15 research outputs found
Effects of metakaolin on compressive strength and permeability properties of pervious cement concrete
No full textThis paper presents the experimental results on the effect of metakaolin (MK)
as a replacement of cement in pervious cement concrete based on
compressive strength, void ratio and permeability test. Metakaolin was used
to replace Portland Cement Composite (PCC) in pervious concrete by 10%
(by wt.). The results show that pervious concrete sample containing 10%
metakaolin with 1% superplasticizer exhibited 4 times higher compressive
strength at 7 days when compared to normal cement concrete. In addition,
the continuous voids of 10%MK concrete sample was found higher than PCC
only, indicating the effectiveness of metakaolin in improving the interfacial
bond of the binders due to micro-filler effect of metakaolin and the additional
CSH gel formation. The continuous voids of pervious concrete with 10% MK is
17%, which is higher than the percentage of continuous voids in normal
pervious concrete. This finding is also supported by the infiltration rate of
concrete samples. Furthermore, the microstructure analysis through
Backscattered Electron Imaging and X-Ray Diffraction reported denser matrix
and CH reduction in polished paste samples due to 10%MK addition
Properties of ultra-high-performance mortar containing eco-friendly wollastonite micro-fibers for green and sustainable infrastructure
No full textWollastonite has become one of the potential pozzolanic microfibers material that can be used to improve the characteristics of cement-matrix composites. This study was conducted with the aim to investigate experimentally the properties of high-strength mortar containing wollastonite as an additive material with percentage of 1.2, 2.4, 4.8, and 9.6% by weight of binders. Water and sand to binder ratio of 0.2 and 2.5, respectively, were used to form high-strength mortar specimens for mechanical properties testing including compressive strength and three-point loading on flexural strength test. Microstructural analysis was also conducted to assess the reinforcing effects and hydration products that might be affected due to the inclusion of wollastonite micro-fibers. The results show that mortar with 1.2-4.8% of wollastonite content reached 12% higher resistance on compression load with respect to the control mortar. More significant improvement can be observed in flexural strength results whereas the wollastonite showed its reinforcing capability in bridging the micro-cracks resulted in more ductile and toughness matrix in carrying the high load carrying capacity. Moreover, wollastonite also has a capability to pore refinement as evident from the sorptivity results. Furthermore, wollastonite micro-fibers can be an alternate source material for durability improver that leads to sustainable infrastructure
Effects of different size of fly ash as cement replacement on self-compacting concrete properties
Get PDFThis paper aims to investigate experimentally the influence of replacing cement with different fineness of fly ash based on flowability, passing ability, compressive strength, tensile strength (splitting). Concretes with 15% fly ash (passed a number 100 sieve) and fine fly ash (passed a number 200 sieve) as cement replacement were cast and tested at 7, 14, 28 days after water curing. A superplasticizer in the form of viscocrete 3115 N was constantly used for each concrete mixtures as much as 1% by weight of cement. The results show that the use of fly ash does not significantly increased the compressive strength and tensile strength of SCC mixtures. However, concrete with 15% fine fly ash its self and combined 7.5% fly ash with 7.5% fine fly ash show better flowability and passing ability when compared to concrete with cement only indicating the performance of using smaller particle sizes of fly ash could lead better properties of SCC that can be potentially used for building construction application
Effects of Coconut Sawdust on Mechanical Properties and Porosity of Concrete Mixtures
Get PDFThe presence of coconut sawdust in North Sulawesi is very potential to be utilized as an alternative material for application in construction field. This paper aims to investigate experimentally the effect of coconut sawdust as an addition on concrete mixtures based on compressive strength, flexural strength and volume permeable voids tests. In this study, coconut sawdust with percentage of 2.5%, 5% and 7.5% by weight of cement was added into concrete mixture. The results show that concrete containing 5% of coconut sawdust exhibited highest compressive strength at 7 days with average value is 25.71 MPa while at 28 days the compressive strength is 30.50 MPa and there is no significant difference compared with 2.5% variation. When comparing the results of flexural strength test between 5% and normal cement concrete, the highest result is achieved by normal concrete reaching the value 6.78 MPa while for the concrete with 5% of coconut sawdust addition is only on 4.82 MPa. In terms of the volume of permeable voids, the results show that the porosity of concrete with coconut sawdust increased with the increase of percentage of coconut sawdust at 7 days but the values decreased as the age of curing increased
PENGARUH SUPERPLASTICIZER POLYMER TERHADAP KUAT TEKAN BETON MUTU TINGGI
Get PDFIn construction field, the use of high performance concrete is essential for pre-cast and pre-stress concrete production where the addition of chemical admixture was found effectively contributes in strength. This research presents the results of using Superplasticizer polymer type Ligno C-165 in making high strength concrete. The percentage use of this material is 0.25%, 0.5%, 0.75%, 1%, 1.25% and 1.5% by weight of cement. The concrete samples were tested at the age of 3, 7, 14, 21 and 28 days after water curing. The results show that the addition of 1.5% SP increased the strength of concrete at 28 days with strength value of 64.97 MPa or 166.08% stronger than the target strength of f”™c=40 MPa. This is an indication that the increase of Superplasticizer polymer type Ligno C-165 dosage in concrete will also increases the strength that can be due to the effect of SP in reducing the water content that may produces denser matrix concrete with less volume of voids resulted in improving the properties of high strength concrete. From the results, the application of this mixture proportions could be used for producing building construction elements in the field of civil engineering
Compressive and Flexural Strength Behavior of Ultra-high Performance Mortar Reinforced with Cellulose Nano-fibers
Get PDFCellulose fibers, because of their chemical and physical characteristics, are compatible with other materials to be used for the production of building components. This paper presents the influence of using cellulose nano fibers (CNFs) made from plant-derived cellulose as a reinforcement in ultra-high performance (UHP) mortar. In this study, the dispersion method of CNFs using manual and mechanical mixing was also observed. The effects of different dosage of CNFs, namely, 0.005%, 0.01% and 0.015% by wt. of binders (premixed low-heat cement and silica fume) with a constant waterto binder ratio of 0.15, were evaluated based on the compressive and flexural strengths at the seventh day after steam curing. Results show that the highest compressive strength value of 184MPa was reached by UHP mortar sample containing 0.005% CNFs by wt. of binders. However, addition of more CNFs content up to 0.015% did not result in further improvement. Based on load-CMOD curves, UHP mortar reinforced with 0.005% CNFs was found most effective in enhancing the energy absorption capacity and toughness index with flexural strength at peak load of 14.44MPa (36% higher than control UHP mortar). The results indicate the well-post crack behavior of CNFs mortars in comparison with control UHP low-heat cement mortar. Moreover, Scanning Electron Microscopy (SEM) analysis shows that the phenomenon of bridging effect of CNFs could not be significantly detected since the short fiber might be fractured under loading due to less bonding. Furthermore, this study concludes that even a low volume fraction, i.e 0.005%, of CNFs is very sufficient in increasing the ductility of ultra-high performance mortar
Performance of Cement Mortar Containing Micro and Ultrafine Metakaolin Binders
Get PDFResearch into the usage of locally available construction material is essential and beneficial in ensuring a cost-effective construction project. One of the natural resources that be used as supplementary cementitious material is metakaolin. This research aims to investigate the performance of mortar reinforced with micro- and ultrafine metakaolin based on compressive strength and water absorption tests. Locally sourced metakaolin was mixed in cement mortar after calcined at 800ï‚°C with a variation amount of 0%, 5%, and 10% by wt. The tests were conducted on the 50mmx50mmx50mm cube specimens after water curing at 7 and 28 days, following the ASTM-standards. Results show that specimens containing 10% of micro- and ultrafine-metakaolin (MK-10 and UM-10) exhibited the highest compressive strength and better water-resistance characteristics when compared to control mortar. In this case, the addition of 10% ultrafine metakaolin (UM-10) reached the highest compressive strength value with approximately 121% and 100% higher than the compressive strength of control mortar on the 7th and 28th day, respectively. Additionally, the water absorption of UM-10 at 28 days was found to be 86% and 30% lower than PCC and MK-10, respectively. Furthermore, X-Ray Diffraction (XRD) and Thermogravimetric graphs of pastes with micro- and ultrafine-metakaolin indicate a reduction of CH; therefore, the production of more CSH gel. The densification of cement paste with ultrafine-metakaolin is also confirmed by nitrogen adsorption analysis indicating ultrafine-metakaolin's inert filler effect in forming a denser matrix
Malawi national bibliography : list of publications deposited in the library of the National Archives of Malawi. 1997 -2001 edition
No full textEmpirical analyses of the length, weight, and condition of adult Atlantic salmon on return to the Scottish coast between 1963 and 2006
Get PDFSea age, size, and condition of adult Atlantic salmon (Salmo salar) are prime determinants of individual, and hence population, productivity. To elucidate potential mechanisms, 151 000 records of salmon returning to six Scottish coastal sites over 44 years were analysedfor length, weight, and condition, by site, sex, sea age, and river age. After correcting for capture effort biases, all sites showed seasonal increases in length and weight for both 1 sea winter (1SW) and 2SW fish. However, whereas condition increased slightly with season for 2SW, it decreased notably for 1SW. Sites showed common decadal trends in length, weight, and condition. Within years, length and weight residuals from trends were coherent across sites, but residuals from condition trends were not. Rates of seasonal condition change also showed decadal trends, dramatically different between sea ages, but common across sites within sea-age groups. Longer salmon were disproportionately heavy in all seasons. 1SW condition was markedly lower in 2006. Detrended correlations withoceanic environmental variables were generally not significant, and always weak. A published correlation between the condition of 1SW salmon caught at a single site and sea surface temperatures in the Northeast Atlantic could not be substantiated for any of the six fisheries over the wider time-scales examined
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On stage at the theatre of state: the monuments and memorials in Parliament Square, London
No full textThis thesis concerns Parliament Square in the City of Westminster, London. It is situated to the west of the Houses of Parliament (or New Palace at Westminster) and to the north of St. Margaret’s Church and Westminster Abbey. This urban space was first cleared at the start of the nineteenth-century and became a “square” in the 1860s according to designs by Edward Middleton Barry (1830-80). It was replanned by George Grey Wornum (1888-1957) in association with the Festival of Britain (1951). In 1998 Norman Foster and Partners drew up an (as yet) unrealised scheme to pedestrianise the south side closest to the Abbey
