Papers by Keyword: Compressive Strength

Abstract: This paper aims to model the effect of density in 7, 14, 28 days on compressive strength of Ultra High Performance Concrete (UHPC) in same compaction and curing conditions by Design of Experiments (DOE) methodology using vary range of 5 variables: Silica fume (SF), Steel Fiber, Cement 42.5, Superplasticizer (SP), and water cemetiotious ratio (w/c).The results shows the significance effect of density on compressive strength of UHPC in different days, The models are valid for the mixes made with 1.0 sand, 0.15-0.30 silica fume amount, 0.70-1.30 cement amount, 0.10- 0.20 steel fiber, 0.04- 0.08 superplasticizer (all values are by sand by weight mass) and 0.18- 0.32 water cementitious ratio.

Abstract: In this paper an attempt has been made to know the effect of Fly Ash (FA) on Roller Compacted Concrete (RCC) properties like strength and abrasion resistance. The Cement was partially replaced by three kinds of replacements (20%, 40% and 60%) of class F Fly Ash. The RCC mixtures were designed to have a 28 days flexural strength of 5.0 N/mm². The specimens were subjected to two types of abrasion resistance tests such as Contabro test and surface abrasion resistance test with rotating cutter besides Compressive and Flexural strength tests. Experimental results shows that the Cantabro loss and surface abrasion loss were increased with increase in Fly Ash content in relation with the strength of roller compacted concrete pavement at the ages from 7days to 180days compared to control mix concrete. Equations were established based on compressive strength and flexural strength which were influenced by cement replacement by Fly Ash and developed to predict abrasion resistance of FRCC at any age. Also a relationship was established between Cantabro loss and surface abrasion loss of FRCC regardless of age and percent replacement of Fly Ash.

Abstract: Sodium silicate bonded and epoxy bonded magnetic NdFeB materials are fabricated, respectively. The magnetic properties, temperature coefficient, heat-corrosion and compressive strength of both bonded magnets are investigated. Results reveal that sodium silicate bonded magnet has a similar comprehensive property to epoxy bonded one. Compared to the epoxy bonded magnets, the sodium silicate bonded NdFeB has better temperature coefficient between 20 and 100 °C. The α value of the sodium silicate bonded NdFeB is-0.127 %/°C while the β value is-0.275 %/°C between 20 and 200 °C. DSC thermogram shows that sodium silicate as a bonder in magnet could exist at a higher temperature (above 1000 °C), which is far bigger than the curie point of NdFeB magnet powder. The weight gains of sodium silicate bonded magnet obtained in heat-corrosion resistance test are smaller than those of epoxy bonded one. Compressive strength test shows that sodium silicate bonded magnet has a larger compressive strength (35 MPa) than that of epoxy bonded magnet (27 MPa). Compared to the epoxy, the sodium silicate as bonder in the bonded magnet shows more compact. As a result, the sodium silicate bonded NdFeB bears better magnetic properties, temperature coefficient, heat-corrosion resistant and compressive strength.

Abstract: Different particle sizes of waste rubber are mixed according to natural fine aggregate gradation to replace the fine aggregate in concrete by weight. And the effect of waste rubber content on performances of concrete mixture, the mechanics, frost resisting, thermal insulation of hardened concrete are studied. The results show that the slump and apparent density of concrete mixture decreases with the increase of waste rubber content. Compressive strength of the hardened concrete also decreases obviously with the increase of waste rubber content and compressive strength decreases by 46.5% when the content is 30%; compared with ordinary concrete, the freeze-thaw resistance of concrete with waste rubber powder is obviously improved; thermal conductivity of concrete with waste rubber is only 13% of ordinary concrete, and the concrete with less than 20% wt. of waste rubber has low water absorption and good water resistance.

Abstract: Titanium and its alloys have been widely used as implants replacing hard human tissues in biomedical fields. To improve the stability of implants in the surrounding bone tissues, the materials with porous structures were fabricated. In this paper powder metallurgy technique was employed to fabricate porous Ti-39Zr-6Nb (wt.%) alloys. The porous structures and mechanical properties of the porous alloys were examined by scanning electron microscopy (SEM) and compressive tests. The results showed that with increasing the sintering temperature the porosity of the alloys decreased and the compressive strength and the elastic modulus increased. The porosity of the alloys was in the range from 20.8% to 23.2%, and the pore sizes mostly centered in 10~30μm. The compressive strength and the elastic modulus were in the range from 110.4 to 292.4MPa and 4.7 to 12.4GPa respectively, which was close to human bone.

Abstract: In recent decades, high-tech electrical equipment has drastically proliferated instead of Cathode Ray Tube (CRT), making CRT funnel glass potential hazardous solid waste. Due to a relatively high level of lead, CRT funnel glass could be used as a potential material for the production of anti-radioactive concrete. In our study the CRT funnel glass , which was separated as aggregate in the concrete, was reduced to 4.75-25 mm (coarse aggregates) and less 4.75 mm (fine aggregates) in the production of anti-radioactive concrete. Mixes containing 0%, 20%, 40% , 60%, 80% and 100% (volume percentage) of CRT funnel glass to replace fine aggregate and coarse aggregate (respectively or simultaneously)) were prepared. The influence of the size, shape and replacement percentage of aggregates on workability, compressive strength and radiation shielding performance were determined. It was found that the replacement of natural aggregate with recycled CRT glass considerably improved the slump and radiation shielding performance but reduced compressive strength. The optimum percentage of waste funnel glass used as fine aggregate and coarse aggregate was 40%. The results clearly showed that the CRT funnel glass performed a significant enhancement in radiation shielding properties.

Abstract: Supplementary cementitious materials are most needed to enhance a sustainable development in poor communities. It is pertinent to investigate the suitability of such alternative materials for construction. The present study evaluates the strength characteristics of concrete made with varied proportion of Cordia millenii ash blended with Portland cement. Chemical composition of Cordia millenii and the setting time when blended with cement was determined. Other laboratory tests performed on Cordia millenii blended cement include: sieve analysis and specific gravity. Five replacement percentages of Cordia millenii (5%, 10%, 15%, and 20%) were blended with cement in concrete. Control specimens were also produced with only cement. Tests to determine the workability, air entrained, bulk density and compressive strength properties of the concrete were also conducted. Results obtained revealed that optimum Cordia millenii mix is 10%, which yielded the highest density and compressive strength in the concrete.

Abstract: The paper presents research in area of the measurement of cement paste creep. The propertiesof four month cement paste mixed with fly ash are presented. The creep and shrinkage are measuredinto the lever mechanism. The basic creep and creep of the saturated cement paste are calculatedfrom data of measurement. Finally, creep of four months old specimens is discussed.

Abstract: Cement is an extremely energy consuming material and its production leads to the emission of a vast amount of greenhouse gases. Cementitious concrete is a universal building material, which is used for the production of various structural elements. The paper describes the problem of cement production and its impact on the environment. This research deals with application of aluminous cement as binder component for the manufacture of refractory composites and with possibilities of further utilization of environmentally friendly materials with pozzolanic properties as a partial replacement of used aluminous cement. These materials are originating as waste in the building industry or by the recycling of cast-off materials. To reduce the costs and adverse effects on the environment was the binder system modified by finely ground ceramic powder and metakaolin. The experimental results present the values of flexural and compressive strength investigated on a series of composite specimens with dimensions of 40×40×160 mm³ and 10, 20 and 30 % of cement replacement. The aim of the present work is to apply the mentioned pozzolanic materials and reach the suitable composite with the sufficient heat resistance and residual mechanical parameters after gradual temperature loading.

Abstract: Unburned clay is a unique building material. It was used for the traditional engineering works for more some 9 thousands years. However, it was almost completely replaced in this role by modern building materials during second half of twentieth century. Because of that, its material characteristics, as its behaviour in the constructions, were never researched very rigorously. In last years, we could see increasing demand for use of this building material. Most of the contemporary unburned clay constructions are made of adobe bricks or pressed-down mud. Brick constructions are made of adobe brick and clay mortar. For both of them it is their mechanical properties, which determine their use in the construction industry. According to our experimental measuring, the tensile strength in bending of common adobe bricks is 2.5 MPa for pressing pressure of 6.6 MPa. The tensile strength in bending in clay mortar made of common clay is 0.45 MPa for pressing pressure of 1.55 MPa.