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The majority of masonry structures exhibit excellent long-term performance with comparative low maintenance cost. Durability of a masonry structure is influenced by many factors including the durability of both blocks units and mortar joint. In this research the specific influence of the varying water cement ratio of the mortar joint is taken into...
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Citations
... Of the three w/c ratios, the mortar mixed at w/c of 0.5 showed the highest compressive strength while the lowest was observed at 0.6. This agreed with previous studies [12,34,35] where the higher w/c ratio reduced the compressive strength. This reduction of strength is due to the increase of porosity (explained detail in Section 3.6) with the increase of w/c ratio, indicating the paste fraction of mortar becomes more porous and the mortar becomes weaker because the pores are interconnected [36]. ...
... Of the three w/c ratios, the mortar mixed at w/c of 0.5 showed the highest compressive strength while the lowest was observed at 0.6. This agreed with previous studies [12,34,35] where the higher w/c ratio reduced the compressive strength. This reduction of strength is due to the increase of porosity (explained detail in Section 3.6) with the increase of w/c ratio, indicating the paste fraction of mortar becomes more porous and the mortar becomes weaker because the pores are interconnected [36]. ...
This study examines the thermal behavior of cement mortar incorporating low-phase transition temperature phase change materials (PCM) (around the freezing point of concrete pore solutions) in an attempt to develop a novel strategy to reduce the expected number of freeze-thaw cycles concrete experiences and possibly to improve the frost resistance. To determine a viable inclusion method for PCM, thermal responses of mortars with two different PCM inclusion methods were tested under a 24-h sinusoidal temperature history, with the maximum and minimum ambient temperatures of 9 °C and −5°C, respectively, considering typical winter climate conditions in South Korea: (1) direct inclusion of non-treated raw PCM; and (2) inclusion of PCM-filled highly absorptive lightweight aggregates (LWA). In addition, another series of testing was conducted to identify the effect of phase transition temperature distribution on the thermal response of cement mortar: (1) inclusion of multi PCMs with three different transition temperatures (4.5 °C, 2.0–2.5 °C, and −0.5 °C); and (2) inclusion of single PCM with a phase transition temperature of 4.5 °C. Lastly, to see the effect of partial PCM embedment, thermal responses of cement mortars overlaid with three different PCM-embedment depths (20 mm, 30 mm, and 40 mm) were evaluated. Results have shown that the minimum specimen temperature was successfully raised by the addition of low-phase transition temperature PCMs. Also, it was revealed that the use of multi PCMs-filled LWA performed most effectively in terms of thermal and mechanical properties as compared to other incorporation methods. The partial PCM embedment improved the thermal performance, but there was no significant effect of PCM embedment depth.
... Of the three w/c ratios, the mortar mixed at w/c of 0.5 showed the highest compressive strength while the lowest was observed at 0.6. This agreed with previous studies [12,34,35] where the higher w/c ratio reduced the compressive strength. This reduction of strength is due to the increase of porosity (explained detail in Section 3.6) with the increase of w/c ratio, indicating the paste fraction of mortar becomes more porous and the mortar becomes weaker because the pores are interconnected [36]. ...
The application of oil-contaminated sand (OCS) in concrete is considered a highly sustainable solution and cost-effective recycling method for minimising its negative effect to the environment. The present study investigated the mechanical characteristics, strength development, hydration and microstructure of cement mortar containing oil-contaminated sand. The parameters investigated in the present study are the level of oil contamination, mixing method, water-to-cement (w/c) ratio, and the age of curing. The microstructural characteristics of hardened samples, physical and mechanical properties and the strength development pattern of cement mortar containing oil-contaminated sand were assessed up to 365 days. Result shows that the presence of crude oil up to 4% can improve the properties of mortar compare to the uncontaminated samples. The mixing of water and cement before adding oil-contaminated sand is found effective method of mixing, while the optimum compressive strength obtained at a w/c ratio of 0.5. The strength of cement-based mortar having contaminated sand with 2% light crude-oil is similar to the cement mortar with uncontaminated sand after one year. However, the rate of gaining strength of cement mortar with high levels of contamination with light crude oil (4–10%) is found slow. The microstructure of mortar containing contaminated fine sand up to 2% oil appeared to be quite dense and have a finer pore structure. The interfacial tension zone (ITZ) is not affected by crude oil up to 2%, however, the higher percentages of oil contamination (6–10%) can increase the porosity and affect the ITZ.
... The strength of concrete and sandcrete physical structures (Nwofor, 2012) powdered portland cement, higher percentage of sand, mod in a mould and left to dry (Anon., 2016 gravel (Anon., 2016) [13]. Dense concrete and sandcrete blocks are used for the construction of mighty buildings such as shopping malls, auditoriums, churches, mosques and flats. ...
Concrete and sandcrete blocks produced from known proportions of cement, coarse and fine aggregates and which were left to cure for various days, were evaluated for changes in weight and uniaxial compressive strength (UCS). The strength of the blocks made from various proportions of materials (cement: coarse aggregate: fine aggregate) was highest for 1:2:1; moderate for combination of 1:2:2; and least for 1:2:4 mixtures. Hence, higher quantity of coarse aggregate in mixtures produced higher strength of blocks. Again higher strength was realised after 28 days curing on mixing ratios of 1:3:2 and 1:2:3; moderate for a combination of 1:0.5:3; and least for 1:3:0.5, 1:2:4 and 1:4:2. Weight of blocks was generally reduced with increase of curing days though this was irregular in concrete blocks. Density of concrete blocks ranged between 2.30 and 2.70 and for sandcrete blocks it ranged between 1.60 and 2.20.
... Nwofor [13] investigated the effect of varying w/c ratios (i.e. 0.5, 0.6 and 0.7) of mortar joint on durability of block work. ...
Durability and the compressive strength of concrete are directly related to the porosity. Water to cement ratio is the main parameter behind the nature and amount of pores within the matrix. Porosity is also influenced by the degree of cement hydration and the length of moist-curing. Even after the standard moist curing period, i.e. 28 days the concrete can gain strength and porosity can be reduced under ambient relative humidity and temperature. However, this fact, that is the age effect on porosity reduction of the cement mortar or concrete, kept in air with ambient relative humidity and temperature for long duration could not be found in
the literature. Therefore, in this research, different w/c were used with constant amount Portland Composite Cement to find out whether the mortar porosity decreases significantly over time, after 28 days of water curing, while kept in air and if there is any interaction effect between the age of the mortar and different w/c; regarding porosity. It was also intended to find out if water-loss rate variation with different w/c has similar trend as porosity variation with different w/c. It was found that, there is significant decrease in porosity with time for the
first six weeks in air and after that it dwindles down gradually, and there is no interaction between age and w/c. Also, after 100 days in air, samples were submerged under water for 24 hours and then kept in air for the evaporation in subsequent days. It has been found that the water evaporation vs. w/c curve, using 11-day evaporation of water from different w/c specimens in ambient condition is almost parallel to porosity vs. w/c curve. Therefore, 11-day evaporation of aged saturated mortar or concrete sample, such as core can also be
used as a durability index, which can be used for old structure evaluation.
... Nwofor [13] investigated the effect of varying w/c ratios (i.e. 0.5, 0.6 and 0.7) of mortar joint on durability of block work. ...
Durability and the compressive strength of concrete are directly related to the porosity. Water to cement ratio is the main parameter behind the nature and amount of pores within the matrix. Porosity is also influenced by the degree of cement hydration and the length of moist-curing. Even after the standard moist curing period, i.e. 28 days the concrete can gain strength and porosity can be reduced under ambient relative humidity and temperature. However, this fact, that is the age effect on porosity reduction of the cement mortar or concrete, kept in air with ambient relative humidity and temperature for long duration could not be found in the literature. Therefore, in this research, different w/c were used with constant amount Portland Composite Cement to find out whether the mortar porosity decreases significantly over time, after 28 days of water curing, while kept in air and if there is any interaction effect between the age of the mortar and different w/c; regarding porosity. It was also intended to find out if water-loss rate variation with different w/c has similar trend as porosity variation with different w/c. It was found that, there is significant decrease in porosity with time for the first six weeks in air and after that it dwindles down gradually, and there is no interaction between age and w/c. Also, after 100 days in air, samples were submerged under water for 24 hours and then kept in air for the evaporation in subsequent days. It has been found that the water evaporation vs. w/c curve, using 11-day evaporation of water from different w/c specimens in ambient condition is almost parallel to porosity vs. w/c curve. Therefore, 11-day evaporation of aged saturated mortar or concrete sample, such as core can also be used as a durability index, which can be used for old structure evaluation.
... 1) and plotted in Figs.(1,2,3). Maximum compressive strength ,corresponding w/c & flow % were found from the curves. ...
The purpose of this study is to investigate the best sand/cement ratio of mortar by using locally available sand and using the same constituent in various concrete mixes of different local coarse aggregate/cement ratio. On the bases of maximum compressive strength and workability of cement mortar, mixes of different sand/cement (s/c) and water/cement (w/c) were prepared. For each mortar mix flow table test was performed to check its consistency and cube samples were prepared for the 28-day compressive strength test. Thus it was decided to consider mortar mixes with a flow value of 90%. Using w/c corresponding 90% flow of the mortar and same mortar constituent (sand/cement) with varying coarse aggregate/cement ratio, 20 concrete mixes were prepared. The aggregate/cement was 2:1 for the richest concrete mix and 9:1 for the poorest mix. On the basis of 28-day compressive strength of mortar of flow 90%, it was found that corresponding rich concrete mix of egg./c 3:1 &3.5:1 had a reduction in 28-day compressive strength of 26% & 24% respectively and had bad workability in its fresh state. Similarly for lean concrete mixes agg./c 7:1 to 9:1 the reduction in compressive strength was 21.8% to 39.6% respectively, while the reduction for the other concrete mixes were less than 15% with reasonable workability. The reduction in compressive strength for concrete mixes of agg./c 4.5:1 to 6:1 corresponding to mortar s/c of 2:1 was almost zero and all mixes had good workability. Thus the best s/c corresponding to 90% mortar flow was 2:1 which can be used in concrete mixes of varying coarse agg./c ratio with good workability and minimum losses in compressive strength.
... Of the three wc ratios used in this study, the compressive strength of the mortar mixes was highest with a 0.5 water cement ratio, whereas a water cement ratio of 0.6 caused a significant reduction in the compressive strength of mortar. These results agreed with previous studies [29][30][31] where it has concluded that increasing the w/c ratio decreased the compressive strength. The compressive strength of the uncontaminated sample of mortar decreased by 6% when a w/c 0.6 compared to the compressive strength obtained when w/c of 0.5 was used. ...
... 1) and plotted in Figs.(1,2,3). Maximum compressive strength ,corresponding w/c & flow % were found from the curves. ...
The purpose of this study is to investigate the best sand/cement ratio of mortar by using locally available sand and using the same constituent in various concrete mixes of different local coarse aggregate/cement ratio. On the bases of maximum compressive strength and workability of cement mortar, mixes of different sand/cement (s/c) and water/cement (w/c) were prepared. For each mortar mix flow table test was performed to check its consistency and cube samples were prepared for 28-day compressive strength test. Thus it was decided to consider mortar mixes with flow value 90%. Using w/c corresponding 90% flow of the mortar and same mortar constituent (sand/cement) with varying coarse aggregate/cement ratio , 20 concrete mixes were prepared .The aggregate/cement was 2:1 for the richest concrete mix and 9:1 for the poorest mix. On the basis of 28-day compressive strength of mortar of flow 90%, it was found that corresponding rich concrete mix of agg./c 3:1 &3.5:1 had a reduction in 28-day compressive strength of 26% & 24% respectively and had bad workability in its fresh state. Similarly for lean concrete mixes agg./c 7:1 to 9:1 the reduction in compressive strength was 21.8% to 39.6% respectively ,while the reduction for the other concrete mixes were less than 15% with reasonable workability. The reduction in compressive strength for concrete mixes of agg./c 4.5:1 to 6:1 corresponding to mortar s/c of 2:1 was almost zero and all mixes had good workability. Thus the best s/c corresponding to 90% mortar flow was 2:1 which can be used in concrete mixes of varying coarse agg./c ratio with good workability and minimum losses in compressive strength.
This study reports on formulations and conditions for producing fly ash-based geopolymers with a view to showing that the compressive strength required for construction applications can be obtained without the addition of aggregates, sand, and/or cement. It was shown in a series of experiments constituting at least 73% fly ash that a compressive strength of up to 90 MPa can be obtained depending on the curing conditions. While high alkalinity resulted in stronger materials, the results showed about 40% savings in CO 2 emissions without using sand and cement. Such materials are suited for construction applications with minimal environmental impact.
