Glass is an unstable alkali that can cause problems in the concrete due to the alkali-silica reaction (ASR). This property is advantageous in crushing glass powder and its use as a pozzolanic material in concrete. The behavior of large glass beads in the alkaline reaction in the laboratory cannot be equated with the actual behavior of glass powder in nature. Experience has demonstrated that the benefits of glass pozzolanic reaction in the concrete. Glass powder can be added up to %30 of the weight of cement in some concrete mixes to create an appropriate resistance.
Introduction
Glass is produced for different usages (packaging, smooth glass, lamp bulbs, etc.). But all of these devices have a service life and need to be reused and recycled to prevent environmental problems caused by their melting or burial.
Commercially used glass goes to specially designed places for recycling, burying, or collecting carbonate and then is transported to a storage site. The biggest goal of environmental law in this regard is to minimize glass waste and transport it to the storage site and then decompose it economically. Glass is a unique material that can be recycled over and over again without changes in its properties. In other words, a bottle can melt and turn into a bottle again without much change in its properties.
Most of the glass is used for producing bottles, and a large amount of the collected bottles is used again to make the new bottles. The effect of this process depends on the method of collecting and arranging the glasses that are produced in different colors. If glasses in different colors can be separated, they can be used to produce glasses with the same colors; otherwise, they can be consumed for other usages or must be buried. These usages may be in pavement aggregate, asphalt mass, concrete aggregate, construction materials (glass tiles, glass wall panels, etc.), fiberglass, art glasses, chemical fertilizers, landscaping, hydraulic cement, and much more. This article considers the use of glass in concrete aggregates. The great concern in the use of glass in concrete is the chemical known as the Alkali Silica Reaction ASR. This reaction can be very harmful for the concrete stability. Therefore, proper prevention should be done to reduce the effect of this reaction.
Proper prevention can be achieved by using suitable pozzolanic materials such as fly ash, blast-furnace slag, or micro silica (Silica Fume SF) with an appropriate ratio in the concrete mix. The sensitivity of glass to alkalis suggests that coarse glass and fiberglass can reduce or eliminate the effect of ASR reaction. However, it is also thought that the glass powder can exhibit pozzolanic properties (such as those listed above) and prevent the effects and reaction of ASR by glass grains.
For example, the use of the sifted silicate calcareous glass powder by sieve #100 is in order to reduce ASR. Furthermore, Clean Earth in Washington states that fine grains (powder) can weaken the concrete by ASR testing. Samtur’s efforts on the subject also suggest that the rejected glass powder from a # 200 sieve could act as a pozzolanic material to reduce the effect of the aggregate reaction (ASR). Pattengil has also achieved the same results.
Glass particles cause a lot of expansion, however, the particles smaller than 0.25 mm did not cause an expansion in the laboratory. It was found that glass particles of about 1.2 mm cause the greatest expansion of mortar among grains measuring 4.75 mm to 0.15 mm. It was also concluded that the greatest expansion occurs when %100 of the glass particles are aggregate. In addition, the green glasses with more than %1 chrome oxide have a positive effect on the ASR reaction. 1.5 mm of glass powder is effective in reducing the effect of ASR reaction on accelerated mortar testing, such as the effect of the fly ash, micro-silica, and slag. This shows that glass powder can stop the expansion caused by ASR in sensitive aggregates and granular glass. From the above, it can be concluded that glass can be used in three forms in concrete: coarse aggregates and fine aggregates that can cause an ASR reaction in concrete, and glass powder that can reduce their ASR effect. In commercial terms, it is very economical to use glass powder instead of cement until the glass is used as aggregate in concrete. Glass powder is a valuable material that is obtained from glass that is not suitable for recycling.
