Assessment of Cohesive Soil - Cow Dung Mortar Properties as Replacement of Cement Mortar for Simple Plastering Works

The development of local construction industry has resulted in the high demand for cement, used not only for structural but also non structural applications, such as finishing. As a consequence cement has been far from being an affordable material for the good part of the population, especially in the rural areas where financial means are still limited. Regarding the finishing exercise, those people have been using soil mortar alone or reinforced with grasses without any strategy about mixture content. The objective of this study was to assess the performance of cohesive soil mortar mixed with cow dung and establish recommended mix content for plastering works. Twelve samples of soil mortar with 10%, 20%, 30% and 40% of cow dung, were prepared and subjected to drying period of 28 days before they were tested for water absorption, shrinkage, weathering resistance, specific gravity and Atterberg limit tests. The tests showed good results for checked properties with 20% of cow dung, and therefore it could be considered as a low-cost alternative plastering material to cement mortar for some structural members under normal weather conditions. In order to avoid the earlier shrinkage and cracks in this mortar due to spontaneous drying by sun, the mortar should be protected and not be left in open area at earlier stage. Keywords: Cohesive Soil, Cow dung, Mortar, Shrinkage, Water absorption, Weathering resistanc

Basalt Powder Waste Application as Affordable Concrete Admixture

Different weather conditions, like temperature and humidity influence on the performance of concrete structures to which they are normally subjected, especially at earlier stage of their service life. One of practical measures has been the regulation of the setting time of fresh concrete. Some admixtures are used in concrete to regulate the setting time and therefore increase structures performance under given situation. Almost all admixtures used in Rwanda are being imported from outside the country and this is one of factors affecting the construction cost. A big quantity of basalt powder at different sites in the country is left without being used and has been negatively impacting the environment. This study aimed at analyzing the potentials of basalt powder waste used in concrete as admixtures in different percentages, e.g. 0%, 5%, 10%, 15% and 20%. Different investigations on concrete incorporating basalt powder as admixture, such as the setting time, workability and compression tests were conducted. The results showed that the gradual incorporation of basalt powder waste as admixture up to 20%, accelerated the setting time more than 13 times, but decreased the compressive strength of concrete by around 24.5%, with comparison to normal concrete strength. The application of basalt waste in concrete would contribute not only to the reduction of environmental pollution but also to the provision of more affordable admixtures for mortar and concrete

Sulfate attack and embedded steel corrosion resistances of volcanic-aggregate concrete with fly ash and silica fume

Construction materials are increasingly on high demand in the developing world. The construction industry has a challenge of discovering, new  alternative construction materials to conventional materials which are locally available materials in environmentally friendly manner. The  experimental tests are conducted on volcanic concrete system to analyze its properties especially corrosion resistance potential for its applicability in construction. The major aim is to investigate its suitability and corrosion resistance potential especially when used in construction of structures with embedded steel. The test results of the material show that volcanic concrete system with 30% fly ash and 10% silica fume cementing materials is an alternative green construction material. Permeability properties are reduced by 8% and 24% with 30% fly ash and 10% silica fume respectively. Tests also indicate that Compressive strength, Corrosion potential and polarization resistance in volcanic concrete system with supplementing  cement materials has more potential to resist sulfate attack when compared with conventional volcanic concrete systems. The supplementary cementing materials (SCM) reduce the pore system and hence decrease the ingress of corrosive ions an  water in concrete. Corrosive ions, moisture and air would initiate corrosion to the embedded steel in concrete leading to reduced service life such structures. Key word: Supplementary Cementing Materials, Sulfate attack, volcanic concrete system, Granite powder, river sand, Corrosion of embedded stee

Experimental investigation on the potentials of Sisal Fibres as Reinforcements for Drainage Concrete Cover Plates

With the development of infrastructures in Rwanda, the roads construction has been one of busiest area, and as the country counts thousands hills the design and construction of drainage systems required a great attention. Most of road drainage channels are covered with concrete plates that are reinforced with ordinary steel bars, while others are not covered due to the high cost of reinforced concrete plates. As the majority of these  plates are only subjected to light pedestrian loads, they should be reinforced accordingly. This study was intended to check the potentials of sisal fibres from Agave Sisalana’ cactus plant which has shown good results in flexural members, as plates reinforcements. At first the quality of ordinary concrete components was checked. Then some of sisal fibres were prepared, manufactured into ropes of 10 mm diameter and then used as replacements of main steel bars in concrete plates before their tensile capacity was checked. Other pieces of sisal fibres of 5 cm length were mixed in concrete mass with different percentages of 0.5%, 1% and 1.5% of concrete volume. Test results showed that the compressive, tensile and flexural strengths for concrete with 1% of sisal fibres were more adequate for M30 concrete and therefore able of sustaining the real loads applied to the  drainage concrete cover plates. As the performance of natural sisal fibres depends on fibres treatment methods, length, and type of required concrete, further studies on the use of sisal fibres should consider those factors. Keywords: Agave sisalana, drainage channel, Reinforced Concrete, Sisal Fibres, Sisal ropes

Strength, sustainability and affordability of bamboo and mud bricks as materials used in local construction

The construction industry is one of the rapidly growing and the cost analysis suggests that the materials cost is constantly increasing. The continuous extraction of aggregates intensively used in the field is negatively acting to the environment. Therefore research in construction materials should focus not only on discovering new alternative materials but also in appreciating the quality of those locally available for their better application. This research aimed at evaluating the performance of bamboo and mud bricks as two available local building materials, especially with regards not only to their strength but also to new performance concepts which are affordability, energy efficiency and environment friendly aspects. The study comprised mainly of laboratory tests of used materials and cost estimation analysis. Study results established that the considered bamboo and mud bricks, made in ordinary soils and reinforced by sisal fibers were reusable, environment friendly materials and energy efficient, with the bamboo showing the thermal conductivity equal to 0.1496 W/mK. Regarding the compressive strength, reinforced mud bricks with sisal fibers showed an increased value from 1.75 MPA to 4.29MPA, what was in line with related previous studies. The average compressive strength of the studied Arundinaria Alpine bamboo was established at 133,7MPA, while its tensile strength was 88.16MPA and these values were reasonable with comparison to other conventional materials. It is recommended that further research in checking the performance of other types of bamboo as well as about new construction technologies be undertaken in order to enhance the service life of both bamboo and mud bricks.Keywords: Affordability, Bamboo, Conventional concrete, Materials strength, Mud reinforced bricks, Sustainabilit

Investigation on application of Rwanda building standards in local construction industry

The Rwanda Building code is in place from 2015, while the development of Rwanda standards dates from 2006 when the reviewed Law establishing Rwanda Bureau of Standards (RBS) was published. The key role of standards is technically to ensure quality, safety, reliability of constructions as stated the relevant codes. With the construction industry growing very fast, the purpose of this study was to investigate on the application of Rwanda building standards, with regards to the existing code requirements and to identify the relevant gaps. The study was conducted based on initially set specific objectives, while the research methodology was mainly comprised of visits to different public and private agencies related to construction industry, observations on the sites and interview with different experts. The study established that Rwanda building standards were still accused of a low awareness and application as well as noticeable gaps. The level of awareness among all professionals was still at 71%. In general about application, only 55% of respondents confirmed the experience in application of Rwanda building standards, even if this level was higher for some categories. A good part of respondents composing around 57% thought that Rwanda building standards documents were still incomplete. Based on the above findings, adequate strategies for improving the awareness, application process and document completion were proposed; with the introduction of Rwanda building standards into academic curriculum, increase the number of awareness meetings and recognition of adequate research before design or review of any standard, among others.Keywords: Building code, Building Standards, awareness strategy, Law and Regulations, Monitoring proces

Study on housing affordability in Rwanda

Abstract: The growing economic opportunities in small and big African cities have seen the exodus of a good part of population, especially young from rural areas. This creates a housing problem in cities not only in terms of quantities but also in terms of quality.The problem of housing affordability is an important handicap for countries to achieve some of Millennium Developments goals in terms of Poverty Eradication and Environmental Sustainability. This research conducted in Rwanda comes in line with support to some of government and cities strategies and policies, such as Vision 2020, Economic Development and Poverty Reduction Strategy (EDPRS I and II) on land use, infrastructure development, etc. It is proposing the possibility of planning and designing residential affordable apartments or single family houses (SFH) to people living in Rwandan cities without going against approved cities ’ Master Plan. The work consists in the detailed analysis of the site, Building Materials, and Structural systems suitable to the site conditions. It was established that comparing with the actual building costs on the markets, the engineering consideration of above three factors may reduce the building cost in 3 – 6 times

Finite Element Analysis of Double-Bolt Shear-Out Fracture Failure

This paper presents the finite element (FE) analysis of double-bolt shear-out (DBSO) fracture failure. The DBSO fracture shape consists of two oppositely: inclined outer main shear fractures, inner main shear fracture, outer shear lips, and curved inner curved fractures. The DBSO begins with two outer main shear fracture initiations under shear, vertical compressive bending, and sideways bending deformations/stresses followed by the two inner main shear fracture initiations under shear and vertical compressive bending deformations. The outer shear lips occurred under vertical compression bending, shear, and sideways tensile bending stresses/deformations while the two inner curved fractures occur under rotational deformation

Reuse of construction and demolished concrete waste by producing affordable high strength concrete block

The issue of achieving sustainable environment is highlighted in different national and international strategic documents, such as Rwanda Viosion 2020, EDPRS II and MDGs. Rwanda on its track towards achieving sustainable environment, is still experiencing some challenges like Environmental degradation for the search of aggregates, energy for extraction of natural aggregates and difficulties in finding dumping sites for demolitions and construction wastes. Therefore, all those problems have created the need for developing a new source of construction materials.The idea of recycling of C&D concrete wastes aims at finding solution to the environment degradation caused by damped demolished wastes as well as producing affordable high strength concrete blocks. This research investigated the availability of C&D concrete wastes and it was discovered that up to 33.33% of C&D waste came from concrete structures while more than 23.75% of people confirmed to have been involved in demolition works more than three times a year.The research was done by collecting sample composed of C&D concrete wastes at construction site of BPR headquarter where they demolished the existed building for construction of a new multistory building in kigali city and the sample was crushed, batched and mixed with a proportion of 1:3 and 1:5 as stated by Rwanda Bureau of Standards and manufactured new concrete blocks. The research performed on series of concrete blocks: 2 series each made of different proportions of cement for recycled concrete blocks, and one serie of reference blocks made of natural aggregates. Compressive strength test gave an average of 5.13N/mm2 for recycled concrete block, which fulfills requirement of Rwanda Bureau of standards for hollow concrete blocks and which is 0.87 times the compressive strength of an ordinary block tested under same conditions. Finally, the cost effectiveness showed that the new recycled concrete block will be affordable by reducing at 15.6% of cost for that one made of natural aggregates.Keywords: Concrete wastes, Recycled concrete block, Mechanical properties, Cost effectiveness and Environmental protectio

Effect of the Roof Slope on the Cost Variation of Residential Houses

The building industry has been one of the fast-growing sectors in Rwanda, and multiple residential houses with amazing pitched roofs are being implemented in different cities. As the country is very hilly, the influence of wind loads on the buildings is high and therefore the selection step of roof slopes needs to be carefully undertaken, in order to ensure not only the structure safety, but also the economy. Available international and national guidelines give details about safety and functionality requirements, but don’t talk much about economic aspect, and this was the purpose of the given study. Using a well elaborated methodology, the influence of the roof slope on its cost was checked, and it was established that the slope’s increase of one degree would raise the roof cost by 3.6%. Therefore, during the roof slope selection and design process, economic requirements need more attention