Cement production generates large quantities of fine grained a (<250µm grain size) waste material called cement kiln dust (CKD).

Abeln et al. (1993) define CKD as a “fine particulate matter that consists of entrained particles of clinker, raw materials, and partially calcined raw materials”.

The production of CKD means there is a financial loss to the cement manufacturing company.

Valuable raw materials are consumed and processed. There is a high energy usage involved and there is a collection, disposal and storage problem of the CKD.

Improvements have been made in cement production to reduce the generation of CKD, but there are still large volumes of the CKD held in stockpiles and land-filled every year.

There are strict environmental regulations associated with the storage and containment of CKD, therefore finding a construction use for it would be beneficial to the cement industry and the environment in general.

In order to maker CKD safe to dispose of washing of CKD is necessary to remove chlorides. this is a costly and energy consuming process, which is not always favoured by the cement producer.

CKD land-filled close to water courses or agricultural areas increases the risk of damage to human health and aquatic life.

It has been suggested long term exposure to CKD can lead to colon, liver and respiratory cancer.

As a partial binder in construction products CKD causes problems with its poor inconsistent reactivity and low strength achievement with OPC, resulting in severe exotherms, delamination of formed materials produced, and retarded hydration.

PowerCem were faced with the problem of incorporating  high percentage mixes of CKD into a safe construction product, whilst immobilizing all sulphates and chlorides.

Having trialled various blends of OPC/CKD and Sand, GGBS was introduced into the blends in the hope that this would help contain the sulphates and chlorides.

With some success progressively, GGBS was used as the co-binder with the CKD and Sand.

This however caused an expulsion of salts, that could be welcomed for some applications, but it was deemed to be of an erratic nature and unpredictable, so we introduced our own product ImmoCem into the various blends.

GGBS/ImmoCem/Sand/CKD did show very much reduced expulsion of salts at the 72 hour mark and beyond.

Having succeeded in containing the sulphates and most of the salts in the matrix, it was decided to introduce the cheaper low lime type F Fly Ash and later the more plentiful Incinerator Bottom Ash into the mix as replacements for GGBS.

This replacement was decided upon to both significantly reduce both cost and also embodied CO2 in the end product.

The mixing was carried out in early December 2013 with all specimens tested for compressive strength and flexural strength carried out at 13 days, just before the Christmas holiday period.

Compressive strength was recorded at 9MPa and flexural strength was an excellent 3.2MPa.

NEN 7375:2004 was chosen to assess the mix against the Dutch Soil Quality Decree for formed/monolithic products.

The test is normally carried out over a 64 day period at 0.25, 1, 2.25, 4, 8, 16, 32 and 64 day intervals. It is though acceptable to use the first 4 stages only and divide the limiting values for Chloride and Sulfate leachate by 4. In this case the limiting values were determined to be 27500mg/m2 for chlorides and 41250mg/m2 for sulphates.

The ImmoCem modified CKD mix achieved leachate values for Chlorides and Sulphates at levels well below the Dutch Soil Quality Decree threshold. The results were 20480mg/m2 for Chlorides and 518mg/m2 for Sulphates.

The material as mixed has a density of 1.7t/m3, so qualifies as a medium light weight material for building blocks, sea defence armour etc. These light concrete products would be extremely low carbon and a very sustainable product for use in the UK construction industry or any organisation seeking closed loop zero carbon solutions. That have the added advantage of recycling two of the UK’s most problematic waste streams.

ImmoCem is a Nano technology cement modifier, which improves the performance of cement and other binders. Eliminating cracking and maximising leach free solidification of organic and inorganic contaminants.

It is supplied to the UK market by PowerCem Technologies (UK) Ltd, based in Derby. We champion the reuse and recycling of waste streams and continue to work with the UK construction industry to achieve the targets of zero carbon and zero waste.

With traditional soil stabilisation rainfall during installation can result in a change in the moisture content of the soils being treated.

This will adversely affect the structure of the stabilisation and its subsequent performance.

However when RoadCem is added to traditional cement stabilisation weakness and/or  failure will only occur in the most extreme of wet conditions.

It has been proved that when RoadCem is used the mechanism of interaction between the stabilised structure and rain or Carbon Dioxide in the atmosphere is totally different than in the case of other stabilisation methods, and as a result neither dilution nor carbonation will  be a problem

The pavement structure is actually isolated from Carbon Dioxide which leads to the elimination of carbonisation.

Other weather conditions that generally affect the performance of stabilisation are high or very low temperatures. The high air and ground temperatures that we experienced last summer accelerated hydration during the stabilisation process, resulting in failures due to loss in flexibility and consequent ravelling of the stabilised soils creating brittle fractures and cracks, even with cement binder mixes of 3% and less.

Even in the coldest spell of the winter it worth noting that adding RoadCem will increase protection against low temperature problems. The dense crystalline structure created by RoadCem, prevents voids, squeezing out or trapping any available water to frost proof the stabilisation against all but the heaviest of frosts.

Roadside Management and Erosion Control for longer lasting Roads

Integrated roadside management programs will always be needed because they combine the multiple missions of roadside vegetation control, roadside beautification, motorist safety, erosion control and preventative maintenance in one cost effective package.

Every year accidents take place with cars slipping off the road. When road shoulders are soft and or weak, wheels get caught in them and subsequently drivers either cause accidents trying to steer back onto the hard road surface or go right off the road all together. A obvious solution for this is the hardening of the shoulders themselves.

There are various systems on the market to make shoulders safer; like grass-concrete tiles, shoulder asphalt, plastic shoulder plates or rubble. The aim is to create a hardened shoulder, on which it is driving is unpleasant, but it is safe.

All these systems require (sometimes expensive) materials to be purchased and brought to site and installed. There is however already on-site the basic material that you need to quickly construct your strengthened verge structure, soil!

Using RoadCem, manufactured by PowerCem Technologies, together with cement it is possible to stabilise the soft/weak shoulder in-situ to form a safe effective shoulder.

By using in-situ shoulder material with RoadCem the original material is converted into a stable, impermeable but rough stabilization, which protects the highway pavement structure from erosion and water damage.

With a milling machine, with a width between 100 to 250 cm, the in-situ soil, the RoadCem and the cement are mixed to a depth of 15 to 20 cm. After compaction, a hard base is created. If required, it is possible to cap this with approx. 3 to 5 cm of soil, sown with grass to create a green shoulder.

RoadCem technology has successfully been applied in many locations in the world, mainly as foundation for roads. Every soil type can be stabilised with high breaking strain and high fatigue resistance.

In addition to the high bearing capacity, a further advantage is the speed of construction. Obstructing traffic flow to a minimum, even with secondary roads, this will be much appreciated by the client/users.

Gone are the days when roadside management meant just periodic mowing and spraying of weeds and a biannual regrading of the road shoulders. Integrated plans need to be incorporated that will require additional treatments or actions that over time will have a big impact on the system and ongoing expenses.

A stable water-resistant roadside shoulder will reduce carriageway maintenance needs and costs, reducing erosion and improving water collection and reducing run off.

A strong roadside verge will maximize safety for vehicles and passengers and also prevent water entering into the vulnerable road base/subgrade.

The primary objective in maintenance of roadside vegetation is to promote the safety of the highway user and preserve the highway infrastructure.

Very simply, roadside vegetation management involves caring for or controlling plants along the highway, the primary objective of providing a safe, unobstructed roadway corridor, and preserving the integrity of the highway infrastructure.

Vegetation, if left alone, can grow out of control and block visibility (signs, traffic, wildlife) which could endanger motorists.

Benefits of an Integrated roadside management programs:

 

Threats:

Summary:

A car width stabilization of the existing pavement shoulder with RoadCem soil stabilisation technology can be quickly applied using just the existing soils, graded to follow the road camber. This will provide a long-lasting maintenance free impermeable barrier preventing water from entering and destroying the road stone sub-base, at the same time funnelling excess water further away from the road and providing a weed/plant free corridor and emergency vehicle standing/breakdown parking area.