Influence of fiber treatment methods on the mechanical properties of high strength concrete reinforced with sisal fibers.

The science of adding natural fibers to concrete results in an engineering material that is environmentally friendly and has the potential of promoting sustainable development in the construction industry. However, the challenge in adding natural fibers to concrete is that, they are hydrophilic in nature and this affects the bonding between the fibers and the concrete. To avert this problem three different fiber treatment methods namely, chemical, thermal and hybrid treatment methods were conducted on the sisal fibers to investigate the effect of the fiber treatment methods on the mechanical properties of sisal fiber reinforced concrete. The treated fibers were mixed with concrete with percentage fiber content of 0.5 %, 1.0 %, 1.5 % and 2 % and their compressive strength, tensile strength and flexural strength were tested. The experimental results showed that all the treatment methods considered led to an improvement in the tensile strength of the sisal fiber reinforced concrete. The compressive strength was also improved by the thermal and hybrid treatment methods, however, the chemical treatment method led to a reduction in the compressive strength. With regard to the flexural strength, all the treatment methods considered led to a reduction in the flexural strength when compared to the concrete without fibers.

Properties of concrete mixes containing tire rubber and brick powder exposed to sulfuric acid and cured in water: A comparative study.

The existing literature shows that rubberised concrete suffers from reduced mechanical properties when it is compared with normal density non-rubberised concrete. This is due to the underlying reduced bonding between tire rubber and other concrete ingredients. The massive sulfuric acid attack in rubberised concrete must have additionally discouraged researchers from attempts to assess the phenomenon of improving performance of rubberised concrete. A research was undertaken to compare the properties of concrete mixes containing tire rubber replacing coarse aggregate and waste clay brick powder (WCBP) replacing cement exposed to sulfuric acid and cured in water. Concrete cubes and cylinders of concrete grades of 20 MPa, 25 MPa and 30 MPa were immersed in 5% sulfuric acid solution up to 90 days following moist curing of 27 days. Other concrete cubes and cylinders were cured in water for comparison. The compressive strength findings indicated that all the specimens exposed to sulfuric acid had lost more than 57% of their compressive strengths after 90 days with reference to the corresponding samples cured in water. In contrast, out of all concrete mixes investigated for all concrete grades, never were the split tensile strength losses of the specimens exposed to sulfuric acid greater than 43.1% compared with those cured in water. In each exposure condition, concrete mixes with 5% WCBP showed slight improvements in compressive and split tensile strengths in contrast with the conventional concrete mixes. Visual inspection of the specimens illustrated depositions of flaky or white substances on the outer layers of specimens exposed to sulfuric acid compared with specimens cured in water. Moreover, the split tensile strengths of specimens were not severely affected with exposure to sulfuric acid in comparison with compressive strengths. Eventually, the research identified the existence of WCBP in rubberised concrete as a promising criterion of minimising strength losses of rubberised concrete.

Behaviour of rubberised concrete with waste clay brick powder under varying curing conditions.

Recently, there has been a worldwide scarcity of pure water for curing concrete and this has called for alternative curing conditions including utilisation of sea water. An experimental study was conducted to examine the mechanical behaviour of rubberised concrete with waste clay brick powder (WCBP) under different conditions of curing including water and sea water. The samples of rubberised concrete incorporated with WCBP were cured in water and sea water for 90 days curing period. The findings showed that the conventional and modified concrete mixtures which were cured in sea water illustrated reduced compressive and split tensile strengths compared with corresponding mixes cured in water. Among specimens cured in each curing condition, concrete mixes with 5% WCBP showed increased compressive and split tensile strengths compared with the control concrete mixes. The lowest compressive and split tensile strength findings were noticed with rubberised concrete incorporated with WCBP. The comparisons of densities of specimens cured in water and sea water showed no significant distinctions between the curing conditions. Compressive strength seemed to be less sensitive to conditions of curing compared with split tensile strength. From the findings, minor reductions in compressive strengths for samples cured in sea water compared with those cured in water were suggested to be reflections of possibility of utilising sea water as a curing agent in areas where pure water is very scarce. The findings in this study seem to suggest that the use of sea water in concrete curing should not be feared and could be welcome, particularly in offshore constructions and isolated islands.

Effects of Alternate Wet and Dry Conditions on the Mechanical and Physical Performance of Limestone Calcined Clay Cement Mortars Immersed in Sodium Sulfate Media.

Sulfate attack in concrete structures significantly reduces their durability. This article reports the experimental findings on the effects of sodium sulfate on limestone calcined clay cement (LC3) in an alternate wet and dry media. The samples underwent wet-dry conditions of 28 cycles. Two types of LC3 were studied, one made from clay (LC3-CL) and the other made from fired rejected clay bricks (LC3-FR). The composition of each LC3 blend by weight was 50% clinker, 30% calcined clay, 15% limestone, and 5% gypsum. The reference compressive strength was evaluated at 2, 7, and 28 days of age. Then, ordinary Portland cement (OPC) and LC3-CL blends were subjected to alternate wet-dry cycle tests, immersion in a 5% sodium sulfate solution, or in water. For all exposed samples, sorptivity tests and compressive strength were done. The results showed that LC3 blends met the requirements for KS-EAS 18-1:2017 standard, which specifies the composition and conformity criteria for common cements in Kenya. The LC3 blend also had a lower rate of initial absorption compared to OPC. Additionally, LC3 blend also showed good resistance to sodium sulfate when exposed to alternating wetting and drying environment. OPC showed higher compressive strength than LC3 blends for testing ages of 2, 7, and 28 days. However, the LC3 samples utilized in the sodium sulfate attack experiment, which were later tested after 84 days, exhibited higher compressive strengths than OPC tested after the same period.

Effect of gum Arabic content on maximum dry density and optimum moisture content of laterite soil.

Soil is a material that has been used in construction for centuries and nowadays represents one third of the world's construction. Cement and lime which are common stabilisers used to make soil-based blocks durable have been found to be harmful to the environment. Therefore, finding environmentally friendly materials as a substitute for cement and lime is of vital importance. In Africa, gum Arabic is a widely available organic material (a biopolymer). The objective of this study was therefore to evaluate the effects of gum Arabic on maximum dry density and optimum moisture content of laterite soil in order to use gum Arabic as a binder for the stabilization of laterite soil blocks. Light compaction test (Standard Proctor Test) was carried out for the mixture of laterite soil, sand, and gum Arabic. The proportion of sand was 20% by mass of laterite soil in this mixture; the gum Arabic was varied from 0 to 10% with a step of 2, by mass of laterite soil. The results showed that the maximum dry density decreased from 1883 kg/m3 to 1693 kg/m3 after the addition of 0%-10% gum Arabic in laterite soil, respectively. Whereas the optimum moisture content increased from 14.88% to 18.38% after the addition of 0%-10% gum Arabic, respectively. The observed results of the maximum dry density have been found to be within the recommended range. Based on the findings from this study, gum Arabic can be recommended as binder in the stabilisation of laterite blocks.

Influence of material composition on the morphology and engineering properties of waste plastic binder composite for construction purposes.

Ways of mitigating the menace caused by the abundance of waste plastic generated have been a global concern. Efforts are geared towards intensification of the recycling culture for circular economy. Recent studies combined waste plastic and sand to make Waste Plastic Binder (WPB) composite materials. However, sand mining operation has been associated with environmental and ecological issues. This study explores the engineering properties of waste plastic and quarry dust composite for sustainable infrastructural development. The polyethylene terephthalate type of plastic (PET) was employed, and which was melted and mixed with QD at different compositions of 1:0, 1:1, 1:2, and 1:3 respectively. The influence of the varying compositions on the morphological and engineering properties of resulting WPB composite was investigated. The scanning electron microscopy image showed that WPB composite with higher percentage of QD possess lesser pore space, and which influenced the high strength values. The findings showed P&QD 1:3 have highest compressive strength value of 20.1MPa, and which meets up with the American Concrete Institute and South African standard minimum requirement of 17MPa for structural lightweight concrete applicable for walkways, walling and water retaining structures constructions.

A study on mechanical properties of rubberised concrete containing burnt clay powder.

An experimental study was conducted to investigate the mechanical performance of rubberised concrete containing Burnt Clay Powder (BCP). Waste Tire Rubber (WTR) and BCP were used to replace coarse aggregate and Ordinary Portland Cement (OPC) respectively. Class 20, 25 and 30 concrete mixes based on British Research Environment (BRE) were cast and tested for compressive, split tensile and flexural strengths. The findings of the tests revealed reductions in compressive and split tensile strengths for concrete mixes with 5% BCP compared to control concrete mixes for 7, 28 and 56 days curing periods. However, inclusion of BCP in concrete seemed to increase the compressive and split tensile strengths of concrete compared to control concrete at 90 days curing period. The findings also demonstrated that WTR content as high as 20% by aggregate total volume could be used to generate rubberised concrete containing 5% BCP with compressive strengths of 18-33 MPa for class 20, 25 and 30 concrete mixes. The flexural strength of unreinforced beams decreased due to inclusion of 5% BCP compared to control concrete after 28 days of curing. Rubberised concrete with BCP was observed to promote ductile failure of concrete cubes while control concrete cubes exhibited brittle failure. The inclusion of 5% BCP in concrete seemed to decrease compressive and split tensile strengths at lower curing periods while still presenting improved results at longer curing period.

Response surface methodology-based optimisation of cost and compressive strength of rubberised concrete incorporating burnt clay brick powder.

Modified concrete is increasingly being produced by substituting concrete constituents with waste materials. Among waste materials are powder from waste clay bricks replacing Ordinary Portland Cement and Waste Tire Rubber (WTR) replacing natural coarse aggregate. However, the use of modified concrete is controlled by its cost-performance balance. This paper investigates the cost advantages of using rubberised concrete incorporated with Burnt Clay Brick Powder (BCBP) where findings are evaluated in comparison with conventional concrete. In this study, compressive strength of rubberised concrete containing BCBP was investigated using mixes generated by Response Surface Methodology (RSM). Central Composite Design (CCD) based on RSM was used to assess the influence of replacement variables of BCBP (0-5%) and WTR (0-20%) on concrete production cost and concrete compressive strength responses. First order and second order mathematical models were developed by RSM with findings from experimental design. The accuracy of the mathematical models established by CCD was tested using Analysis of Variance (ANOVA). Desirability analysis was then employed to optimise BCBP and WTR contents yielding maximum compressive strength at lower cost. Moreover, under the established optimum conditions, the performance of the optimum independent variables was experimentally verified by testing 6 cubes. Production cost of concrete containing these waste materials reduced up to 4.23% compared to conventional concrete. RSM evaluation demonstrated that the empirical findings were well suited into linear and quadratic models for cost and compressive strength responses respectively. The coefficients of determination of greater than 0.85 for all responses established that the models were capable of explaining variability in the responses. 5% BCBP and 6.875% WTR were optimum contents establishing maximum 7-days compressive strength of 27.607 MPa at lower cost of KSh 13 718.43. Optimisation of cost and 28-days compressive strength from desirability analysis gave 5% BCBP and 5.844% WTR contents as optimum values. This optimum combination resulted to maximum compressive strength of 33.970 MPa and lower cost of KSh 13 734.64. Verification of the model findings indicated considerable agreement with the verified values. From the findings, it was confirmed that a reasonable cost-performance balance for modified concrete can be achieved using BCBP and WTR.

Ductility performance of reinforced rubberised concrete beams incorporating burnt clay powder.

Application of rubberised concrete in earthquake prone areas is of significant importance. Although investigations have been conducted to research on the ductility of rubberised concrete, the behaviour of rubberised concrete with Burnt Clay Brick Powder (BCBP) is not well understood. This paper captures the ductility behaviour of rubberised concrete containing BCBP. In this study, 3 beams were investigated in flexure while the other 3 beams were made to fail in shear and flexure. For the beams that failed in flexure, ductility of concrete beams containing 5% BCBP and 10% Waste Tire Rubber (WTR) improved by 23.47% compared to control beam. This increase in ductility was evidenced with only 15.31% reduction in flexural load. Moreover, the beam containing 5% BCBP and 10% WTR failing in shear and flexure exhibited 14.59% ductility improvement with 16.33% load reduction in comparison to the control beam. Eventually, the study concluded that it is possible to achieve improved ductility without substantial loss in ultimate failure load by using 5% BCBP and 10% WTR. Such properties demonstrated that this rubberised concrete with 5% BCBP can be used in seismic applications.