Flexural Behavior of High Strength RC Beams Incorporating Nano-Silica and Macro-Polypropylene Fiber

Many researches were carried out to investigate the properties and structural performance of high strength concrete for many decades. While these researches have produced relevant and useful results, there are several properties of high strength concrete like compressive and tensile strengths, stiffness, durability, modulus of rupture, cracking shear load and ultimate load that need to investigate to determine an accurate evaluation of beams made of high strength concrete. This study investigates the effect of shear span-depth ratio (a/d) on the statical behavior of HSCB subjected to transverse loading. The effect of shear span to depth ratio includes some main mutual factors such as grade of concrete and stirrups spacing. The studied statical behavior includes: evaluation of pattern of cracks, modes of failure, concrete and steel strains, maximum deflection, flexural cracking load (Pcr), modulus of rupture, cracking shear load (Vcr) and finally ultimate load (Pu). For this purpose, an experimental test program was performed which included testing twenty four large scale simply supported rectangular high strength concrete beams under one concentrated transverse load at mid span. The values of the main factors were; the shear span to depth ratio (a/d) were taken (3, 2, 1.5 and 1), the cube compressive strength (fcu) were (575, 766 and 890) kg/cm2and the stirrups spacing were (20, 14.28, 11.11and without stirrups) cm, while the longitudinal reinforcement was kept constant for all tested beams. For all tested beams, max. Deflections, strains in the longitudinal reinforcement, and strains in concrete were measured and recorded. Also, the initiation and propagation of cracks were recorded. Cracking patterns and failure modes were observed. Cracking and failure loads were recorded. The test results were compared with different codes and formulas. Based on this, conclusions were drawn out for induced measured maximum deflection, steel and concrete strain, the cracking load the modulus of rupture, shear cracking load and ultimate load for beams with and without stirrups. In addition, ultimate shear load for beams without stirrups utilizing different code provisions was predicted and compared with the obtained test results.

Effect of nano and micro-silica on bond behaviour of steel and polypropylene fibres in high volume fly ash mortar

Self-compacting concrete (SCC) is profusely utilized in building construction due to its unique design and mechanism of flow without segregation by occupying the corners and preventing the voids to achieve better compaction and mechanical strength. This work addresses the effect of colloidal nano-silica (NS) of size 5-40nm with an active nano solids content of 32% on the high-strength SCC containing Ground Granulated Blast Furnace Slag (GGBFS) and Ordinary Portland Cement as binders in addition to NS. The liquid content of 68% in NS was added to the water content in the mix. The ratios of NS were evaluated at 0%,0.5%,1%,1.5%, 2% and GGBFS as 20% by weight of binder in concrete. The water to binder ratio was 0.33 with a water and binder content of 184kg/m3 and 557.58 kg/m3. The optimum mix was 1.5% NS based on the concrete’s slump and compressive strength at 28 days. The slump was reduced with a rise in NS beyond 1.5% due to the accumulation of NS particles causing the reduction in flowability. The density of SCC for all the mixes was satisfactory. The compressive strength of optimum SCC, M21.5NS20G was decreased by 5.88% and increased by 0.49% and 2.45% at 7, 28 and 91 days to that of the reference mix whereas its split tensile strength was risen by 31.13%, 9.27%, and 12.41% and flexural strength was risen by 5.8% and reduced by 8.17% and 4.06% to that of the reference mix at aforementioned durations. The SEM and XRD analyses were conducted on the optimum hardened SCC mix at 28 days in which the presence of Calcium silicate hydrate compounds of different crystalline structures, viz., Ettringite, and Portlandite were observed. The SCC designed in the work can be used for structural applications such as beam-column joints.

Properties of sustainable high-strength concrete containing large quantities of industrial wastes, nanosilica and recycled aggregates

Performance assessment of high strength concrete two-sided corbels with embedded stiffened web-rolled steel

Evaluation survey of concrete composite using nano and micro silica materials for better properties

Influence of nano-silica on the microstructural and mechanical properties of high-performance concrete of containing EAF aggregate and processed quarry dust

Experimental study on strength and microstructure of mortar in presence of micro and nano-silica

WITHDRAWN: An experimental and numerical investigation on flexural characteristics of wire mesh reinforced concrete beam blended with rice husk ash (RHA) and nano silica

Self-compacting concrete (SCC) is voluminously utilized in building construction due to its distinct design. This work depicts the effect of colloidal nano-silica (NS) of size 5-40nm with an active nano solids content of 32% on SCC of grade 30 containing Ground Granulated Blast Furnace Slag (GGBFS) and Ordinary Portland Cement as binders in addition to NS. The liquid content of 68% in NS was added to the water content in the mix. The ratios of NS were evaluated at 0%,0.5%,1%,1.5%, 2% and GGBFS as 20% by weight of binder in concrete. The water to binder ratio was 0.38 with a water and binder content of 201kg/m3 and 528.95 kg/m3 respectively. The optimum mix was 1.5% NS as per the slump and compressive strength at 28 days. The slump was reduced with a rise in NS beyond 1.5% due to the accumulation of NS particles causing the reduction in flowability. The density of SCC for all the mixes was satisfactory. The compressive strength of optimum SCC, M-1.5NS20G was increased by 11.71%, 8.58% and 17.45% at 7, 28 and 91 days respectively to that of the reference mix whereas its split tensile strength was risen by 43.40%, 23.11% and 9.51% and flexural strength was risen by 26.28%, 15.17% and 6.29% to that of the reference mix at aforementioned durations respectively. The microstructural studies on the optimum hardened SCC mix at 28 days revealed the presence of calcium silicate hydrate compounds of different crystalline structures and portlandite.

Ductility response of RC beams composed of limestone calcined clay cement (LC3) and polypropylene (PP) fibre

This paper presents an experimental investigation on the properties of concrete in which like cement is partially replacing by used nano silica and is partially replacing by used waste foundry sand. Because now a day the world wide consumption of sand as cement and as fine aggregate in concrete production is very high. Nano silica and waste foundry sand are major by product of casting industry and create land pollution. The cement will be replaced with nano silica and the river sand will be replaced with waste foundry sand (0%, 5%, 10%, 15%, 20%). This experimental investigation was done and found out that with the increase in the nano silica and waste foundry sand ratio. Compression test has been done to find out the compressive strength of concrete at the age of 7, 14, 21, and 28. Test result indicates in increasing compressive strength of plain concrete by inclusion of nano silica as a partial replacement of cement and waste foundry sand as a partial replacement of fine aggregate.

Because the joists in the wall-beams are in eccentric tension during work and the concrete tensile strength is low, the bending capacity of normal section of wall-beams is not too large. Steel fibers mixed into the concrete, playing enhancement and crack-resistance roles would lead to changes in the nature of concrete materials so that it is impossible to fully use the existing research results of ordinary concrete wall-beams simply supported when studying bending behavior of normal section of steel fiber reinforced concrete wall-beams simply supported. Therefore, it is necessary to do pilot studies on bending behavior of normal section of steel fiber reinforced concrete wall-beams simply supported. Based on the vertical static load test of 12 steel fiber reinforced concrete wall-beams simply supported specimens under different fiber volume ratio conditions, the strains of steel and concrete, cracking load, failure load and development situation in the cracks were tested while working characteristics of steel fiber reinforced concrete wall-beams simply supported were studied. This paper discussed the effect of fiber volume ratio on cracking moment and ultimate moment of steel fiber reinforced concrete wall-beams simply supported, which shows that the optimum mixing amount of steel fiber is 1.2%. The conclusion is of great significance in both theory and engineering practice, and it helps to guide the application of practical engineering.

In this project work, organized study was carried out to evaluate the fatigue performance of dense bituminous macadam (DBM) mix using nano silica as an additive and the results were compared with the conventional DBM mix. For this purpose, Marshall stability and indirect tensile strength (ITS) tests were conducted to find out optimum bitumen content, optimum nano silica content and tensile strength of the mix. Repeated load fatigue test was carried out for DBM mix with and without nano silica at different failure loading or stress level which was obtained from ITS test. The nano silica modified DBM mixes shows higher fatigue life across all failure loading compared to conventional DBM mix. Also, it was seen that the increase in failure loading resulted in decrease of number of fatigue cycles and increase in the initial tensile strain of the mix. The DBM mix with 4% (optimum) nano silica shows 1.85, 1.67, 1.74, 2.16 and 1.98 times higher resilient modulus when compared to conventional DBM mix at 10%, 20%, 30%, 40% and 50% failure load respectively. Fatigue line constants were calculated for both conventional and nano silica modified DBM mixes and the values were comparable with the literature.

Since cement manufacturing causes 7– 8% of total global CO 2 emissions, attempts have been made to minimize cement consumption. One method is to introduce pozzolans, commonly fly ash (FA), as supplementary materials to Ordinary Portland Cement (OPC). The main drawback of incorporating FA into cement is the reduction of early strength in concrete. This can be countered by incorporating Nano silica (NS) into the FA - OPC mix. Workability, compressive strength (3, 7, 28 & 100 day), sorptivity and thermogravimetric analysis (TGA) testing was carried out on cement paste specimens with FA replacements from 0% to 70% and NS percentages from 0 to 6%. All mixes were prepared with a 0.4 water binder ratio and a superplasticizer dosage to achieve equal workability for all mixes. Results showed that workability reduces with the increase of NS. Also, for a given %NS, compressive strength reduces with the increase of FA for early age strength, while 30% FA replacement gives optimum strength at 100 days. A 3% NS content for constant %FA gives optimum strength beyond 28 days. Sorptivity too is lowest at 30% FA replacement with 3% NS. Therefore 30% FA replacement with 3% NS gives optimum performance for both strength and durability. The mix with 50% FA replacement and 3% NS (a genuinely HVFA mix) is promising as a practically useful mix. The TGA enables us to obtain the Calcium Hydroxide (CH) consumed for pozzolanic reactions; this is used to validate a model that explains the strength variations in these mixes.