一、混凝土的凝結時間
根據水泥(ni)的具體(ti)性質(zhi)及混(hun)凝(ning)土(tu)所(suo)摻外(wai)加(jia)劑的性能不(bu)(bu)同,混(hun)凝(ning)土(tu)的初(chu)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)及終(zhong)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)會有差別。為(wei)便于(yu)施工,常態混(hun)凝(ning)土(tu)的初(chu)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)不(bu)(bu)得小(xiao)(xiao)(xiao)于(yu)3~4小(xiao)(xiao)(xiao)時(shi)(shi)(shi)(shi)(shi);終(zhong)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)不(bu)(bu)得大于(yu)12小(xiao)(xiao)(xiao)時(shi)(shi)(shi)(shi)(shi)。一般控制在6~10小(xiao)(xiao)(xiao)時(shi)(shi)(shi)(shi)(shi)。根據施工需要,選(xuan)擇適合的外(wai)加(jia)劑,可以在一定的范圍內改(gai)變(bian)混(hun)凝(ning)土(tu)的初(chu)、終(zhong)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)。國(guo)家標準規定水泥(ni)初(chu)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)不(bu)(bu)得早于(yu)45分鐘,一般為(wei)1~3小(xiao)(xiao)(xiao)時(shi)(shi)(shi)(shi)(shi);終(zhong)凝(ning)時(shi)(shi)(shi)(shi)(shi)間(jian)不(bu)(bu)得遲(chi)于(yu)12小(xiao)(xiao)(xiao)時(shi)(shi)(shi)(shi)(shi),一般為(wei)5~8小(xiao)(xiao)(xiao)時(shi)(shi)(shi)(shi)(shi)。
二、混凝土一方多少噸
普通混凝土因為強度和等級的不同,在重量上也有一定的差異,常規的混凝土一般有C10、C15、C20、C25、C30、C35、C40等級,最高的能達到C80。以C10為例,一立方C10混凝土通常需要用到水泥100公斤,砂石780公斤,碎石1025公斤,水160公斤,摻合料220公斤,總重量2285公斤。通常混凝土的等級越高,重量約大,選擇的混凝土品牌以強度等級高為宜。
三、混凝土配合比
混(hun)凝(ning)(ning)土(tu)(tu)(tu)施(shi)工(gong)配合(he)比是(shi)指(zhi)混(hun)凝(ning)(ning)土(tu)(tu)(tu)中各組成材(cai)料之(zhi)間的(de)比例關系,混(hun)凝(ning)(ning)土(tu)(tu)(tu)配合(he)比設(she)計(ji)(ji)是(shi)混(hun)凝(ning)(ning)土(tu)(tu)(tu)工(gong)程中很(hen)重(zhong)要的(de)一項工(gong)作,它直接(jie)影響到混(hun)凝(ning)(ning)土(tu)(tu)(tu)的(de)順利施(shi)工(gong)、混(hun)凝(ning)(ning)土(tu)(tu)(tu)工(gong)程的(de)質量和混(hun)凝(ning)(ning)土(tu)(tu)(tu)工(gong)程的(de)成本。設(she)計(ji)(ji)混(hun)凝(ning)(ning)土(tu)(tu)(tu)配合(he)比的(de)基(ji)(ji)本要求是(shi)滿足混(hun)凝(ning)(ning)土(tu)(tu)(tu)設(she)計(ji)(ji)的(de)強度(du)等(deng)級、施(shi)工(gong)要求的(de)混(hun)凝(ning)(ning)土(tu)(tu)(tu)和易性、混(hun)凝(ning)(ning)土(tu)(tu)(tu)使用(yong)要求的(de)耐久(jiu)性,在滿足以上(shang)要求的(de)基(ji)(ji)礎上(shang)降低成本。
四、混凝土強度低怎么辦
混凝(ning)(ning)土強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du)低可(ke)通過(guo)(guo)(guo)提高(gao)水(shui)泥強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du)等(deng)級來(lai)增大(da)混凝(ning)(ning)土強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du);施工時,一般通過(guo)(guo)(guo)降低水(shui)灰(hui)比來(lai)提高(gao)混凝(ning)(ning)土強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du)。適(shi)當降低水(shui)灰(hui)比,可(ke)有效控制漿集(ji)比和(he)水(shui)泥漿層厚度(du)(du)(du),使集(ji)料的(de)骨架作用得到(dao)充分發揮(hui),最終能增強(qiang)(qiang)(qiang)(qiang)(qiang)混凝(ning)(ning)土強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du)。此外,還可(ke)以通過(guo)(guo)(guo)優化設(she)計工藝(yi)流程、選擇級配(pei)優良、砂率(lv)適(shi)中的(de)高(gao)強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du)碎石、采用濕(shi)熱(re)處理養護混凝(ning)(ning)土、適(shi)量添加(jia)外加(jia)劑和(he)摻合(he)料等(deng)方法來(lai)增加(jia)強(qiang)(qiang)(qiang)(qiang)(qiang)度(du)(du)(du)。