Papers by Keyword: Compressive Strength

Abstract: The use of huge amounts of concrete has led to an increase in the focus on High Performance Concrete (HPC). This study examined how Waste Paper Pulp Ash (WPPA) pozzolanic qualities affected HPC. WPPA was used to replace PLC at levels of 5, 10, 15 and 20%, respectively. With a characteristic strength of 50N/mm², the COREN Mix Design Manual was followed in the adoption of the concrete mix design. A 150 by 150 by 150 mm concrete cube was cast, and it was cured in water for 7, 28, and 56 days. The X-ray fluorescence (XRF) method was used to ascertain the chemical composition of the WPPA. For fresh concrete, tests for compacting factor and slump were performed; for hardened concrete, tests for density and compressive strength were performed. The concrete gets less workable (stiff) as the proportion increases, according to the workability data. The compressive strength results at 56 days revealed that 5% of WPPA exceeded the 56.56N/mm² design target mean strength, 10% of WPPA met the 50N/mm² designed target mean strength, and 15% and 20% of WPPA fell short of both the designed target mean strength and characteristic strength. SEM analysis showed that up to 5% WPPA maintains a dense microstructure and high strength in concrete, while higher WPPA levels result in increased porosity and reduced mechanical performance. In comparison to traditional HPC, 5% WPPA replacement of PLC would result in concrete that is stronger after a longer curing period.

Abstract: The feasibility of molten polyethylene terephthalate (PET) and laterite as composite for the production of masonry units was investigated. This aligns with the United Nations sustainable development goals of a cleaner environment, sustainable and affordable mass housing through innovative materials with low CO₂ emissions. Using standard testing procedures, cubes of molten PET and laterite composite of 150 mm by 150 mm were used to assess the compressive strength of both the treatment and control groups. The treatment groups were formulated in mix ratios of 1:1, 1:1.5 and 1:2 of PET to laterite while the control group was made of 100% PET. The results recorded were 1.53N/mm² for the control group, 4.7 N/mm², 9.9 N/mm² and 9.17 N/mm² in ratios 1:1, 1:1.5 and 1:2. Furthermore, there was an upward trend in the density of the test cubes recorded as 15.30kg/m³, 16.6 kg/m³ and 17.4 kg/m³ for ratios 1:1, 1:1.5 and 1:2 respectively. However, despite the increase in density in ratio 1:2, there was a reduction in strength. This could be due to a trade-off in the bonding quality between PET and laterite at that ratio. Nevertheless, given the values of compressive strength recorded and the remarkable difference between the control group and the treatment group, there is are prospects of the suitability of the composite for sustainable building construction.

Abstract: This study investigates the utilization of corn cob ash as a partial replacement for cement in the production of sandcrete bricks. This was necessitated due to the high cost of cement and the eco-friendly alternative to cement potentials the corn cob ash may possess. The corn cob was obtained from locals in Uselu, Benin City and was washed, dried for 24 hours then burnt in the furnace at 700 °C for 12 hours to obtain the ash at Engineering Faculty Workshop, University of Benin, Benin City. The corn cob ash substitution with cement, were done in weighted percentages, between 10 % and 20 %, cured for 3 days, 16 days and 28 days in a laboratory controlled environment using varying water/cement ratios and fine aggregates. Response surface methodology in Design- Expert 7.0 software was used to produce the experimental designs. The results obtained, reveal that corn cob ash can replace cement, up to 10 % weighted percentages in sandcrete brick, without reducing its compressive strength below 2.5 N/mm² and it also had 11.98 % of water absorption, which satisfied the standards for non-load bearing sandcrete bricks. The quadratic model formulated for the blended sandcrete brick was significant possessing a p-value of 0.02 and 0.047 with an adjusted R² value of 0.65 and 0.56 for the compressive strengths and water absorption properties respectively.

Abstract: Lignin is the largest component of biomass and the second most abundant natural polymer. Lignin-based products are commonly applied as binders, and are utilized for polymer applications. The purpose of this study is to use lignin as an admixture in mortar. The lignin dissolved in 1M NaOH solution, and the ratio was 1:5 by weight. The lignin contents utilised in this study were 1%, 2%, 3% by weight of cement and a cement water rasio of 0.4. Lignin as an admixture in mortar increased the flowability value. The flowability value increased as the lignin content rose. the highest compressive strength and flexural strength occured at 1% lignin content. They were 35.71 MPa and it was 5.49 MPa, at the age of 28 days. The longest setting time was obtained at 3% lignin content for initial setting time of 285 minutes, and final setting time of 540 minutes. Based on the results of the setting time test, it has been determined that the more lignin was mixed in, the longer the setting time will be. Therefore lignin as an admixture to the mortar makes changes its characteristics.

Abstract: Cement contributes CO₂ emissions to the atmosphere, which is harmful for human health. Several researchers have conducted experiments to find materials that have the potential to be used as cement substitutes. Fly ash and perlite are wastes that contain silica as well as high aluminum, so they have potential as cement replacement materials. In this study, geopolymer concrete mixtures were made using fly ash and perlite with a NaOH concentration of 10M – 16 M, a Na₂SiO₃/NaOH ratio of 2.5 and alkaline solution to fly ash ratio (AA/FA) of 0.5. The curing method used was using an oven at 80 °C for 16 hours. From the experimental results, the optimum compressive strength was 28.470 MPa with a 12M NaOH concentration. The optimum flexural strength was 2.387 MPa with a NaOH concentration of 12M.

Abstract: Geopolymer concrete is an environmentally friendly alternative to cement as it can reduce carbon dioxide gas emissions during the production process. This study uses fly ash, a waste from the combustion of steam power plants, and perlite, a silicate glass rock with high alumina content, as cement replacement materials. Variations of perlite were used in geopolymer concrete mixtures to replace fly ash with percentages of 0%, 10%, 20%, and 30%, with a concentration of 12 M, and a Na₂SiO₃/NaOH ratio of 2.5 and AA/PM of 0.5. For the treatment of geopolymer concrete using oven curing method at 80°C for 16 hours. The results showed that variation 4 (fly ash 70% + perlite 30%) had an optimum compressive strength value of 27.145 MPa at the age of 28 days. The optimum split tensile strength value at the age of 28 days also occurred in variation 4 with a value of 3.130 MPa. In addition, variation 1 (100% fly ash + 0% perlite) had the highest slump value of 9.15 cm, while variation 4 (70% fly ash + 30% perlite) had the lowest density value of 2047.014 kg/m³.

Abstract: Rigid pavement is a type of pavement that uses cement as the main binding material and has a high level of stiffness. The prolonged use of cement has increasingly negative impacts on the environment. Using geopolymer as a substitute for cement can be an eco-friendly alternative solution. Geopolymer is an environmentally friendly material that can be developed as an alternative to cement concrete in the future. The purpose of this study is to determine the compressive strength of geopolymer concrete using rice husk ash and shell as fine aggregates in rigid pavement. The research method used is experimental. The method used for mix design calculation is AASHTO 1993, by making 8 test specimens. Each test specimen uses 4 aggregate and binder ratios, which are 75:25, 70:30, 65:35, and 75:25, each with 2 alkaline activator ratios, which are 3:1 and 5:2. The compressive strength testing of the specimens was conducted at 28 days. The concrete quality used, K225, is equivalent to 18.68 MPa. The compressive strength testing of geopolymer concrete achieved optimum compressive strength at a variation of 65:35 aggregate, 3:1 alkaline, 5% rice husk ash, and 5% shell, which was 18.9667 MPa. At the variation of 75:25 aggregate, 3:1 alkaline, 5% shell, the highest value was 21.4013 MPa. Based on the type of concrete according to its compressive strength, geopolymer concrete with fly ash, rice husk ash, and shell is classified as normal concrete because its compressive strength exceeds 15 MPa and can be a substitute for cement with relatively low strength.

Abstract: Water shortage is a major global issue affecting the construction industry. One possible solution is to use seawater instead of tap water in cement-based materials. However, this raises concerns about the impact on material properties. In addition, it is known that the use of volcanic pumice powder in cement mortar can improve its properties, but the combined effects of seawater and volcanic pumice powder have not been thoroughly investigated. This study aims to fill this gap by investigating the synergistic effects of seawater and volcanic pumice powder on the slump flow, compressive and flexural strengths, water absorption, and fracture toughness of cement mortar. The main variables in this study are the type of water (Mediterranean water and tap water) and the percentage of volcanic pumice powder (VPP). The volcanic pumice powder content is 0%, 10%, 20%, and 30%, replacing cement by mass. Based on investigation results, it was shown that the combination of seawater and volcanic pumice powder leads to less fluid and more viscous mortars compared to those made with tap water (TW). However, in the hardened state, seawater promoted the early precipitation of cement hydration, resulting in an increase in compressive strength from the second day until 28-days, along with an improvement in the transport properties of mortar at 28 days. Meanwhile, a noticeable decline in both strength and fracture toughness was recorded for ages more than 28 days and up to 90 days, compared to mortars cast and cured with tap water.

Abstract: PC is a type of concrete which is well known for its low strength and high infiltration rate. PC is made up of cement, coarse aggregate, water and with little or no fine, that is the reason PC is also known as no fine concrete. The fine content in PC tends to improve the strength of the concrete yet it adversely affects the infiltration of the PC. Therefore, in this study the pumice stone fine was incorporated in pervious concrete to make a PC with improve strength without sacrificing its infiltration. This experimental investigation helps to explain the effect of pumice stone when used as fine aggregate on the density, void content, compressive strength, flexure strength, and infiltration rate of PC. All PC mixtures were proportioned with a fixed water-to-cement ratio (w/c) of 0.30. The fresh and hardened voids of PC containing pumice fine were up to 9% greater than the PC without fine resulting in about 11% reduction in the hardened density of PC with fine. Moreover, the compressive strength of pervious concrete with incorporation of pumice fine shows a significant increase of about 30% compressive and 40% flexural strength. Moreover, the infiltration rate of PC made with pumice fine showed about 60% improvement. Therefore, pumice fine is a great option for incorporating in PC to improve its overall performance.

Abstract: This study investigates the influence of curing regimes on the microstructure and mechanical properties of alkali-activated concrete (AAC) containing coarse recycled aggregates (CRA) for structural applications. Building on prior research at BITS, Pilani Hyderabad Campus, AAC specimens were prepared by replacing natural aggregates (NA) with processed and unprocessed CRAs. Class F fly ash and ground granulated blast furnace slag (GGBFS) served as precursors, activated by sodium hydroxide and sodium silicate solutions. A consistent mix design employed a 4% sodium concentration and 60:40 fly ash-to-slag ratio. The target compressive strength was 40 MPa for structural use. Curing conditions are known to affect various AAC properties, including early and long-term strength, hydration kinetics, durability, and dimensional stability. While prior research explored these aspects under different curing regimes, the influence on microstructure development in AACs with high CRA content remains under-reported, especially considering curing regime variations. This research addresses this gap by employing three distinct curing regimes: ambient temperature (30°C) for 28 days, ambient temperature with plastic wrap for 28 days, and oven curing at 75°C for 72 hours followed by 25 days at 30°C. Microstructural investigations using XRD, FESEM, and stereo microscopy were complemented by ultrasonic pulse velocity and compressive strength tests. Notably, specimens subjected to oven curing at 75°C exhibited superior performance compared to those cured at ambient temperature with or without plastic wrapping