such as C-A-S-H with a higher Al absorption in the binder structure. The incorporation of 5% and 7.5% nSiO2 resulted in the refinement of the pore structure due to enhanced polycondensation. Consequently, there was considerable improvement in the mechanical properties. The experimental data indicated that the pore structure evaluation through NMR has served as a tool to understand the relation between the micro- and macro-level performance of the developed AAC.
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Arabian Journal for Science and Engineering
In the reported study, the effect of slag content and curing methods on the strength development ... more In the reported study, the effect of slag content and curing methods on the strength development of alkaline activated (AA) silico-manganese fume (SiMnF (S)) and ground granulated blast furnace slag (GBSF (G)) blended mortar using NaOHaq and Na2SiO3aq was studied. The mixtures were prepared with 100% SiMnF (AAS100G0), i.e. control binder or 70% SiMnF plus 30% GBFS (AAS70G30), i.e. optimum binder and subjected to room-curing (CR) (25±2 °C) and heat-curing (CH) (60 °C for 24 h in oven) were examined. The raw materials and binders were characterized, while flow and compressive strength of mortar was evaluated. A linear increase in strength was noted in the room-cured specimens, regardless of binder type. The 3-day strength (42.6 MPa) of heat-cured AAS70G30CH specimens was 189 and 97% of the 3-day and 28-day strength, respectively, of room-cured specimens. However, a curing temperature beyond room-temperature did not favour the reaction of AAS100G0 system due to high Mn/Ca ratio and carbonation. It is postulated that the addition of 30% GBFS contributed to the strength and stability in the development of AASG mortar. Heat-curing of AAS70G30CH resulted in highest early-age strength due to dense microstructure induced by conspicuous embedment of Ca ions to the skeletal framework thereby increasing the amorphousity of the binder.
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Construction and Building Materials
Abstract In the present work, an experimental investigation was carried out to evaluate the radia... more Abstract In the present work, an experimental investigation was carried out to evaluate the radiation shielding performance of heavy-weight concrete mixtures prepared using different high-density coarse aggregates that included steel slag, steel shot, and iron ore. Normal-weight limestone aggregate was also used in control mixture as well as for partial replacement of the high-density aggregates in some of the heavy-weight concrete mixtures. Considering different combinations of the normal and high-density coarse aggregates and keeping cement content and water/cement ratio constant, a total of nineteen heavy-weight concrete mixtures were prepared and tested for their dry-density, compressive strength, and nuclear radiation response through gamma-ray intensity measurement. Except the control mixture containing normal-weight limestone aggregate, all eighteen heavy-weight concrete mixtures achieved 28-day dry unit weight in the acceptable range of 2600–3563 kg/m 3 . The compressive strength of the mixtures varied in the range of 26–45 MPa, all satisfying the requirements of a structural concrete. Radiation shielding performance was influenced by the unit weight of the concrete mixtures regardless of the type of coarse aggregates and the strength class of the concrete mixture. Based on the experimental data, correlations between indicator of the radiation shielding performance and unit-weight of concrete was obtained with a high degree of fit.
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Journal of Testing and Evaluation
This article presents the results of an experimental study conducted to assess the effect of sust... more This article presents the results of an experimental study conducted to assess the effect of sustained elevated temperature on the mechanical properties of ultrahigh performance concrete (UHPC). UHPC mixtures were prepared with four different dosages of polypropylene (PP) fibers, and each mixture was exposed to a sustained pre-spalling elevated temperature of 300°C for five durations. The experimental data indicate that the used PP fibers were effective in providing sufficient strength and ductility to UHPC mixtures at room temperature. However, the PP fibers ceased to function as reinforcement in UHPC specimens that were exposed to the elevated temperature for 60 minutes. With an increase in the exposure period after melting of the fibers, the specimens exhibited a brittle mode of failure accompanied with an enhancement in the compressive strength and compressive modulus of toughness and a reduction in the modulus of elasticity and flexural strength. The significance of two variables (exposure duration and fiber content) was evaluated, and correlations between the mechanical properties and selected parameters were obtained by conducting a statistical analysis of the experimental data.
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Construction and Building Materials
Abstract Development of alkali-activated binder (AAB) is fast becoming a viable alternative to or... more Abstract Development of alkali-activated binder (AAB) is fast becoming a viable alternative to ordinary portland cement (OPC). However, key engineering properties of such a binder depend strongly on the chemical composition and fineness of the source materials in addition to the concentration of alkaline activators. In order to improve the reaction kinetics and subsequently, the mechanical strength of alkali activated concrete (AAC), nano-SiO2 was proposed as a partial replacement to natural pozzolan (NP) in this study. As the composition of alkaline activators also plays a vital role on the properties of AAC, trial mixtures were prepared with varying sodium silicate to sodium hydroxide (SS/SH) ratio. Subsequently, NP was partially replaced with nano-SiO2 in the selected mix to enhance the properties further. Fresh properties, such as, setting time of alkali-activated pastes (AAP) and the workability in terms of flow of mortar were determined. Evolution of compressive strength of concrete cured at 60 °C was monitored. Scanning electron microscopy (SEM) and X-ray diffration (XRD) were utilized to determine the morphology and mineralogy of the AAP, respectively. In addition, FTIR was used to identify functional groups formed in the AAP. The study reveals that a SS/SH ratio of 2.5 was suitable in achieving superior strength. AAC prepared using NP and nano-SiO2 exhibited improved strength and microstructural characteristics. However, 5% nano-SiO2 showed significant enhancement in the compressive strength and microstructural characteristics as compared to those prepared with other replacement levels. Consequently, the results of this study provides important information on developing NP-based sustainable building material with remarkable enhancement in the properties by adding nano-SiO2.
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The durability performance of palm oil fuel ash engineered alkali-activated cementitious composit... more The durability performance of palm oil fuel ash engineered alkali-activated cementitious composite (POFA-EACC) mortar exposed to different acid solutions is assessed in this study. 50 mm cubic specimens used for the study were prepared from 100% POFA, alkali-activator (Na 2 SiO 3(aq) /NaOH (aq)) ratios of 2.5, different molarities (10, 12 and 14 M) of NaOH (aq) and 2% volume fraction of polyvinyl alcohol (PVA) fibres. Specimens were exposed to 10% H 2 SO 4(aq) , 10% HNO 3(aq) and 10% HCl (aq) at pH of 0.56, 0.52 and 0.42 respectively for 3, 6 and 9 months, with unexposed specimens as control. Small changes in compressive strength were identified with POFA mortar specimens during exposure to H 2 SO 4(aq) , while exposure to HNO 3(aq) and HCl (aq) greatly reduced the strength of the POFA mortar specimens. The results were supported through microstructural examinations using SEM, while the characterization was done using XRD and FTIR. The high resistance of POFA-EACC mortar to H 2 SO 4...
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Proceedings of the Institution of Civil Engineers - Construction Materials
Palm oil fuel ash (Pofa) and polyvinyl alcohol fibres were used to make an alkali-activated cemen... more Palm oil fuel ash (Pofa) and polyvinyl alcohol fibres were used to make an alkali-activated cementitious composite mortar, which was then tested. Based on the test results, a support vector regression model was developed to estimate the effect of the alkaline activator/Pofa ratio on early compressive strength at different added water contents. The results from the model show that the mortar strength increased as the sodium silicate+sodium hydroxide/Pofa ratio increased up to an optimum, after which the strength declined considerably. The sodium hydroxide molarity and added water were also found to have a significant effect on strength. Excellent agreement was found between the model results and test results. The precision and accuracy of the developed model show its potential for reducing the challenges of acquiring experimental data.
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Papers by Mohammed Maslehuddin