Low-cost housing projects are characterised by an increasing demand mainly due to urbanisation. The selection of building materials should meet the needs of local conditions to improve quality of life for the most needed ones by building new structures and/or by improving existing structures. Sustainability regarding urban housing intends to develop new approaches to manage human settlements and integrate energy and environmental issues. To achieve a sustainable housing project is required a balance of environmental, economical and social issues with technical issues. Findings show that up to 60 % of the total cost of a low-income housing project is allocated to engineering design and construction materials. Moreover, walls constitute up to 50% of the total cost of materials and up to 45% of total construction time. Material origin, production techniques and labour requirements all have major impacts on the selection of wall building material. The analysis of particular local conditions will determine where materials are most suitable for their use. Furthermore, the time when materials and techniques were / are mostly used will determine whether they could be classified as traditional or contemporary. The regularity of use will determine whether materials and methods could be classified as conventional or alternative.
Building components can be interrelated through different systems. There are three building systems considered in this study:
– Massive system; a solid construction based on one type of material.
– Frame system; vertical, horizontal and angular members joined together to form a load-bearing framework. The space between the members can remain open or be filled with different materials.
– Core system; a combination of materials with an inner, or core, part and an outer layer for cladding/reinforcement.
The advantages and disadvantages of each system is shown in Figure 1.
Various studies showed that a big variety of wall materials have been used in different building systems with traditional and modern construction methods, but only few of them (extruded clay bricks, hollow concrete blocks) have successfully been implemented in low-cost housing projects. Conventional materials (e.g. cement, steel, concrete) in low-cost houses constitute up to 98% of the materials used. Non-conventional materials (polymers, composites, recycled) have been left aside despite better thermal and condensation characteristics for local conditions. Alternative design including use of non-conventional materials have also been left aside despite reduction of construction time of more than 50%.
Some of the aspects/criteria most frequently considered in the comparison of technical advantages and disadvantages of building material are shown in Figure 2.
Materials for Low Cost Housing
Some of the materials used in low cost housing are described as below:
Cement Plant (capacity from 300tpd to 12000tpd) – It’s the mother of all the building materials and is required in every aspect of a building construction. Raw materials required limestone, clay, iron stone and gypsum. Schematic diagram of a typical cement plant is shown in Figure 3.
Lime-Sand Brick – This is used for load bearing walls of low-rise buildings and is a good substitute for clay brick. Raw materials required are lime and sand. Refer Figure 4.
Cement-Waste Slag Brick – This is used for load bearing walls of low rise buildings. The main feature of this is that a lot of waste slag can be recycled and either natural curing or steam curing for bricks can be adopted. Raw materials required are waste slag (80%) (fly ash, coal gangue, slag, etc.), Aggregate (stone powder or river sand) and Bonding agent (20%) (Cement or gypsum). Refer Figure 5.
Concrete Hollow Block – This is used for walls. The main features are:
– Wide source of raw materials
– Simple manufacturing process
– High construction speed
– The same process for Fly ash concrete block
– The same process for Lightweight concrete hollow block
The raw materials required are:
(a) For Concrete Hollow Block: Cement, sand, aggregates
(b) For Fly ash concrete block: Cement, fly ash, aggregates and
(c) For Lightweight concrete hollow block: Cement, lightweight aggregate, such as, fly ash, ceramisite, pumice, furnace slag, cinder, pearlite and other waste slags. Refer Figure 6 below.
Decorative Concrete Block – These blocks come with a combination of structural and decorative function and are used for decoration of exterior walls. The raw materials required are sand, stone, admixture and pigment. Refer Figure 7.
Lightweight Concrete Block (3E) Panel – This panel is used for walling system of steel reinforced concrete – lightweight panel system. Main features are:
– 3E panel (Ecological, Extruding Process, Economical)
– Specially designed for low-cost house
– 3E house (Easy, Energy-saving, Ensure) can be installed and rapidly constructed with 3E panels
– Excellent shock resistance: post-casted stem, panel and ring beam form an integrated structure
The raw materials used are cement, fly ash (optional), glass fiber or steel wire, aggregate (optional: sand, stone, blast-furnace slag, pearlite, ceramisite, pumice, and other slags). Refer Figure 8.
Foam Concrete Panel – This is used for concrete panel for partition wall, EPS sandwiched external wall panel, reinforced hollow floor panel, EPS sandwiched roof panel. The main features are:
– Easily worked and rapid on-site assembly
– Light weight
– Fire resistant
– Energy efficient: 80%
– Excellent acoustic performance
– Designed for inner comfort: cooler in summer, warmer in winter
Raw materials required are Fly ash (50-70%), cement, forming agent, reinforced materials. Refer Figure 9.
Hooking Panel – This panel can be used for wall of low-rise and high-rise buildings. Main features are :
– The wall is assembled by concrete hooking panel and concrete or steel hook.
– No auxiliary materials are needed for assembling. No need for bonding or anchoring for the panel.
– The house built with hooking panel is quake-proof and fireproof
– The machine can produce many kinds of panels
– Low-cost: US$40/m2 building area
Raw materials required are cement, sand, waste slag, glass fiber (for non-bearing wall) or steel wire (bearing wall). Refer Figure 10.
Glass-fiber Reinforced Concrete (GRC) panel – Suitable for load bearing wall of 1 to 2 stories buildings and non-load bearing wall of high-rise buildings. Main features are :
– Easy and quick construction: all the building materials needed for a 280m2 house can be transported by a truck; 8 workers can complete the house in 2 weeks
– Light weight: 35-50kg/m2
– High shock resistance
– Good heat insulation
– High durability
– Low-cost house: building cost is only US$60/m2.
Raw Materials required are Cement, EPS panel, reinforced materials, sand, blast-furnace slag, pearlite, ceramisite, pumice, and other slags. Refer Figure 11.
Straw Panel – This is used for wall of low-rise buildings and partition wall of high-rise buildings. Main features are:
– Green Building Material – 70% straw
– Low-cost: 35%-50% of gypsum product 10%-20% of wood product
– Lightweight – 33kg/m2
– Waterproof, Fireproof, Crack resistant
Raw materials required are (i) Straw (wheat straw, rice straw, maize stalk), sawdust, maize stalk, sawdust, sugarcane pole, husk, etc, (ii) Bonding and anti-burning agent and (iii) Reinforced material: mainly glass fiber. Refer Figure 12.
S Panel (Steel Wire-EPS Composite Panel) – S Panel system is a composite construction system. It is used for load bearing walls for low-rise buildings and non-load bearing walls for high-rise buildings, also for floor board and roofing board; It consists of S Panels -three-dimensional welded wire mesh and a built-in expanded polystyrene insulation core. The panels are erected over steel reinforcing bars embedded in a concrete foundation, then fastened to one another with wire – splice mesh. Concrete is sprayed to both sides of the panels to the desired thickness. The result is a homogenous structure with excellent thermal and acoustic properties. Main features are:
– Fast and simple erection, creating a monolithic structure
– Cost effective way of creating a quality, plaster finished structure
– Light weight – only 3.9 kg per m2, 110 kg with cement mortar of 30 mm thick on both sides, easy to handle and suitable for area with soft foundation
– High energy efficient system – Efficient thermal barrier, thermal resistance (50 mm in thickness) is 0.825 m2.k/w
– Excellent Sound Insulation – STC rating up to 52.6 dBA
– Superior fire resistance – tested to 2 hours fire rating
– Earthquake resistance – As a monolithic structural element with superior strength and ductility; it is ideal solution for high seismic areas. Also hurricane and typhoon proof design, even at the highest wind loads
– Long life, high durability, low maintenance, strong and modern
– Healthy and secure – Insect, termite, mildew and fungi resistance
– Greater design flexibility, easily to be adopted to curved/arched application. S Panel System is stronger than rock and more versatile than timber.
Raw materials are Steel wires: Ø2.0-2.2mm and EPS resin: density 15-20kg/m3. Refer Figure 13.
Colored Cement Tile for Roofing – Colored cement tile is an ideal roofing materials used for residential and industrial buildings. Main features are
– High flexural strength
– Low water absorption
– Waterproof and good impermeability durable
Raw materials required are cement, sand and pigment. Refer Figure 14.
Concrete Paving Block – Used for road paving. Main features are:
– Flexible design of shape and size;
– Good abrasion resistance
– High compressive strength
Raw materials are cement, fly ash, sand and stone etc. Refer Figure 15.
Hollow Gypsum Board & Blocks – Used for interior wall. Main features are:
– Lightweight, fireproof and heat – insulative;
– Easy & quick construction
Raw materials required are Building gypsum, supplementary materials, such as, lightweight aggregate, fly ash, filler, etc. Refer Figure 16.
Wall Plaster – Used plaster for interior wall. Main features are :
– Good workability and micro-expansion;
– Easy & quick construction;
– Good adhesion with basement;
– Lightweight, fireproof and heat – insulative
Raw materials required are building gypsum, supplementary materials, such as, lightweight aggregate, fly ash, filler, etc. Refer Figure 17.
Paint for Interior & Exterior Wall – Used for decoration for interior and exterior wall. Main features are :
– Easy construction
– Convenient maintenance
– Wide color option upon demand
Raw materials required are Polymer emulsion, titanium white, filler, additive. Refer Figure 18.
The selection of building materials can promote better quality of structures, faster construction solutions and foster new economical development. This selection will have to deal with “appropriateness” and “adequacy” within energy efficiency and environmental approaches for local conditions (social, economical, financial, institutional, environmental, etc.). Both concepts will need to be clarified through interviews and literature investigations from many publications regarding building materials properties.
– International Centre for Materials Technology Promotion United Nations Industrial Development Organization Beijing, P.R.China
– Building Materials & Engineering Design Low-Income Housing Projects Port Elizabeth-South Africa, By Camila Cortés Ballerino – Chile, In the subject of Built Environment Analysis, the Master programme Environmental Engineering and Sustainable Infrastructure at The Royal Institute of Technology, Stockholm, Sweden
– Affordable Housing Materials & Techniques for Urban Poor’s, S.S. Shinde, A.B. Karankal, North Maharashtra University Department of Civil Engineering & S.S.V.P.S.B.S.D.College of Engineering, Deopur, Dhule (MS) India