Prospective Materials for Building Construction in Hot Countries: The Case of Straw Blocks

Background: The negative impacts of the construction industry are compelling arguments for embracing technology that contributes to carbon footprint reduction and resources conservation. Toward the achievement of objective 9 of the Sustainable Development Goals, the development of new building’s materials like straw bale has advanced in the construction industry. As demonstrated in the literature, straw bale is an eco-friendly material that presents many advantages, like its contribution towards a circular economy. However, it has low compressive strength and displays high displacement under compression load. So far, no attempt has been made in order to enhance the strength of straw bales. Objective: This study aimed to develop alternative material to straw bale using chopped straw stems mixed with a binder (gum Arabic) and determine its stress-strain characteristic. Methods: The manufacturing process of the new material involved the use of chopped straw and gum Arabic to form straw blocks. Results: Results obtained show that the compressive strength of straw block (1.25MPa) is greater than the strength of straw bale (0.02MPa). Also, the average displacement recorded during compression load on straw blocks (29mm) was 2.8 times smaller than the displacement in straw bale (80mm). In terms of shape and size, straw blocks match with conventional materials like cement or compressed block. This will facilitate their use in construction compared to straw bales that require skilled laborers for pre-compression and plastering. Conclusion: The use of gum arabic helps in holding straw stems together and forms a compact material with improved strength compared to straw bale. Performance improvement of the characteristics of load-bearing straw bale walls can be addressed by using straw blocks.

Multifactorial behavior of the elastic modulus and compressive strength in masonry prisms of hollow concrete blocks

The interlocking concrete pavement blocks are quite commonly used to construct the pedestrian walkways and parking lots of transport infrastructure. Such blocks need adequate compressive strength to withstand the design live loads. In this paper, the influence of admixtures on the compressive strength of the blocks are studied through a series of laboratory investigations. The M35 grade of concrete conforming to the Indian Standard code of practice has been used with a standard superplasticizer as admixtures added at specified weights. The study implied that the use of admixtures alters the compressive strength of concrete blocks significantly.

Characterization of the clay masonry units and construction technique at the ancient city of Nippur

Water absorption characteristics and rate of strength development of mortar with slag-based alkali-activated binder and 25% fly ash replacement

Background:In recent decades, the enduring interest and continued development of straw bale as a walling material are based on its beneficial properties. Straw bale is a biomaterial that contributes greatly to carbon footprint reduction and offers excellent thermal insulation. It is proved that plastered straw bale assemblies have good mechanical properties and can be used for the construction of a single storey building. It is known that straw bale presents high displacement in the assemblies; thus, pre-compression is a major step that helps to push down straw bale so as to avoid future structural failure in the wall. There is no clue yet if this method is structurally beneficial than to stabilized single straw bales before assembling them into a structural panel.Objective:This paper presents the structural performance of straw block assemblies under compression loads.Method:Straw blocks and mortar were used to construct plastered and un-plastered wall panels, which were tested under uniformly distributed compression load till failure.Results:The results obtained show that plastered straw block assemblies can support at least 286 KN/m2, which is higher than the minimum slab load 18.25KN/m2, including imposed load for a residential house. In addition, the strength of plastered straw block assemblies plastered with cement-gum mortar, 0.3 N/ mm2is greater than the strength of a single storey building (0.19N/mm2). Furthermore, results indicate that un-plastered and plastered straw block assemblies perform better than un-plastered and plastered straw bale assemblies. Plastered straw block assemblies support up to 52KN while plastered straw bale assemblies support only 41.1KN.Conclusion:Under compression load, straw block assemblies have a load carrying capacity greater than the minimum slab load. Therefore, Straw block can be used for the construction of a single storey building.

Interest of using straw bale as construction material has increased worldwide. This result from the need of developing building envelopes which are climate responsive and can significantly reduce building’s energy consumption. Research on straw bale has shown that straw bale has good thermal conductivity while plastered straw bale assemblies has good mechanical properties. Up to date, straw bale construction consists of stacking straw bale in a running bond and use different techniques to push down straw bale wall before plastering them. No clue has been given if this method is structurally beneficial than to stabilized single straw bale before assembling them into a structural panel. This paper presents a method of construction that consist of manufacturing straw blocks before using them in masonry. Blocks of dimension 29 × 14 × 14 mm were manufactured using chopped straw with a natural binder. The average compressive strength and density of blocks are respectively 1.25 MPa and 522 kg/m3; which are respectively 73 and 5 times greater than that of straw bale. Also the average thermal conductivity of straw block and straw are similar (0.06 W/mK). Thus the use of straw blocks will improve the structural performance of straw houses.

One practical substitute for aggregate in concrete that can be used in sustainable building methods is waste tyre rubber and metakaolin a significant advancement in sustainable building methods. This study addresses the main problem of limited knowledge on optimizing crumb rubber proportions in concrete bricks, aiming to fill the research gap regarding their impact on brick properties. Bricks were manufactured using various crumb rubber proportions (CR5%, CR10%, CR15%, and CR20%) in a 215×103×65mm mould, maintaining a consistent water-to-cement ratio of 0.6 for all mixes. Rubberized concrete bricks were evaluated at 28 days for efflorescence, water absorption, initial rate of water absorption, density, physical observation, and compressive strength, compared to control specimens. The results revealed no efflorescence in any bricks, with a 38% density reduction in the CR20% mix compared to the control. Water absorption increased linearly with higher crumb rubber content, while the initial rate of water absorption rose to 15% crumb rubber before decreasing with further increases. Compressive strength ranged from 12 to 22 MPa, 17% higher than the minimum required for conventional bricks, although the CR20% mix's strength of 4.3 MPa was 60% lower than the control mix, rendering it unsuitable for non-load-bearing elements. The optimal combination for structurally sound concrete bricks was achieved by replacing up to 15% sand with crumb rubber and adding 10% MK. This study demonstrates that incorporating these materials can enhance the sustainability and structural integrity of concrete bricks.

Experimental study on water absorption of unsaturated concrete: w/c ratio, coarse aggregate and saturation degree

Two series of load-bearing horizontal-hole interlocking hollow concrete blocks, referred to as H-shaped series and cross-shaped series, were developed, including three geometric types: type BH-290 (H-shaped), type BH-240 (H-shaped), and type BC-240 (cross-shaped). The research presented in this article investigated the compressive behavior of the proposed load-bearing horizontal-hole interlocking hollow concrete blocks and aimed at analyzing the influence of geometric parameters on the block capacity. First, compressive tests of the horizontal-hole interlocking hollow concrete blocks were carried out. The compressive strength, elastic modulus, and compressive failure mechanism were analyzed. Second, the feasibility of the finite element analysis model was verified by experimental results presented in this article, as well as by available test data from other researchers. The influences of vertical ribs, horizontal ribs, and concrete strength on the compressive strength of horizontal-hole interlocking hollow concrete blocks were investigated. Ultimately, based on the numerical modeling results, linear equations were proposed to predict the compressive strength of H-shaped series and cross-shaped series blocks. The results show that the compressive strengths of types BH-240, BH-290, and BC-240 are 15.9, 13.4, and 13.0 MPa, respectively. For the H-shaped series, the core horizontal rib is the key part that can significantly constrain the vertical ribs so that the block can achieve higher compressive bearing capacity. For the cross-shaped series, core horizontal ribs cannot improve the compressive strength of the block because core horizontal ribs and joints near them become damaged early. Improving the concrete strength and the width of the vertical rib can effectively improve the compressive bearing capacity for both H-shaped and cross-shaped series blocks. The accuracy of the proposed equations for predicting the compressive strength of H-shaped and cross-shaped blocks is acceptable, according to the current verification.

Employment of crumb rubber tyre in concrete masonry bricks

Objective: To evaluate parameters about wettability, water absorption or swelling of excipients in forms of powders or dosage through various methods systematically and explore its correlation with tablet disintegration.Material and methods: The water penetration and swelling of powders with different proportions of excipients including microcrystalline cellulose (MCC), mannitol, low-substituted hydroxypropyl cellulose (L-HPC), crospolyvinylpyrrolidone (PVPP), carboxymethyl starch sodium (CMS-Na), croscarmellose sodium (CCMC-Na) and magnesium stearate (MgSt) were determined by Washburn capillary rise. Both contact angle of water on the excipient compacts and surface swelling volume were measured by sessile drop technique. Moreover, the test about water absorption and swelling of compacts was fulfilled by a modified method. Eventually, the disintegration of tablets with or without loratadine was performed according to the method described in USP.Results and discussion: These parameters were successfully identified by the methods above, which proved that excipient wettability or swelling properties varied with the structure of excipients. For example, MgSt could improve the water uptake, while impeded tablet swelling. Furthermore, in the present study it is verified that tablet disintegration was closely related to these parameters, especially wetting rate and initial water absorption rate. The higher wetting rate of water on tablet or initial water absorption rate, the faster swelling it be, resulting in the shorter tablet disintegration time.Conclusion: The methods utilized in the present study were feasible and effective. The disintegration of tablets did relate to these parameters, especially wetting rate and initial water absorption rate.

The rapid growth of today’s construction sector requires high amount of building materials. Bricks, known to have solid properties and easy to handle, which leads to the variety of materials added or replaced in its mixture. In this study, high density polyethylene (HDPE) was selected as the substitute materials in the making of bricks. The reason behind the use of HDPE is because of its recyclable properties and the recycling process that do not emit hazardous gases to the atmosphere. Other than that, the use of HDPE will help reducing the source of pollution by avoiding the millions of accumulated plastic waste in the disposal sites. Furthermore, the material has high endurance level and is weatherproof. This study was carried out on experimenting the substitute materials in the mixture of cement bricks, a component of building materials which is normally manufactured using the mixture of cement, sand and water, following a certain ratios, and left dried to produce blocks of bricks. A series of three different percentages of HDPE were used, which were 2.5%, 3.0% and 3.5%. Tests were done on the bricks, to study its compressive strength and the initial water absorption rate. Both tests were conducted on the seventh and 28th day. Based on the results acquired, for compressive strength tests on the 28th day, the use of 2.5% of HDPE shown values of 12.6 N/mm2 while the use of 3.0% of HDPE shown values of 12.5 N/mm2. Onto the next percentage, 3.5% of HDPE shown values of 12.5 N/mm2.

Compressed stabilized soil block is a sustainable building material primarily made up of stabilized damp soil compressed under pressure. Soil properties and the type of the stabilizer used in producing compressed soil blocks have a significant impact on the quality and behavior of the soil blocks. This study presents the physical and mechanical behavior of lime-cement-stabilized compressed interlock soil blocks produced from two types of natural soil. The two types of soil have different index properties and mineral oxide compositions. Lime-cement combination and cement standalone was used as a binder in the production of test sample blocks depending on the index properties of the soil. 2%lime + 6%cement, 3%lime + 8%cement, and 4%lime + 10%cement were used for the soil block produced from silty clay soil of medium plasticity index. On the other hand, 6%, 8%, and 10% cement by dry mass of soil were used to stabilize silty sand soil. The behaviors of the blocks, such as dry density, the initial rate of water absorption, saturated absorption of water, compressive strength, and stress-strain relation, were examined. The result shows that the compressed soil blocks produced from lime-cement-stabilized silty clay soil has a low rate of initial water absorption and a low dry unit weight when compared to cement-stabilized sandy soil blocks. Soil blocks produced from cement-stabilized silty sand soil attain greater compressive strength by more than 50% of the compressive strength of silty clay soil blocks stabilized by a combination of lime and cement at 60 days after production. The initial tangent modulus of the soil blocks produced using a manual compressing machine from a clay soil stabilized by the lime-cement proportions of 2%L + 6%C, 3%L + 8%C, and 4%L + 10%C is about 1,700 MPa–2,300 MPa with a dry density greater than 1,660 kg/m3.

Burnt clay bricks are one of the most important building units worldwide, are easy and cheap to make, and are readily available. However, the utilization of fertile clay in the production of burnt clay bricks is also one of the causes of environmental pollution because of the emission of greenhouse gases from industrial kilns during the large-scale burning process. Therefore, there is a need to develop a new class of building units (bricks) incorporating recycled industrial waste, leading toward sustainable construction by a reduction in the environmental overburden. This research aimed to explore the potential of untreated coal ash for the manufacturing of building units (coal ash unburnt bricks). Coal ash unburnt bricks were manufactured at an industrial brick plant by applying a pre-form pressure of 3 MPa and later curing them via water sprinkling in a control shed. Various proportions of coal ash (i.e., 30, 35, 40, 45, 50, and 55%) were employed to investigate the mechanical and durability-related properties of the resulting bricks, then they were compared with conventional burnt clay bricks. Compressive strength, flexural strength, an initial rate of water absorption, efflorescence, microstructural analysis via scanning electron microscopy, and cost analysis were conducted. The results of the compressive strength tests revealed that the compressive strength of coal ash unburnt brick decreased with an increase in the content of coal ash; however, up to a 45% proportion of coal ash, the minimum required compressive strength specified by ASTM C62 and local building codes was satisfied. Furthermore, bricks incorporating up to 45% of coal ash also satisfied the ASTM C62 requirements for water absorption. Coal ash unburnt bricks are lighter in weight owing to their porous developed microstructure. The cost analysis showed that the utilization of untreated, locally available coal ash in brick production leads us on the path toward more economical and sustainable building units.