China
Africa
Explore chapters and articles related to this topic
Comparison of methods for early age strength testing of shotcrete
Published in Erik Stefan Bernard, Shotcrete: More Engineering Developments, 2004
As an example: for a mix containing 400 kg/m3 cement, accelerator with specific gravity (SG) = 1.4, 6% dose rate required results in 400 kg × 6% = 24 kg of accelerator, which, given the SG, equates to 24 kg/1.4 = 17 litres per m3 required. Accelerator dose rates vary widely around Australia from 10 to 30 litres per m3. Similarly, re-entry times vary from one to four hours after spraying.
Effect of fly ash and red mud on strength and electrochemical properties of seawater mixed concrete
Published in European Journal of Environmental and Civil Engineering, 2023
Arpit Goyal, Sukhdeo R. Karade
The compressive strength of S1 mix with 100% OPC and S10 mix with 40% FA and 10% RM at 7, 28 and 90 days is shown in Figure 7 and is compared with reference concrete specimens made with freshwater concrete. It can be observed that the strength of the S1 mix was higher than freshwater concrete (Reference specimen) by 14% and the S10 mix by 23% at 28 days. This is mainly due to the presence of chloride in SW which acts as a cement accelerator (Kaushik & Islam, 1995). At 90 days, freshwater and S10 mix continued to increase, however, for S1 mix drastically decreases due to the crystallisation of salts present in the SW (Goyal & Karade, 2020). In contrast, at 90 days, the pozzolanic activity of FA continues to increase the fch and fst when the rate of strength contribution of PC decreases. This is mainly because FA slows the hydration of cement in the early period and accelerated in later age (Narmluk & Nawa, 2011). Moreover, increased fineness of FA and RM results in highly dense microstructure, reduced porosity and higher strength (Figure 8) (Shaikh & Dobson, 2019). This 90-day strength of the S10 mix was close to the strength of freshwater concrete specimens.
Influence of alkali activators on thermo-physical properties of ecofriendly unfired clay bricks from anthill mounds
Published in European Journal of Environmental and Civil Engineering, 2022
Banjo A. Akinyemi, Blessing O. Orogbade, Ayavoro Ogheneyome, Mohamed A. Abeer, Anish Khan, Ali H. Mahmoud, Abdullah Asiri
The activators used were powdered form of SS comprising of 28% Na2O and 55% SiO chemical compounds. SS has a density of 1.27 g/cm3 and a pH of 10.54, respectively. It has a silica modulus of 1.96. The sodium hydroxide (NaOH) is a solid pellet of 98% purity added to the anthill mound clay soil to improve its pH. Calcium chloride (CaCl2) was used as cement accelerator because of its rich form of calcium ions in solution. These activators were sourced from SJZ Chenghui Chemical Co., Ltd., China.