Strength and microstructure of lightweight concrete with palm kernel shell and rice husk ash substitutions: A technological conciliation for facilities management

This study aims to develop suitable formulations of geopolymer concrete (GPC) by varying the percentages of the geopolymer with aggregates and evaluating the performances in thermal and mechanical properties of palm kernel shell ash (PKSA)-GPC compared to rice husk ash (RHA)-GPC and ordinary Portland cement concrete (OPCC). Preliminary tests were conducted to select the best mix design ratios before casting the specimens. Then, the performance of the PKSA-GPC, RHA-GPC and OPCC specimens was evaluated based on their thermal performance and drying shrinkage. The mix designs of PKSA-GPC 70:30, PKSA-GPC 60:40, PKSA-GPC 50:50 and PKSA-GPC 66.6:33.3 were found to produce an acceptable consistency, rheological and thixotropic behaviour for the development of the GPC. PKSA-GPC showed a better thermal performance than the RHA-GPC and OPCC due to their strong and dense intumescent layers and slow temperature increment upon exposure to a high flame temperature from ambient temperature to 169 °C. The low molar ratio of the Si/Al present in the PKSA-GPC created a thermally stable intumescent layer. In the drying shrinkage test, PKSA-GPC 60:40 and RHA-GPC 60:40 shared an equal drying shrinkage performance (5.040%) compared to the OPCC (8.996%). It was observed that microcrack formation could significantly contribute to the high shrinkage in the PKSA-GPC 50:50 and RHA-GPC 70:30 specimens. The findings of this study show that PKSA could be incorporated into GPC as a fire-retardant material due to its capability of prolonging the spread of fire upon ignition and acting as an alternative to the conventional OPCC.

The evaluation of agro-industrial by-products as alternative construction materials is becoming more significant as the demand for environmentally friendly construction materials increases. In this study, the workability and compressive strength of concrete produced by combining Palm Kernel Shell (PKS) and Rice Husk Ash (RHA) was investigated. Concrete mixes using a fixed content of 15% RHA as replacement for cement and 20, 40, 60, 80 and 100% PKS as replacement for crushed granite by volume with the mix ratios of 1:1½:3, 1:2:4 and 1:3:6 were produced. The water-to-cement ratios of 0.5, 0.6 and 0.7 were used for the respective mix ratios. Concrete without PKS and RHA served as control mix. The fresh concrete workability was evaluated through slump test. The concrete hardened properties determined were the density and compressive strength. The results indicated that the workability and density of PKSC were lower than control concrete, and they decreased as the PKS content in each mix ratio was increased. The compressive strength of concrete at 90 days decreased from 27.8-13.1 N/mm2, 23.8-8.9 N/mm2and 20.6-7.6 for 1:1½:3, 1:2:4 and 1:3:6, respectively as the substitution level of PKS increased from 0-100%. However, the compressive strength of concrete increased with curing age and the gain in strength of concrete containing RHA and PKSC were higher than the control at the later age. The concrete containing 15% RHA with up to 40% PKS for 1:1½:3 and 20% PKS for 1:2:4 mix ratios satisfied the minimum strength requirements for structural lightweight aggregate concrete (SLWAC) stipulated by the relevant standards. It can be concluded that the addition of 15% RHA is effective in improving the strength properties of PKSC for eco-friendly SLWAC production..

Consolidation characteristics of compacted clayey soils treated with various biomass ashes

As already known, cement production is one of the biggest contributors to CO2 emissions due to combustion processes that require high temperatures. This can trigger global warming so the solutions to reduce or even eliminate the use of cement continue to be developed. Geopolymer concrete is one solution to reduce the use of cement in the construction industry in the world. This study has the main objective to examine the effect of the use of palm kernel shell and ash rice husk ash in geopolymer concrete mixes on the strength of geopolymer concrete then compared with the use of palm kernel shell ash and rice husk ash on Portland cement concrete. In this study concluded that increasing the strength of geopolymer concrete with the use of palm kernel shell ash and rice husk ash tends to be insignificant when compared to the increase in strength in Portland cement concrete. The changes in the concentration of NaOH solution is more effective to increase the strength of geopolymer concrete.

The purpose of this study was to investigate the properties of Rice Husk Ash (RHA) as a partial cement replacement material in concrete production based on analysis of its contribution to strength in comparison with Ordinary Portland Cement (OPC). The analysis was focused on: the chemical properties of RHA, workability, density, compressive strength, and tensile strength of concrete. The RHA was obtained from Mwea, Kirinyaga County, Kenya and burned in a kiln to produce white ash which was tested. Chemical analysis to determine the pozzolanic properties of RHA was done using the Gravimetric method, Flame Photometry and Atomic Absorption Spectroscopy while particle size distribution of RHA was carried out using sieve analysis and hydrometer analysis. Concrete mixes with different ratios of OPC to RHA binder were cast into cuboid and cylindrical samples. The binder was made by replacing OPC with RHA at intervals of 10% by mass to a maximum of 50% replacement. A binder, sand, and ballast ratio of 1:1.5:3 were maintained with a constant water-cement ratio of 0.6. The cast samples were subjected to water curing on the third day at room temperature. Workability tests were performed on fresh concrete while compressive strength tests and tensile strength tests were performed on hardened concrete in all the mixes. The results were compared with OPC concrete. Results indicated that Kenyan RHA has high silica, alumina, and iron oxide content of about 92%. The workability slightly improves with 10% partial replacement of OPC with RHA but decreases with further addition of RHA. It was also deduced that the optimal binder mix was 10% partial replacement of OPC with RHA however the compressive strength was lower than the OPC concrete by 2.3%. The tensile strength of concrete increased with the addition of RHA up to an optimum of 10%.

The fire resistance of concrete has become a major design concern due to various high profile fire incidents such as the collapse of the Twin Towers (September 11), USA and several tunnel fires around the world. Concrete although described as incombustible, undergoes physical and chemical transformations when exposed to elevated temperatures, as in a fire event. Above 400oC, one of the main hydrates of ordinary Portland cement (OPC) paste, calcium hydroxide (CaOH2) dehydrates into calcium oxide (CaO) causing the OPC paste to shrink and crack. After cooling and in the presence of air moisture, the CaO rehydrates into CaOH2 causing the OPC paste to expand, crack and completely disintegrate. However, the long-term effects of the CaO rehydration on the mechanical properties of OPC pastes are unknown and therefore, are investigated by the present thesis. In addition, the effects of elevated temperatures and CaOH2 dehydration/CaO rehydration on the microstructure and mechanical properties of concrete are still unclear. This issue has been of much debate and due to the conflicting nature of the available literature, is not fully understood. Therefore, this thesis investigates these effects on the microstructure and mechanical properties of OPC concrete. Furthermore, despite the continuous growing popularity of ground granulated blast furnace slag (GGBFS or ‘slag’) as a partial replacement of OPC in concrete, limited research has focused on how this replacement influences the microstructure and mechanical properties of paste and concrete exposed to elevated temperatures. Therefore, this thesis also addresses this issue. The study shows that partial replacement of OPC with slag resulted in a significant and beneficial reduction of the amount of CaOH2. An increase in the proportion of slag in the cement paste led to an improvement in the mechanical properties following exposure to temperatures beyond 400oC. The long-term effects of CaO rehydration on the mechanical properties of OPC and OPC/slag pastes exposed to 800oC were investigated using differential thermogravimetric analysis (DTG). Test results showed that CaO rehydration continued to take place throughout the period of one year, leading to a progressive deterioration of the OPC paste. After one year, the OPC paste completely disintegrated to a powder. In contrast, OPC/slag pastes were not affected by the progressive CaO rehydration as mechanical properties remained unchanged after one year. The study of the role of paste hydrates, rather than CaOH2, in the deterioration of mechanical properties of OPC and OPC/slag pastes was performed by nuclear magnetic resonance (NMR), X-ray diffraction (XRD), infrared spectroscopy (IR) and Synchrotron NEXAFS. Test results showed differences in the resulting calcium silicate hydrate (C-S-H gel) and aluminate phases of OPC and OPC/slag pastes after exposure to elevated temperatures. This indicates that the silicate and aluminate phases play a role in the higher degree of deterioration observed for OPC pastes when compared to OPC/slag pastes. The study of the effects of elevated temperatures on the mechanical properties of concrete revealed that OPC concrete heated to 800oC followed by exposure to air moisture presented strength loss of 65% while OPC pastes presented total strength loss and complete disintegration. This shows that the dehydration of CaOH2 and rehydration of CaO is significantly less detrimental for OPC concrete than it is for OPC paste. Techniques such as sorptivity tests and nitrogen adsorption were used to determine the differences in the CaO rehydration of paste and concrete. The rate of water absorption determines the growth rate of CaOH2 crystals during CaO rehydration and ultimately the type of CaOH2 crystals formed. Different rates of water absorption result in different CaOH2 crystal formation. This leads to differences in levels of deterioration, which not always result in total disintegration of the constraining body. In this study, the rate of water absorption of OPC paste and concrete was found to significantly differ. The test results revealed that the extent of the deterioration is not only related to the CaO rehydration occurrence, but most importantly, it is related to the rate at which rehydration occurs, i.e., the rate of water absorption. The rate of water absorption is the determining factor controlling the extent of deterioration caused by CaO rehydration.

This chapter reviews the performance of rice husk ash (RHA) as partial cement replace in ordinary Portland cement concrete. After pyroprocessing with controlled combustion, highly pozzolanic RHA can be produced. Due to the high specific surface area and pozzolanic properties, RHA shows very good performance as a supplementary cementitious material in concrete. For early age properties, concrete made of RHA needs more water and high dosages of superplasticizer compared to ordinary Portland cement concrete. The RHA concrete has slightly longer setting times than ordinary Portland cement concrete. When the replacement level of ordinary Portland cement by RHA is about 20% by weight of the total binder material, the compressive strength, tensile strength and flexural strength of concrete made of RHA are enhanced. Due to the special porous structures, RHA shows excellent capacity to keep high relative humidity in the concrete, thus RHA significantly mitigates the autogenous shrinkage of concrete, especially high performance or ultra-high performance concrete made with RHA as addition. From water permeability and chloride diffusivity tests the coefficient of water absorption of RHA concrete is lower and the chloride diffusion coefficient is reduced.

Effect of electric arc furnace dust on the properties of OPC and blended cement concretes

Effect of curing conditions on the strength and durability of air entrained concrete with and without fly ash

This study investigates the stabilization of lateritic soil sourced from a roadside along Iraa Road, near the Nigeria Navy School in Kwara State, Nigeria. The soil was sampled at a depth of 1 meter following the removal of topsoil. Initial testing revealed a California Bearing Ratio (CBR) of 27%, meeting the minimum requirements for subgrade suitability. The addition of 4% Palm Kernel Shell Ash (PKSA) and 2% Rice Husk Ash (RHA) significantly improved the CBR to 41%, reflecting enhanced load-bearing capacity. These findings align with previous research demonstrating the efficacy of PKSA and RHA in improving soil strength. However, stabilization beyond the optimal content of 4% PKSA and 2% RHA resulted in declining CBR values, underscoring the critical importance of maintaining optimal stabilizer proportions for effective performance. The study further observed an increase in the optimum moisture content (OMC) of the soil, rising from 12.60% to 16.10% upon the addition of stabilizers, consistent with the moisture requirements induced by pozzolanic materials. Similarly, the Maximum Dry Density (MDD) of the natural soil increased from 1.67 kg/m3 to 1.72 kg/m3 with the inclusion of 4% PKSA and 2% RHA, indicating enhanced compaction properties. These improvements correspond with established standards and corroborate findings from related studies. To comprehensively assess the effects of stabilization, the research also examined mixtures incorporating incremental proportions of RHA (0%, 2%, 4%, 6%, 8%, and 10%) combined with 4% PKSA, previously identified as optimal for enhancing soil properties. The goal was to improve the soil's CBR values, particularly for application in base course construction. The results demonstrate that while PKSA and RHA are effective stabilizers, exceeding optimal levels leads to reduced performance, emphasizing the need for precise proportioning to achieve desired outcomes in lateritic soil stabilization.

Geopolymer concrete (GPC) is an emerging construction material that uses a by-product material such as fly ash as a complete substitute for cement. This paper evaluates the bond strength of fly ash based geopolymer concrete with reinforcing steel. Pull-out test in accordance with the ASTM A944 Standard was carried out on 24 geopolymer concrete and 24 ordinary Portland cement (OPC) concrete beam-end specimens, and the bond strengths of the two types of concrete were compared. The compressive strength of geopolymer concrete varied from 25 to 39 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 20 mm and 24 mm diameter 500 MPa steel deformed bars. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. Failure occurred with the splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This is because of the higher splitting tensile strength of geopolymer concrete than of OPC concrete of the same compressive strength. A comparison between the splitting tensile strengths of OPC and geopolymer concrete of compressive strengths ranging from 25 to 89 MPa shows that geopolymer concrete has higher splitting tensile strength than OPC concrete. This suggests that the existing analytical expressions for bond strength of OPC concrete can be conservatively used for calculation of bond strength of geopolymer concrete with reinforcing steel.

Insights into water absorption characteristics of various waste-based inorganic additives and their application for soil stabilization

The extraction of lime stone for the manufacturing of cement is a highly energy consuming process that demands high embodied energy. Consumption of supplementary cementitious materials (SCMs) like fly ash (FA) and granulated blast furnace slag (GBFS) results in reduction in energy and carbon emission. Ternary blended composite cement (CC), binary blended Portland slag cement (PSC) and Portland pozzolana cement (PPC) and reference Ordinary Portland Cement (OPC) are used in this study to prepare three grades of concrete viz. M20, M30 and M40 designed as per IS 10262:2019. The energy demand, carbon footprint and cost involved in the preparation are estimated and compared with OPC, PPC, PSC and CC concretes. At 28 days, PPC, PSC and CC concretes exhibited 11.48%, 8.43% and 15.6% lower compressive strength respectively compared to OPC concretes. With respect to M20 grade, PPC, PSC and CC concretes respectively consumed 14.64%, 24.11% and 27.52% less energy than OPC concrete for the same grade. The carbon emission intensity is estimated to be 14.63%, 27.93% and 28.9% less for PPC, PSC and CC concretes respectively compared to OPC. The cost of producing M20 grade of PPC, PSC and CC concretes is about 10.2%, 14.64% and 19.8% lower than OPC concrete production. This difference in energy, carbon emission and cost is found to reduce with increase in grade of concrete for all the blended cements. Composite cement concretes have proven to be energy efficient with less carbon emission and cost compared to OPC, PPC and PSC concretes.KeywordsComposite cementSustainabilityCarbon footprintEmbodied energyCompressive strength

This paper describes how tests were carried out on a series of concrete mixes that were designed to equal workability and compressive strength with a range of pulverized fuel ash (PFA) levels in order to study the effect of curing on the strength and permeability of PFA concrete. Concrete specimens were subjected to a range of moist-curing periods prior to air storage. Compressive strength was determined at various ages and permeability to oxygen and water was determined at 28 days. Results confirm the importance of curing, with reductions in the curing period resulting in lower strength, more permeable concrete. The strength of the PFA concretes appears to be more sensitive to poor curing than ordinary portland cement (OPC) concrete, the sensitivity increasing with increasing PFA content. However, despite exhibiting lower strengths, PFA concretes moist-cured for only one day were, generally, no more permeable to water and substantially less permeable to oxygen than similarly cured OPC concretes. As the period of curing increased, the PFA concretes became considerably more impermeable to water and oxygen than the OPC concretes. These results are discussed in the context of the minimum periods of curing and protection recommended in BS 8110. It is argued that although the increased curing periods suggested for PFA concrete are justified on the basis of concrete strength, PFA concrete may require no more curing than OPC concrete to achieve equal durability, as measured by oxygen and water permeability.

Deicer-scaling resistance of phosphate cement-based binder for rapid repair of concrete