Use-It: making building blocks from rubble

Submitted by: Margaret McKenzie, Thursday, November 1, 2012

<p>House being constructed out of compressed earth blocks in Giba Gorge, KwaZulu-Natal (Image Source: Use-It).</p>

House being constructed out of compressed earth blocks in Giba Gorge, KwaZulu-Natal (Image Source: Use-It).

Use-It, a Durban based section 21 company, has developed the technology to make compressed earth blocks from a combination of soil and waste material says Chris Whyte managing director of Use-It.  “Durban currently has a housing backlog in the region of 450,000 houses …… if we re-direct all of the current builders rubble that is landfilled [in Durban] we could create 10,000 houses a year” observes Whyte. 

Waste recovery

Use-It was established with support from eThekwini Municipality to unlock projects in the Durban area that will divert material from landfill and at the same time create jobs.  Use-It currently has seventeen different waste recovery projects.  However the compressed earth block project has been a particular focus because of the need for more affordable building materials to address the housing backlog. 

Compressed earth blocks

There are three main steps to creating a compressed earth block that encapsulates inert waste material says Whyte.  Firstly the mixed waste is crushed using a crushing unit.   Secondly the crushed waste and soil are combined in a mixing and blending unit that spins the material and breaks up any clods in the soil.  At this stage cement is added to act as a stabilising agent.  Finally the mixed material is compressed into a block using a hydraulic ram.

Compressor unit used at the final stage of the process to manufacture the completed blocks (Image source: Use-It).

The blocks are made from 25% mixed waste, 5% cement stabilising agent and 70% soil.   Whyte explains that the mixed waste can be crushed from a variety of sources such as builder’s rubble and even sand blasting grit.  Most recently, says Whyte, Use-It has signed an agreement to crush a number of defective ceramic mugs for Unilever.   

Most types of soils can be used to make the blocks provided it has a minimum of 20% clay content says Whyte.  Currently Use-It sources soil from the unusable overburden of a nearby quarry.  However, soil suitable for agriculture purposes can’t be used because the organic material in the soil interferes with the machinery.

“Compressed earth blocks are the greenest building material available” says Whyte.  They have a lower embodied energy than any other building material because the raw materials are easy to source and there is no need for heating in the manufacture process.   Because the blocks have a much higher thermal efficiency than conventional materials buildings made from compressed earth blocks have lower heating and cooling requirements explains Whyte. 

A major focus of current Use-It work with the blocks is to establish financial viability for wide scale roll out.  If the blocks are used in a large scale development Whyte estimates the building material savings will be in the region of 30% to 40%.  “One of the problems we face is the system is designed for large application and a lot more costs are involved for single house building” says Whyte. Fortunately Use-It has secured funding from the DBSA Jobs Fund to implement a large scale roll out in the near future. 

Certification

The blocks have Agrément certification which is required for non-conventional building materials.  To meet Agrément standards the blocks have to include 5% cement explains Whyte.  However, he hopes to cut the amount of cement required to 3% in the near future.   The blocks are also certified by SABS and National Home Builders Registration Council.  

Since the technology has been developed to promote the diversion of waste from landfill, Whyte invites anyone interested in using the technology to visit Use-It.  To make arrangements for a site visit contact chriswhyte@use-it.co.za

Margaret McKenzie