Giving a second life to construction waste containing gypsum and polymers, leading researchers in the Riga Technical University Building Materials and Construction Products Laboratory of the Faculty of Construction and Mechanical Sciences are developing a new type of material to produce thermal insulation and sound-absorbing panels.
«Construction is no longer imaginable without heat and sound insulation materials - in parallel with the insulation of the external enclosing structures of buildings, more and more attention is being paid to sound insulation in mezzanine covers. Styrofoam and stone wool sheets are traditionally used for these works. The composite material of polystyrene foam granules and binders, which builders often refer to as liquid foam, is also starting to gain popularity in the market. It can be produced on site at the construction site using existing concrete screed mixing equipment. The material makes it possible to create seamless floor insulation, it is easy and effective to cover the engineering communications built into the floor, it can be made to the desired thickness,» explained FCME associate professor Ģirts Būmanis.
Properties can be affected by various factors – such as mixing, compaction, used binders, etc. The largest manufacturers of dry construction mixes offer ready-made mixes, but due to economic restraints, construction sites often choose to use Portland cement as a binder, obtaining liquid foam at low costs, but without guarantees about the properties of the material.
RTU scientists created a new composition of liquid foam plastic using only recycled materials in the Latvian Science Council project «Use of construction waste containing gypsum and polymers for the production of panels with increased sound absorption and heat insulation properties» (LZP-2020/1–0010). They use a recycled gypsum binder obtained from plasterboard construction waste. This waste is processed, and the resulting gypsum powder is burned at a temperature of 145 degrees.
The developed material has been compared in laboratory conditions with the widely used liquid foam material in construction, which is made with cement binder and is taken directly from the construction site. The scientists determined the bulk density of the material, performed compressive strength tests, and examined thermal parameters to determine heat loss through the material. Tests confirm that both materials are similar, the material made with gypsum has a slightly higher heat capacity, which means that it can accumulate and release more heat, causing smaller temperature changes in the room. However, it has a lower volumetric weight and strength, which is related to the mechanical properties of gypsum.
The material is also able to effectively absorb sound. The drying properties of the material were also tested. According to scientists, proper drying is one of the most important prerequisites for safe and effective use of the material. Covering the material too soon can lead to moisture in the structures, which will cause long-term problems. Tests show that the new material dries in seven days in a warm and dry room. Moisture on its surface decreases after two days, and after six days on the bottom of the material. In comparison, the material covered with a foam film had not dried even after 45 days.
«The construction industry, and especially the extraction of raw materials and the production of building materials, is an important source of greenhouse gas emissions. To promote Europe's green transformation and reduce the industry's negative impact on the environment, it is encouraged to use sustainable building materials and develop a circular economy by recycling waste into new products. Our study confirms that a fully recycled material can be obtained by replacing a commercial binder. To ensure guaranteed material properties, certified product systems should be chosen as the binder,» the RTU associate professor added.
