Lightweight foam concrete performance introduction
Lightweight foam concrete is a new type of building economical material. It uses cement, admixtures (i.e., fly ash, stone powder, ore powder, slag, etc.) as the primary gelling materials, adds super plasticizers agents, reinforcing agents, foam stabilizers and water to make slurry, and cement foaming agent to foam, It is built into small stable bubbles and then mixed with the freshly made cement slurry to form a fluid. It is poured at the construction site or factory or poured into a mold to create a finished product — lightweight concrete material with independent, evenly distributed bubbles.
Lightweight foam concrete has the advantages of a lightweight, convenient construction, stable performance, strong uprightness, excellent thermal insulation performance, and low environmental impact. At present, it is widely used in roofing insulation, floor heating insulation, exterior wall insulation, non-load-bearing. Lightweight blocks for walls, backfilling of ground subgrade, etc.
The application of lightweight foam concrete in the field of building insulation has gradually expanded to the area of geotechnical engineering. According to the statistics in 2019, the amount of lightweight foam concrete has exceeded 35 million m3. At present, China's real estate construction projects are hot, and it will take at least 30 years in the future. The scope and amount of lightweight foam concrete will continue to expand. But lightweight foam concrete is prone to cracks, affecting its application in some projects. At present, the most widely used material on the market is fiber. Fiber is one of the practical components to improve the crack resistance and toughness of cement substrates.
Polyvinyl alcohol fiber effect
The Polyvinyl alcohol fiber, as a low elastic modulus and high ductility fiber, has the advantages of acid and alkali resistance, good toughness and crack resistance, and low price. It has attracted the attention of experts at home and abroad. Experiments have shown that adding a suitable amount of Polyvinyl alcohol fiber to the cement substrate can increase the tensile strength of the cement substrate, prevent the expansion of the original micro-cracks in the cement, delay the generation of new cracks, improve the deformability of the adhesive and improve the toughness of the cement With impact resistance.
At present, the Polyvinyl alcohol fibers used in light concrete in the market are mainly the following six kinds of lengths: 3mm, 6mm, 9mm, 12mm, 15mm, 19mm.
We conducted compressive strength tests, split tensile strength tests, and flexural strength tests for polypropylene fibers with different amounts, and analyzed the compressive strength, elastic modulus, and break tensile strength of polypropylene fibers for foamed lightweight concrete. The impact of power and flexural strength provides a specific reference for engineering construction and light concrete applications.
Experiment of Polyvinyl alcohol fiber in lightweight concrete
1 Preparation of lightweight foam particular objects first. To better analyze the effect of fiber content on the mechanical indexes of foamed lightweight concrete, the test specimens of this test were cured under the same conditions to reduce the impact of external environmental differences on the samples. . The age of the test pieces was 28 days. The fiber content is the ratio of fiber mass to cement mass.
Light concrete object test specimen size is 100 mm × 100 mm × 100 mm, and flexural strength test specimen size is 40 mm × 40 mm × 160 mm. There are three specimens in each group, and three samples are taken for each mechanical parameter. The arithmetic means of the pieces.
2 Test the compressive strength separately, split tensile strength test, flexural strength test, (the detailed experimental method for the experiment is too long for details, if you want to know, you can personally trust me to understand)
1) When the length of Polyvinyl alcohol fiber is 3, 6, 9, 12 mm, the unconfined compressive strength, elastic modulus, split tensile strength and flexural strength of lightweight foam concrete increase with the amount of fiber First increase and then decrease; when the length of polypropylene fiber is 15, 19 mm, and the content is ≤ 0.2%, its unconfined compressive strength, elastic modulus, split tensile strength and flexural strength are compared with the benchmark The value is slightly increased compared to when the amount of Polyvinyl alcohol fiber is higher than 0.2%, each parameter decreases as the number of fiber increases.
2) When the fiber length is 6 mm, and the content is 0.6%, the unconfined compressive strength, split tensile strength, and flexural strength of foamed lightweight concrete reach the maximum values of 3. 022, 0.444, respectively. , 0. 675 MPa, compared with the benchmark value, respectively increased by 33.3%, 28%, 46.7%
3) The foamed lightweight concrete is brittle before and after the fiber is added, but the fiber can significantly increase the toughness of the foamed light concrete.
The addition of Polyvinyl alcohol fiber can increase the toughness and tensile strength of lightweight foam concrete. At the same time, it can be seen in the later destructive experiments that the addition of fiber can improve the problem of light concrete cracking in the later stage.